WO2023144880A1 - 光送信機、光受信機、光送信方法及び光受信方法 - Google Patents

光送信機、光受信機、光送信方法及び光受信方法 Download PDF

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Publication number
WO2023144880A1
WO2023144880A1 PCT/JP2022/002651 JP2022002651W WO2023144880A1 WO 2023144880 A1 WO2023144880 A1 WO 2023144880A1 JP 2022002651 W JP2022002651 W JP 2022002651W WO 2023144880 A1 WO2023144880 A1 WO 2023144880A1
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Prior art keywords
optical
signal
narrowband
wideband
modulated signal
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PCT/JP2022/002651
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English (en)
French (fr)
Japanese (ja)
Inventor
福太郎 濱岡
政則 中村
孝行 小林
宗彦 長谷
斉 脇田
裕史 山崎
義弘 小木曽
裕 宮本
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NTT Inc
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Nippon Telegraph and Telephone Corp
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Priority to PCT/JP2022/002651 priority Critical patent/WO2023144880A1/ja
Priority to JP2023576280A priority patent/JP7689277B2/ja
Priority to US18/730,707 priority patent/US20250233670A1/en
Publication of WO2023144880A1 publication Critical patent/WO2023144880A1/ja
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    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04J—MULTIPLEX COMMUNICATION
    • H04J14/00—Optical multiplex systems
    • H04J14/02—Wavelength-division multiplex systems
    • H04J14/0201—Add-and-drop multiplexing
    • H04J14/0202—Arrangements therefor
    • 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
    • H04B10/50—Transmitters
    • 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
    • H04B10/50—Transmitters
    • H04B10/501—Structural aspects
    • 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
    • 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
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04J—MULTIPLEX COMMUNICATION
    • H04J14/00—Optical multiplex systems
    • H04J14/02—Wavelength-division multiplex systems

Definitions

  • the present invention relates to an optical transmitter, an optical receiver, an optical transmission method, and an optical reception method.
  • IC-TROSA integrated coherent transmit-receiver optical subassembly
  • Non-Patent Document 2 describes a configuration incorporating a semiconductor optical amplifier as an optical preamplifier for an IC-TROSA with a data transmission rate of 400-600 Gb/s and a symbol rate of 64 GBd.
  • Kitayama “Experimental Study on Impact of SOA Nonlinear Phase Noise in 40Gbps Coherent 16QAM Transmissions,” ECOC2012, P1.04.
  • the symbol rate of optically modulated signals handled by optical transceivers is usually several tens of GBd.
  • the fluctuation time of the optical modulated signal is the reciprocal of the symbol rate, which is approximately several tens of ps.
  • the carrier lifetime of a semiconductor optical amplifier is usually several hundred ps, which is close to the fluctuation time of an optical modulated signal.
  • One aspect of the present invention is an optical transmitter comprising: a multiplexed signal generator that multiplexes a plurality of narrowband signals to generate a broadband optical modulated signal; and a semiconductor optical amplifier that amplifies the intensity of the wideband optical modulated signal.
  • One aspect of the present invention is an optical receiver comprising a semiconductor optical amplifier that amplifies the intensity of a wideband modulated optical signal, and a demultiplexer that separates the wideband modulated optical signal into narrowband signals.
  • An aspect of the present invention is an optical transmission method comprising: a multiplexed signal generating step of multiplexing a plurality of narrowband signals to generate a broadband optical modulated signal; and a semiconductor optical amplification step of amplifying the intensity of the wideband optical modulated signal.
  • One aspect of the present invention is an optical receiving method comprising a semiconductor optical amplification step of amplifying the intensity of a broadband optical modulated signal, and a demultiplexing step of demultiplexing the wideband optical modulated signal into narrowband signals.
  • the technology of the present invention can reduce the effects of nonlinear distortion caused by semiconductor optical amplifiers.
  • FIG. 1 is a diagram showing the configuration of an optical transmission system 1 according to a first embodiment
  • FIG. 1 is a diagram showing the configuration of an optical transmitter 2 according to a first embodiment
  • FIG. 4 is a flow chart showing the operation of the optical transmitter 2 according to the first embodiment; It is a modification of the optical transmitter 2 according to the first embodiment.
  • 1 is a diagram showing the configuration of an optical receiver 4 according to a first embodiment
  • FIG. 4 is a flow chart showing the operation of the optical receiver 4 according to the first embodiment
  • FIG. 3 is a diagram showing the configuration of an optical transmitter 2 according to a second embodiment
  • FIG. 8 is a flow chart showing the operation of the optical transmitter 2 according to the second embodiment
  • FIG. 4 is a diagram showing the configuration of an optical receiver 4 according to a second embodiment
  • FIG. 9 is a flow chart showing the operation of the optical receiver 4 according to the second embodiment
  • FIG. 11 is a diagram showing configurations of a digital signal processing unit 21 and a digital signal processing unit 43 according to a third embodiment
  • It is a table
  • 4 is a graph showing the relationship between the magnitude of the injection current (SOA injection current) to the semiconductor optical amplifier and the SNR penalty; It is a figure which shows the optical transmitter-receiver 100 which concerns on this embodiment.
  • 1 is a diagram showing an optical transceiver 100 that performs polarization multiplexing according to this embodiment;
  • FIG. 1 is a diagram showing the configuration of an optical transmission system 1 according to the first embodiment.
  • the optical transmission system 1 is communication equipment using optical signals.
  • the optical transmission system comprises an optical transmitter 2 , a transmission line 3 and an optical receiver 4 .
  • the optical transmitter 2 is a communication device that transmits optical signals.
  • the transmission line 3 transmits an optical signal transmitted from the optical transmitter 2 to the optical receiver 4 .
  • the optical receiver 4 is a communication device that receives optical signals.
  • FIG. 2 is a diagram showing the configuration of the optical transmitter 2 according to the first embodiment.
  • the optical transmitter 2 comprises a digital signal processor 21 , a multiplexed signal generator 22 and a semiconductor optical amplifier 23 .
  • the multiplexed signal generator 22 is implemented by a broadband signal generator 221 , an optical modulator 222 and a signal light source 223 .
  • the digital signal processing unit 21 includes a signal generation unit 211, a band division unit 212, a narrow band signal processing unit 213, and a digital-analog conversion unit 214.
  • Signal generation section 211 generates a modulated signal sequence (I(n), Q(n)) from a transmission data sequence, which is binary information.
  • I(n) and Q(n) are electrical signals representing the in-phase and quadrature components of the modulated signal.
  • Signal generating section 211 outputs the generated modulated signal sequence (I(n), Q(n)) to band dividing section 212 .
  • Band division section 212 divides the modulated signal sequence input from signal generation section 211 into narrowband signals, and inputs the narrowband signals to narrowband signal processing section 213 .
  • a narrowband signal is a signal whose band is narrower than the modulated signal sequence.
  • the narrowband signal processing unit 213 performs addition and subtraction processing of the narrowband signals and inputs them to the digital-analog conversion unit 214 .
  • the digital-analog converter 214 converts the modulated signal sequence input from the narrowband signal processor 213 into an analog signal.
  • the digital-analog converter 214 converts the converted analog signal sequences (I 1 ′′(t), Q 1 ′′(t)) and (I 2 ′′(t), Q 2 ′′(t)) into broadband Output to the signal generator 221 .
  • the wideband signal generator 221 generates a wideband signal from a plurality of narrowband analog signals preprocessed by the band divider 212 and the narrowband signal processor 213 and input from the digital-analog converter 214 . Division of the modulated signal sequence into narrowband signals in the band division unit 212, addition and subtraction processing of the narrowband signals in the narrowband signal processing unit 213, and wideband processing from a plurality of narrowband analog signals in the wideband signal generation unit 221.
  • Signal generation can be implemented in any manner. For example, using the method disclosed in Japanese Patent Application Laid-Open No. 2018-019255 results in the following processing.
  • Band dividing section 212 divides the modulated signal sequence (I(n), Q(n)) input from signal generating section 211 into an upper sideband and a lower sideband, and frequency-shifts them.
  • the band dividing unit 212 divides the frequency-shifted upper sideband signal (narrowband signal, (I 1 '(n), Q 1 '(n)) and lower sideband signal (narrowband signal (I 2 '(n) , Q 2 ′(n)) to the narrowband signal processing unit 213 .
  • Narrowband signal processing section 213 performs at least one of addition processing and subtraction processing between the upper sideband signal and the lower sideband signal input from band dividing section 212. conduct.
  • the narrowband signal processing unit 213 processes the narrowband signals (I 1 ''(n), Q 1 ''(n) and (I 2 ''(n)) that have undergone at least one of addition and subtraction processing. , Q 2 ′′(n)) to the digital-analog converter 214 .
  • the wideband signal generation unit 221 frequency-shifts each of the plurality of analog signals input from the digital-analog conversion unit 214 .
  • the wideband signal generation unit 221 adds a plurality of frequency-shifted analog signals to generate a wideband signal.
  • the bandwidth of the wideband signal is greater than the bandwidth of the analog signal to be summed.
  • the wideband signal generator 221 outputs the generated wideband signals (I(t), Q(t)) to the optical modulator 222 . Since the wideband signal (I(t), Q(t)) is generated by adding a plurality of different frequency-shifted analog signal sequences, the frequency band of the wideband signal sequence is wider than that of the analog signal sequence.
  • the optical modulator 222 modulates the optical signal as a carrier wave output from the signal light source 223 with the broadband signal input from the wideband signal generator 221 to generate a wideband optical modulated signal.
  • the optical modulator 222 outputs the generated broadband optical modulated signal to the semiconductor optical amplifier 23 .
  • the semiconductor optical amplifier 23 amplifies the intensity of the broadband optical modulated signal input from the optical modulator 222 .
  • the semiconductor optical amplifier 23 outputs the amplified optical modulated signal to the optical receiver 4 via the transmission line 3 .
  • the modulation signal sequence may be divided into three or more narrowband signals and output from the digital/analog converter to generate a wideband optical modulation signal.
  • a configuration may be adopted in which a driver amplifier is inserted between the wideband signal generator 221 and the optical modulator 222 to amplify the wideband signal.
  • the multiplexed signal generator 22 may have a structure in which the broadband signal generator 221 and the optical modulator 222 are integrated.
  • a signal light source 223 and a driver amplifier may be added to the integrated multiplexed signal generator 22 and integrated.
  • the narrowband signal processing unit 213 may be configured as an analog circuit and inserted between the digital-analog converting unit 214 and the wideband signal generating unit 221 . Also, the narrowband signal processing unit 213 may be integrated by adding it to the integrated multiplexed signal generation unit 22 .
  • FIG. 3 is a flow chart showing the operation of the optical transmitter 2 according to the first embodiment.
  • the signal generator 211 generates a modulated signal (step S1).
  • the band division unit 212 converts the modulated signal into a narrowband signal (step S2).
  • the wideband signal generator 221 generates a wideband signal based on a plurality of narrowband signals (step S3).
  • the optical modulator 222 generates a wideband optical modulated signal based on the wideband signal (step S4).
  • the semiconductor optical amplifier 23 amplifies the broadband optical modulated signal (step S5).
  • the optical transmitter 2 according to the first embodiment generates a broadband signal wider than the narrowband signals based on a plurality of narrowband signals. Since the variation time of the wideband optical modulated signal is equal to the reciprocal of the optical signal bandwidth, the wideband optically modulated signal generated based on the wideband signal is faster than the optical modulated signal generated based on the narrower band signal than the wideband signal. is also a signal with a short fluctuation time. Therefore, the optical transmitter 2 according to the first embodiment can make the fluctuation time of the optical modulation signal sufficiently shorter than the carrier lifetime of the semiconductor optical amplifier. Therefore, the optical transmitter 2 according to the first embodiment can reduce the influence of nonlinear distortion caused by the semiconductor optical amplifier.
  • DACs digital-to-analog converters
  • ADCs analog-to-digital converters
  • CMOS Complementary Metal Oxide Semiconductor
  • the broadband signal generated by the optical transmitter 2 according to the first embodiment has a sufficiently wide band.
  • the optical transmitter 2 according to the first embodiment may have the configuration shown in FIG. As illustrated, the optical transmitter 2 according to the first embodiment outputs independent narrowband signals from a plurality of digital signal processing units (digital signal processing unit 21-1 and digital signal processing unit 21-2). and a wideband signal generated based on the independent narrowband signals.
  • the optical transmitter 2 includes two digital signal processing units 21 (21-1, 21- 2), the narrowband signal processor 213, the wideband signal generator 221, the optical modulator 222, and the signal light source 223, and the multiplexed signal generator 22.
  • a signal generator 211-1 of the digital signal processor 21-1 generates a modulated signal sequence (I 1 (n), Q 1 (n)), which is a narrowband signal, from a transmission data sequence, which is binary information. good too.
  • the signal generator 211-1 of the digital signal processor 21-1 may output the generated modulated signal sequence (I 1 (n), Q 1 (n)) to the digital-analog converter 214-1.
  • the signal generation unit 211-2 of the digital signal processing unit 21-2 generates a modulated signal sequence (I 2 (n), Q 2 (n)), which are narrowband signals, from the transmission data sequence, which is binary information. may be generated.
  • the signal generator 211-1 of the digital signal processor 21-2 may output the generated modulated signal sequence (I 2 (n), Q 2 (n)) to the digital-analog converter 214-1. .
  • the digital-analog converter 214-1 of the digital signal processor 21-1 may convert the modulated signal sequence input from the signal generator 211-1 into an analog signal.
  • the digital-analog converter 214-1 of the digital signal processor 21-1 may output the converted analog signals (I 1 (t), Q 1 (t)) to the narrowband signal processor 213.
  • the digital-analog converter 214-2 of the digital signal processor 21-2 may convert the modulated signal sequence input from the signal generator 211-2 into an analog signal.
  • the digital-analog converter 214-2 of the digital signal processor 21-2 may output the converted analog signals (I 2 (t), Q 2 (t)) to the narrowband signal processor 213.
  • the narrowband signal processing unit 213 is an analog signal input from the digital-analog conversion unit 214-1 of the digital signal processing unit 21-1 and the digital-analog conversion unit 214-2 of the digital signal processing unit 21-2. At least one of addition and subtraction of the narrowband signals may be performed on the narrowband signals.
  • the optical transmitter 2 need not perform the operation of converting the modulated signal into the narrowband signal (step S2 in the flowchart of FIG. 3). Also, the optical transmitter 2 shown in FIG. 4 may include three or more digital signal processing units 21 .
  • FIG. 5 is a diagram showing the configuration of the optical receiver 4 according to the first embodiment.
  • the optical receiver 4 comprises a semiconductor optical amplifier 41 , a demultiplexer 42 and a digital signal processor 43 .
  • the multiplexed signal separator 42 is implemented by a photoelectric converter 421 , a local light source 422 , a wideband signal-narrowband signal converter 423 and a narrowband signal processor 424 .
  • the semiconductor optical amplifier 41 amplifies the intensity of the broadband optical modulated signal received via the transmission line 3 .
  • the semiconductor optical amplifier 41 outputs the amplified optical signal to the photoelectric conversion section 421 .
  • the photoelectric conversion unit 421 converts the optical signal input from the semiconductor optical amplifier 41 into an electrical signal.
  • the photoelectric conversion unit 421 causes the broadband optical modulated signal input from the semiconductor optical amplifier 41 to interfere with the local light output from the local light source 422, thereby converting the optical signal into an analog wideband signal (I(t) , Q(t)).
  • the photoelectric converter 421 outputs the electrical signal to the wideband signal-narrowband signal converter 423 .
  • the photoelectric conversion unit 421 includes, for example, a 90-degree optical hybrid, a photodiode, and a transimpedance amplifier (TIA).
  • the photoelectric conversion unit 421 generates interference light from the optical signal input from the semiconductor optical amplifier 41 and local light by, for example, a 90-degree optical hybrid.
  • the in-phase and quadrature components of the interfering light are respectively input to photodiodes.
  • the current signal generated by the photodiode is converted into a voltage signal by the TIA, and the voltage signal is output to the wideband signal-narrowband signal converter 423 .
  • the wideband signal-narrowband signal converter 423 separates the wideband signal into a plurality of narrowband signals and inputs them to the narrowband signal processor 424 .
  • the narrowband signal processing unit 424 performs signal processing between narrowband signals and outputs the processed signals to the digital signal processing unit 43 .
  • Separation of a wideband signal into narrowband signals in the wideband signal-narrowband signal converter 423 and signal processing between narrowband signals in the narrowband signal processor 424 can be performed by any method. For example, using the method disclosed in International Publication No. 2019/031447 results in the following processing.
  • the wideband signal-narrowband signal conversion unit 423 divides the wideband signals (I(t), Q(t)) input from the photoelectric conversion unit 421 into a plurality of (two in this embodiment) wideband signals. do.
  • the wideband signal-narrowband signal converter 423 frequency-shifts the divided wideband signals to obtain narrowband signals.
  • the wideband signal-narrowband signal conversion unit 423 converts a plurality of frequency-shifted narrowband signals ((I 1 '(t), Q 1 '(t)), (I 2 '(t), Q 2 '(t) ) are respectively output to narrowband signal processing section 424.
  • Each of the narrowband signals is represented by (Equation 1).
  • Narrowband signal processing section 424 performs at least one of addition and subtraction processing of a plurality of narrowband signals input from wideband signal-narrowband signal conversion section 423 among the plurality of narrowband signals.
  • the narrowband signal processing unit 424 performs a plurality of narrowband signals ((I 1 (t), Q 1 (t)), (I 2 (t), Q 2 (t)) to the analog-digital converter 431 .
  • the narrow band signal processing section 424 may be configured to be provided in the decoding section 432 of the digital signal processing section 43 .
  • the digital signal processing section 43 includes an analog-digital conversion section 431 and a decoding section 432 .
  • the analog-to-digital converter 431 converts the narrow-band analog signal series input from the multiplexed signal separator 42 into digital signal series ((I 1 (n), Q 1 (n)), (I 2 (n), Q 2 (n))
  • the decoding unit 432 converts the narrowband signal into a wideband signal, equalizes the waveform distortion caused by the optical transmitter 2, the transmission line 3, and the optical receiver 4, and converts it into a digital signal. Decode the sequence.
  • the decoding unit 432 does not convert the narrowband signal into a wideband signal, and independently equalizes waveform distortion generated in the narrowband signal by the optical transmitter 2, the transmission line 3, and the optical receiver 4, and then converts the digital signal into a digital signal.
  • a configuration for decoding a sequence may be used.
  • FIG. 6 is a flow chart showing the operation of the optical receiver 4 according to the first embodiment.
  • the semiconductor optical amplifier 41 amplifies the broadband optical modulated signal received by the optical receiver 4 with the semiconductor optical amplifier (step S11).
  • the multiplexed signal demultiplexer 42 demultiplexes the wideband optical modulated signal into narrowband signals (step S12).
  • the digital signal processing unit 43 converts the narrowband analog signal series into a digital signal series by the analog-digital conversion unit 431, and decodes the narrowband signal by the decoding unit 432 (step S13).
  • the semiconductor optical amplifier 23 and the optical receiver 4 provided in the optical transmitter 2 The influence of nonlinear distortion caused by the provided semiconductor optical amplifier 41 can be reduced.
  • the optical receiver 4 according to the first embodiment may have the configuration shown in FIG. As illustrated, the optical receiver 4 according to the first embodiment may be configured to include a plurality of digital signal processing units 43 (a digital signal processing unit 43-1 and a digital signal processing unit 43-2). Also, the optical receiver 4 may be configured to include three or more digital signal processing units.
  • FIG. 8 is a diagram showing the configuration of the optical transmitter 2 according to the second embodiment.
  • the optical transmitter 2 according to the second embodiment multiplexes a plurality of modulated optical signals with different center wavelengths in a wavelength multiplexing section to generate a wideband modulated optical signal. It is characterized by generating
  • the optical transmitter 2 according to the second embodiment includes a plurality of digital signal processing units 21 (two in this embodiment).
  • the configuration of each digital signal processing section 21 according to the second embodiment is the same as that of the digital signal processing section 21 according to the first embodiment, and includes a band dividing section 212 and a narrow band signal processing section 213 .
  • a plurality of digital signal processing units 21 may be integrated into one digital signal processing unit 21 , and the band dividing unit 212 and the narrowband signal processing unit 213 may be provided.
  • the plurality of digital signal processing units 21 include only the signal generation unit 211 and the digital-analog conversion unit 214, and the I(n) and Q(n) signals are DA-converted without dividing the band. It may be something to do.
  • the multiplexed signal generator 22 does not include the broadband signal generator 221, and optically modulates the plurality of analog narrowband signals output from the plurality of digital signal processors 21, and multiplexes the wavelengths. good.
  • the optical transmitter 2 integrates a plurality of digital signal processing units 21 into one digital signal processing unit 21, and includes only the signal generation unit 211 and the digital-analog conversion unit 214, and transmits a plurality of narrowband signals. may be configured to output .
  • the multiplexed signal generator 22 includes a plurality of broadband signal generators 221 , optical modulators 222 and signal light sources 223 (two in this embodiment), and a wavelength multiplexer 224 . Further, the optical transmitter 2 according to the second embodiment does not include a plurality of signal light sources 223, and the signal light source 223 is a supercontinuum light source having a plurality of optical carriers. Signal light may be output to the modulation section 222 .
  • the optical modulation section 222 modulates each analog signal sequence input from the digital signal processing section 21 to generate an optical modulated signal.
  • the optical modulator 222 according to the second embodiment outputs the modulated optical signal to the wavelength multiplexer 224 .
  • the wavelength multiplexing unit 224 multiplexes the optical modulated signals input from the plurality of optical modulators 222 to generate a wideband optical modulated signal.
  • the frequency band of the wideband optical modulated signal is larger than the frequency band of the optical modulated signal.
  • the wavelength multiplexer 224 outputs the broadband optical modulated signal to the semiconductor optical amplifier 23 .
  • the semiconductor optical amplifier 23 according to the second embodiment amplifies the intensity of the broadband optical modulated signal input from the wavelength multiplexing section 224 .
  • the semiconductor optical amplifier 23 according to the second embodiment outputs the amplified optical signal to the optical receiver 4 via the transmission line 3 .
  • FIG. 9 is a flow chart showing the operation of the optical transmitter 2 according to the second embodiment.
  • the signal generator 211 generates a modulated signal (step S21).
  • the band division unit 212 converts the modulated signal into a narrowband signal (step S22).
  • the wideband signal generator 221 generates a wideband signal based on the multiple narrowband signals (step S23).
  • the wavelength multiplexing unit 224 multiplexes the plurality of modulated optical signals output from the optical modulation unit 222 to generate a wideband optical modulated signal (step S24).
  • the semiconductor optical amplifier 23 amplifies the broadband optical modulated signal (step S25). As described above, when the digital signal processor 21 includes only the signal generator 211 and the digital-analog converter 214 and the multiplexed signal generator 22 does not include the wideband signal generator 221, step S22 can be omitted. .
  • the optical transmitter 2 according to the second embodiment can generate an optical signal with a wide band by multiplexing the modulated optical signals with the wavelength multiplexing unit 224 . Therefore, the fluctuation time of the modulated optical signal handled by the optical transmitter 2 according to the second embodiment is shorter than the carrier lifetime of the semiconductor optical amplifier, like the optical transmitter 2 according to the first embodiment. Therefore, the optical transmitter 2 according to the second embodiment can reduce the influence of nonlinear distortion caused by the semiconductor optical amplifier.
  • FIG. 10 is a diagram showing the configuration of the optical receiver 4 according to the second embodiment.
  • the optical receiver 4 according to the second embodiment demultiplexes the broadband optical modulated signal with a wavelength demultiplexer 425 to generate a narrowband signal.
  • the optical receiver 4 according to the second embodiment includes a semiconductor optical amplifier 41 , a multiplexed signal separator 42 and a plurality (two in this embodiment) of digital signal processors 43 .
  • the multiplexed signal separator 42 includes a wavelength demultiplexer 425, a plurality of (two in this embodiment) photoelectric converters 421, a local light source 422, a broadband signal-narrowband signal converter 423, and a narrowband signal processor. 424.
  • Each digital signal processing unit 43 according to the second embodiment has the same configuration as the digital signal processing unit 43 according to the first embodiment, and includes an analog-digital conversion unit 431 and a decoding unit 432 .
  • the demultiplexing unit 42 includes only the wavelength demultiplexing unit 425, photoelectric conversion unit 421, and local light source 422, and I( t) and Q(t) signals.
  • the optical receiver 4 may include one digital signal processing unit 43 to AD-convert and decode the signal input from the photoelectric conversion unit 421 .
  • the optical receiver 4 according to the second embodiment does not include a plurality of local light sources 422, and the local light source 422 is a supercontinuum light source having a plurality of optical carriers. Local light may be output to the photoelectric conversion unit 421 .
  • the wavelength demultiplexer 425 demultiplexes the broadband optical modulated signal input from the semiconductor optical amplifier 41 .
  • the wavelength demultiplexing units 425 output the demultiplexed optical signals to the corresponding photoelectric conversion units 421 .
  • the photoelectric converter 421 converts the optical signal input from the wavelength demultiplexer 425 into an electrical signal.
  • the wideband signal-narrowband signal conversion unit 423 according to the second embodiment separates the wideband signal input from the photoelectric conversion unit 421 into a plurality of narrowband signals and inputs the narrowband signals to the narrowband signal processing unit 424 .
  • the narrowband signal processing unit 424 according to the second embodiment performs addition and subtraction processing of the plurality of narrowband signals input from the wideband signal-narrowband signal conversion unit 423. Do at least one process.
  • the analog-to-digital converter 431 converts the narrow-band analog signal series input from the multiplexed signal separator 42 into a digital signal series.
  • the decoding unit 432 according to the second embodiment converts the narrowband signal into a wideband signal, equalizes the waveform distortion caused by the optical transmitter 2, the transmission line 3, and the optical receiver 4, and then converts the digital signal sequence into Decrypt.
  • FIG. 11 is a flow chart showing the operation of the optical receiver 4 according to the second embodiment.
  • the semiconductor optical amplifier 41 amplifies the broadband optical modulated signal received by the optical receiver 4 (step S31).
  • the wavelength demultiplexer 425 provided in the multiplexed signal demultiplexer 42 demultiplexes the broadband optical modulated signal into narrowband signals (step S32).
  • the digital signal processing unit 43 converts the narrowband analog signal series into a digital signal series by the analog-digital conversion unit 431, and decodes the narrowband signal by the decoding unit 432 (step S33).
  • the frequency band of the optical signal transmitted by the optical transmitter 2 is a wide band. 2 and the semiconductor optical amplifier 41 provided in the optical receiver 4 can reduce the influence of nonlinear distortion.
  • FIG. 12 is a diagram showing configurations of the digital signal processing section 21 and the digital signal processing section 43 according to the third embodiment.
  • the digital signal processing section 21 according to the third embodiment includes an SOA distortion compensation section 215 inside the digital signal processing section 21 .
  • the digital signal processor 43 according to the third embodiment includes an SOA distortion estimator 434 and a physical parameter estimator 435 unlike the digital signal processor 43 according to the first or second embodiment. Note that if the physical parameters are known, the digital signal processing section 43 according to the third embodiment does not need to include the SOA distortion estimating section 434 and the physical parameter estimating section 435 .
  • any method can be used for the SOA distortion compensator 215, the SOA distortion estimator 434, and the physical parameter estimator 435.
  • FIG. For example, using the method described in Japanese Patent Application Laid-Open No. 2018-019255, the distortion caused by SOA can be compensated as follows.
  • the SOA distortion compensator 215 compensates for distortion caused by the semiconductor optical amplifier 23 for the modulated signal generated by the signal generator 211 .
  • SOA distortion compensating section 215 outputs the compensated signal to band dividing section 212 .
  • the SOA distortion compensator 215 acquires the estimated values of the physical parameters of the semiconductor optical amplifier 23 from the physical parameter estimator 435 of the optical receiver 4 .
  • the SOA distortion compensator 215 estimates nonlinear signal distortion occurring in the optical signal input to the semiconductor optical amplifier 23 based on the estimated values of the physical parameters of the semiconductor optical amplifier 23, and compensates for the nonlinear signal distortion. Note that if the physical parameters are known, the physical parameters may be set in the SOA distortion compensator 215 .
  • the SOA distortion compensator 215 calculates the gain coefficient h(t) of the nonlinear signal distortion generated in the optical signal input to the semiconductor optical amplifier 23 by the semiconductor optical amplifier 23 based on the estimated value of the physical parameter of the semiconductor optical amplifier 23. do.
  • SOA distortion compensator 215 uses gain coefficient ⁇ h(t), which is the inverse characteristic of gain coefficient h(t) for nonlinear signal distortion, to obtain a value (exp Calculate ((-h(t)(1+j ⁇ ))/2)).
  • the SOA distortion compensator 215 inputs the value (exp(( ⁇ h(t)(1+j ⁇ ))/2)) representing the inverse characteristic of the gain coefficient h(t) of the nonlinear signal distortion to the semiconductor optical amplifier 23. Multiply the optical signal.
  • the SOA distortion compensator 215 can pre-equalize the nonlinear signal distortion that occurs in the optical signal input to the semiconductor optical amplifier 23 .
  • E I (t) represents the complex amplitude of the optical signal acquired by the semiconductor optical amplifier 23 (the optical modulated signal output by the optical modulator 222).
  • E o (t) represents the complex amplitude of the optical signal transmitted by the semiconductor optical amplifier 23 .
  • h(t) denotes a gain factor.
  • ⁇ indicates the linewidth enhancement factor.
  • j indicates the imaginary unit.
  • exp(h(t)(1+j ⁇ )/2) represents the nonlinear signal distortion caused by the semiconductor optical amplifier 23 to the optical modulation signal.
  • Equation (1) the gain coefficient h(t) is expressed by the differential equation shown in Equation (2).
  • ⁇ c denotes the carrier lifetime.
  • h 0 denotes the non-saturated gain.
  • P sat indicates the saturation power.
  • Expression (2) shows that the time change of the gain coefficient h(t) depends on the power of the optical signal acquired by the semiconductor optical amplifier 23 . Therefore, if the physical parameters of the semiconductor optical amplifier 23 are known, the gain coefficient h(t) dependent on the power of the optical signal can be obtained from equation (2).
  • the SOA distortion compensator 215 can obtain the gain coefficient h(t) as a numerical solution from Equation (2) by, for example, the Euler method or the time evolution solution by the N-th order (N is a positive integer) Runge-Kutta method.
  • SOA distortion compensating section 215 may use an analytical solution if it exists when obtaining gain coefficient h(t) from equation (2).
  • SOA distortion compensation section 215 uses the gain coefficient ( ⁇ h(t)) of the inverse characteristic of gain coefficient h(t) to obtain a value (exp( ⁇ Calculate h(t)(1+j ⁇ )/2)).
  • the SOA distortion compensator 215 multiplies the modulated optical signal E I (t) by a value (exp( ⁇ h(t)(1+j ⁇ )/2)) representing the inverse characteristic of the gain coefficient h(t) of the nonlinear signal distortion. This compensates for the nonlinear signal distortion that occurs in the optical modulated signal in the semiconductor optical amplifier 23 . As a result, the SOA distortion compensator 215 can pre-equalize the nonlinear signal distortion caused in the optical modulated signal by the semiconductor optical amplifier 23 .
  • the SOA distortion compensator 215 may obtain the gain coefficient h(t) from Equation (2) by a solution method other than the time evolution solution method. If the physical parameters of the semiconductor optical amplifier 23 are not estimated, the SOA distortion compensator 215 may set the gain coefficient h(t) to 0 and may be configured so as not to compensate for the nonlinear signal distortion that occurs in the optical modulated signal in the semiconductor optical amplifier 23. good. When the physical parameters of the semiconductor optical amplifier 23 are not estimated, the modulated signal output from the signal generator 211 bypasses the SOA distortion compensator 215 and compensates for the nonlinear signal distortion that occurs in the optical modulated signal in the semiconductor optical amplifier 23. You can take a configuration that does not.
  • the SOA distortion estimator 434 acquires the received signal, which is a digital signal based on the transmission signal of the optical transmitter 2, from the analog-digital converter 431.
  • the SOA distortion estimator 434 acquires the transmission signal of the optical transmitter 2 from the optical transmitter 2 as a reference signal.
  • the SOA distortion estimating unit 434 uses a communication channel (see Non-Patent Document 5), an optical A transmission signal of the transmitter 2 is obtained from the optical transmitter 2 as a reference signal.
  • the SOA distortion estimator 434 acquires a part of the known signal of the transmission data sequence from the optical transmitter 2 as a reference signal.
  • the SOA distortion estimator 434 acquires a sequence of symbol values of the received signal from the optical transmitter 2 as a reference signal.
  • the SOA distortion estimator 434 calculates the nonlinear signal generated in the transmission signal by the semiconductor optical amplifier 23 based on the result of dividing the measured optical signal E o (t) by the optical signal E I (t) and equation (1).
  • a value representing the distortion (exp(h(t)(1+j ⁇ )/2)) and the linewidth enhancement factor ⁇ are obtained as shown in Equation (3).
  • the SOA distortion estimator 434 may calculate the average value of the same symbol using the reference signal as a repeated signal. This allows the SOA distortion estimator 434 to reduce signal distortion due to white noise. The SOA distortion estimator 434 can improve the estimation accuracy of nonlinear signal distortion.
  • the SOA distortion estimator 434 may not be able to accurately estimate the nonlinear signal distortion due to deterioration in signal quality.
  • the SOA distortion estimating section 434 may repeat the estimation by feeding back the estimated value once. As a result, the SOA distortion estimator 434 can compensate the transfer function with higher accuracy even when the nonlinear signal distortion caused by the semiconductor optical amplifier 23 is large.
  • the measured values of the physical parameters of the semiconductor optical amplifier 23 may differ from the design values of the physical parameters of the semiconductor optical amplifier 23 due to individual differences caused by manufacturing errors of the semiconductor optical amplifier 23 and the like. Therefore, the physical parameter estimator 435 estimates physical parameters of the semiconductor optical amplifier 23 by digital signal processing. As a result, the SOA distortion compensator 215 of the optical transmitter 2 can absorb individual differences in the semiconductor optical amplifiers 23 of the optical transmitter 2 and compensate for nonlinear signal distortion. The SOA distortion estimator 434 can compensate nonlinear signal distortion even for the semiconductor optical amplifier 23 having unknown physical parameters. The physical parameter estimator 435 estimates the physical parameter of the semiconductor optical amplifier 23 based on the result of the SOA distortion estimator 434 estimating the nonlinear signal distortion based on the reference signal.
  • the physical parameter estimator 435 estimates the physical parameters of the semiconductor optical amplifier 23 from the gain coefficient h(t) obtained using the equation (3) and the equation (2).
  • the physical parameters of the semiconductor optical amplifier 23 are, for example, carrier lifetime ⁇ c , non-saturation gain h 0 , and saturation power P sat .
  • the method of estimating the physical parameters of the semiconductor optical amplifier 23 by the physical parameter estimation unit 435 is not limited to a specific method.
  • the physical parameter estimator 435 may estimate the physical parameters of the semiconductor optical amplifier 23 by fitting using the method of least squares, calculation using simultaneous equations, or the like.
  • the physical parameter estimator 435 feeds back the physical parameters of the semiconductor optical amplifier 23 to the SOA distortion compensator 215 through the communication channel (see Non-Patent Document 5), control channel 5 such as NE-OpS or NW-OpS.
  • the physical parameter estimating unit 435 detects the semiconductor optical amplifier based on the optical signal transmitted over the dedicated line instead of the transmission line 3. Twenty-three physical parameters may be estimated. After estimating the physical parameters of the semiconductor optical amplifier 23, the physical parameter estimator 435 transmits to the optical transmitter 2 and the decoder 432 a signal resulting from deleting the reference signal from the transmission signal added with the reference signal. can be done. After this, if the physical parameter needs to be re-estimated, the physical parameter estimator 435 may re-add the reference signal to the transmission signal.
  • the physical parameter estimator 435 continues the estimation result of the physical parameter of the semiconductor optical amplifier 23 when the current injected into the semiconductor optical amplifier 23 does not change or when the intensity of the optical signal acquired by the semiconductor optical amplifier 23 does not change. can be used as intended. In these cases, the physical parameter estimator 435 may temporarily stop estimating the physical parameters of the semiconductor optical amplifier 23, or may calculate the physical parameters of the semiconductor optical amplifier 23 continuously and periodically. The physical parameter estimator 435 recalculates the physical parameters of the semiconductor optical amplifier 23 when the current injected into the semiconductor optical amplifier 23 does not change or when the intensity of the optical signal acquired by the semiconductor optical amplifier 23 changes.
  • the optical transmitter 2 can compensate for the distortion caused by the semiconductor optical amplifier 23 with respect to the modulated signal generated by the signal generation unit 211.
  • the influence of nonlinear distortion can be reduced.
  • the SOA distortion estimator 434 and the physical parameter estimator 435 are not limited to the digital signal processor 43 .
  • both the physical parameter estimating unit 435 or the SOA distortion estimating unit 434 and the physical parameter estimating unit 435 are provided in the corresponding digital signal processing unit 21, and the digital signal processing unit 43 and the digital signal processing unit 21 , may send and receive signals.
  • the SOA distortion compensator is not limited to the digital signal processor 21 .
  • the decoding unit 432 of the digital signal processing unit 43 is provided with an SOA distortion compensation unit, and a value (exp( ⁇ h(t)(1+j ⁇ )/2)) may be used to compensate for non-linear signal distortion that occurs in the transmitted signal at the semiconductor optical amplifier 23 .
  • the SOA distortion compensator provided in the SOA distortion compensator 215 and the decoder 432 compensates for the nonlinear signal distortion caused by the semiconductor optical amplifier 41 provided in the optical receiver 4 as well as the nonlinear signal distortion caused by the semiconductor optical amplifier 23.
  • the symbol rates of wideband optical modulated signals input from the optical modulator 222 of the optical transmitter 2 to the semiconductor optical amplifier 23 are 42 GBd, 84 GBd, and 168 GBd.
  • the modulation method is polarization multiplexed 16QAM (quadrature amplitude modulation) with stochastic constellation shaping. Also, the current injected into the semiconductor optical amplifier 23 was changed to change the amplification factor.
  • FIG. 13 is a table showing signal space diagrams under each condition.
  • the six signal space diagrams shown in FIG. 13 are output from the optical transmitter 2 when the currents injected into the semiconductor optical amplifier 23 are 100 mA and 350 mA, and the symbol rates of the broadband optical modulation signal are 42 GBd, 84 GBd and 168 GBd.
  • 2 is a signal space diagram showing a signal that By increasing the symbol rate of the optical modulation signal from 42 GBd to 84 GBd, and from 84 GBd to 168 GBd, the boundaries between signal points became clearer and the nonlinear distortion caused by the semiconductor optical amplifier was reduced. It was confirmed when it was 350mA.
  • the SN ratio of the optical signal output from the semiconductor optical amplifier 23 of the optical transmitter 2 and the output from the EDFA when the semiconductor optical amplifier 23 of the optical transmitter is replaced with an EDFA (Erbium Doped Fiber Amplifier) The dependence of the injection current to the semiconductor optical amplifier was shown with the difference from the SN ratio of the optical signal as the SNR penalty.
  • FIG. 14 is a graph showing the relationship between the magnitude of the injection current (SOA injection current) into the semiconductor optical amplifier and the SNR penalty.
  • SOA injection current was 350 mA
  • the SNR penalty for the symbol rate of 168 GBd of the optical modulation signal was about 2 dB less than the SNR penalty for the symbol rate of 42 GBd, and about 1 dB less than the SNR penalty for the symbol rate of 84 GBd. Therefore, it was shown that nonlinear distortion caused by the semiconductor optical amplifier is reduced by using an optically modulated signal with a high symbol rate, especially when the amplification factor of the semiconductor optical amplifier is high.
  • the signal generator 211 generates a modulated signal sequence (I(n), Q(n)), which is an electrical signal representing the in-phase component and the quadrature component of the optical signal, but is not limited to this.
  • a modulated signal sequence I(n), Q(n)
  • electric signals XI(n), XQ(n), YI(n), YQ(n ) may be generated.
  • the semiconductor optical amplifier 23 of the optical transmitter 2 amplifies the intensity of the optical modulated signal generated by the optical modulation section 222, but it is not limited to this.
  • the semiconductor optical amplifier 23 may be provided between the optical modulator 222 and the signal light source 223 , amplify the signal light input from the signal light source 223 , and output the amplified signal light to the optical modulator 222 .
  • the semiconductor optical amplifier 23 is included in the optical modulation unit 222, and only one of the X polarized wave component and the Y polarized wave component, or the semiconductor optical amplifier 23 may be included in the optical modulation section 222 and both may be amplified.
  • the semiconductor optical amplifier 41 of the optical receiver 4 amplifies the intensity of the optical signal input to the optical receiver 4, but is not limited to this.
  • the semiconductor optical amplifier 41 is included in the photoelectric conversion unit 421, and only one of the X polarized wave component and the Y polarized wave component, or the semiconductor optical amplifier 41 may be included in the photoelectric conversion unit 421 and both may be amplified.
  • the optical transmitter 2 and the optical receiver 4 may be realized by the same device.
  • the signal light source 223 and the local light source 422 may be the same light source.
  • the configuration example handles the IQ modulated signal, but the configuration example handles the intensity modulated signal.
  • the local light source 422 and the 90-degree optical hybrid that constitutes the photoelectric conversion unit 421 can be omitted.
  • FIG. 15 is a diagram showing the optical transceiver 100 according to this embodiment.
  • the optical transceiver 100 comprises a processing unit 101 and an optical front end 102 .
  • the processing device 101 includes a digital signal processing section 21 and a digital signal processing section 43 .
  • the optical front end 102 includes a multiplexed signal generator 22 , a semiconductor optical amplifier 23 , a semiconductor optical amplifier 41 and a multiplexed signal separator 42 .
  • the multiplexed signal generator 22, the semiconductor optical amplifier 23, the semiconductor optical amplifier 41, and the multiplexed signal separator 42 forming the optical front end 102 may be integrated.
  • a signal light source 223 may be integrated into the optical front end 102 .
  • the demultiplexer 42 may have the function of the local light source 422 by branching the signal light source 223 without having the local light source 422 .
  • FIG. 16 is a diagram showing an optical transceiver 100 that performs polarization multiplexing according to this embodiment.
  • the signal generation unit 211 generates electrical signals (XI(n), XQ(n) , YI(n), YQ(n)), and the band division unit 212, the narrowband signal processing unit 213, and the digital-analog conversion unit 214 generate an electric signal related to the X polarization and an electric signal related to the Y polarization. are processed independently.
  • the wideband signal generator 221 independently processes the electrical signal associated with the X-polarized wave and the electrical signal associated with the Y-polarized wave, and the optical modulator 222 performs polarization synthesis in addition to optical modulation. to generate an optical signal.
  • the photoelectric conversion unit 421 depolarizes the optical signal and then photoelectrically converts the optical signal, thereby generating broadband signals related to the X polarization and the Y polarization.
  • the wideband signal-narrowband signal conversion unit 423, the narrowband signal processing unit 424, and the analog-digital conversion unit 431 independently process the electrical signal related to the X polarized wave and the electrical signal related to the Y polarized wave.
  • the decoding unit 432 decodes the electrical signal associated with the X polarized wave and the electrical signal associated with the Y polarized wave to generate a reception data sequence.
  • the multiplexed signal generator 22 , the semiconductor optical amplifier 23 , the semiconductor optical amplifier 41 and the multiplexed signal separator 42 may be integrated to form the optical front end 102 .
  • a signal light source 223 may be integrated into this optical front end 102 .
  • optical transmission system 1 optical transmission system, 2 optical transmitter, 3 transmission line, 4 optical receiver, 21 digital signal processing unit, 211 signal generation unit, 212 band division unit, 213 narrowband signal processing unit, 214 digital-analog conversion unit, 22 Multiplexed signal generator 221 Broadband signal generator 222 Optical modulator 223 Signal light source 224 Wavelength multiplexer 23, 41 Semiconductor optical amplifier 42 Multiplexed signal separator 421 Photoelectric converter 422 Local light source 423 Wideband signal-narrowband signal converter, 424 narrowband signal processor, 425 wavelength demultiplexer

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PCT/JP2022/002651 2022-01-25 2022-01-25 光送信機、光受信機、光送信方法及び光受信方法 Ceased WO2023144880A1 (ja)

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WO2025069261A1 (ja) * 2023-09-27 2025-04-03 日本電信電話株式会社 光送信機

Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2004112781A (ja) * 2002-08-28 2004-04-08 Matsushita Electric Ind Co Ltd 光伝送システム
JP2018019255A (ja) * 2016-07-28 2018-02-01 日本電信電話株式会社 光送信機、光受信機及び光送受信機
JP2019220773A (ja) * 2018-06-15 2019-12-26 富士通株式会社 光伝送システム、制御装置、光伝送方法及び伝送装置

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2004112781A (ja) * 2002-08-28 2004-04-08 Matsushita Electric Ind Co Ltd 光伝送システム
JP2018019255A (ja) * 2016-07-28 2018-02-01 日本電信電話株式会社 光送信機、光受信機及び光送受信機
JP2019220773A (ja) * 2018-06-15 2019-12-26 富士通株式会社 光伝送システム、制御装置、光伝送方法及び伝送装置

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2025069261A1 (ja) * 2023-09-27 2025-04-03 日本電信電話株式会社 光送信機

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