USRE43403E1 - Distributed terminal optical transmission system - Google Patents

Abstract

The invention facilitates optical signals generated from customer premise equipment (CPE) at the edges of the metro domain networks. The CPEs are connected to extension terminals that transform the optical signal originating at the CPE into a suitable format for long haul transmission. The optical signal then propagates to a primary terminal where the signal is multiplexed with other optical signals from other extension terminals. The multiplexed signals are then transmitted over LH or ULH network to a second primary terminal where the signal is then demultiplexed from other optical signals and transmited to the proper extension terminal. At the extension terminal, the demultiplexed optical signal is transformed from its LH format back into a format suitable for inter-connection to a CPE. Using this architecture, the signal under goes optical-to-electrical conversion only at the extension terminals or end points. These end points can be located in lessee's facility. The only equipment located in lessor's facility is the primary terminal containing line amplifiers and add/drop nodes.

Description

CROSS-REFERENCE TO RELAYED APPLICATIONS

This application is a continuation of U.S. application Ser. No. 10/402,840 filed Mar. 27, 2003, which claims benefit of U.S. Provisional Application No. 60/368,545, filed Mar. 29, 2002, each of which is hereby incorporated by reference in its entirety.

FIELD OF THE INVENTION

This invention relates to a computer system for transporting optical signals between coupled metro domains using an optical transport networking system and more particularly using a lessor's optical transport networking system to transport a lessee's signal.

BACKGROUND OF THE INVENTION

The transmission, routing and dissemination of information has occurred over computer networks for many years via standard electronic communication lines. These communication lines are effective, but place limits on the amount of information being transmitted and the speed of the transmission. With the advent of light-wave technology, a large amount of information is capable of being transmitted, routed and disseminated across great distances at a high rate over fiber optic communication lines.

In traditional optical networks, long haul (LH) and ultra-long haul (ULH) optical networks typically connect major cities. The LH and ULH optical networks can span local geographical regions, countries, continents and even large bodies of water. The construction and maintenance costs of these long haul and ultra-long haul optical networks are prohibitively large. Because of these prohibitive costs, few communication service providers own their own optical networks. Many communication service providers lease the right to transmit optical signals over another communication service provider's optical network. The communication service providers that construct their national networks through the leasing of the optical networks from other communication service providers incur disadvantages, including increased cost versus chose communication service providers that own their own optical networks.

A typical communication service provider leasing “space” on another communication service provider's optical network must provide optical data networking equipment at their own local facilities in a metropolitan area and must also provide optical data networking equipment at the lessor's facility which may be in the same metropolitan area or a short distance away in another metropolitan area. In addition to the cost of maintaining multiple sets of optical data networking equipment, there is an additional penalty from the requirement to use metro transmission systems to connect the lessee communication system provider's facility to the lessor communication service provider's facility and then to use the LH and ULH optical data networking equipment to traverse the LH and ULH optical network. This system results in excessive optical-to-electrical conversions and increases the operational complexity of the overall systems.

What is needed is an optical transmission system that would locate all terminal equipment in the lessee's facility. It would also be beneficial if only line amplifiers and add/drop nodes were in the lessor's facilities. The signal should undergo optical-to-electrical conversion only at the endpoints, preferably in the lessee's facility and at any regeneration points required by physical constraints.

SUMMARY OF THE INVENTION

The present invention provides an architecture and method for transmitting signals over a network which allows for all of lessee's equipment to be located at a extension terminal in lessee's facility. It allows for efficient optical-to-electrical conversions and does not require multiple sets of optical data networking equipment.

Prior art systems suffer from the limitation that a typical communication service provider leasing “space” must provide optical data networking equipment at their own local facilities and must also provide optical data networking equipment at the lessor's facility. In addition to the cost of maintaining multiple sets of optical data networking equipment, there is an additional penalty from the requirement to use metro transmission systems to connect the lessee communication system provider's facility to the lessor communication service provider's facility and then to use the LH and ULH optical data networking equipment to traverse the LH and ULH optical network. This system results in excessive optical-to-electrical conversions and increases the operational complexity of the overall systems. In addition, prior art systems suffer from the requirement to convert customer premise equipment signals into short haul format for transport to a facility, usually a lessor's, and then at the facility, to be converted into a LH format for transport over a LH network. Certain prior art systems have attempted to address these problems with varying success.

U.S. Pat. No. 5,726,784 to Alexander, et al., entitled WDM OPTICAL COMMUNICATION SYSTEM WITH REMODULATORS AND DIVERSE OPTICAL TRANSMITTERS, discloses an invention which is capable of placing information from incoming information-bearing optical signals onto multiple optical signal channels for conveyance over an optical waveguide. A receiving system is configured to receive an information bearing optical signal at a particular reception wavelength and each receiving system must include at least one Bragg grating member for selecting the particular reception wavelength. However, Alexander is intended to provide compatibility with existing systems and does not disclose or suggest a system that allows for efficient optical-to-electrical conversions or one that would locate all terminal equipment in the lessee's facility.

U.S. Pat. No. 5,613,210 to Van Driel, et al., entitled TELECOMMUNICATION NETWORK FOR TRANSMITTING INFORMATION TO A PLURALITY OF STATIONS OVER A SINGLE CHANNEL, discloses an invention which uses a method wherein a signal to be transmitted is modulated on a subcarrier having its own frequency and then modulated on a main carrier in each sub-station. While Van Driel does utilize subcarrier multiplexing, only two wavelengths are involved and the multiplexing is therefore limited. Van Driel does not disclose transmitting the signals over a LH network. Nor does Van Driel disclose or suggest a system that allows for efficient optical-to-electrical conversions or one that would locate all terminal equipment in the lessee's facility.

U.S. Pat. No. 5,559,625 to Smith, et al., entitled DISTRIBUTIVE COMMUNICATIONS NETWORK, discloses a method and system for increasing the amount of re-use of information transmission wavelengths within a network. A distributive communications network includes groups of nodes at different levels. At each level of nodes, wavelength traffic is either passed on to a higher level, or looped back according to the band of wavelengths to which it is assigned. Philip does not disclose or suggest a system that allows for efficient optical-to-electrical conversions or one that would locate all terminal equipment in the lessee's facility.

Other patents such as U.S. Pat. No. 5,778,116 to Tomich, entitled PHOTONIC HOME AREA NETWORK FIBER/POWER INSERTION APPARATUS, and U.S. Pat. No. 5,914,799 to Tan, entitled OPTICAL NETWORK disclose an invention that is limited to signal transfer from a central station to subscriber stations. Neither of the patents disclose a method or apparatus for transmitting signals over a LH network, disclose or suggest a system that allows for efficient optical-to-electrical conversions or one that would locate all terminal equipment in the lessee's facility.

The present invention is an improvement over the prior art because it allows for efficient optical-to-electrical conversions and does not require multiple sets of optical data networking equipment. The present invention provides for coupled metro domain networks which are a part of a larger inter-domain network. The invention facilitates optical signals generated from customer premise equipment (CPE) at the edges of the metro domain networks. The CPEs are connected to extension terminals preferably in lessee's facility. The extension terminals transform the optical signal originating at the CPE into a suitable format for long haul transmission. One or more CPEs may be connected to one or more extension terminals. The optical signal then propagates from an extension terminal to a primary terminal along a metro fiber. At the primary terminal, the optical signal is multiplexed with other optical signals from other extension terminals. The multiplexed signals are then transmitted over LH or ULH network to a second primary terminal via core fiber. The optical signal may propagate along the core fiber with the help of a chain of amplifiers and optical add/drops. The second primary terminal then demuxes the optical signal from other optical signals and transmits the demuxed signal to the proper extension terminal. At the extension terminal, the demuxed optical signal is transformed from its LH format back into a format suitable for inter-connection to a CPE. Using this architecture, the signal under goes optical-to-electrical conversion only at the extension terminals. These extension terminals can be located in lessee's facility. The only equipment located in lessor's facility is the primary terminal containing line amplifiers and add/drop nodes. The transport system meets the networking requirements of intercity connections without the need for complex and costly metro transport gear. Also, the core extension terminals may be physically distributed across several metro network nodes.

The invention will be better understood from the following more detailed description taken in conjunction with the accompanying drawings.

DETAILED DESCRIPTION OF THE DRAWINGS

A better understanding of the invention can be obtained from the following detailed description of one exemplary embodiment as considered in conjunction with the following drawings in which:

FIG. 1 is a block diagram depicting a prior art inter-domain optical networking between core networks and metro/regional networks;

FIG. 2 is a block diagram of the detail of the prior art end-terminals and the interconnections between optical transport systems inFIG. 1;

FIG. 3 is a block diagram depicting an inter-domain optical transport system according to the present invention;

FIG. 4 is a block diagram of the detail of a primary terminal for use in the present invention;

FIG. 5 is a block diagram of a type one extension terminal for use in the present invention;

FIG. 6 is a block diagram of a type two extension terminal for use in the present invention;

FIG. 7 is a block diagram showing a multiplexer-demultiplexer architecture based on optical interleaver and deinterleaver filters for use in the present invention;

FIG. 8 is a block diagram showing a multiplexer-demultiplexer architecture based on banded DWDM filters for use in the present invention;

FIG. 9 is a block diagram showing a tunable demultiplexer architecture for use in the present invention;

FIG. 10 is a block diagram showing a tunable multiplexer for use in the present invention;

FIG. 11 is a block diagram of shelf configurations according to the present invention; and

FIGS. 12a and 12b are block diagrams of alternate shelf configurations according to the present invention.

DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS

In the descriptions that follow, like parts are marked throughout the specification and drawings with the same numerals, respectively. The drawing figures are not necessarily drawn to scale and certain figures may be shown in exaggerated or generalized form in the interest of clarity and conciseness. Reference of an A-Z signal or direction means from the left side of the drawing to the right side of the drawing while Z-A means from the right side to the left side. The A-Z or Z-A designation is used for illustrative purposes only.

The prior art as it relates to optical transport networking between domains is shown inFIG. 1 andFIG. 2. Referring toFIG. 1, an optical transport network may be composed of several domains: acore network100 with a geographic extent of typically between 100 km and 1500 km and a plurality ofmetro network domains130a-d with geographic extents typically of 3 km to 100 km.

Customer premise equipment (CPE)190a-h are considered to beoutside metro domains130a,130b,130c, and130d. CPE190a-h is sometimes referred to as client equipment or end-user equipment. CPE190a-h are connected tometro domain130a-d via interoffice fiber,151c,151d,151e,151j-l, and151p-s.

Metro domains130a-d vary widely in extent interconnection, and in the types of systems that are deployed within them.Metro domain130a shows a plurality of ring-protected systems.Metro domain130a is composed of primaryring end terminal135a, extensionring end terminal136a, primarymulti-node terminal145, and extensionmulti-node terminals146a and146b. Optical signals are propagated to and from primaryring end terminal135a and extensionring end terminal136a onmetro fibers152a and152b. Optical signals may propagate on either or both legs of the ring so that in theevent fiber152a orfiber152b fails, a connection is continually maintained between primaryring end terminal135a and extensionring end terminal136a.

A more complex, multi-node protected ring is indicated by primary multi-nodering end terminal145 and extension multi-nodering end terminals146a and146b, whereby, all three nodes are interconnected viametro fiber152c and152d.Metro fiber152c and152d may be a single fiber or a plurality of fibers. Methods for ring protection are well known in the art and will not be discussed further.

Metro domain130b is different frommetro domain130a in thatmetro domain130b consist ofprimary end terminals125a-c andextension end terminals126a-c being connected bymetro fiber152e-g in a linear fashion as opposed to a ring protected system as shown inmetro domain130a.Metro domain130b provides a network consisting of a plurality of unprotected linear links where the optical signals are propagated along a single path of fiber in an unprotected way. For example, ifmetro fiber152e is cut or fails, then optical signals terminating at and originating fromCPE190d will no longer be connected withcore end terminal110c. By the interconnection ofCPE190e toextension end terminals126b and126c andextension end terminals126b and126c being connected to core end-terminal110c viaprimary end terminal125b and125c an economical path protection can be realized at the client equipment layer. Path protection at the client equipment layer is realized because if one interconnection ofCPE190e to eitherextension end terminal126b or126c fails, the other interconnection can still transmit signals to110c.

Metro domain130c indicates a combination of protected and unprotected links.Primary end terminal125d is connected to extension end terminal126d in a linear fashion viafiber152h.Primary end terminal135b is connected to extension end terminal136b in a ring-protected system viafibers152i and152j.Primary end terminal125e is connected to extension end terminal126e viametro fiber152k.Core end terminal110b is ultimately connected toCPE190h by the transiting link ofprimary end terminal125f and extension end terminal126f indomain130d viafiber152m and by the transiting link ofprimary end terminal125e andextension end terminal126e indomain130c viafiber152k.Secondary end terminal126e is connected toprimary end terminal125f viamultiple fiber151r. Such architecture may occur, for example, because the geographical distance betweencore end terminal110b andCPE190h is too large for one domain. More relevant to this invention, the situation may occur because different entities own and manage the twodomains130c and130d and there is no way to connectdomain130d to core end-terminal110b without some type of intermediate equipment and associated fiber.

Metro-systems may multiplex more than one optical signal onto a single fiber using methods that are well known in the art as such as code wave division multiplexing (CWDM), wavelength division multiplexing (WDM), or dense wavelength division multiplexing (DWDM) methods. Starting from core end-terminal110b in thecore network100, a plurality of tributary signals are interconnected and terminated onprimary end terminal125e via multiple fiber151o.Primary end terminal125e muxes the plurality of tributary signals together and transmits the muxed signals to extension end terminal126e viametro fiber152k.Secondary end terminal126e demuxes the plural tributary signals and transmits them via multiple pairs ofintra-office fibers151r toprimary end terminal125f indomain130d.Primary end terminal125f muxes the plurality of tributary signals together and transmits the muxed signals to extension end terminal126h viametro fiber152m. Finally, extension end terminal126h demuxes the plural tributary signals and connects them, via multipleintra-office fibers151s toCPE190h where the signals terminate. If the signals originated atCPE190h the process would be reversed.

Core network100 is sometimes referred to as a long haul network and may be composed of a plurality of linear DWDM systems or more complex ring structures employing SONET ADMs or a mix of each type. A linear DWDM system is shown inFIG. 1. Signals are transferred into and out ofcore network100 bycore end terminals110a-c viaintra-office fiber151a,151b,151f-i, and151m-o. The tributary interfaces will be described in more detail inFIG. 2 as are the methods used to transmit signals through thecore end terminals110a-c. The transmitted signals from onecore end terminal110a-c propagate through a set of coreoptical amplifiers115a-d and optical add-drop multiplexing device (OADM)116 oncore fiber150a,150x, and150z before reaching a secondcore end terminal110a,110b, and110c where the signals are transmitted into ametro network domain130a-d.

Core amplifiers115a-d perform the function of compensating for loss of optical signal power as the optical signals propagate throughcore fiber150a,150x, and150z. The amplifiers are spaced typically 60 km to 120 km apart. The ellipsis in the drawing indicates that there could be any number amplifiers between115a and115b and between115c and115d. Also, there may be more than one OADM alongcore fiber150a,150x and150z.OADM116 performs the function of extracting and inserting optical signals fromcore fiber150a,150x and150z, and placing or acquiring the signals on or fromintra-office fiber151a,151b,151f-i, and151m-o.

InFIG. 2, the details of signals paths from core fiber150 (shown as a block),core end terminal110,primary end terminals125g and125h, to themetro fiber152n and152o (shown as blocks) are shown. These signals paths occur between, for example,110c and125a-c inFIG. 1. With the exception ofcore fiber150 andmetro fiber152n and152o, all the elements ofFIG. 2 are physically co-located in a metro central office (CO) or a core network point-of-presence (POP) facility. Moreover, typically all end-terminal components incore end terminal110 andmetro terminal125g and125k must be co-located in the same facility and within adjacent bays according to prior art.

Continuing inFIG. 2, intra-office fibers usually consist of a fiber pair, for example intra-office fiber151t-1 and151u-1, whereby the transmit and receive optical signals usually propagate on separate fibers. Optical or WDM signals fromcore fiber150 entercore end terminal110 via intra-office fiber151t-1. Intra-office fiber151t-1 is connected tooptical amplifier155 where the propagating signals are amplified.Optical amplifier155 is further connected to DWDM demux165 via coreend terminal fiber161a. Coreend terminal fiber161a carries composite optically muxed signals. The composite signals are deconstructed into their constituent and individual optically modulated signals by DWDM demux165 and appear onfiber interconnects163a-c. Optical signals onfiber interconnects163a-c are received by Long Haul (LH)transponders160a-c.LH transponders160a-c electrically process and optically remodulate the signals, and transmit the LH remodulated signals through tributary interfaces151v-1 and152v-2 to short haul (SH)transponders170a and170b orSH transceiver180 via intra-office fibers151v-3.

LH transponders160a-c may be varied in their capability and composition. For example, they may employ internal modulation or external modulation using NRZ, RZ, or other formats as known by those skilled in the art.LH transponders160a-c have the primary function of converting short and intermediate reach intra-office signals typically generated by directly modulated lasers to long reach signals; long reach signals (LH format) being compatible with intercity propagation of hundreds or thousands of kilometers.

TheSH transponders170a and170b andSH transceiver180 may be of different varieties typically found in metro domain systems and known well to those skilled in the art. The distinguishing feature ofSH transponder170a and170b andSH transceiver180 fromLH transponders160a-c is in the propagation distance limitation on theSH transponders170a and170b andSH transceiver180.SH transponders170a and170b andSH transceiver180 have a propagation distance limited to less than or about 80 km.

The term transponder applies to both the LH and SH applications wherein the input optical signal to the device is narrow band and occurs at a particular input wavelength or frequency and wherein the device converts the input signal to an output optical signal of a different wavelength or frequency and may be narrowband or broadband in nature. In general, a transponder will operate in full-duplex mode. The term transceiver applies to a device that converts input signals at a particular wavelength or frequency to an output signal at the same wavelength or frequency while maintaining similarity between the optical bandwidth and dispersive capacity of the input signal to the optical bandwidth and dispersive capacity of the output signal.

Both LH and SH devices perform the functions of regeneration or amplification and reshaping, and may or may not employ retiming. Further details of the LH or SH receiver technology and transmitter technology, that is the transponders and transceivers, are known in the art and will not be described further.

Continuing the description ofFIG. 2, the optical signals on intra-office fibers151v-1,151v-2, and151v-3 are received bySH transponders170a and170b andSH transceiver180. The optical signals on151v-3 are converted bytransponder180 to optical signals that propagate directly on the intra-office fibers151x-2 to metro fiber152o. Alternatively, the optical signals appearing on intra-office fiber151v-1 and151v-2 are converted bySH transponders170a and170b, respectively, to intermediate signals and transmitted toWDM mux175 viafiber interconnect173a and173d, respectively.WDM mux175 muxes the intermediate signals and transmits them to themetro fiber152n via intra-office fiber151x-1 and ultimately to a extension end terminal.

In the Z-A direction, optical signals frommetro fiber152n propagate along intra-office fiber151y-1 toWDM demux176.WDM demux176 extracts the optical signals propagated along intra-office fiber151y-1, and transmitts the extracted signals toSH transponders170a and170b viainterconnects173b and173c.SH transponders170a and170b electronically process and optically remodulate the extracted signals for transport over a SH network and transmit the remodulated signals toLH transponders160a and160b via intra-office fibers151w-1 and151w-2.LH transponders160a and160b convert the signals for into a format suitable for LH transporting and transmits the prepared signals toDWDM mux166 viafiber interconnects163d and163e.

Optical signals from metro fiber152o propagate along intra-office fiber151y-2 toSH transceiver180.SH transceiver180 electronically processes and optically remodulates the extracted signals for transport over a SH network and transmits the remodulated signal toLH transponder160c via intra-office fiber151w-3 and tributary interface155c. LH transponder converts the signal into a format suitable for LH transporting and transmits the prepared signal toDWDM mux166 viafiber interconnect163f.

DWDM mux166 muxes the signals received fromfiber interconnects163d-f and transmits the muxed signals to transmittingoptical amplifier156 via coreend terminal fiber161b. Transmittingoptical amplifier156 amplifies the muxed signals and transmits the amplified signals tocore fiber150 via intra-office fiber151u-1.

The preferred and alternate embodiments of the invention are described with reference toFIGS. 3-12. Beginning withFIG. 3, the invention includes a set of coupledmetro networks230a-d which are a part of a largerinter-domain network200. Themetro networks230a-d are connected by a plurality of linear DWDM systems or more complex ring structures employing SONET ADMs or a mix of each type. A linear DWDM system is shown inFIG. 3, but the invention encompasses other structures. The invention facilitates optical signals generated fromCPE290a-p at the edges ofmetro networks230a-d to be interconnected directly with each other.CPEs290a-p are the same type as CPEs190a-h shown inFIG. 1. Those skilled in the art will recognize that the configuration of metro network domains may take many forms and that those depicted are exemplary. Similarly, the invention can be applied to a widely varying arrangement of interconnections of metro optic networks, as will be appreciated by those skilled in the art.CPEs290a-d,290f-i and290l-p are in communication withextension terminals220a-h viaintra-office fiber251a-d,251g-i and251o-s.Intra-office fibers251a-s are the same type of fiber asintra-office fibers151a-s shown inFIG. 1.CPE290d is connected toprimary terminal210a viaintra-office fiber251e.CPE290e is connected toprimary terminal210c viaintra-office fiber251f. CPEs290j and290k are connected to primary terminal210b viaintra-office fibers251k and251l.

Extension terminals220a-f are connected toprimary terminals210a and210c viametro fiber252b-d and252f-h. Metro fiber252a-k is the same type of fiber asmetro fiber152a-m.Primary terminals210a and210c are connected tojunctions211a and211b viametro fiber252a and252e.Extension terminal220g is connected tojunction211c via metro fiber252i.Extension terminal220h is connected tojunction211e viametro fiber252k.Junction211e is connected tojunction211d viametro fiber252j.Junction211a is connected tocore amplifier215a viacore fiber250a.Amplifiers215a-d are the same type of amplifiers as115a-d.Core fiber250a,250x and250z is the same type of fiber ascore fiber150a,150x and150z.

Junction211b is connected toOADM216 viainteroffice fiber251u.Junctions211c and211d are connected to primary terminal210b viaintra-office fiber251m and251n. Also connected to primary terminal210b areCPE290j and290k throughintra-office fiber251k and251l.

To accomplish the interconnection ofmetro networks230a,230b,230c,230d, coreoptical amplifiers215a-d are connected toOADM216 viacore fiber250a,250x and250z. The ellipses in the drawing indicate there can be any number ofcore amplifiers215a-d betweenjunction211a andOADM216 and between primary distributed terminal210b andOADM216. Also, there may be more than oneOADM216 alongcore fiber250a,250x and250z. EitherOADM216 orcore amplifiers215a-d are connected to a sub-system ofprimary terminals210a-c andextension terminals220a-h composed of terminal shelves.CPE290a-p may be interconnected directly toprimary terminals210a-c orextension terminals220a-h to accomplish the transfer of optical signals from a particular CPE to a different CPE that may be in a geographically distinct location.OADM216 can be fixed or not fixed as in broadcast and select architectures. In the preferred embodiment,OADM216 includes a broadcast and select architecture as is known in the art. Core optical amplifiers215 andOADM216 may or may not contain components to perform optical dispersion compensation and other components to perform gain equalization, both of which may employ techniques known in the art.

Referring toFIG. 3, a link betweenCPE290a andCPE290p in the A-Z direction of a full-duplex signal path will now be described as an example.CPE290a is connected toextension terminal220a viaintra-office fiber251a.Extension terminal220a transforms the signal originating at290a into a suitable format for LH transmission.Extension terminal220a transmits the transformed signal toprimary terminal210a viametro fiber252b. Atprimary terminal210a, the transformed signal is optically muxed with other signals fromextension terminals220b and220c and with signals generated atCPE290d. The multiplexed signals are transmitted tojunction211a via metro fiber252a. Atjunction211a, metro fiber252a is connected tocore fiber250a and the optical signal propagates alongcore fiber250a,250x and250z through the chain ofcore amplifiers215a-d andOADM216 to the primary distributed terminal210b. At primary distributed terminal210b, the desired signal forCPE290p is optically demuxed from the other signals and transmitted along intra-office fiber251n tojunction211d. Atjunction211d, intraoffice fiber251n is coupled tometro fiber252j. The desired optical signal propagates alongmetro fiber252j tojunction211e. Atjunction211e,metro fiber252j is coupled tometro fiber252k. The desired optical signal continues to propagate onmetro fiber252k toextension terminal220h. Atextension terminal220h, the desired optical signal is received and transformed from its LH format into a format suitable for interconnection withCPE290p throughintra-office fiber251s. The optical signal terminates atCPE290p. In the Z-A direction of the full duplex signal can be described in a similar way, so that signals originating fromCPE290p and terminating atCPE290a are propagated in a similar manner.

There are many optical links that can be established in theinter-domain network200. For example, the present invention allows forCPE290c to be interconnected to any one of the other CPE shown inFIG. 3. Also, more than one CPE may be connected to a single extension terminal or primary terminal. For example,CPE290a andCPE290b are both connected toextensionterminal220a CPE290a and290b may be co-located together or geographically separate and neitherCPE290a or290b need be co-located withextension terminal220a. Although in practice they are usually co-located and interconnected byintra-office fiber251a and251b as shown. Additionally, one CPE may be connected to a plurality of extension terminals or primary terminals. For example,CPE290c is shown having at least two distinct optical interfaces, one being connected toextension terminal220b and the other connected toextension terminal220c. By interconnectingextension terminals220b and220c toprimary terminal210a withmetro fiber252c and252d, a protected connection can be made betweenCPE290c andprimary terminal210a. If a fiber failure occurs on eithermetro fiber252c or252d theother metro fiber252c or252d may carry the optical signals safely fromCPE290c to other points ininter-domain network200.

Another link example will illustrate further features of the current invention. Simultaneous multiple interconnections betweenmetro networks230b and230c consisting of links betweenCPE290e to CPE290o,CPE290h toCPE290k, and CPE290i toCPE290p is described. In particular,CPEs290h and290i are connected toextension terminal220f viaintra-office fiber251i and251j, respectively.Secondary terminal220f converts the originating signals fromCPEs290h and290i to a LH format.Secondary terminal220f optically muxes the converted signals and transmits the muxed signals toprimary terminal210c viametro fiber252h. Also,CPE290e is connected toprimary terminal210c viaintra-office fiber251f and transmits an SH signal toprimary terminal210c.

Atprimary terminal210c, the optical signal originating fromCPE290e is converted to a LH format and optically muxed with the other optical signals originating fromextension terminal220f. The muxed optical signals fromprimary terminal210c propagate onmetro fiber252e tojunction211b. The signals propagate throughjunction211b tointra-office fiber251u and continues on toOADM216.OADM216 muxes the signals fromintra-office fiber251u ontocore fiber250x. The optical signals propagate oncore fiber250x and250z towards primary terminal210b. Multiplecore amplifiers215c and215d may be used to boost the signal.Additional OADMs216 may also be present oncore fiber250x and250z.

At primary terminal210b, the optical signals oncore fiber250z are optically demuxed in such a way that optical signals destined forCPE290e and CPE290i are transmitted on intra-office fiber251n while optical signals destined forCPE290h are transmitted on intra-office fiber251l. The signal on intra-office fiber251l terminates atCPE290k and the signal fromCPE290h has been successfully transmitted toCPE290k.CPE290k is considered local to core distributed terminal210b.

The signals originating fromCPE290e and CPE290i on intra-office fiber251n propagate along intra-office fiber251n throughjunction211d and ontometro fiber252j insidemetro network230c. The LH signals propagate alongmetro fiber252j throughjunction211e and ontometro fiber252k insidemetro network230d. The optical signals propagate alongmetro fiber252k toextension terminal220h. Atextension terminal220h, the optical signals are demuxed and converted from a LH format to a format suitable for interconnection to CPEs290o and290p. The converted signals are transmitted to CPEs290o and290p viaintra-office fiber251r and251s, respectively, where the signals terminate. The signal fromCPE290e has been successfully transmitted to CPE290 and the signal from290i has been successfully transmitted to290p. In the Z-A direction of the full duplex signal can be described in a similar way so that originating signals from290k,290r, and290q destined for290h,290e, and290i respectively, are propagated in a similar manner to that just described.

The above explains how a signal may propagate through more than one metro network230 without conversion from an LH format. In the preferred embodiment, the links betweenprimary terminals210a-c andextension terminals220a-h may be more than 100 km and may include optical amplifiers with or without dispersion compensators and gain equalizers.

The invention allows forprimary terminals210a-c to be placed outside or within a metro network230 as required by the location of CPEs290a-p.Primary terminals210a and210c are insiderespective metro networks230a and230b while primary terminal210b isoutside metro networks230c and230d.

The invention also allows for remote interconnections betweenOADM216 andprimary terminals210a-c to be of distances greater than those found in most interoffice networks. The distance for the remote interconnection is similar in nature to the long distances betweenprimary terminals210a-c andextension terminals220a-p and could be around 100 km. Interconnection betweenprimary terminals210a-c,extension terminals220a-h andOADM216 are accomplished with a single pair of fibers. This feature is further described in relation toFIG. 4.

FIG. 4 depicts the preferred embodiment of a primary terminal.Primary terminal210 allows for the interconnection of full duplex signals from core fiber250 (shown as a block) to variousdistinct CPEs290s-x.CPEs290s-x are the same type as CPEs290a-pFIG. 3 and CPEs190a-hFIG. 1.CPEs290s-x maybe geographically diverse from one another. In the A-Z direction, an LH format optical signal is transmitted from thecore fiber plant250 to receivingamplifier255 viaintra-office fiber251v-1.Intra-office fibers251v-a,251x-1,251x-2,251x-3,251y-1,251y-2,251y-3,251z-1,251z-2,251z-3,251z-4,251z-5,251z-6,251w-1 are the same type of fiber asintra-office fibers251a-s and151a-s. Receivingamplifier255 performs the function of amplifying the incoming multiplexed WDM or DWDM signals fromintra-office fiber251v-1 to a known level, so the signal has enough optical power to transmit to other components such asextension terminals220i-k. The amplified signal is transmitted tofine demux265 viafiber261a. The signal can contain any number of muxed optical signals. In the preferred embodiment, there are twelve optical signals, referred to as M (12) to denote any arbitrary number of twelve signals.

Fine demux265 demuxes the M (12) muxed signals in such a way as to leave N (4) smaller groups of M/N (3) optical signals. The N (4) smaller groups are muxed onto 4intra-office fiber interconnections271a-d. These smaller groups of approximately M/N (3) optical signals will be called “optical mux groups” or simply “mux groups” hereinafter. One mux group onintra-office fiber interconnection271a remains inside theprimary terminal210 for further processing while the other mux groups onintra-office fiber interconnections271b-d exit for distribution to distinct locations, such asCPE290v-x.

The mux group onfiber interconnection271a is transmitted fromfine demux265 tocoarse demux267.Coarse demux267 demuxes the approximately M/N (3) optical signals into individual optical signals and transmits the individual signals totransponders260a-c viaoutput fiber connections263a-c.Transponders260a-c convert the individual LH format signals into optical signals for transmission on intra-officeoptical fibers251x-1,251x-2, and251x-3. The transmitted optical signals are suitable for use byCPEs290s-u, and therefore theprimary terminal210 serves as the interface device for the local traffic (optical signals) intended forCPEs290s-u. As shown by the ellipsis, there may be a plurality of CPEs290 connected to any one of thetransponders260a-c.

For the delivery of remote traffic (optical signals) toremote CPE290v-x,fine demux265 transmits the mux groups onintra-office fiber interconnections271b-d tometro fiber252. The optical mux groups are transported frommetro fiber252 toextension terminals220i-k via geographicallydistinct fiber interconnections271e-i.Secondary terminals220i-k demux the optical mux groups into individual optical signals and transmit the individual signals to CPEs290v-x viaintra-office fibers251z-1, z-3, and z-5. As shown by the ellipsis, there may be a plurality of CPEs connected to any one of theextension terminals220i-k.

The optical signals, being in full duplex, also flow in a direction opposite to that just described and in a similar way. Individual optical signals that originate fromCPE290v-x are transmitted toextension terminals220i-k via intra-officeoptical fibers251z-2, z-4, z-6.Secondary terminals220i-j mux the optical signals into optical mux groups and transmit the mux groups tometro fiber252 viafiber interconnections271f,271h, and271j. The optical mux groups propagating onmetro fiber252 are transmitted tofine mux266 viafiber interconnections271f-h. The optical mux groups are muxed into one mux group byfine mux266.Fine mux266 transmits a signal containing the mux group tooutput amplifier256 viafiber261b.Output amplifier256 then amplifies the signal for transmission onintra-office fiber251w-1 tocore fiber250.

Similarly, optical signals originating fromCPEs290s-u flow in the Z-A direction throughtransponders260a-c via intra-office fiber151y-1,151y-2 and151y-3.Transponders260a-c convert the individual optical signals to a LH format and send the converted signals tocoarse mux268 viaoutput fiber connection263d-f.Coarse mux268 muxes the converted signals together into an optical mux group and transmitts the optical mux group tofine mux266 viafiber interconnection271e. The optical mux groups propagating onfiber interconnections271e-h are muxed into one mux group byfine mux266.Fine mux266 transmitts the signal containing the mux group tooutput amplifier256 viafiber261b.Output amplifier256 then amplifies the signal for transmission onintra-office fibers251w-1 tocore fiber250. The combination ofprimary terminal210 and extension terminals.220i-k form a system of distributed terminals, which is a preferred embodiment of the present invention.

InFIG. 5, the preferred embodiment of a type oneextension terminal220 is shown. A mux group containing approximately M/N, for example 3, optical signals is propagated from metro fiber252 (shown as a block) toterminal220 viafiber interconnection271k. The mux group traverses terminal220 receivingamplifier285 which may be or may not be the same type of amplifier as receivingamplifier255 inprimary terminal210,FIG. 4.Terminal220 receivingamplifier285 amplifies the incoming approximately M/N (3) multiplexed optical WDM or DWDM signals from 271 k to a known level so the signals have enough optical power to be transmitted to the other components in type oneextension terminal220 and connecting devices such as CPE290aa-cc. The approximately M/N (3) multiplexed optical signals are transmitted from extensionterminal receiving amplifier285 to extension terminalcoarse demux287 viaextension terminal interconnection281a. Secondary terminalcoarse demux287 demuxes the approximately M/N (3) multiplexed optical signals into individual optical signals for transmission totransponders260d-f via extension terminaloutput fiber connections283a-c.Transponders260d-f are the same type of transponders astransponders260a-c inFIG. 4.

Transponders260d-f convert the LH format optical signals on extension terminaloutput fiber connections283a-c into signals suitable for use by CPEs290aa-cc.Transponders260d-f are connected to CPE290aa-cc via intra-office fibers251aa-1,251aa-2 and251aa-3.

Terminal220 serves as the interface device for the local traffic (optical signals) intended for CPE290aa-cc. Intra-office fibers251aa-1,251aa-2 and251aa-3 are usually physically co-located withterminal220, but they may incorporate long reach capability including optical amplifiers to connect to an individual port on a remote CPE290 via an intra-office fiber.

The full duplex optical signals also flow in the Z-A direction, from CPEs290aa-cc through intra-office fibers251bb-1,251bb-2 and251bb-3 totransponders260d-f.Transponders260d-f convert the signal formats used by CPEs290aa-cc to a LH format. The converted LH format signals are sent to extension coarsemux288 via extension terminaloutput fiber connections283d-f. Secondary terminalcoarse mux288 combines the optical signals into an optical mux group and transmits the optical mux group tooptical amplifier286 viaextension terminal interconnection281b. The mux group is amplified byterminal220 transmittingoptical amplifier286 for propagation alongfiber interconnection271m tometro fiber252 and on to a primary terminal210 (FIG. 4).

The preferred embodiment of a type oneextension terminal220 is capable of transmitting and receiving signals fromprimary terminal210 from distances on the order of but possibly even larger than 100 km For distances much larger than 100 km a stand-alone optical amplifier or chain of such devices can be inserted between the extension terminals and the primary terminal.

A type twoextension terminal225 is depicted inFIG. 6.Terminal225, can be used for short distance connections, of the order of 5 km or less, that require a physical separation between theprimary terminal210 and multiple CPEs. The primary difference between a type twoextension terminal225 and type oneextension terminal220 is that receivingoptical amplifier285 and transmittingamplifier286 are not found in type twoterminal225. With the exception of the optical amplifiers, the signal propagation is the same to that described for type oneextension terminal220.

In the A-Z direction, an optical mux group containing approximately M/N optical signals are propagated from metro fiber252 (shown as a block) to type twoextension terminal225 viafiber interconnection271p. The optical mux group propagates to short extensioncoarse demux297.Coarse demux297 demuxes the approximately M/N (3) optical signals into individual optical signals and transmits the individual signals totransponders260g-i via terminaloutput fiber connections293a-c.Transponders260g-i are the same type oftransponders260d-f as shown inFIG. 5.

Transponders260g-i convert the LH format optical signals onoutput fiber connections293a-c into signals suitable for use by CPEs290pp-rr.Transponders260g-i are connected to CPEs290pp-rr via intra-office fibers251cc-1,251cc-2 and251cc-3.

Terminal225 can also serve as the interface device for the local traffic (optical signals) intended for CPE290pp-rr. Intra-office fibers251cc-1,251cc-2 and251cc-3 are usually physically co-located withterminal225, but they may incorporate long reach capability including optical amplifiers to connect to an individual port on a remote CPE290 via intra-office fiber251.

The full duplex optical signals also flow in the Z-A direction from CPE290pp-rr through intra-office fibers251dd-1,251dd-2 and251dd-3 totransponders260g-i.Transponders260g-i convert the optical signal formats from that used by CPEs290pp-rr to a LH format. The converted LH format signals are sent to terminalcoarse mux297 via terminaloutput fiber connections293d-f Coarse mux298 combines the optical signals into an optical mux group for propagation alongfiber interconnection271q tometro fiber252 and on toprimary terminal210.

In both terminal220 and terminal225,coarse demux287, terminalcoarse demux297,coarse mux288, andcoarse mux298 may perform the function of attenuating the individual optical signals. In this way, the invention can launch or detect the appropriate optical powers without the need of gain equalization provided by optical amplifiers. Furthermore, the attenuation function in extension terminalcoarse demux287 and extension terminalcoarse mux288 alleviate the need for tightly controlled gain equalization in the extension terminal receivingoptical amplifier285 and transmittingoptical amplifier286 thereby lowering the cost.

FIGS. 7 through 10 depict various embodiments of mux and demux architectures which constitute a part of the invention. InFIG. 7,mux500 is made up of twosubmultiplexers550a and550b.Submuxers550a and550b are capable of taking four times N optical signals at different wavelengths and combining them onto oneoutput fiber connection515a and515b. N can be any number, for example, 10 as shown inFIG. 7.Mux500 is capable of taking 8×N (10) optical signals at different wavelengths and combining them onto one output optical connection505. Thus, the architecture is scaleable up or down in the number of wavelengths, for example a 50/25 GHz interleaver may be placed in conjunction with twomuxs500 to form a 16×N multiplexer unit.

The function of an optical interleaver is to combine a “comb” of optical wavelengths consisting of even and odd numbered wavelengths ordered by integers as a monotonically increasing sequence with wavelength or frequency of the optical carrier. The function of an optical de-interleaver is to separate a “comb” of optical wavelengths consisting of even and odd numbered wavelengths ordered as before. Specific interleaver or de-interleaver device implementations are known in the art and will not be described further. Interleavers known in the art and can be obtained from, for example, JDS Uniphase, model number IBC-LW1D00310.

In what follows, the muxing function will be described along with the demuxing function that utilizes the same basic architecture and connectivity. Demuxing is described in parentheses. In the A-Z direction, Z-A in parentheses, signals enter (leave)mux500 through a set of 400GHz filters540a-h, known in the art as optical thin film filters or layered dielectric optical filters and available from JDS Uniphase as model number DWS-2F3883P20.

Filters540a and540b mux (demux) the received N (10) optical signals together (apart) into (from) a “comb” of wavelengths separated by 400 GHz and connected to 400/200GHz interleaver530a byfiber connections535a and535b. Because an interleaver for signals in the A-Z direction is also a deinterleaver for signals in the Z-A direction, the term interleaver will be used to describe both an interleaver and deinterleaver. Similarly, 400 GHz filter pairs540c and540d,540e and540f, and540g and540h mux (demux) together (apart) the received optical signals into (from) a “comb” of wavelengths separated by 400 GHz. The filter pairs540c and540d,540e and540f, and540g and540h are in communication with 400/200GHz interleavers530b,530c and530d, respectively, via 400/200GHz fiber connections535c-h, respectively. 400/200 GHz interleavers530a-d combine (separate) optical signals from (for) filters540a-h into (from) a single “comb” of wavelengths separated by 200 GHz. The combined (separated) output (input) is transmitted (received) to (from) 200/100GHz interleaver520a via 200/100GHz fiber connection525a and525b where they are combined (separated) into (from) a single “comb” ofwavelengths 100 GHz apart. Similarly, output from530c and530d propagate viafiber connection525c and525d to (from) interleaver520b where they are combined (separated) into (from) a single “comb” ofwavelengths 100 GHz apart Finally, the output (input) “combs” of interleavers520a and520b are transmitted to (from) 100/50GHz interleaver510 via 100/50fiber connections515a and515b. 100/50interleaver510 combines (separates out) the single comb of wavelengths to form (from) composite optical connection505 made up of a comb ofwavelengths 50 GHz apart.

In reference toFIG. 4,primary terminal210 is shown to be composed of acoarse mux268, acoarse demux267, afine mux266, and afine demux265. Thefine demux265 andfine mux266 coincide with the preferred embodiment inFIG. 7 of the combination of 100/50 GHzinterleavers510, 200/100GHz interleavers520a-b, and 400/200GHz interleavers530a-d. Thecoarse demux267 andcoarse mux268 coincide with the preferred embodiment inFIG. 7 of 400GHz filters540a-h. Thecoarse mux288 andcoarse demux287 in the extension terminals ofFIG. 5 andcoarse mux298 andcoarse demux297 ofFIG. 6 also coincide with 40Ghz filters540a-h.Optical connection505, 100/50fiber connections515a-d, 200/100fiber connections525a-c, andfiber connections535a-h may function as simple fiber jumpers or optical amplifiers or optical attenuators or some combination thereof to achieve required fiber distances between the various stages of a distributed terminal.

FIG. 8 indicates an alternate embodiment of a mux and demux structure. Mux/demux600 comprises twosubmuxs650a anddemuxs650b. Because mux/demux600 comprises twosubmux650a anddemux650b pairs, mux/demux600 is capable of taking 8×N optical signals (10 are shown inFIG. 8) at different wavelengths and combining them onto one output/input connection605. Because submux650a anddemux650b are capable of taking four times N optical signals at different wavelengths and combining them onto one 2000GHz fiber connection615a and615b, the architecture is scaleable up or down in the number of wavelengths. For example, a 4000 GHz Band combiner may be placed in conjunction with two mux/demuxes to form a 16×N (10) multiplexer unit.

The function of an optical band splitter/combiner is to split/combine a specified band of optical wavelengths consisting of tightly spaced optical wavelengths oftypical separation 50 GHz or 25 GHz into or out of two coarse bands of such wavelengths. Specific band splitters or band combiner device implementation are well known in the art and not described further. Band filtering devices can be obtained from, for example, Oplink Corporation model number CR000001111.

In the A-Z direction, signals enter mux/demux600 through a set of fine 50GHz filters640a-h, known in the art. 50GHz filters640a-h may also be 25 GHz filters also known in the art. Two examples of fine 50 GHz filters640 are the arrayed waveguide filters and layered dielectric optical filters available as, for example, JDS Uniphase model numbers AWG-5NBUC003T and DWM-5F8DSX2, respectively.

Starting with fine 50Hz filter640a and640b, the N(10) optical signals are muxed together into a band of wavelengths contained within about 500 GHz and transmitted to 500GHz band combiner630a via 500GHz fiber connections635a and635b. Similarly, fine 56 Hz filter pairs640c and640d,640e and640f and640g and640h mux N(10) optical signals together and transmit the muxed signals to 500GHz band combiners630b,630c and630d respectively via 500GHz fiber connections635c-h respectively. 500GHz band combiner630a combines the optical signals fromfilters640a and640b into a single broader band of wavelengths contained within about 1000 GHz. Similarly, 500GHz band combiners630b-d combine received optical signals into a single broader band of wavelengths.

The single broader band of wavelengths fromextension band combiners630a and630b are transmitted to 1000GHz band combiner620a via 1000GHz fiber connections625a and625b. 1000GHz band combiner620a combines the signals from 500GHz band combiners630a and630b into a single band of wavelengths contained within about 2000 GHz. Similarly, 1000GHz band combiner620b combines the wavelengths transmitted from 500GHz band combiners630c and630d via 1000 GHz fiber connection.625c and625d into a single band of wavelengths. Each 1000GHz band combiner620a and620b transmits the single band of wavelengths to 2000GHz combiner610 via 2000GHz fiber connections615a and615b. 2000GHz combiner610 combines the received single band of wavelengths into a composite signal band contained within about 4000 GHz. The composite signal band is transmitted on output/input connection605.

In the Z-A direction, 2000GHz combiner610 receives a composite signal band contained within about 4000 GHz on output/input connection605. Because a combiner for signals in the A-Z direction can also be a splitter for signals in the Z-A direction, the term combiner will be used to describe both a combiner and a splitter. 2000GHz combiner610 splits the composite signal into two single band of wavelengths contained within about 2000 GHz. The bands of wavelengths within 2000 GHz are transmitted to 1000GHz band combiners620a and620b via 2000GHz fiber connections615a and615b. 1000GHz combiners620a and620b each separate the single band of wavelengths within 2000 GHz into two single band of wavelengths within about 1000 GHz. The single band of wavelengths within 1000 GHz is transmitted from 1000GHz combiners620a and620b to 500GHz band combiners630a-d via 1000GHz fiber connections625a-d. 500GHz band combiners630a-d each split the single band of wavelengths contained within about 1000 GHz into a single band of wavelengths contained within about 500 GHz. The single band of wavelengths contained within 500 GHz is transmitted from 500GHz band combiners630a-d to fine 50Hz filters640a-h via 500GHz fiber connections635a-h.Fine 50Hz filters640a-d demux the single band of wavelengths within 500 GHz into N(10) bands of wavelengths wherein the N(10) wavelengths are transmitted out of mux/demux600.

The fine filter function performed by 50 Hzfilters640a-h and the coarse filtering functions performed by the combination of 2000Ghz combiner610, 1000GHz combiners620a and620b, and 500GHz band combiners630a-d can be separated. The coarse and fine filtering functions are reversed in the hierarchy of the interleaver basedmux500. Also, output/input connection605, 2000GHz fiber connection615a and615b, 1000GHz fiber connection625a-h, and 500GHz fiber connection635a-h may function as simple fiber jumpers, optical amplifiers, optical attenuators, or some combination thereof to achieve required fiber distances between the various stages ofprimary terminal210.

A second alternative embodiment of the multiplexing and demultiplexing function of the present invention is indicated inFIGS. 9 and 10. The embodiment depicts a means of implementing a wavelength tunable system with primary terminals. Beginning withFIG. 9 tunable demux700 is composed primarily of firstoptical splitter710, secondoptical splitter720a and720b, and thirdoptical splitter730a-h Thirdoptical splitter730a-h is operationally connected to tunable filters740 via tunablefilter fiber connection731.

In the Z-A direction, firstoptical splitter710 receives a composite signal band contained within about 4000 GHz ontunable input connection705. The embodiment shown is one way of constructing a “tree” whereby a single band of wavelengths transmitted ontunable input connection705 is demuxed so as separate out groups of wavelengths. The exact nature and combining ratio is not essential. Firstoptical splitter710 splits the composite signal ontunable input connection705 into two single bands of wavelengths contained within about 2000 GHz. The bands of wavelengths within 2000 GHz are transmitted to secondoptical splitters720a and720b via firstsplitter fiber connections715a and715b. Secondoptical splitters720a and720b each separate the single bands of wavelengths within 2000 GHz into two single band of wavelengths within about 1000 GHz. The single bands of wavelengths within 1000 GHz are transmitted from secondoptical splitters720a and720b to thirdoptical splitters730a-h via secondsplitter fiber connection725a-h. Thirdoptical splitters730a-h each split the single band of wavelengths contained within about 1000 GHz into a single band of wavelengths contained within about 500 GHz. The single band of wavelengths contained within 500 GHz is transmitted from thirdoptical splitters730a-h totunable filters740a-x via tunablefilter fiber connections731.

While the order could be greater, in the preferred embodiment,tunable filters740a-x operate as narrow spectral width bandpass filters with a passband in the order of two and one-half to three times the bandwidth of the carrier frequency; for example, 30 GHz or more for a 10 GHz optical signal.Tunable filters740a-x are tuned to pass any one of the signals appearing at the outputs of thirdoptical splitters730a-h. Optical splitters are known in the art, an example being JDS Uniphase model number NEM-221003119. Tunable optical filters are also known in the art, examples being JDS Uniphase model number VCF050 or NORTEL model number MT-15-025.Tunable input connection705, firstsplitter fiber connections715a and715b, and secondsplitter fiber connection725a-h may function as simple fiber jumpers or optical amplifiers or optical attenuators or some combination thereof to achieve required fiber distances between the various stages of a distributed terminal.

With reference toFIG. 10tunable mux701 is composed of firstoptical combiner711, secondoptical combiner760a and760b, and thirdoptical combiner770a-h. Thirdoptical combiner770a-h is operationally connected totunable lasers780a-x.Tunable lasers780a-x may be narrowly tunable around 200 GHz or broadly tunable, for example, over the entire C or L band of Erbium-doped fiber amplifiers, the spectral width being of the order of 4000 GHz. The laser components may have an optical output power on the order of 20 mW, wavelength stability on the order of 2.5 GHz or better, side-mode suppression ratio on the order of 35 dB, and relative intensity noise (RIN) on the order of −140 dB. Optical combiners are known in the art, an example being JDS Uniphase model number NEM-221003119. Tunable lasers are known in the art, one example, JDS Uniphase CQF310/208-19365.

In the Z-A direction,tunable lasers780a-x receives a composite signal. The exact nature and combing ratio is not essential, the embodiment shown is one way of constructing a “tree” whereby one or more optical signals generated by one or more different tunable lasers are wavelength muxed so as to appear atoutput fiber connection706 as a single band of wavelengths.

Tunable lasers780 receive a band of wavelengths. The wavelengths are tuned and transmitted to thirdoptical combiner770a-h via tunablelaser fiber connection775. Thirdoptical combiner770a-h muxes the received signal fromtunable lasers780a-x into a single band of wavelengths within 500 GHz. The single band of wavelengths within 500 GHz is transmitted to extensionoptical combiner760a and760b via secondoptical fiber connections726a-h. Secondoptical combiners760a and760b mux the received single band of wavelengths within 500 GHz into a single band of wavelengths contained within about 1000 GHz. The single band of wavelengths contained within about 1000 GHz is transmitted to firstoptical combiner711 via first fiber connections716a and716b. Primaryoptical combiner711 muxes the received single band of wavelengths within 1000 GHz into a single band of wavelengths within about 2000 GHz. The single band of wavelengths within about 2000 GHz is transmitted overoutput fiber connection706.

Output fiber connections706, first fiber connections716a and716b,second fiber connections726a-h, and tunablelaser fiber connection775 may function as simple fiber jumpers or optical amplifiers or optical attenuators or some combination thereof to achieve required fiber distances between the various stages of a distributed terminal.

Valid and useful multiplexer and demultiplexer designs can be constructed with combinations of parts shown inFIGS. 7-10. Fine mux/demux640a-b fromFIG. 8 can individually replaceblocks740a-x as shown inFIG. 9 orblocks780a-x as shown inFIG. 10 to form splitter/combiner based fixed filters. This alternate arrangement is advantageous because the cost of components would scale with the deployed bandwidth. Likewise,tunable components740a-x from FIG.9 and780a-x fromFIG. 10 can individually replace the fixedfilters640a-h inFIG. 8 to form banded DWDM based tunable filters. Another advantageous embodiment is that of replacing coarse mux/demux filters540a-h inFIG. 7 with thetunable filter components780a-x from FIG.9 and740a-x fromFIG. 10 to form a mux and demux, respectively.

FIGS. 11 and 12 show different shelf connection configurations of the preferred embodiment that result from integrating the sub-systems ofFIGS. 4-7 into a distributed terminal system. Each numbered block inFIGS. 11 and 12 is a self-contained shelf within the optical transmission system: themaster terminal shelf910 embodies theprimary terminal210, theslave shelves920a-b embody the type oneextension terminal220; and thedual slaves shelf925a-b embody two type twoextension terminals225 in one unit. In the preferred embodiment, eight optical mux groups are made up of 10 optical signal-carrying wavelengths.

FIG. 11 depicts a star configuration900, whereby the submuxs are both contained within themaster terminal shelf910 along with one local 400 GHz filter. Theshelves910 and920a-c are interconnected usingfiber jumpers916,914 and912.Dual slave shelves925a-b are interconnected usingfiber jumpers902,904,906 and908.

FIG. 12a depicts a second configuration940 whereby twomaster shelves911a and911b are utilized to distribute the optical mux groups.Shelf911a, is similar in function toprimary terminal210, and a 100/506 Hz interleaver, submux, and a 400 GHz filter.Shelf911b, which is also similar in function toprimary terminal210, contains submuxs and a 400 GHz filter. The interconnection betweenmaster shelves911 a and911b is accomplished byfiber interconnection932 which is a 100/50 fiber connection. The configurations940 and960service 8 optical mux groups or up to 80 optical signal wavelengths in six shelves.Line941 is an optical input/output connection.Slave shelves920a and920b anddual slave shelves925a and925b contain the same equipment as described in relation toFIG. 11.Dual slave shelves925a and925b are coupled to master shelf via dual slave-to-master connections918,922 and924.Slave shelves920a and920b are coupled tomaster shelf911b via slave-to-master connections926 and928. Dual slave-to-master connections918 and922 may be as long as about 5 km in the preferred embodiment. Slave-to-master connections926 and928 may be as long as about 100 km without additional optical amplifiers.

FIG. 12b depicts a third configuration960 similar to configuration940 but utilizing onlydual slave shelves925a-c attached to themaster shelves911a and911b. Configuration960 achieves the highest system density of the configurations of the preferred embodiment. Two master shelves,911a and911b, and threedual slave shelves925a-c can be used to service all 8 optical mux groups or up to 80 optical signal wavelengths in less than two standard 19 or 23 inch wide seven foot equipment racks.Master shelf911a is connected tomaster shelf911b byconnection933. Master shelf a and b contain the same components as described in relation toFIG. 12a. Master shelf a is connected todual slave shelf925a byjumpers923 and925.Master shelf911a is connected todual slave shelf925c byjumper919.Master shelf911b is connected todual slave shelf925b byjumpers929 and931.Master shelf911b is connected todual slave shelf925c throughjumper927.

Dual slave shelves925a, b and c contain the same equipment as described inFIG. 12a. Thefiber shelf interconnections919,923,927,925,929 and931 may be as long as about 5 km in the preferred embodiment while the master-to-master fiber connection933 may be on the order of 100 km (without additional optical amplifiers).

Although the invention has been described with reference to one or more preferred embodiments, this description is not to be construed in a limiting sense. There is modification of the disclosed embodiments, as well as alternative embodiments of this invention, which will be apparent to persons of ordinary skill in the art, and the invention shall be viewed as limited only by reference to the following claims.

Claims (65)

1. A primary terminal of an optical transport system, the primary terminal comprising:

a transponder coupled to a customer premise equipment, wherein the transponder is configured to convert a first optical signal from the customer premise equipment into a first individual long-haul optical signal, and wherein the first optical signal is in a format suitable for use by the customer premise equipment;

a coarse multiplexer coupled to the transponder, wherein the coarse multiplexer is configured to multiplex the first individual long-haul optical signal into a first mux group of long-haul optical signals; and

a fine multiplexer coupled to the coarse multiplexer and to an extension terminal via a metro fiber, wherein the fine multiplexer is configured to receive a second mux group of long-haul optical signals from the extension terminal,

wherein the fine multiplexer is configured to multiplex the first mux group from the coarse multiplexer and the second mux group from the extension terminal into a third mux group of long-haul optical signals, and

wherein the primary terminal is configured to transmit the third mux group over a long-haul network.

2. The primary terminal ofclaim 1 further comprising an amplifier coupled to the fine multiplexer, wherein the amplifier is configured to amplify the third mux group from the fine multiplexer.

3. The primary terminal ofclaim 1, wherein the coarse multiplexer and the fine multiplexer each include one of an optical interleaver, a banded dense wavelength division multiplexing (DWDM) filter, or a tunable filter.

4. The primary terminal ofclaim 1 further comprising a first demultiplexer coupled to the long-haul network,

wherein the first demultiplexer is configured to demultiplex a fourth mux group of long-haul optical signals from the long-haul network into a fifth mux group of long-haul optical signals and a sixth mux group of long-haul optical signals, and

wherein the primary terminal is configured to transmit the fifth mux group to the extension terminal via the metro fiber.

5. The primary terminal ofclaim 4 further comprising an amplifier coupled to the first demultiplexer, wherein the amplifier is configured to amplify the fourth mux group from the long-haul network.

6. The primary terminal ofclaim 4 further comprising a second demultiplexer coupled to the first demultiplexer and to the transponder, wherein the second demultiplexer is configured to demultiplex the sixth mux group from the first demultiplexer into a second individual long-haul optical signal.

7. The primary terminal ofclaim 6, wherein the first demultiplexer comprises a fine demultiplexer and the second demultiplexer comprises a coarse demultiplexer.

8. The primary terminal ofclaim 6, wherein the first and second demultiplexers each include one of an optical de-interleaver, a banded dense wavelength division multiplexing (DWDM) filter, or a tunable filter.

9. The primary terminal ofclaim 6, wherein the transponder is further configured to convert the second individual long-haul optical signal from the second demultiplexer into a second optical signal, and

wherein the second optical signal is in the format suitable for use by the customer premise equipment.

10. The primary terminal ofclaim 9, wherein the primary terminal is further configured to transmit the second optical signal to the customer premise equipment.

11. A method for transporting optical signals at a primary terminal, the method comprising:

converting a first optical signal from a customer premise equipment into a first individual long-haul optical signal, wherein the first optical signal is in a format suitable for use by the customer premise equipment;

multiplexing, via a coarse multiplexer, the first individual long-haul optical signal into a first mux group of long-haul optical signals,

receiving a second mux group of long-haul optical signals from an extension terminal via a metro fiber;

multiplexing, via a fine multiplexer, the first mux group and the second mux group into a third mux group of long-haul optical signals; and

transmitting the third mux group over a long-haul network.

12. The method ofclaim 11 further comprising amplifying the third mux group.

13. The method ofclaim 11 further comprising:

demultiplexing a fourth mux group of long-haul optical signals from the long-haul network into a fifth mux group of long-haul optical signals and a sixth mux group of long-haul optical signals; and

transmitting the fifth mux group to the extension terminal via the metro fiber.

14. The method ofclaim 13 further comprising amplifying the fourth mux group.

15. The method ofclaim 13 demultiplexing the sixth mux group into a second individual long-haul optical signal.

16. The method ofclaim 15 further comprising converting the second individual long-haul optical signal into a second optical signal, wherein the second optical signal is in the format suitable for use by the customer premise equipment.

17. The method ofclaim 16 further comprising transmitting the second optical signal to the customer premise equipment.

18. An optical transport system for transporting optical signals, the optical transport system comprising:

an extension terminal coupled to a first customer premise equipment; and

a primary terminal coupled to the extension terminal via a metro fiber, wherein the primary terminal comprises a coarse multiplexer and a fine multiplexer,

wherein the extension terminal is configured to receive a first optical signal suitable for use by the first customer premise equipment and to convert the first optical signal into a first individual long-haul optical signal,

wherein the extension terminal is further configured to multiplex the first individual long-haul optical signal into a first mux group of long-haul optical signals and to transmit the first mux group to the fine multiplexer of the primary terminal via the metro fiber.

19. The optical transport system ofclaim 18, wherein the primary terminal is configured to transmit the first mux group over a long-haul network.

20. The optical transport system ofclaim 18, wherein the primary terminal is coupled to a second customer premise equipment,

wherein is the primary terminal configured to receive a second optical signal suitable for use by the second customer premise equipment and to convert the second optical signal into a second individual long-haul optical signal, and

wherein the primary terminal is further configured to multiplex, via the coarse multiplexer, the second individual long-haul optical signal into a second mux group of long-haul optical signals.

21. The optical transport system ofclaim 20, wherein the primary terminal is further configured to multiplex, via the fine multiplexer, the first mux group and the second mux group into a third mux group of long-haul optical signals, and

wherein the primary terminal is further configured to transmit the third mux group over a long-haul network.

22. The optical transport system ofclaim 21, wherein the primary terminal is further configured to amplify the third mux group.

23. The optical transport system ofclaim 18, wherein the extension terminal is further configured to amplify the first mux group.

24. An optical transport system for transporting optical signals, the optical transport system comprising:

an extension terminal coupled to a first customer premise equipment; and

a primary terminal coupled to the extension terminal via a metro fiber,

wherein the primary terminal comprises a coarse demultiplexer and a fine demultiplexer,

wherein the primary terminal is configured to receive a first mux group of long-haul optical signals from a long-haul network,

wherein the fine demultiplexer configured to demultiplex the first mux group into a second mux group of long-haul optical signals and a third mux group of long-haul optical signals,

wherein the coarse demultiplexer is configured to demultiplex the second mux group,

wherein the primary terminal is further configured to transmit the third mux group to the extension terminal via the metro fiber,

wherein the extension terminal is configured to demultiplex the third mux group into a first individual long-haul signal, and

wherein the extension terminal is further configured to convert the first individual long-haul signal into a first optical signal suitable for use by the first customer premise equipment and to transmit the first optical signal to the first customer premise equipment.

25. The optical transport system ofclaim 24, wherein the primary terminal is coupled to a second customer premise equipment,

wherein the coarse demultiplexer is configured to demultiplex the second mux group into a second individual long-haul optical signal, and

wherein the primary terminal is further configured to convert the second individual long-haul optical signal into a second optical signal suitable for use by the second customer premise equipment and to transmit the second optical signal to the second customer premise equipment.

26. The optical transport system ofclaim 24, wherein the primary terminal is further configured to amplify the first mux group.

27. The optical transport system ofclaim 24, wherein the extension terminal is further configured to amplify the second mux group.

28. A primary terminal of an optical transport system, the primary terminal comprising:

a fine demultiplexer coupled to a long-haul network and to an extension terminal, wherein the fine demultiplexer is configured to demultiplex a first mux group of long-haul optical signals from the long-haul network into a second mux group of long-haul optical signals and a third mux group of long-haul optical signals;

a coarse demultiplexer coupled to the fine demultiplexer, wherein the coarse demultiplexer is configured to demultiplex the second mux group into a first individual long-haul optical signal; and

a transponder coupled to the coarse demultiplexer and to a customer premise equipment, wherein the transponder is configured to convert the first individual long-haul optical signal into a first optical signal that is in a format suitable for use by the customer premise equipment,

wherein the transponder is configured to transmit the first optical signal to the customer premise equipment, and

wherein the primary terminal is configured to transmit the third mux group to the extension terminal over a metro fiber.

29. The primary terminal ofclaim 28 further comprising an amplifier coupled between the long-haul network and the fine demultiplexer, wherein the amplifier is configured to amplify the first mux group from the long-haul network.

30. The primary terminal ofclaim 28, wherein the coarse demultiplexer and the fine demultiplexer each include one of an optical interleaver, a banded dense wavelength division multiplexing (DWDM) filter, or a tunable filter.

31. The primary terminal ofclaim 28, wherein the transponder is further configured to receive a second optical signal from a second customer premise equipment and to convert the second optical signal into a second individual long-haul optical signal.

32. The primary terminal ofclaim 31 further comprising a coarse multiplexer coupled to the transponder, wherein the coarse multiplexer is configured to multiplex the second individual long-haul optical signal into a fourth mux group of long-haul optical signals.

33. The primary terminal ofclaim 32 further comprising a fine multiplexer coupled to the coarse multiplexer and the extension terminal, wherein the fine multiplexer is configured to receive a fifth mux group of long-haul optical signals from the extension terminal.

34. The primary terminal ofclaim 33, wherein the fine multiplexer is configured to multiplex the fourth mux group and the fifth mux group into a sixth mux group of long-haul optical signals.

35. The primary terminal ofclaim 34 further comprising an amplifier coupled to the fine multiplexer, wherein the amplifier is configured to amplify the sixth mux group from the fine multiplexer.

36. The primary terminal ofclaim 34, wherein the primary terminal is configured to transmit the sixth mux group over the long-haul network.

37. A primary terminal of an optical transport system, the primary terminal comprising:

a transponder configured to convert a first optical signal from a customer premise equipment into a first individual long-haul optical signal, and wherein the first optical signal is in a format suitable for use by the customer premise equipment;

a coarse multiplexer coupled to the transponder, wherein the coarse multiplexer is configured to multiplex the first individual long-haul optical signal into a first mux group of long-haul optical signals; and

a fine multiplexer coupled to the coarse multiplexer, wherein the fine multiplexer is configured to receive a second mux group of long-haul optical signals from an extension terminal via a metro fiber,

wherein the fine multiplexer is configured to multiplex the first mux group from the coarse multiplexer and the second mux group from the extension terminal into a third mux group of long-haul optical signals, and

wherein the primary terminal is configured to transmit the third mux group over a long-haul network.

38. The primary terminal of claim 37 further comprising an amplifier coupled to the fine multiplexer, wherein the amplifier is configured to amplify the third mux group from the fine multiplexer.

39. The primary terminal of claim 37, wherein the coarse multiplexer and the fine multiplexer each include one of an optical interleaver, a banded dense wavelength division multiplexing (DWDM) filter, or a tunable filter.

40. The primary terminal of claim 37 further comprising a first demultiplexer,

wherein the first demultiplexer is configured to demultiplex a fourth mux group of long-haul optical signals from the long-haul network into a fifth mux group of long-haul optical signals and a sixth mux group of long-haul optical signals, and

wherein the primary terminal is configured to transmit the fifth mux group to the extension terminal via the metro fiber.

41. The primary terminal of claim 40 further comprising an amplifier coupled to the first demultiplexer, wherein the amplifier is configured to amplify the fourth mux group from the long-haul network.

42. The primary terminal of claim 40 further comprising a second demultiplexer coupled to the first demultiplexer and to the transponder, wherein the second demultiplexer is configured to demultiplex the sixth mux group from the first demultiplexer into a second individual long-haul optical signal.

43. The primary terminal of claim 42, wherein the first demultiplexer comprises a fine demultiplexer and the second demultiplexer comprises a coarse demultiplexer.

44. The primary terminal of claim 42, wherein the first and second demultiplexers each include one of an optical de-interleaver, a banded dense wavelength division multiplexing (DWDM) filter, or a tunable filter.

45. The primary terminal of claim 42, wherein the transponder is further configured to convert the second individual long-haul optical signal from the second demultiplexer into a second optical signal, and

wherein the second optical signal is in the format suitable for use by the customer premise equipment.

46. The primary terminal of claim 45, wherein the primary terminal is further configured to transmit the second optical signal to the customer premise equipment.

47. An optical transport system tor transporting optical signals, the optical transport system comprising:

an extension terminal configured to receive a first optical signal from a first customer premise equipment, the first optical signal suitable for use by the first customer premise equipment; and

a primary terminal coupled to the extension terminal, wherein the primary terminal comprises a coarse multiplexer and a fine multiplexer,

wherein the extension terminal is configured to convert the first optical signal into a first individual long-haul optical signal,

wherein the extension terminal is further configured to multiplex the first individual long-haul optical signal into a first mux group of long-haul optical signals and to transmit the first mux group to the fine multiplexer of the primary terminal via a metro fiber.

48. The optical transport system of claim 47, wherein the primary terminal is configured to transmit the first mux group over a long-haul network.

49. The optical transport system of claim 47,

wherein the primary terminal is configured to receive a second optical signal from a second customer premise equipment, the second optical signal suitable for use by the second customer premise equipment, and the primary terminal is configured to convert the second optical signal into a second individual long-haul optical signal, and

wherein the primary terminal is further configured to multiplex, via the coarse multiplexer, the second individual long-haul optical signal into a second mux group of long-haul optical signals.

50. The optical transport system of claim 49, wherein the primary terminal is further configured to multiplex, via the fine multiplexer, the first mux group and the second mux group into a third mux group of long-haul optical signals, and

wherein the primary terminal is further configured to transmit the third mux group over a long-haul network.

51. The optical transport system of claim 50, wherein the primary terminal is further configured to amplify the third mux group.

52. The optical transport system of claim 47, wherein the extension terminal is further configured to amplify the first mux group.

53. An optical transport system for transporting optical signals, the optical transport system comprising:

an extension terminal; and

a primary terminal coupled to the extension terminal,

wherein the primary terminal comprises a coarse demultiplexer and a fine demultiplexer,

wherein the primary terminal is configured to receive a first mux group of long-haul optical signals from a long-haul network,

wherein the fine demultiplexer is configured to demultiplex the first mux group into a second mux group of long-haul optical signals and a third mux group of long-haul optical signals,

wherein the coarse demultiplexer is configured to demultiplex the second mux group,

wherein the primary terminal is further configured to transmit the third mux group to the extension terminal via a metro fiber,

wherein the extension terminal is configured to demultiplex the third mux group into a first individual long-haul signal, and

wherein the extension terminal is further configured to convert the first individual long-haul signal into a first optical signal suitable for use by a first customer premise equipment and to transmit the first optical signal to the first customer premise equipment.

54. The optical transport system of claim 53,

wherein the coarse demultiplexer is configured to demultiplex the second mux group into a second individual long-haul optical signal, and

wherein the primary terminal is further configured to convert the second individual long-haul optical signal into a second optical signal suitable for use by a second customer premise equipment and to transmit the second optical signal to the second customer premise equipment.

55. The optical transport system of claim 53, wherein the primary terminal is further configured to amplify the first mux group.

56. The optical transport system of claim 53, wherein the extension terminal is further configured to amplify the second mux group.

57. A primary terminal of an optical transport system, the primary terminal comprising:

a fine demultiplexer configured to demultiplex a first mux group of long-haul optical signals from a long-haul network into a second mux group of long-haul optical signals and a third mux group of long-haul optical signals;

a coarse demultiplexer coupled to the fine demultiplexer, wherein the coarse demultiplexer is configured to demultiplex the second mux group into a first individual long-haul optical signal; and

a transponder coupled to the coarse demultiplexer, wherein the transponder is configured to convert the first individual long-haul optical signal into a first optical signal that is in a format suitable for use by a customer premise equipment,

wherein the transponder is configured to transmit the first optical signal to the customer premise equipment, and

wherein the primary terminal is configured to transmit the third mux group to an extension terminal over a metro fiber.

58. The primary terminal of claim 57 further comprising an amplifier coupled to the fine demultiplexer, wherein the amplifier is configured to amplify the first mux group from the long-haul network.

59. The primary terminal of claim 57, wherein the coarse demultiplexer and the fine demultiplexer each include one of an optical interleaver, a banded dense wavelength division multiplexing (DWDM) filter, or a tunable filter.

60. The primary terminal of claim 57, wherein the transponder is further configured to receive a second optical signal from a second customer premise equipment and to convert the second optical signal into a second individual long-haul optical signal.

61. The primary terminal of claim 60 further comprising a coarse multiplexer coupled to the transponder, wherein the coarse multiplexer is configured to multiplex the second individual long-haul optical signal into a fourth mux group of long-haul optical signals.

62. The primary terminal of claim 61 further comprising a fine multiplexer coupled to the coarse multiplexer, wherein the fine multiplexer is configured to receive a fifth mux group of long-haul optical signals from the extension terminal.

63. The primary terminal of claim 62, wherein the fine multiplexer is configured to multiplex the fourth mux group and the fifth mux group into a sixth mux group of long-haul optical signals.

64. The primary terminal of claim 63 further comprising an amplifier coupled to the fine multiplexer, wherein the amplifier is configured to amplify the sixth mux group from the fine multiplexer.

65. The primary terminal of claim 63, wherein the primary terminal is configured to transmit the sixth mux group over the long-haul network.

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