US20080298748A1 - Direct-connect optical splitter module - Google Patents

Abstract

A compact optical splitter module is disclosed. One type of compact optical splitter module is a planar attenuated splitter module that includes a branching waveguide network having j≧1 50:50 splitters that form up to n≦2^joutput waveguides having associated n output ports, wherein only m<n output ports are suitable for transmitting light to the at least one external output device. This provides a 1×m splitter module wherein each output port has the attenuation of a 1×n splitter module, thereby obviating the need for external attenuation. Another type of compact optical splitter module is a direct-connect splitter module that eliminates the need for an optical fiber array when coupling to external optical fibers. Another type of compact optical splitter module is a microsplitter module that serves as device and module at the same time and that eliminates the differentiation between device and module. The integration of device and module also makes manufacturing the microsplitter module cost-effect. Embodiments of microsplitter modules that account for differences in the coefficient of thermal expansion of the materials making up the microsplitter are also disclosed.

Description

BACKGROUND OF THE INVENTION
• 1. Field of the Invention
• The present invention relates generally to passive optical devices used in optical telecommunication systems, and particularly to optical splitters modules.
• 2. Technical Background
• One of the current trends in telecommunications is the use of optical fibers in place of the more conventional transmission media. One advantage of optical fibers is their larger available bandwidth handling ability that provides the capability to convey larger quantities of information for a substantial number of subscribers via a media of considerably smaller size. Further, because lightwaves are shorter than microwaves, for example, a considerable reduction in component size is possible. As a result, a reduction in material, manufacturing, and packaging costs is achieved. Moreover, optical fibers do not emit electromagnetic or radio frequency radiation of any consequence and, hence, have negligible impact on the surrounding environment. As an additional advantage, optical fibers are much less sensitive to extraneous radio frequency emissions from surrounding devices and systems.
• With the advent of optical fiber networks, flexible switching devices are needed to direct light signals between fibers in an all-optical domain fiber network. An optical splitter is a type of optical switching device that takes an incoming optical signal and splits it between two or more outputs. The number of splits depends on the particular application. Because the signal is split into two or more signals, the splitter is also an attenuator whose attenuation is proportional to the number of splits. Optical splitters, also referred to as “splitter modules” because of their modular construction, have a number of shortcomings that, if improved upon, would result in a more robust splitter module for certain applications.
• One splitter module shortcoming involves the need to use external attenuators for certain applications. For FTTx systems with link budgets designed for a particular number of splits, a reduced number of splits may be required, but with the same attenuation. For example, for a splitter module having a splitter chip designed for 1×32 splits (15-17 dB IL), a 1×4 splitter chip may be needed, where each of the 4 splitter output ports serves electronics that connect eight customers in a multi-dwelling unit (MDU) (the 1×4 optical split still serves thirty-two customers). The optical power required by the receiving electronics, however, may still be in the 15-17 dB range, while the 1×4 splitter module delivers 6-8 dB. of optical power. This necessitates attenuation of the splitter output from 6-8 dB to 15-17 dB. This is typically accomplished using an attenuator external to the splitter. However, this adds complexity and expense to the splitter system and also makes it less compact.
• Another shortcoming is that present-day splitter modules consist of separate parts: a standard splitter unit (that includes a fiber array, a splitter chip, and a ferrule) and external connectors that attach thereto. External connectors are connected to the module to establish communication through the module between remote devices. Considerable simplification and cost reduction for splitter modules could be realized if an external multi-fiber connector could be directly connected to the planar splitter chip rather than using separate connectors. Likewise, considerable simplification and cost reduction (and cost predictability) for splitter modules could be realized if a compact splitter module could be constructed that serves as both as device and module without the usual distinction between the two.
SUMMARY OF THE INVENTION
• One aspect of the invention is a direct-connect splitter module for providing optical communication with at least one external output device. The splitter module includes a ferrule having a central axis, and adjacent input-end and output-end sections. The input-end and output-end sections include respective input and output ends and connecting input and output channels that run along the central axis and that have respective open ends at the respective input and output ends. The splitter module also includes a splitter chip that includes input and output ends and a branching waveguide network. The branching waveguide network includes at least one input waveguide at its input end and at least two output waveguides each having an output end at the splitter chip output end. The splitter chip is fixed in the output channel with its output end at the output channel open end. The splitter module also has at least one input ferrule connected to the input end of the splitter chip and that resides in the input-end channel, and also has at least one input optical fiber having an output end and an input end that is optically coupled to the at least one input waveguide of the splitter chip via the at least one input ferrule. A thermosetting resin that substantially fills the input channel fixes the at least one input ferrule and the at least one input optical fiber in position within the input-end channel. A housing generally surrounds at least a portion of the ferrule so as to cover the input end of the input-end channel and to provide conformity with a connector associated with the at least one external output device.
• Additional features and advantages of the invention will be set forth in the detailed description which follows, and in part will be readily apparent to those skilled in the art from that description or recognized by practicing the invention as described herein, including the detailed description which follows, the claims, as well as the appended drawings.
• It is to be understood that both the foregoing general description and the following detailed description present embodiments of the invention, and are intended to provide an overview or framework for understanding the nature and character of the invention as it is claimed. The accompanying drawings are included to provide a further understanding of the invention, and are incorporated into and constitute a part of this specification. The drawings illustrate various embodiments of the invention, and together with the description serve to explain the principles and operations of the invention.
BRIEF DESCRIPTION OF THE DRAWINGS
• FIG. 1 is generalized schematic diagram of a splitter module system that includes the splitter module of the present invention optically coupled to an input device and at least one output device;
• FIG. 2 is a plan schematic diagram of an example embodiment of an attenuated planer splitter module according to the present invention as connected to input and output devices, wherein at least one of the waveguides in the branching waveguide array has an associated termination so that the light from the input device and carried therein is not communicated to the external device;
• FIG. 3 is a plan schematic diagram of an example of an attenuated planar splitter module similar to that ofFIG. 2, wherein the module is used as a 1×4 splitter module having the attenuation of a 1×32 splitter module;
• FIG. 4 is a plan schematic diagram of an embodiment of a 1×8 attenuated planer splitter module having a branching waveguide network that includes two non-branching waveguides whose energy is outputted at their respect output ports and is dissipated by the output waveguide device, thereby providing the 1×8 splitter module with the attenuation of a 1×32 splitter module;
• FIG. 5 is a plan schematic diagram of an example embodiment of the 1×8 attenuated planer splitter module similar to that ofFIG. 4, wherein the two branch waveguides are terminated prior to reaching the splitter chip end;
• FIG. 6 is a plan cut-away view of an example embodiment of a direct-connect splitter module according to the present invention;
• FIG. 7 is an end-on view of the multi-fiber output end of the direct-connect splitter module ofFIG. 6;
• FIG. 8 is a plan cut-away view of the ferrule body used in the direct-connect splitter module ofFIG. 6;
• FIG. 9 is an end-on view of the single-fiber input end of the direct-connect splitter module ofFIG. 6;
• FIG. 10 is a plan cut-away view similar to that ofFIG. 6 but showing an outer housing formed to have features associated with an MTP-type connector;
• FIG. 11 is an end-on view similar to that ofFIG. 7, but showing the outer housing;
• FIG. 12 is a perspective end-on view of the output end of the direct-connect splitter module having the form an MTP-type connector, shown along with a MTP-type mating connector that establishes optical communication with an external device;
• FIG. 13 is a schematic side cut-away view of an example embodiment of a microsplitter module according to the present invention;
• FIG. 14 is a perspective view of an example embodiment of a microsplitter module according to the present invention wherein the housing is formed so that the module is compatible with an MTP-type connector;
• FIG. 15 is a side cut-away view similar toFIG. 13 that illustrates another example embodiment of microsplitter module that includes a fiber array arranged between the splitter chip and the ferrule, and also including a fiber pigtail at the input end; and
• FIG. 16 is a side cut-away view similar toFIG. 13, illustrating another example embodiment of a microsplitter module wherein the fiber array is replaced by a direct fiber bonding unit.
DETAILED DESCRIPTION OF THE INVENTION
• FIG. 1 illustrates a generalized example embodiment of asplitter module system8 that includes asplitter module10 according to the present invention.Splitter module10 is connected to anexternal input device12 via an inputoptical fiber56 and to one or moreexternal output devices14 via corresponding outputoptical fibers78. Bothexternal input device12 andexternal output device14 can be capable of transmitting and receiving signals and communicating with each other viamodule10 in both directions, but are referred to as input and output devices for the sake of simplicity and establishing an orientation in the Figures.
• The present invention is directed to various types ofsplitter modules10 that provide enhanced performance as well as other advantages. Example embodiments of the various types of optical splitter modules are described in detail below.
Attenuated Planar Splitter Module
• FIG. 2 is a schematic plan view of an attenuatedplanar splitter module10 according to the present invention shown connected toexternal input device12 and one external output devices14 (one such external output device is shown by way of illustration), such as shown inFIG. 1.
• Module10 includes asplitter chip20 having abody22, anupper surface24, aninput end26 and anoutput end28. Formed in or on body22 (i.e., on or below surface24) is a branchingwaveguide network30. Branchingwaveguide network30 starts out as asingle input waveguide32 with an input end (port)33 atinput end26 and splits j times at various 50:50splitters36 to ultimately form n=2^joutput waveguides40 each having an output end (port)41 atoutput end28. Note that branchingwaveguide network30 can have one ormore input waveguides32; one such waveguide is shown for ease of illustration.
• For theexample splitter chip20 ofFIG. 2, j=5, so that the number n ofoutput waveguides40 is 2⁵=32. The output power associated with eachoutput port41 is 1/n as compared to the power inputted atinput port33, so that for n=32, the output power at each port is 1/32. In the convention of optical fiber telecommunications, the attenuation is expressed in decibels (dB). Thus, the attenuation A_Oassociated with each of the n output ports41 (for the case where n=2^j) is given by A_O=−10 log(P_IN/P_OUT), which for P_INnormalized to 1 and n=2 is given by A_O(n)=−10 log(1/n)=10 log(n). Thus, for n=2, A_O(2)=3dB; for n=4, A_O(4)=6 db; for n=8, A_O(8)=is 9 dB; for n=16, A_O(16)=12 dB, etc.
• Module10 includes aninput ferrule50 operably connected to inputport33 ofinput waveguide32.Input ferrule50 allows an inputoptical fiber56 to be optically coupled to inputwaveguide32. Connecting inputoptical fiber56 toexternal input device12 allows the input device to be in optical communication with one or moreexternal output device14 viamodule10.
• Module10 also includes afiber array60 having abody61, andinput end62 and anoutput end64.Fiber array60 includes a plurality ofoptical fiber sections74, supported by substrate body61 (e.g., via v-grooves formed therein).Fiber array60 is arranged with itsinput end62 fixed to splitterchip output end28 so thatoptical fiber sections74 align withoutput ports41. This provides optical coupling betweenoptical fiber sections74 andoutput waveguides40 ofsplitter chip20.Fiber array60 thus allows corresponding one or more outputoptical fibers78 to be placed in optical communication with theirrespective output waveguides40 ofsplitter chip20, thereby providing optical communication betweenexternal input device12 and one or moreexternal output devices14.
• It often happens that a 1×n splitter chip20 has one ormore output ports41 that do not meet specification and are therefore unsuitable for use. This can occur due to, for example manufacturing errors in branchingwaveguide network30 or because of problems in the output ports themselves. Such errors lead to, for example, broken or otherwise defective waveguides that do not meet the required transmission-related specifications. Splitter chips that do not meet specification for all n output ports are considered to have little if any value and are typically scrapped. Given that the typical yield in splitter chip production is about 60%, this leaves 40% of product being scrapped.
• However, where there are at least “m” good (i.e., suitable)ports41 remaining on the 1×n splitter chip20 that can be used for communicating withexternal device14, the present invention exploits these m remaining suitable ports and utilizes the otherwise “damaged” splitter chip as a 1×m splitter, with each output port having the attenuation of a 1×n splitter. If necessary, the unsuitable and therefore unused (n-m)output ports41 are terminated (e.g., usingterminations88, discussed below) in a manner that prevents any light that could be emitted by these ports from being transmitted to an external device. For example, the correspondingoptical fiber section74 infiber array60 is terminated, e.g., by allowing the light associated therewith to dissipate either insubstrate body12 or the material making up fiber array body61 (e.g., potting compound or glass). In an example embodiment, light associated with anunsuitable output port41 can be dissipated by allowing it to exit the output port and be transmitted into free space. In another example embodiment, such light is dissipated by atermination88 in the form of a short section of optical fiber connected to a corresponding optical fiber section infiber array60, wherein the termination has an absorbing material at its output end. This is illustrated inFIG. 2, whereinmodule10 is shown with a number ofoutput fibers78 optically coupled to selectoperable output ports41 viaoutput waveguide device66. Thoseoutput ports41 whereother output fibers78 would connect tooutput waveguide device66 are shown as having correspondingterminations88 at the correspondingoptical fiber sections74Terminations88 include, for example, short optical fiber sections as mentioned above, a light-absorbing material, or a light-dissipating material (e.g., potting compound).
• FIG. 3 is a plan schematic diagram of an example embodiment of a planarattenuated splitter module10 similar to that ofFIG. 2, wherein the 1×32splitter chip20 meets specification on only m=4 adjacent channels (output ports)41, thereby forming a 1×4 splitter module having the same attenuation as the 1×32 module. Fouroptical fibers78 are coupled to the four operable channels via anoutput waveguide device66 having awaveguide array72 with four waveguides.Terminations88 are provide at the remainingunsuitable output ports41.
• In an example embodiment of the invention, rather than using a splitter chip that includes one or more unsuitable output ports due to manufacturing errors, a 1×msplitter chip20 is fabricated to have the attenuation of a 1×n splitter but with only m<n output ports. This is accomplished, for example, by incorporating one or moreadditional splitters36 intosplitter chip20, with corresponding one or more waveguides associated therewith that carry light that is not meant to be provided toexternal device14. In this case, the one or moreextra splitters36 act as attenuators, thereby obviating the need for external attenuators. Such a 1×msplitter chip20 is less expensive than a 1×n splitter chip because it can be made smaller and does not require external attenuators. In this example embodiment wherein each split does not lead to anoperable output port41, the number ofoutput ports41 is less than 2^j. The overall attenuation of such a splitter is given by the more general expression
• 
  A_O(j)=−10 log(½^j)=10 log(2^j),
• where j is the number ofsplitters36.
• FIG. 4 is a plan schematic diagram of an example embodiment of anattenuated splitter module10 according to the present invention that includes a 1×10splitter chip20 wherein branching waveguide network includes j=5splitters36.Splitter chip20 includes abranch waveguide100 that branches off at the first (i.e., the most input-end-wise)splitter36 and that proceeds directly to itscorresponding output port41. This particular output port provides approximately ½ output power (i.e., has 3 dB attenuation) as compared to the power inputted intoinput waveguide32. (minus insertion loss and excess loss). This amount of output power is more than what is wanted in the output signal and so the correspondingport41 is therefore considered unsuitable for use.Splitter chip20 also includes asecond branch waveguide102 that branches off at thesecond splitter36 and that proceeds directly to itscorresponding output port41. This particular output port provides approximately ¼ output power (i.e., has 6 dB attenuation). This amount of output power is also more than what is wanted in the output signal and so the correspondingport41 is also considered unsuitable for use.
• The remaining portion of branchingwaveguide network30 includesadditional splitters36 that form eightoutput waveguides40 each having correspondingoutput ports41 that provide 1/32 output power (i.e., 15 dB attenuation). These eightoutput ports41 are shown as optically coupled to correspondingoptical fibers78 viafiber array60 that has eightoptical fiber sections74. Light carried bywaveguides100 and102 exits theirrespective ports41 and is dissipated by material (e.g., glass) ofbody61 offiber array60.Waveguides100 and102 are thus “dead-ended” byoutput waveguide device60 and are only present to provide the desired 15 dB attenuation for the other eight output ports.
• FIG. 5 is a plan schematic diagram of an example embodiment of an attenuated planer splitter module similar to that shown inFIG. 4, but whereinwaveguides100 and102 haverespective terminations88 prior to the waveguide reachingsplitter chip end28.Terminations88 absorb the light energy inwaveguides100 and102, or cause some or all of the light to be absorbed or otherwise dissipated bysplitter chip body22. This obviates the need to dissipate the light energy carried by these waveguides usingfiber array60.
• Using any of the above methods, various splitter modules, e.g., 1×4, 1×8 and 1×16 splitter modules, can be produced with about 15 to about 17 dB insertion loss using a branchingwaveguide network30 that includes n=32 output ports (e.g., j=5 splitters36) (“ 1/32 splits”). Additionally, 1×4 and 1×8 splitters can be produced with about 12 to about 14 dB insertion loss using a branchingwaveguide network30 that includes n=16 output ports (i.e., j=4 splitters36) (“ 1/16 splits”). Using these methods, any combination of 1×m splitter modules with 1×n splitter loss may be made, such as 1×2 splitter module with about 15 to about 17 dB insertion loss using 1/32 splits or with about 12 to about 14 dB loss using 1/16 splits; 1×32s with 1/64 splits, etc. Also as discussed above, configurations with j splitters wherein the number of suitable output ports m<2^jare also possible, where these suitable output ports have an associated attenuation in dB given by A_O=10 log (2^j).
Direct-Connect Splitter Module
• As discussed above, present-day splitter modules are made up of separate main parts: a splitter chip, an input connector (ferrule), and an output waveguide device (waveguide array), as well as the external connectors that attached thereto. External connectors are connected to the module so that communication through the module between external input and output devices can be established.
• FIG. 6 is a plan schematic diagram of an example embodiment of a direct-connect splitter module10 according to the present invention. X-Y-Z Cartesian coordinates are provided for the sake of reference (Z is out of the page).Module10 includes asplitter chip20 as described above, and aninput ferrule50 attached to splitterchip input end26.Ferrule50 accommodates inputoptical fiber56 that is optically coupled to inputwaveguide32. Notably absent fromsplitter module10 ofFIG. 6 isoptical fiber array60 normally located atoutput end28 ofsplitter chip20 to facilitate connecting the splitter chip to external optical fibers78 (seeFIG. 2).FIG. 7 is an end-on view of direct-connect splitter module10 as seen looking along arrow114 (i.e., in the −X direction).
• With reference toFIG. 6 throughFIG. 8,splitter module10 includes a ferrule130 (e.g., a multi-fiber ferrule) having a central axis A₁, abody131, and anupper surface132.Splitter module10 includes anoutput end portion134 that includes anoutput end138 and aninput end portion174 that includes aninput end176.FIG. 8 is a plan schematic diagram similar toFIG. 6, but showing justferrule130.Ferrule130 includes an output-end channel142 formed inupper surface132 and centered along central axis A₁and that includes anopen end144 atoutput end138. Output-end channel142 is defined by alower wall146 and two opposingsidewalls148 that define an output-end channel width W_O. Channel width W_Ois sized so that output-end channel142 closely accommodates at least the output-end section ofsplitter chip20 so that splitterchip output end28 substantially coincides with the Y-Z plane defined byoutput end138.
• Splitter chip20 (or at least the output-end portion thereof) is axially aligned within output-end channel142 and is closely held therein using, for example, anadhesive layer150 provided onlower wall146 and/orsidewalls148. An important step forming direct-connect splitter module10 is the close controladhesive layer150.Adhesive layer150 is preferably as thin as possible. Further, the shrinkage and potential rate actions ofadhesive layer150 needs to be taken into account so that proper alignment is maintained. In an example embodiment,adhesive layer150 is formed using a two-step process. The first step involves prefixing with a very little amount of adhesive to minimize the adverse effects of adhesive shrinkage. The second step uses a larger amount of adhesive to achieve long-term fixing ofsplitter chip20 towalls146 and/or148.
• In an example embodiment, aplanar glass cover143 is fixed atopupper surface24 ofsplitter chip20 and is sized to fill the remaining space in output-end channel142 up toupper surface132 offerrule body131.
• Output end138 includes one ormore guide members152 on either side of output-end opening144 that correspond to the position ofoutput ports41 ofoutput waveguides40 inplanar splitter chip20. In an example embodiment, one ormore guide members152 are guide pins or guide holes—for example of the type used with a standard MTP connector and/or the connector of the type disclosed in U.S. patent application Ser. No. 11/076,684 filed Mar. 10, 2005 and assigned to the present assignee, the disclosure of which is hereby incorporated by reference. In general, the type and position of theguide members152 correspond to the particular connector type being used.
• FIG. 9 is an end-on view ofinput end176 of direct-connect splitter module10 as seen looking along arrow170 (i.e., in the +X direction). Input-end section174 offerrule130 includes an input-end channel182 formed insurface132 ofbody131 and centered along central axis A₁. Input-end channel182 has anopen end184 atinput end176. Input-end channel182 is defined by alower wall186 and two opposingsidewalls188 that define an input-end channel width W_I. Channel width W_Iis sized so that input-end channel182 axially accommodates the input-end section ofsplitter chip20 as well asferrule50. Input-end interior width W_Iis preferably greater than output-end interior width W_Oso that the remainder of input-end channel182 can be filled with a thermosetting resin192 (e.g., potting compound) that serves to holdsplitter chip20,ferrule50 and inputoptical fiber56 in mutual alignment within input-end section174 offerrule130.
• In an example embodiment illustrated inFIG. 10 andFIG. 11, direct-connect splitter module10 includes ahousing200 that surrounds at least a portion offerrule130.Housing200 includes aninput end206 that covers inputopen end184 so as to containthermosetting resin192, and that includes aopening210 sized to pass inputoptical fiber56 toferrule50. In an example embodiment,housing200 also includes asection220 that makes the module output-end section134 conform or otherwise be compatible with a particular type of multi-fiber connector, such an MTP connector. For example,housing200 can be formed to be compatible with spring-and-locktype guide members152, and can have dimensions similar to an MTP connector, which dimensions are 30 mm×7 mm×12 mm.
• FIG. 12 is a perspective end-on view ofoutput end138 of direct-connect module10, wherein the output end is in the form an MTP connector. Also shown inFIG. 12 is amating connector250 that establishes optical communication with an external device (not shown). Direct-connect splitter module10 allowsexternal connector250, such as an MTP mating connector, to be directly connected to output ends (ports)41 ofoutput waveguides40 insplitter chip20 without the need forfiber array60 or like waveguide array.
• In an example embodiment, direct-connect splitter module10 includes aplanar splitter chip20 with a glued single-fiber ferrule50 in an MTP-adapted output end138 (FIG. 12). Also in an example embodiment,output waveguides40 ofplanar splitter chip20 have the same pitch as an MTP ferrule. Therefore, instead of a ferrule, the planar splitter chip can be placed inside an elongated MTP-ferrule housing200. Alignment and fixation withexternal connector250 is achieved usingguide members152, e.g., guide pins and/or other types of retention members, such as clips.
• The direct-connect splitter module10 of the present invention provides a number of advantages over a conventional splitter module. First, there is a significant reduction in cost, since for each direct-connect splitter module the expense and labor associated with includingfiber array60 and the associated connectors is avoided. In addition, labor costs can be reduced by using automated image recognition ofsplitter waveguides40 andguide members152, which allow a faster alignment without any optical connections. In addition, the size of direct-connect splitter module10 can be made significantly smaller than a conventional splitter module, so that the splitter module of the present invention can be used in smaller cabinets, closures, or other small access points, or can be directly integrated into cables or ducts. Overall, better optical and reliability performance may be achieved because the additional loss that usually occurs between the fiber array and the planar splitter chip is avoided.
• In an example embodiment,housing200 is formed from or otherwise includes the same basic material (or a material with similar thermal expansion coefficient) as an MTP ferrule, and has the same form as an MTP-connector on the connector side, such as shown inFIG. 12. A standardplanar splitter chip20 already has the same output waveguide pitch as an MTP-ferrule.
• In an example embodiment, the alignment ofsplitter output waveguides40 relative to guidemembers152 is performed by automated image recognition. In this case, no optical connections are necessary.Housing200 has a fixed position, withsplitter chip20 mounted to an alignment station so that it can be moved in all directions inside a slot of the housing. In an example embodiment, the housing is moved whilesplitter chip20 is fixed in position.
• The direct-connect splitter module10 of the present invention as described above provides for a direction connection atoutput end138 of output-end section174. However, the direct connection can be formed on input-end section174 at splitterchip input end26 using the same or similar approach. Likewise, a direct-connect module10 can be formed that has a splitting ratio besides the 1×8 ratio shown (e.g. 1×2, 1×4, 1×16, 1×32, 1×64, 2×16, 2×32, 2-1×8, 2-1×16, 4-1×8, etc) using the methods of the present invention. Any other PLC (planar lightwave circuit) chip can be assembled using the same technology. In an example embodiment, the use of materials in direct-connect module10 that have the same or like coefficients of thermal expansion (CTE) of the particular connector used with the module is preferred. For example, it may be advantageous to use a polymer-based material forsplitter chip body22 when the intended use for the module is with a polymer-based connector250 (FIG. 12).
Microsplitter Module
• Present-day splitter devices are on the order of 50 mm×10 mm×4 mm and are integrated in a larger splitter module, typically on the order of 150 mm×100 mm×30 mm. In present-day splitter modules, one can differentiate between the splitter device and the splitter module. Such splitter modules are currently extensively used in FTTx applications. The microsplitter module according to the present invention and described immediately below seeks to provide a very small connectorized splitter that serves as device and module at the same time so that the differentiation between device and module is, for all practical purposes, eliminated.
• FIG. 13 is a side cross-sectional diagram of an example embodiment of amicrosplitter module10 according to the present invention.Module10 includes asplitter chip assembly316 that has abody318 made up ofplanar splitter chip20 andplanar glass cover143. In an example embodiment,splitter chip assembly316 includes beveled input and output ends26 and28 and the corresponding ends ofplanar glass cover143 are also beveled to match.
• Module10 also includesinput ferrule50 attached to input end26 ofsplitter chip20 and that provides optical coupling between inputoptical fiber56 andinput waveguide36 of branchingwaveguide network30. In an example embodiment,input ferrule50 is an angled polished connector (APC) having abeveled end326 that matches input beveledend26 ofsplitter chip assembly20. Aconnector sleeve330 coversinput ferrule50 and has anopen end332 that opens to an interior336.Connector sleeve330 is adapted to facilitate optically connecting inputoptical fiber56 to an externaloptical fiber cable350.
• Module10 further includes amulti-fiber ferrule360 having abody361 that supports a plurality of outputoptical fibers362 that each include aninput end363 and anoutput end364. Outputoptical fibers362 are arranged inholes365 that run throughferrule360 from aninput end366 to anoutput end367.Holes365 are formed to have the same pitch asoutput waveguides40 ofsplitter chip20 so that optical fiber output ends364 have the same pitch as the output waveguides.
• In an example embodiment,multi-fiber ferrule360 is attached (e.g., bonded) to output end28 ofsplitter chip20 so that output waveguide ends41 ofoutput waveguides40 are optically coupled (e.g., butt-coupled) to the corresponding input ends363 of outputoptical fibers362. In an example embodiment,multi-fiber ferrule360 includes a beveled end368 that matches output beveled end28 ofsplitter chip assembly316.
• Microsplitter module10 includes ahousing200 that contains most if not all of each of theinput ferrule50,multi-fiber ferrule360 andsplitter chip assembly316. In an example embodiment,housing200 is formed (e.g., molded) to conform to a particular multi-fiber connector type to be used with the module, such as an MTP-type multi-fiber connector.Housing200 also serves to support theinput ferrule50,multi-fiber ferrule360 andsplitter chip assembly316 and to maintain these elements in mutual alignment, particularly during use in the field.
• FIG. 14 is a perspective view of anexample microsplitter module10 according to the present invention, whereinhousing200 is formed so that the module is amenable for use with MTP-type connectors.Housing200 also includes aboot section202 that containsinput ferrule50 and inputoptical fiber56 in a pigtail configuration. Themicrosplitter module10 ofFIG. 14 illustrates the utility of the present invention with respect to incorporating the module directly into a cable assembly.
• FIG. 15 is a side cut-away view similar toFIG. 13 that illustrates another example embodiment ofmicrosplitter module10 that includesfiber array60 arranged between splitterchip output end28 andmulti-fiber ferrule360.Microsplitter module10 is also shown as having pigtail input380 formed byinput ferrule50 and inputoptical fiber56.
• Inmicrosplitter module10 ofFIG. 15, input end62 offiber array60 is attached (e.g., bonded) to output end28 ofsplitter chip assembly316 so thatoptical fiber sections74 supported byfiber array60 are optically coupled tooutput waveguides40 ofsplitter chip20 atoutput ports41.Optical fiber sections74 then serve as theoutput fibers362.Optical fiber sections74 run throughholes365 inmulti-fiber ferrule360.Multi-fiber ferrule360 is spaced apart fromwaveguide device60 by a distance d (e.g., d=1 cm). This configuration (called a “CTE-matched output configuration”) is advantageous in that it avoids adverse thermal effects due to differences in the CTE betweenfiber array body61, which is typically made of glass, andmulti-fiber ferrule body361, which is typically made of a glass-filled plastic having a substantially different CTE than glass
• FIG. 16 is a cut-away side view of another example embodiment ofmicrosplitter module10 similar to that ofFIG. 15, whereinfiber array60 is replaced by a directly bondedfiber assembly400 having aninput end402 and anoutput end404.Thermal stabilization unit400 is mechanically decoupled frommulti-fiber ferrule360. In an example embodiment, directly bondedfiber assembly400 includesglass plates410 arranged to support outputoptical fibers362.
• In an example embodiment, input end402 ofthermal stabilization unit400 is attached (e.g., bonded) to output end28 ofsplitter chip20 so that input ends363 of outputoptical fibers362 are aligned with and contacted to output ends41 ofoutput waveguides40 ofsplitter chip20. Directly bonded fiberassembly output end404 is attached to ferrule360 using a soft-interfacing adhesive420 that accommodates different expansion rates between directly bondedfiber assembly400 andmulti-fiber ferrule360.
• Themicrosplitter module10 according to the present invention provides a very small connectorized splitter that serves as device and module at the same time (i.e., the differentiation between device and module is, for all practical purposes, eliminated). The microsplitter module can be used as a single-to multi-fiber connector adapter, such as to connect a single SC/APC connectorized cable to an MTP connectorized eight-fiber-ribbon cable, or any other suitable type of single-fiber connector to multi-fiber connector.
• Embodiments of the microsplitter module of the present invention that use a standard pigtail interface at the input side are particularly suitable for use in high density MDU cabinets. In an example embodiment, inputoptical fiber56 is a bend performance fiber, which further reduces the space requirement for the module. The microsplitter module of the present invention integrates the device assembly process and the module assembly process into one step, thereby significantly reducing the variable cost associated with producing splitter modules. In addition, the size of the microsplitter module can be made much smaller (e.g., 60 mm×12 mm×8 mm), so that it is more amenable for use in reduced size cabinets, closures, other small size access points. Further, as mentioned above, the microsplitter module of the present invention can be directly integrated into cables or ducts.
• Various embodiments of the present invention are adapted to include bend performance optical fibers. One example of bend performance optical fiber is a microstructured optical fiber having a core region and a cladding region surrounding the core region, the cladding region comprising an annular hole-containing region comprised of non-periodically disposed holes such that the optical fiber is capable of single mode transmission at one or more wavelengths in one or more operating wavelength ranges. The core region and cladding region provide improved bend resistance, and single mode operation at wavelengths preferably greater than or equal to 1500 nm, in some embodiments also greater than about 1310 nm, in other embodiments also greater than 1260 nm. The optical fibers provide a mode field at a wavelength of 1310 nm preferably greater than 8.0 microns, more preferably between about 8.0 and 10.0 microns. In preferred embodiments, optical fiber disclosed herein is thus single-mode transmission optical fiber.
• In some embodiments of the present invention, the microstructured optical fibers disclosed herein comprises a core region disposed about a longitudinal centerline and a cladding region surrounding the core region, the cladding region comprising an annular hole-containing region comprised of non-periodically disposed holes, wherein the annular hole-containing region has a maximum radial width of less than 12 microns, the annular hole-containing region has a regional void area percent of less than about 30 percent, and the non-periodically disposed holes have a mean diameter of less than 1550 nm.
• By “non-periodically disposed” or “non-periodic distribution”, it is meant that when one takes a cross-section (such as a cross-section perpendicular to the longitudinal axis) of the optical fiber, the non-periodically disposed holes are randomly or non-periodically distributed across a portion of the fiber. Similar cross sections taken at different points along the length of the fiber will reveal different cross-sectional hole patterns, i.e., various cross-sections will have different hole patterns, wherein the distributions of holes and sizes of holes do not match. That is, the holes are non-periodic, i.e., they are not periodically disposed within the fiber structure. These holes are stretched (elongated) along the length (i.e. in a direction generally parallel to the longitudinal axis) of the optical fiber, but do not extend the entire length of the entire fiber for typical lengths of transmission fiber.
• For a variety of applications, it is desirable for the holes to be formed such that greater than about 95% of and preferably all of the holes exhibit a mean hole size in the cladding for the optical fiber which is less than 1550 nm, more preferably less than 775 nm, most preferably less than 390 nm. Likewise, it is preferable that the maximum diameter of the holes in the fiber be less than 7000 nm, more preferably less than 2000 nm, and even more preferably less than 1550 nm, and most preferably less than 775 nm. In some embodiments, the fibers disclosed herein have fewer than 5000 holes, in some embodiments also fewer than 1000 holes, and in other embodiments the total number of holes is fewer than 500 holes in a given optical fiber perpendicular cross-section. Of course, the most preferred fibers will exhibit combinations of these characteristics. Thus, for example, one particularly preferred embodiment of optical fiber would exhibit fewer than 200 holes in the optical fiber, the holes having a maximum diameter less than 1550 nm and a mean diameter less than 775 nm, although useful and bend resistant optical fibers can be achieved using larger and greater numbers of holes. The hole number, mean diameter, max diameter, and total void area percent of holes can all be calculated with the help of a scanning electron microscope at a magnification of about 800× and image analysis software, such as ImagePro, which is available from Media Cybernetics, Inc. of Silver Spring, Md., USA.
• The optical fibers disclosed herein may or may not include germania or fluorine to also adjust the refractive index of the core and or cladding of the optical fiber, but these dopants can also be avoided in the intermediate annular region and instead, the holes (in combination with any gas or gases that may be disposed within the holes) can be used to adjust the manner in which light is guided down the core of the fiber. The hole-containing region may consist of undoped (pure) silica, thereby completely avoiding the use of any dopants in the hole-containing region, to achieve a decreased refractive index, or the hole-containing region may comprise doped silica, e.g. fluorine-doped silica having a plurality of holes.
• In one set of embodiments, the core region includes doped silica to provide a positive refractive index relative to pure silica, e.g. germania doped silica. The core region is preferably hole-free. In some embodiments, the core region comprises a single core segment having a positive maximum refractive index relative to pure silica Δ₁in %, and the single core segment extends from the centerline to a radius R1. In one set of embodiments, 0.30%<Δ₁<0.40%, and 3.0 μm<R1<5.0 μm. In some embodiments, the single core segment has a refractive index profile with an alpha shape, where alpha is 6 or more, and in some embodiments alpha is 8 or more. In some embodiments, the inner annular hole-free region extends from the core region to a radius R2, wherein the inner annular hole-free region has a radial width W12, equal to R2−R1, and W12 is greater than 1 μm. Radius R2 is preferably greater than 5 μm, more preferably greater than 6 μm. The intermediate annular hole-containing region extends radially outward from R2 to radius R3 and has a radial width W23, equal to R3−R2. The outerannular region186 extends radially outward from R3 to radius R4. Radius R4 is the outermost radius of the silica portion of the optical fiber. One or more coatings may be applied to the external surface of the silica portion of the optical fiber, starting at R4, the outermost diameter or outermost periphery of the glass part of the fiber. The core region and the cladding region are preferably comprised of silica. The core region is preferably silica doped with one or more dopants. Preferably, the core region is hole-free. The hole-containing region has an inner radius R2 which is not more than 20 μm. In some embodiments, R2 is not less than 10 μm and not greater than 20 μm. In other embodiments, R2 is not less than 10 μm and not greater than 18 μm. In other embodiments, R2 is not less than 10 μm and not greater than 14 μm. Again, while not being limited to any particular width, the hole-containing region has a radial width W23 which is not less than 0.5 μm. In some embodiments, W23 is not less than 0.5 μm and not greater than 20 μm. In other embodiments, W23 is not less than 2 μm and not greater than 12 μm. In other embodiments, W23 is not less than 2 μm and not greater than 10 μm.
• Such fiber can be made to exhibit a fiber cutoff of less than 1400 nm, more preferably less than 1310 nm, a 20 mm macrobend induced loss at 1550 nm of less than 1 dB/turn, preferably less than 0.5 dB/turn, even more preferably less than 0.1 dB/turn, still more preferably less than 0.05 dB/turn, yet more preferably less than 0.03 dB/turn, and even still more preferably less than 0.02 dB/turn, a 12 mm macrobend induced loss at 1550 nm of less than 5 dB/turn, preferably less than 1 dB/turn, more preferably less than 0.5 dB/turn, even more preferably less than 0.2 dB/turn, still more preferably less than 0.01 dB/turn, still even more preferably less than 0.05 dB/turn, and a 8 mm macrobend induced loss at 1550 nm of less than 5 dB/turn, preferably less than 1 dB/turn, more preferably less than 0.5 dB/turn, and even more preferably less than 0.2 dB-turn, and still even more preferably less than 0.1 dB/turn.
• The fiber of some embodiments of the present invention comprises a core region that is surrounded by a cladding region that comprises randomly disposed voids which are contained within an annular region spaced from the core and positioned to be effective to guide light along the core region. Other optical fibers and microstructured fibers may be used in the present invention. Additional features of the microstructured optical fibers of additional embodiments of the present invention are described more fully in pending U.S. patent application Ser. No. 11/583,098 filed Oct. 18, 2006, and provisional U.S. patent application Ser. Nos. 60/817,863 filed Jun. 30, 2006; 60/817,721 filed Jun. 30, 2006; 60/841,458 filed Aug. 31, 2006; and 60/841,490 filed Aug. 31, 2006; all of which are assigned to Corning Incorporated and the disclosures of which are incorporated by reference herein.
• Still further embodiments of the present invention comprise fiber optic cables comprising bend resistant multimode optical fibers which comprise a graded-index core region and a cladding region surrounding and directly adjacent to the core region, the cladding region comprising a depressed-index annular portion comprising a depressed relative refractive index, relative to another portion of the cladding (which preferably is silica which is not doped with an index of refraction altering dopant such as germania or fluorine). Preferably, the refractive index profile of the core has a parabolic shape. The depressed-index annular portion may comprise glass comprising a plurality of holes, fluorine-doped glass, or fluorine-doped glass comprising a plurality of holes. The depressed index region can be adjacent to or spaced apart from the core region.
• In some embodiments that comprise a cladding with holes, the holes can be non-periodically disposed in the depressed-index annular portion. By “non-periodically disposed” or “non-periodic distribution”, we mean that when viewed in cross section (such as a cross section perpendicular to the longitudinal axis) of the optical fiber, the non-periodically disposed holes are randomly or non-periodically distributed across the hole containing region. Cross sections taken at different points along the length of the fiber will reveal different cross-sectional hole patterns, i.e., various cross sections will have different hole patterns, wherein the distributions of holes and sizes of holes do not match. That is, the voids or holes are non-periodic, i.e., they are not periodically located within the fiber structure. These holes are stretched (elongated) along the length (i.e. parallel to the longitudinal axis) of the optical fiber, but do not extend the entire length of the entire fiber for typical lengths of transmission fiber.
• The multimode optical fiber disclosed herein exhibits very low bend induced attenuation, in particular very low macrobending. In some embodiments, high bandwidth is provided by low maximum relative refractive index in the core, and low bend losses are also provided. In some embodiments, the core radius is large (e.g. greater than 20 μm), the core refractive index is low (e.g. less than 1.0%), and the bend losses are low. Preferably, the multimode optical fiber disclosed herein exhibits a spectral attenuation of less than 3 dB/km at 850 nm.
• The numerical aperture (NA) of the optical fiber is preferably greater than the NA of the optical source directing signals into the fiber; for example, the NA of the optical fiber is preferably greater than the NA of a VCSEL source. The bandwidth of the multimode optical fiber varies inversely with the square of Δ1_MAX. For example, a multimode optical fiber with Δ1_MAXof 0.5% can yield a bandwidth 16 times greater than an otherwise identical multimode optical fiber except having a core with Δ1_MAXof 2.0%.
• In some embodiments, the core extends radially outwardly from the centerline to a radius R1, wherein 12.5≦R1≦40 microns. In some embodiments, 25≦R1≦32.5 microns, and in some of these embodiments, R1 is greater than or equal to about 25 microns and less than or equal to about 31.25 microns. The core preferably has a maximum relative refractive index, less than or equal to 1.0%. In other embodiments, the core has a maximum relative refractive index, less than or equal to 0.5%. Such multimode fibers preferably exhibit a 1turn 10 mm diameter mandrel attenuation increase of no more than 1.0 dB, preferably no more than 0.5 dB, more preferably no more than 0.25 dB, even more preferably no more than 0.1 dB, and still more preferably no more than 0.05 dB, at all wavelengths between 800 and 1400 nm.
• If non-periodically disposed holes or voids are employed in the depressed index annular region, it is desirable for the holes to be formed such that greater than 95% of and preferably all of the holes exhibit a mean hole size in the cladding for the optical fiber which is less than 1550 nm, more preferably less than 775 nm, most preferably less than about 390 nm. Likewise, it is preferable that the maximum diameter of the holes in the fiber be less than 7000 nm, more preferably less than 2000 nm, and even more preferably less than 1550 nm, and most preferably less than 775 nm. In some embodiments, the fibers disclosed herein have fewer than 5000 holes, in some embodiments also fewer than 1000 holes, and in other embodiments the total number of holes is fewer than 500 holes in a given optical fiber perpendicular cross-section. Of course, the most preferred fibers will exhibit combinations of these characteristics. Thus, for example, one particularly preferred embodiment of optical fiber would exhibit fewer than 200 holes in the optical fiber, the holes having a maximum diameter less than 1550 nm and a mean diameter less than 775 nm, although useful and bend resistant optical fibers can be achieved using larger and greater numbers of holes. The hole number, mean diameter, max diameter, and total void area percent of holes can all be calculated with the help of a scanning electron microscope at a magnification of about 800× and image analysis software, such as ImagePro, which is available from Media Cybernetics, Inc. of Silver Spring, Md., USA.
• The optical fiber disclosed herein may or may not include germania or fluorine to also adjust the refractive index of the core and or cladding of the optical fiber, but these dopants can also be avoided in the intermediate annular region and instead, the holes (in combination with any gas or gases that may be disposed within the holes) can be used to adjust the manner in which light is guided down the core of the fiber. The hole-containing region may consist of undoped (pure) silica, thereby completely avoiding the use of any dopants in the hole-containing region, to achieve a decreased refractive index, or the hole-containing region may comprise doped silica, e.g. fluorine-doped silica having a plurality of holes.
• The outer annular portion of a cross-section of the glass portion of an embodiment of a multimode optical fiber has a substantially constant refractive index profilewith a constant Δ4(r); in some of these embodiments, Δ4(r)=0%. The “relative refractive index percent” is defined as Δ%=100×(n_i²−n_REF²)/2n_i². The relative refractive index percent is measured at 850 nm unless otherwise specified. In certain embodiments, the reference index n_REFis the refractive index of inner annular portion. The core is surrounded by and in direct contact with the inner annular portion, which has a substantially constant refractive index profile Δ2(r). The inner annular portion is surrounded by and in direct contact with the depressed-index annular portion having refractive index profile Δ3, and the depressed-index annular portion is surrounded by and in direct contact with the outer annular portion, which has a substantially constant refractive index profile Δ4(r).
• The core has an entirely positive refractive index profile, where Δ1(r)>0%. In some embodiments, the inner annular portion has a relative refractive index profile Δ2(r) having a maximum absolute magnitude less than 0.05%, and Δ2_MAX<0.05% and Δ2_MIN>−0.05%, and the depressed-index annular portion begins where the relative refractive index of the cladding first reaches a value of less than −0.05%, going radially outwardly from the centerline. In some embodiments, the outer annular portion has a relative refractive index profile Δ4(r) having a maximum absolute magnitude less than 0.05%, and Δ4_MAX<0.05% and Δ4_MIN>−0.05%, and the depressed-index annular portion ends where the relative refractive index of the cladding first reaches a value of greater than −0.05%, going radially outwardly from the radius where Δ3 MIN is found. In some embodiments, the inner annular portion comprises pure silica. In some embodiments, the outer annular portion comprises pure silica. In some embodiments, the depressed-index annular portion comprises pure silica comprising with a plurality of holes. Preferably, the minimum relative refractive index, or average effective relative refractive index, such as taking into account the presence of any holes, of the depressed-index annular portion is preferably less than −0.1%. The holes can contain one or more gases, such as argon, nitrogen, or oxygen, or the holes can contain a vacuum with substantially no gas; regardless of the presence or absence of any gas, the refractive index in the annular portion is lowered due to the presence of the holes. The holes can be randomly or non-periodically disposed in the annular portion of the cladding500, and in other embodiments, the holes are disposed periodically in the annular portion. In some embodiments, the plurality of holes comprises a plurality of non-periodically disposed holes and a plurality of periodically disposed holes. Alternatively, or in addition, the depressed index in annular portion can also be provided by downdoping the annular portion (such as with fluorine) or updoping one or more portions of the cladding and/or the core, wherein the depressed-index annular portion is, for example, pure silica or silica which is not doped as heavily as the inner annular portion.
• Preferably, the inner annular portion has a radial width of greater than 4 microns. In some embodiments, the minimum relative refractive index of the depressed-index annular portion, Δ3 MIN, is less than −0.10%; in other embodiments, Δ3 MIN is less than −0.20%; in still other embodiments, Δ3 MIN is less than −0.30%; in yet other embodiments, Δ3 MIN is less than −0.40%.
• Δ1_MAXis preferably less than or equal to 2.0%, more preferably less than or equal to 1.0%, even more preferably less than 1.0%, and still more preferably less than or equal to 0.8%; in some embodiments Δ1_MAXis greater than or equal to 0.4% and less than or equal to 1.0%, and in other embodiments Δ1_MAXis greater than or equal to 0.5% and less than or equal to 0.75%.
• The numerical aperture (NA) of the optical fiber is preferably greater than the NA of the optical source directing signals into the fiber; for example, the NA of the optical fiber is preferably greater than the NA of a VCSEL source. The bandwidth of the multimode optical fiber varies inversely with the square of Δ1_MAX. For example, a multimode optical fiber with Δ1_MAXof 0.5% can yield a bandwidth 16 times greater than an otherwise identical multimode optical fiber except having a core with Δ1_MAXof 2.0%.
• In some embodiments, the core outer radius, R₁, is preferably not less than 12.5 μm and not more than 40 μm, i.e. the core diameter is between about 25 and 80 μm. In other embodiments, R1>20 microns; in still other embodiments, R1>22 microns; in yet other embodiments, R1>24 microns.
• It will be apparent to those skilled in the art that various modifications and variations can be made to the present invention without departing from the spirit and scope of the invention. Thus it is intended that the present invention cover the modifications and variations of this invention provided they come within the scope of the appended claims and their equivalents.

Claims (19)

1. A direct-connect splitter module for providing optical communication with at least one external output device via a module output end, comprising:

a ferrule having a central axis, adjacent input-end and output-end sections that include respective input and output ends and that respectively include connecting input and output channels that run along the central axis and that have respective open ends at the respective in put and output ends;

a splitter chip that includes input and output ends and a branching waveguide network that includes at least one input waveguide at its input end and at least two output waveguides each having an output end at the splitter chip output end, wherein the splitter chip is fixed in the output channel with its output end at the output channel open end;

at least one input ferrule connected to the input end of the splitter chip and that resides in the input-end channel;

at least one input optical fiber having an output end and an input end that is optically coupled to the at least one input waveguide of the splitter chip via the at least one input ferrule;

a thermosetting resin that substantially fills the input channel so as to fix the at least one input ferrule and the at least one input optical fiber in position within the input-end channel; and

a housing generally surrounding at least a portion of the ferrule so as to cover the input end of the input-end channel and to provide conformity with a connector associated with the at least one external output device.

2. The direct-connect splitter module ofclaim 1, wherein at least a portion of the input end of the splitter chip resides within the input channel so that said portion is held in place within the input channel by the thermosetting resin.

3. The direct-connect splitter module ofclaim 1, wherein the output-end channel has a bottom wall and opposing sidewalls, and wherein the splitter chip is closely arranged and fixed in the outer-end channel by a layer of adhesive between the splitter chip and the bottom wall and/or opposing sidewalls.

4. The direct-connect splitter module ofclaim 1, wherein the ferrule output end includes at least one guide member that facilitates connecting the module to the at least one external output device.

5. The direct-connect splitter module ofclaim 1, wherein the corresponding output ends of the ferrule and the splitter chip are formed such that the module output end is compatible with an MTP-type connector.

6. The direct-connect splitter module ofclaim 1, wherein the input-end channel has a channel width W_l, the output-end channel has a channel width W_o, and wherein W_l>W_o.

7. The direct-connect splitter module ofclaim 1, including the at least one external output device as optically coupled to at least one of the output waveguides of the splitter chip.

8. The direct-connect splitter module ofclaim 7, including an external input device optically coupled to the at least one input optical fiber input end.

9. The direct-connect splitter module ofclaim 1, including a single input optical fiber and a single input waveguide.

10. The direct-connect splitter module ofclaim 1, including an external connector having connector waveguides, wherein the external connector is optically coupled to the module output end so that the connector waveguides are optically coupled to the splitter chip output waveguides.

11. A direct-connect splitter module for providing optical communication with at least one external output device via a module output end, comprising:

a ferrule having a central axis, adjacent input-end and output-end sections that include respective input and output ends and that respectively include connecting input and output channels that run along the central axis and that have respective open ends at the respective input and output ends;

a splitter chip that includes input and output ends and a branching waveguide network that includes at least one input waveguide at its input end and at least two output waveguides each having an output end at the splitter chip output end, wherein the splitter chip is fixed in the output channel with its output end at the output channel open end;

at least one input ferrule connected to the input end of the splitter chip and that resides in the input-end channel;

at least one input optical fiber having an output end and an input end that is optically coupled to the at least one input waveguide of the splitter chip via the at least one input ferrule; and

a housing generally surrounding at least a portion of the ferrule so as to cover the input end of the input-end channel and to provide conformity with a connector associated with the at least one external output device.

12. The direct-connect splitter module ofclaim 11, wherein the output-end channel has a bottom wall and opposing sidewalls, and wherein the splitter chip is closely arranged and fixed in the outer-end channel by a layer of adhesive between the splitter chip and the bottom wall and/or opposing sidewalls.

13. The direct-connect splitter module ofclaim 11, wherein the ferrule output end includes at least one guide member that facilitates connecting the module to the at least one external output device.

14. The direct-connect splitter module ofclaim 11, wherein the corresponding output ends of the ferrule and the splitter chip are formed such that the module output end is compatible with an MTP-type connector.

15. The direct-connect splitter module ofclaim 11, wherein the input-end channel has a channel width W_l, the output-end channel has a channel width W_o, and wherein W_l>W_o.

16. The direct-connect splitter module ofclaim 11, including the at least one external output device as optically coupled to at least one of the output waveguides of the splitter chip.

17. The direct-connect splitter module ofclaim 16, including an external input device optically coupled to the at least one input optical fiber input end.

18. The direct-connect splitter module ofclaim 11, including a single input optical fiber and a single input waveguide.

19. The direct-connect splitter module ofclaim 11, including an external connector having connector waveguides, wherein the external connector is optically coupled to the module output end so that the connector waveguides are optically coupled to the splitter chip output waveguides.

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