CN112583478A - Nonlinear characteristic testing device and method of coherent optical receiver - Google Patents
Nonlinear characteristic testing device and method of coherent optical receiverDownload PDFInfo
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- CN112583478A CN112583478ACN201910935728.6ACN201910935728ACN112583478ACN 112583478 ACN112583478 ACN 112583478ACN 201910935728 ACN201910935728 ACN 201910935728ACN 112583478 ACN112583478 ACN 112583478A
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04B—TRANSMISSION
- H04B10/00—Transmission systems employing electromagnetic waves other than radio-waves, e.g. infrared, visible or ultraviolet light, or employing corpuscular radiation, e.g. quantum communication
- H04B10/07—Arrangements for monitoring or testing transmission systems; Arrangements for fault measurement of transmission systems
- H04B10/075—Arrangements for monitoring or testing transmission systems; Arrangements for fault measurement of transmission systems using an in-service signal
- H04B10/079—Arrangements for monitoring or testing transmission systems; Arrangements for fault measurement of transmission systems using an in-service signal using measurements of the data signal
- H04B10/0795—Performance monitoring; Measurement of transmission parameters
- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04B—TRANSMISSION
- H04B10/00—Transmission systems employing electromagnetic waves other than radio-waves, e.g. infrared, visible or ultraviolet light, or employing corpuscular radiation, e.g. quantum communication
- H04B10/07—Arrangements for monitoring or testing transmission systems; Arrangements for fault measurement of transmission systems
- H04B10/075—Arrangements for monitoring or testing transmission systems; Arrangements for fault measurement of transmission systems using an in-service signal
- H04B10/079—Arrangements for monitoring or testing transmission systems; Arrangements for fault measurement of transmission systems using an in-service signal using measurements of the data signal
- H04B10/0795—Performance monitoring; Measurement of transmission parameters
- H04B10/07955—Monitoring or measuring power
- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04B—TRANSMISSION
- H04B10/00—Transmission systems employing electromagnetic waves other than radio-waves, e.g. infrared, visible or ultraviolet light, or employing corpuscular radiation, e.g. quantum communication
- H04B10/60—Receivers
- H04B10/61—Coherent receivers
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Abstract
Translated fromChinese
Description
Technical Field
The invention relates to the technical field of communication.
Background
The coherent optical communication system occupies an important position in a communication transmission network by the advantages of huge transmission bandwidth, great capacity expansion potential, extremely low transmission loss, low manufacturing cost and the like. In a coherent optical communication system, with the improvement of communication baud rate, the coherent optical receiver damages signals more and more seriously, wherein because the influence caused by the nonlinear characteristics of each component inside the coherent optical receiver cannot be ignored, the noise caused by testing the nonlinear characteristics through proper design has an important role in better using the coherent optical receiver.
In the study on the nonlinear characteristics of the coherent optical receiver, the existing method generally uses a low-frequency single tone signal as a test signal, and describes the nonlinear characteristics of the coherent optical receiver by studying Total Harmonic Distortion (THD) of an output signal.
It should be noted that the above background description is only for the sake of clarity and complete description of the technical solutions of the present invention and for the understanding of those skilled in the art. Such solutions are not considered to be known to the person skilled in the art merely because they have been set forth in the background section of the invention.
Disclosure of Invention
The inventors have found that, as the communication baud rate increases, the nonlinear damage due to the high-frequency component becomes more and more serious, and in the above conventional method, the THD parameter obtained based on the low-frequency monophonic test signal reflects only the nonlinear characteristic of the coherent optical receiver to a certain extent, and the THD parameter cannot be applied in the high-frequency stage.
The embodiment of the invention provides a device and a method for testing the nonlinear characteristic of a coherent optical receiver, which can accurately measure the nonlinear characteristic of the coherent optical receiver in an optical communication system with a higher communication baud rate, do not need to recover a signal constellation diagram, have simple measurement and processing processes, and have certain robustness for resisting frequency deviation due to certain bandwidth of band notch.
According to a first aspect of the embodiments of the present invention, there is provided a nonlinear characteristic testing apparatus of a coherent optical receiver, the apparatus including: a measuring section that measures nonlinear noise power at each frequency within a bandwidth of the coherent optical receiver, respectively; and a determination section that determines a nonlinear noise power spectrum of the coherent optical receiver from nonlinear noise powers at respective frequencies within a bandwidth of the coherent optical receiver, wherein the measurement section includes: a first signal generating section that generates a first test signal having at least one band notch whose center frequency corresponds to at least one frequency within a bandwidth of the coherent optical receiver; a first determination unit configured to determine a frequency of the local oscillator laser based on a frequency range of the first test signal and at least one notch of the first test signal; a first power measuring unit that inputs the first test signal and the laser light output from the local oscillator laser to the coherent optical receiver and measures an output power spectrum of the coherent optical receiver; and a second determination section that determines a nonlinear noise power at the at least one frequency in the output power spectrum from a center frequency of the at least one notch that the first test signal has.
According to a second aspect of the embodiments of the present invention, there is provided a method for testing nonlinear characteristics of a coherent optical receiver, the method including: respectively measuring the nonlinear noise power at each frequency in the bandwidth of the coherent optical receiver; and determining a nonlinear noise power spectrum of the coherent optical receiver according to nonlinear noise power at each frequency within a bandwidth of the coherent optical receiver, wherein measuring the nonlinear noise power at least one frequency of each frequency within the bandwidth of the coherent optical receiver comprises: generating a first test signal having at least one band notch, a center frequency of the at least one band notch corresponding to at least one frequency within a bandwidth of the coherent optical receiver; determining the frequency of a local oscillator laser according to the frequency range of the first test signal and at least one band notch of the first test signal; inputting the first test signal and laser output by the local oscillator laser into the coherent optical receiver, and measuring an output power spectrum of the coherent optical receiver; and determining a non-linear noise power at the at least one frequency in the output power spectrum from the at least one notched center frequency of the first test signal.
The invention has the beneficial effects that: the method comprises the steps of generating a test signal with band notches, determining the frequency of a local oscillator laser according to the frequency range of the test signal and the band notches of the test signal, outputting the test signal and laser output by the local oscillator laser to a coherent optical receiver to be tested, and determining the nonlinear noise power at the corresponding frequency in the output spectrum of the coherent optical receiver according to the center frequency with the band notches of the test signal, so that for the coherent optical receiver in an optical communication system with a high communication baud rate, the nonlinear characteristic of the coherent optical receiver can be accurately measured, a constellation diagram of the signal does not need to be restored, the measuring and processing processes are simple, and in addition, the band notches have certain bandwidth, so that the measuring method has certain robustness for frequency offset resistance.
Specific embodiments of the present invention are disclosed in detail with reference to the following description and drawings, indicating the manner in which the principles of the invention may be employed. It should be understood that the embodiments of the invention are not so limited in scope. The embodiments of the invention include many variations, modifications and equivalents within the spirit and scope of the appended claims.
Features that are described and/or illustrated with respect to one embodiment may be used in the same way or in a similar way in one or more other embodiments, in combination with or instead of the features of the other embodiments.
Drawings
The accompanying drawings, which are included to provide a further understanding of the embodiments of the invention and are incorporated in and constitute a part of this specification, illustrate embodiments of the invention and together with the description serve to explain the principles of the invention. It is obvious that the drawings in the following description are only some embodiments of the invention, and that for a person skilled in the art, other drawings can be derived from them without inventive effort. In the drawings:
fig. 1 is a schematic diagram of a nonlinear characteristic testing apparatus of a coherent optical receiver according to embodiment 1 of the present invention;
fig. 2 is a schematic view of themeasuring section 110 according to embodiment 1 of the present invention;
FIG. 3 is a diagram of a first test signal according to embodiment 1 of the present invention;
FIG. 4 is an output power spectrum derived from the first test signal shown in FIG. 3;
FIG. 5 is another diagram of the first test signal according to embodiment 1 of the present invention;
FIG. 6 is an output power spectrum derived from the first test signal shown in FIG. 5;
FIG. 7 is a further schematic diagram of the first test signal of embodiment 1 of the present invention;
FIG. 8 is a further schematic diagram of the first test signal of embodiment 1 of the present invention;
FIG. 9 is a schematic block diagram showing the constitution of a nonlinear characteristic test system according to embodiment 2 of the present invention;
fig. 10 is a schematic diagram of a nonlinear characteristic testing method of a coherent optical receiver according to embodiment 3 of the present invention;
fig. 11 is a schematic diagram of a method for measuring nonlinear noise power at least one of frequencies in the bandwidth of the coherent optical receiver instep 1001 according to embodiment 3 of the present invention.
Detailed Description
In the embodiments of the present invention, the terms "first", "second", and the like are used for distinguishing different elements by name, but do not denote a spatial arrangement, a temporal order, or the like of the elements, and the elements should not be limited by the terms. The term "and/or" includes any and all combinations of one or more of the associated listed terms. The terms "comprising," "including," "having," and the like, refer to the presence of stated features, elements, components, and do not preclude the presence or addition of one or more other features, elements, components, and elements.
In embodiments of the invention, the singular forms "a", "an", and the like include the plural forms and are to be construed broadly as "a" or "an" and not limited to the meaning of "a" or "an"; furthermore, the term "comprising" should be understood to include both the singular and the plural, unless the context clearly dictates otherwise. Further, the term "according to" should be understood as "at least partially according to … …," and the term "based on" should be understood as "based at least partially on … …," unless the context clearly dictates otherwise.
The foregoing and other features of the invention will become apparent from the following description taken in conjunction with the accompanying drawings. In the description and drawings, particular embodiments of the invention have been disclosed in detail as being indicative of some of the embodiments in which the principles of the invention may be employed, it being understood that the invention is not limited to the embodiments described, but, on the contrary, is intended to cover all modifications, variations, and equivalents falling within the scope of the appended claims.
Example 1
The embodiment of the invention provides a nonlinear characteristic testing device of a coherent optical receiver, which is arranged at an optical receiver end of an optical communication system.
Fig. 1 is a schematic diagram of a nonlinear characteristic testing apparatus of a coherent optical receiver according to embodiment 1 of the present invention. As shown in fig. 1, the nonlinearcharacteristic testing apparatus 100 of the coherent optical receiver includes:
ameasurement unit 110 that measures nonlinear noise power at each frequency within the bandwidth of the coherent optical receiver; and
and adetermination unit 120 for determining a nonlinear noise power spectrum of the coherent optical receiver from nonlinear noise powers at respective frequencies within a bandwidth of the coherent optical receiver.
In the present embodiment, themeasuring part 110 measures the nonlinear noise power at each frequency within the bandwidth of the coherent optical receiver, and the determiningpart 120 determines the nonlinear noise power spectrum of the coherent optical receiver, that is, the nonlinear noise power spectrum of the coherent optical receiver within the whole bandwidth according to the nonlinear noise power at each frequency.
In this embodiment, the bandwidth of the coherent optical receiver may be a bandwidth of 10GHz or more, for example, 20GHz or more, and a specific example is 37GHz, but the bandwidth of the coherent optical receiver is not limited in the embodiments of the present invention.
Fig. 2 is a schematic view of themeasurement unit 110 according to embodiment 1 of the present invention, and as shown in fig. 2, themeasurement unit 110 includes:
a firstsignal generating section 111 that generates a first test signal having at least one band notch whose center frequency corresponds to at least one frequency within a bandwidth of the coherent optical receiver;
afirst determination unit 112 that determines the frequency of the local oscillator laser based on the frequency range of the first test signal and at least one notch of the first test signal;
a first power measuringunit 113 that inputs the first test signal and laser light output from the local oscillator laser to the coherent optical receiver and measures an output power spectrum of the coherent optical receiver; and
asecond determination section 114 that determines a nonlinear noise power at the at least one frequency in the output power spectrum from the at least one notched center frequency of the first test signal.
In this way, by generating a test signal with a notch, determining the frequency of the local oscillator laser according to the frequency range of the test signal and the notch of the test signal, outputting the test signal and the laser output by the local oscillator laser to the coherent optical receiver to be tested, and determining the nonlinear noise power at the corresponding frequency in the output spectrum of the coherent optical receiver according to the center frequency with the notch in the test signal, for the coherent optical receiver in the optical communication system with a higher communication baud rate, the nonlinear characteristic of the coherent optical receiver can be accurately measured, and the constellation diagram of the signal does not need to be restored, so that the measurement and processing process is simple, and in addition, because the notch has a certain bandwidth, the measurement method has a certain robustness for resisting frequency offset.
In the present embodiment, the firstsignal generating section 111 generates the first test signal having at least one band notch whose center frequency corresponds to the at least one frequency. In addition, at the center frequency of the band notch, the signal amplitude is 0 or close to 0.
In this embodiment, the first test signal has at least one band notch, and the number and distribution position of the band notches and the bandwidth of each band notch can be set according to actual needs.
In the present embodiment, the structure of the firstsignal generating section 111 and the method of generating the first test signal may refer to the related art. For example, the firstsignal generation section 111 includes a signal source, a laser, and a modulator.
In this embodiment, the frequency range of the first test signal is determined according to the bandwidth of the coherent optical receiver.
For example, the frequency range of the first test signal is the same as the coherent optical receiver bandwidth, for which case the present embodiment refers to the band notch in this case as a "single-side band notch", and for which case the first test signal may have M band notches, the center frequency of each band notch being the frequency of the center of the band notch bandwidth from one boundary of the first test signal, M being a positive integer.
For the case of the single-side band trap, thefirst determination section 112 aligns the frequency of the local oscillator laser to one boundary frequency of the first test signal; when the first test signal has M notches, themeasurement section 110 can obtain the nonlinear noise power at M frequencies, the center frequencies of which are the M frequencies, respectively, at each measurement.
The firstpower measuring section 113 inputs the first test signal and laser light output from the local oscillator laser to a coherent optical receiver, and measures an output power spectrum of the coherent optical receiver, and the second determiningsection 114 determines a nonlinear noise power at least one band-notched center frequency in the output power spectrum, based on the at least one band-notched center frequency of the first test signal. Since the signal amplitude at the center frequency of the band notch in the first test signal is 0 or close to 0, the output power at the center frequency in the output power spectrum is the nonlinear noise power.
In this embodiment, the firstpower measuring unit 113 may measure the output power spectrum of the coherent optical receiver by using a correlation technique, for example, measure one path of the output of the coherent optical receiver, for example, the I path of the X polarization state by using an electric spectrometer.
For single-side notches, the present embodiment is described by taking the example that the first test signal has 1 and 2 notches, but the number of notches is not limited by the embodiment of the present invention.
Fig. 3 is a schematic diagram of a first test signal according to embodiment 1 of the present invention. As shown in FIG. 3, the frequency range F of the first test signal is equal to the coherent optical receiver bandwidth B, the first test signal has a band notch with a center frequency ω1And aligning the frequency of the local oscillator laser to the frequency of the left boundary of the first test signal.
Fig. 4 is an output power spectrum obtained from the first test signal shown in fig. 3. As shown in FIG. 4, a notch is formed in the output power spectrum, and the center frequency of the notch is the center frequency ω of the notch in FIG. 31Since the amplitude of the signal at the center frequency of the band notch is 0 or close to 0, the center frequency ω is1The output power is the frequency omega1The nonlinear noise power of (d).
Fig. 5 is another schematic diagram of the first test signal according to embodiment 1 of the present invention. As shown in FIG. 5, the frequency range F of the first test signal is equal to the coherent optical receiver bandwidth B, the first test signal has 2 band notches, and the center frequencies of the band notches are ω1And ω2。
Fig. 6 is an output power spectrum obtained for the first test signal shown in fig. 5. As shown in FIG. 6, 2 notches are formed in the output power spectrum, and the center frequencies of the 2 notches are the center frequencies ω of the 2 notches in FIG. 3, respectively1And ω2Since the amplitude of the signal at the center frequency of the band notch is 0 or close to 0, the center frequency ω is1And ω2The output power is the frequency omega1And ω2The nonlinear noise power of (d).
For another example, the frequency range of the first test signal is 2 times the bandwidth of the coherent optical receiver, for which case the present embodiment refers to the band notch in this case as "double-sideband notch", for which case the first test signal has 2N band notches, each two of the 2N band notches are symmetric about the center frequency of the first test signal, N is an integer greater than or equal to 1, and the center frequency of each band notch is the frequency at which the center of the bandwidth of the band notch is away from the center frequency of the first test signal.
For the case of double-sideband trap, thefirst determination section 112 aligns the frequency of the local oscillator laser with the center frequency of the first test signal; when the first test signal has 2N notches, themeasurement section 110 can obtain the nonlinear noise power at N frequencies each measurement, and N center frequencies of the 2N notches are the N frequencies, respectively.
The firstpower measuring unit 113 inputs the first test signal and laser light output from the local oscillator laser to the coherent optical receiver, and measures an output power spectrum of the coherent optical receiver, and the second determiningunit 114 determines nonlinear noise power at N center frequencies in the output power spectrum, based on the N center frequencies with 2N notches included in the first test signal. Since the signal amplitude at the center frequency of the band notch in the first test signal is 0 or close to 0, the output power at the center frequency in the output power spectrum is the nonlinear noise power.
For double-side band notch, the present embodiment is described by taking the example that the first test signal has 2 and 4 band notches, but the number of band notches is not limited by the embodiment of the present invention.
Fig. 7 is another schematic diagram of the first test signal according to embodiment 1 of the present invention. As shown in FIG. 7, the frequency range F of the first test signal is 2 times the bandwidth B of the coherent optical receiver, the first test signal has 2 notches that are symmetric about the center frequency of the first test signal, and the center frequencies of the 2 notches each correspond to ω1And aligning the frequency of the local oscillator laser to the central frequency of the first test signal.
The first test signal shown in fig. 7 and the first test signal shown in fig. 3 have the same output power spectrum, i.e., the output power spectrum shown in fig. 4. As shown in FIG. 4, a notch is formed in the output power spectrum, and the center frequency of the notch is the center frequency ω corresponding to the 2 notches in FIG. 71Since the amplitude of the signal at the center frequency of the band notch is 0 or close to 0, the center frequency ω is1The output power is the frequency omega1The nonlinear noise power of (d).
Fig. 8 is another schematic diagram of the first test signal according to embodiment 1 of the present invention. As shown in FIG. 8, the frequency range F of the first test signal is equal to 2 times the bandwidth B of the coherent optical receiverThe first test signal has 4 band notches, the 4 band notches are symmetric with respect to the center frequency of the first test signal in pairs, and the center frequencies of the two pairs of the 4 band notches correspond to omega respectively1And ω2。
The first test signal shown in fig. 8 and the first test signal shown in fig. 5 have the same output power spectrum, i.e., the output power spectrum shown in fig. 6. As shown in FIG. 6, 2 notches are formed in the output power spectrum, and the center frequencies of the 2 notches are the center frequencies ω corresponding to two pairs of the 4 notches in FIG. 81And ω2Since the amplitude of the signal at the center frequency of the band notch is 0 or close to 0, the center frequency ω is1And ω2The output power is the frequency omega1And ω2The nonlinear noise power of (d).
The above is exemplified by the case that the first test signal has a single side band notch and a double side band notch, and for the case that the first test signal has a single side band notch, the requirement on the generating device of the first test signal is lower, and only the frequency range of the first test signal is required to be the bandwidth of the coherent optical receiver; for the case where the first test signal has double side band notches, the frequency range of the first test signal is 2 times the coherent optical receive bandwidth, which is more compatible with existing systems.
In the present embodiment, themeasurement section 110 can obtain the nonlinear noise power at least one of the frequencies within the bandwidth of the coherent optical receiver in one measurement, and the measurement process described above is repeated by changing the center frequency of the notch that the first test signal has, thereby obtaining the nonlinear noise power at all the frequencies within the bandwidth of the coherent optical receiver.
Thedetermination section 120 determines a nonlinear noise power spectrum of the coherent optical receiver from nonlinear noise powers at respective frequencies within a bandwidth of the coherent optical receiver. For example, the nonlinear noise power at each frequency in the bandwidth of the coherent optical receiver is a curve formed by the nonlinear noise power at each frequency in the bandwidth of the coherent optical receiver, i.e. the nonlinear noise power spectrum of the coherent optical receiver.
In this embodiment, as shown in fig. 1, the nonlinearcharacteristic testing apparatus 100 of the coherent optical receiver may further include:
a second signal generating section 130 that generates a second test signal having no band notch;
a second power measuring unit 140 that inputs the second test signal and the laser light output from the local oscillator laser to the coherent optical receiver to obtain a signal power spectrum of the coherent optical receiver; and
and a calculation unit 150 for calculating a nonlinear noise-to-signal ratio of the coherent optical receiver based on the signal power spectrum and the nonlinear noise power spectrum of the coherent optical receiver.
In the present embodiment, the second signal generating unit 130 and the firstsignal generating unit 110 may be independent components or may be the same component.
In this embodiment, the second test signal is a second test signal without a band notch, the second test signal and the first test signal having the same frequency range and amplitude.
For example, the second test signal differs from the first test signal shown in fig. 3, 5, 7, 8 only in that no band-notch is generated at the band-notch of the first test signal, but maintains the same amplitude as at other frequencies.
In the present embodiment, the second power measuring unit 140 and the firstpower measuring unit 113 may be independent components or may be the same component. The second power measurement unit 140 may measure the signal power spectrum by the same method as the method used by the firstpower measurement unit 113 to measure the output power spectrum.
For example, the signal power spectrum measured by the second power measurement section 140 is different from the output power spectrum shown in fig. 4 and 6 only in that the signal power spectrum does not have a notch due to a band notch.
In this embodiment, the calculating unit 150 calculates the nonlinear noise-to-signal ratio of the coherent optical receiver based on the signal power spectrum of the coherent optical receiver and the nonlinear noise power spectrum obtained by the determiningunit 120, and a specific calculating method may refer to a related art.
For example, the power spectrum of the signal in decibel-milliwatt (dBm) is directly subtracted from the power spectrum of the nonlinear noise, so as to obtain the nonlinear noise-signal ratio of the coherent optical receiver at each frequency within the bandwidth.
In addition, in the present embodiment, the nonlinear characteristic measured by the nonlinearcharacteristic testing apparatus 100 is related to the output power of the local oscillator laser, that is, the measured nonlinear characteristic is different for different output powers of the local oscillator lasers. Therefore, the output power of the local oscillator laser when the nonlinearcharacteristic testing device 100 measures the nonlinear characteristic can be determined according to the output power of the local oscillator laser actually used in the optical communication system, and therefore, the device can have good compatibility with the existing system.
It can be known from the above embodiments that, by generating a test signal with a notch, determining the frequency of a local oscillator laser according to the frequency range of the test signal and the notch of the test signal, outputting the test signal and the laser output by the local oscillator laser to a coherent optical receiver to be tested, and determining the nonlinear noise power at a corresponding frequency in the output spectrum of the coherent optical receiver according to the center frequency of the notch in the test signal, in this way, for a coherent optical receiver in an optical communication system with a higher communication baud rate, the nonlinear characteristic of the coherent optical receiver can be accurately measured, and there is no need to recover the constellation diagram of the signal, the measurement and processing process is simple, and in addition, since the notch has a certain bandwidth, the measurement method has a certain robustness against frequency offset.
Example 2
The embodiment of the present invention further provides a nonlinear characteristic testing system, which corresponds to the nonlinear characteristic testing apparatus of the coherent optical receiver according to embodiment 1, and the same contents are not repeated.
Fig. 9 is a schematic block diagram of the configuration of the nonlinear characteristic test system in embodiment 2 of the present invention. As shown in fig. 9, the nonlinearcharacteristic test system 900 includes: a test signal generating device 910, alocal oscillator laser 920, anelectric spectrum instrument 930, aprocessing device 940 and a coherent optical receiver 950 to be tested.
In the present embodiment, the test signal generating means 910 corresponds to the firstsignal generating section 110 and the second signal generating section 130 in embodiment 1, thelocal oscillator laser 920 corresponds to the local oscillator laser in embodiment 1, thespectrometer 930 corresponds to the firstpower measuring section 113 and the second power measuring section 140 in embodiment 1, and the processing means 940 corresponds to the first determiningsection 112, the second determiningsection 114, the determiningsection 120, and the calculating section 150 in embodiment 1.
As shown in fig. 9, the test signal generating device 910 generates a first test signal with at least one band gap, and the processing device 940 determines the frequency of the local oscillator laser 920 according to the parameter of the first test signal, i.e. the frequency range and the at least one band gap of the first test signal; the first test signal generated by the test signal generating device 910 and the laser output by the local oscillator laser 920 are input to the coherent optical receiver 950 together, and the electric spectrum instrument 930 measures the I-path signal of the X polarization state output by the coherent optical receiver 950 to obtain the output power spectrum of the coherent optical receiver 950; processing means 940 determines a nonlinear noise power at least one frequency in the output power spectrum from the notched center frequency of the first test signal; changing the frequency of the band notch in the first test signal, and repeating the measurement process to obtain the nonlinear noise power at each frequency in the bandwidth of the coherent optical receiver; the processing device 940 determines a nonlinear noise power spectrum of the coherent optical receiver according to nonlinear noise power at each frequency within a bandwidth of the coherent optical receiver; the test signal generating device 910 generates a second test signal without band notch, the second test signal and the laser output by the local oscillator laser 920 are input to the coherent optical receiver 950, and the electric spectrum meter 930 measures the I-path signal of the X polarization state output by the coherent optical receiver 950 to obtain a signal power spectrum of the coherent optical receiver 950; the processing device 940 calculates the nonlinear noise-to-signal ratio of the coherent optical receiver according to the signal power spectrum and the nonlinear noise power spectrum of the coherent optical receiver.
In this embodiment, the functions of theprocessing device 940 may be executed by a stand-alone electronic device, such as a computer, or may be executed by a Processor of a coherent optical receiver, such as a Digital Signal Processor (DSP) of the receiver.
It can be known from the above embodiments that, by generating a test signal with a notch, determining the frequency of a local oscillator laser according to the frequency range of the test signal and the notch of the test signal, outputting the test signal and the laser output by the local oscillator laser to a coherent optical receiver to be tested, and determining the nonlinear noise power at a corresponding frequency in the output spectrum of the coherent optical receiver according to the center frequency of the notch in the test signal, in this way, for a coherent optical receiver in an optical communication system with a higher communication baud rate, the nonlinear characteristic of the coherent optical receiver can be accurately measured, and there is no need to recover the constellation diagram of the signal, the measurement and processing process is simple, and in addition, since the notch has a certain bandwidth, the measurement method has a certain robustness against frequency offset.
Example 3
The embodiment of the invention also provides a nonlinear characteristic testing method of the coherent optical receiver, which corresponds to the nonlinear characteristic testing device of the coherent optical receiver in the embodiment 1.
Fig. 10 is a schematic diagram of a method for testing the nonlinear characteristic of the coherent optical receiver according to embodiment 3 of the present invention. Such as
As shown in fig. 10, the method includes:
step 1001: respectively measuring the nonlinear noise power at each frequency in the bandwidth of the coherent optical receiver; and
step 1002: determining a nonlinear noise power spectrum of the coherent optical receiver from nonlinear noise power at various frequencies within a bandwidth of the coherent optical receiver.
Fig. 11 is a schematic diagram of a method for measuring nonlinear noise power at least one of frequencies in the bandwidth of the coherent optical receiver instep 1001 according to embodiment 3 of the present invention. As shown in fig. 11, the method includes:
step 1101: generating a first test signal having at least one band notch, a center frequency of the at least one band notch corresponding to at least one frequency within a bandwidth of the coherent optical receiver;
step 1102: determining the frequency of the local oscillator laser according to the frequency range of the first test signal and at least one band notch of the first test signal;
step 1103: inputting the first test signal and the laser output by the local oscillator laser into the coherent optical receiver, and measuring the output power spectrum of the coherent optical receiver; and
step 1104: the nonlinear noise power at the at least one frequency in the output power spectrum is determined based on the at least one notched center frequency of the first test signal.
In the present embodiment, the execution of the above steps can refer to the implementation of the functions of the components in embodiment 1, and the description is not repeated here.
It can be known from the above embodiments that, by generating a test signal with a notch, determining the frequency of a local oscillator laser according to the frequency range of the test signal and the notch of the test signal, outputting the test signal and the laser output by the local oscillator laser to a coherent optical receiver to be tested, and determining the nonlinear noise power at a corresponding frequency in the output spectrum of the coherent optical receiver according to the center frequency of the notch in the test signal, in this way, for a coherent optical receiver in an optical communication system with a higher communication baud rate, the nonlinear characteristic of the coherent optical receiver can be accurately measured, and there is no need to recover the constellation diagram of the signal, the measurement and processing process is simple, and in addition, since the notch has a certain bandwidth, the measurement method has a certain robustness against frequency offset.
An embodiment of the present invention further provides a computer-readable program, where when the program is executed in a nonlinear characteristic testing apparatus or a nonlinear characteristic testing system of a coherent optical receiver, the program causes a computer to execute the nonlinear characteristic testing method of the coherent optical receiver described in embodiment 3 in the nonlinear characteristic testing apparatus or the nonlinear characteristic testing system of the coherent optical receiver.
An embodiment of the present invention further provides a storage medium storing a computer-readable program, where the computer-readable program enables a computer to execute the method for testing nonlinear characteristics of a coherent optical receiver described in embodiment 3 in a nonlinear characteristic testing apparatus or a nonlinear characteristic testing system of the coherent optical receiver.
The method for performing nonlinear characteristic testing in the nonlinear characteristic testing apparatus or the nonlinear characteristic testing system of the coherent optical receiver described in connection with the embodiments of the present invention may be directly embodied as hardware, a software module executed by a processor, or a combination of the two. For example, one or more of the functional block diagrams and/or one or more combinations of the functional block diagrams illustrated in fig. 1 and 2 may correspond to individual software modules of a computer program flow or individual hardware modules. These software modules may correspond to the corresponding steps shown in fig. 10 and 11, respectively. These hardware modules may be implemented, for example, by solidifying these software modules using a Field Programmable Gate Array (FPGA).
A software module may reside in RAM memory, flash memory, ROM memory, EPROM memory, EEPROM memory, registers, hard disk, a removable disk, a CD-ROM, or any other form of storage medium known in the art. A storage medium may be coupled to the processor such that the processor can read information from, and write information to, the storage medium; or the storage medium may be integral to the processor. The processor and the storage medium may reside in an ASIC. The software module may be stored in the memory of the mobile terminal or in a memory card that is insertable into the mobile terminal. For example, if the apparatus (e.g., mobile terminal) employs a relatively large capacity MEGA-SIM card or a large capacity flash memory device, the software module may be stored in the MEGA-SIM card or the large capacity flash memory device.
One or more of the functional block diagrams and/or one or more combinations of the functional block diagrams described with respect to fig. 1 and 2 may be implemented as a general purpose processor, a Digital Signal Processor (DSP), an Application Specific Integrated Circuit (ASIC), a Field Programmable Gate Array (FPGA) or other programmable logic device, discrete gate or transistor logic, discrete hardware components, or any suitable combination thereof designed to perform the functions described herein. One or more of the functional block diagrams and/or one or more combinations of the functional block diagrams described with respect to fig. 1 may also be implemented as a combination of computing devices, e.g., a combination of a DSP and a microprocessor, a plurality of microprocessors, one or more microprocessors in conjunction with a DSP communication, or any other such configuration.
While the invention has been described with reference to specific embodiments, it will be apparent to those skilled in the art that these descriptions are illustrative and not intended to limit the scope of the invention. Various modifications and alterations of this invention will become apparent to those skilled in the art based upon the spirit and principles of this invention, and such modifications and alterations are also within the scope of this invention.
Claims (10)
1. An apparatus for testing nonlinear characteristics of a coherent optical receiver, the apparatus comprising:
a measuring section that measures nonlinear noise power at each frequency within a bandwidth of the coherent optical receiver, respectively; and
a determination section that determines a nonlinear noise power spectrum of the coherent optical receiver from nonlinear noise powers at respective frequencies within a bandwidth of the coherent optical receiver,
wherein the measuring section includes:
a first signal generating section that generates a first test signal having at least one band notch whose center frequency corresponds to at least one frequency within a bandwidth of the coherent optical receiver;
a first determination unit configured to determine a frequency of the local oscillator laser based on a frequency range of the first test signal and at least one notch of the first test signal;
a first power measuring unit that inputs the first test signal and the laser light output from the local oscillator laser to the coherent optical receiver and measures an output power spectrum of the coherent optical receiver; and
a second determination section that determines a nonlinear noise power at the at least one frequency in the output power spectrum from a center frequency of the at least one notch that the first test signal has.
2. The apparatus of claim 1, wherein the apparatus further comprises:
a second signal generating section that generates a second test signal having no band trap;
a second power measuring unit configured to input the second test signal and the laser light output from the local oscillator laser to the coherent optical receiver to obtain a signal power spectrum of the coherent optical receiver; and
and a calculation unit that calculates a nonlinear noise-to-signal ratio of the coherent optical receiver from the signal power spectrum and the nonlinear noise power spectrum of the coherent optical receiver.
3. The apparatus of claim 1, wherein,
the center frequency of the at least one notch of the first test signal generated by the first signal generating section is the at least one frequency,
the first determining section aligns a frequency of the local oscillator laser with a boundary frequency of the first test signal.
4. The apparatus of claim 1, wherein,
the first test signal generated by the first signal generation section has 2N notches, each two notches of the 2N notches being symmetric with respect to a center frequency of the first test signal, N being an integer greater than or equal to 1;
the first determination section aligns the frequency of the local oscillator laser with the center frequency of the first test signal,
the second determination section determines nonlinear noise power at the N center frequencies in the at least one frequency in the output power spectrum from the N center frequencies of the 2N notches that the first test signal has.
5. The apparatus of claim 1, wherein,
the frequency range of the first test signal is determined according to the bandwidth of the coherent optical receiver.
6. A method for testing nonlinear characteristics of a coherent optical receiver, the method comprising:
respectively measuring the nonlinear noise power at each frequency in the bandwidth of the coherent optical receiver; and
determining a nonlinear noise power spectrum of the coherent optical receiver from nonlinear noise powers at various frequencies within a bandwidth of the coherent optical receiver,
wherein measuring nonlinear noise power at least one of the frequencies within a bandwidth of the coherent optical receiver comprises:
generating a first test signal having at least one band notch, a center frequency of the at least one band notch corresponding to at least one frequency within a bandwidth of the coherent optical receiver;
determining the frequency of a local oscillator laser according to the frequency range of the first test signal and at least one band notch of the first test signal;
inputting the first test signal and laser output by the local oscillator laser into the coherent optical receiver, and measuring an output power spectrum of the coherent optical receiver; and
determining a nonlinear noise power at the at least one frequency in the output power spectrum from the at least one notched center frequency of the first test signal.
7. The method of claim 6, wherein the method further comprises:
generating a second test signal without band notch, and inputting the second test signal and laser output by the local oscillator laser into the coherent optical receiver to obtain a signal power spectrum of the coherent optical receiver; and
and calculating the nonlinear noise signal ratio of the coherent optical receiver according to the signal power spectrum and the nonlinear noise power spectrum of the coherent optical receiver.
8. The method of claim 6, wherein,
the center frequency of the at least one notch of the first test signal is the at least one frequency,
determining the frequency of the local oscillator laser according to the frequency range of the first test signal and the at least one notch of the first test signal, including: and aligning the frequency of the local oscillator laser to a boundary frequency of the first test signal.
9. The method of claim 6, wherein,
the first test signal has 2N notches, each two of the 2N notches being symmetric about a center frequency of the first test signal, N being an integer greater than or equal to 1;
determining the frequency of the local oscillator laser according to the frequency range of the first test signal and the at least one notch of the first test signal, including: aligning the frequency of the local oscillator laser to the center frequency of the first test signal,
said determining a nonlinear noise power at said at least one frequency in said output power spectrum from at least one notched center frequency that said first test signal has, comprising: determining a nonlinear noise power at the N center frequencies in the at least one frequency in the output power spectrum from the N center frequencies of the 2N notches that the first test signal has.
10. The method of claim 6, wherein,
the frequency range of the first test signal is determined according to the bandwidth of the coherent optical receiver.
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