WO2024042630A1 - Optical transmission device and optical signal generation method - Google Patents

Optical transmission device and optical signal generation method Download PDF

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Publication number
WO2024042630A1
WO2024042630A1 PCT/JP2022/031807 JP2022031807W WO2024042630A1 WO 2024042630 A1 WO2024042630 A1 WO 2024042630A1 JP 2022031807 W JP2022031807 W JP 2022031807W WO 2024042630 A1 WO2024042630 A1 WO 2024042630A1
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optical
signal
optical comb
light
comb
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PCT/JP2022/031807
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French (fr)
Japanese (ja)
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利明 下羽
陽一 深田
暁弘 田邉
遼 宮武
真良 関口
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日本電信電話株式会社
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Priority to PCT/JP2022/031807 priority Critical patent/WO2024042630A1/en
Publication of WO2024042630A1 publication Critical patent/WO2024042630A1/en

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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
    • H04B10/50—Transmitters
    • H04B10/516—Details of coding or modulation

Definitions

  • the present invention relates to an optical transmitter and an optical signal generation method.
  • FIG. 2 is a diagram schematically showing an optical video distribution system.
  • the optical video distribution system shown in FIG. 2 includes an optical transmitter and an optical receiver. The optical transmitter and the optical receiver are connected by an optical network.
  • the optical transmitter includes an FM batch conversion section and an electrical/optical conversion section.
  • the FM batch conversion unit batch converts input signals such as frequency-multiplexed video signals into wideband FM signals centered around 3 GHz.
  • the electrical/optical converter converts the broadband FM signal into a light intensity modulation signal and outputs the signal.
  • the output optical intensity modulated signal is transmitted through the optical network.
  • Optical networks enable wide-area optical transmission by connecting optical amplifiers such as EDFAs (erbium-doped fiber amplifiers) and optical distributors in multiple stages.
  • the optical receiver receives the optical intensity modulated signal transmitted through the optical network.
  • the optical receiving device includes an optical/electrical conversion section, a delay detection section, and an amplification section.
  • the optical/electrical converter converts the received optical intensity modulation signal into a wideband FM signal.
  • the delay detection section demodulates the wideband FM signal into the original signal.
  • the amplification section amplifies the demodulated signal to a level suitable for the system, and then outputs the amplified signal.
  • FIG. 3 is a diagram illustrating an example of functional blocks of an optical transmitter in the FM batch conversion method (see, for example, Non-Patent Document 3).
  • the optical transmitter shown in FIG. 3 includes a first light source, an optical phase modulation section, a multiplexing section, a second light source, a light receiving section, a light intensity modulation section, and a third light source.
  • the output light from the first light source is input to the subsequent optical phase modulation section.
  • the optical phase modulation section phase modulates the output light from the first light source using the first input signal and the second input signal.
  • the first input signal is a frequency multiplexed signal from 90 to 770 MHz
  • the second input signal is a frequency multiplexed signal from 1.0 to 2.1 GHz.
  • the multiplexer multiplexes the light phase-modulated by the optical phase modulator and the output light from the second light source.
  • the light receiving section optically heterodyne receives the output light multiplexed by the multiplexing section.
  • a broadband FM signal centered at a frequency equal to the frequency difference between the light from the first light source and the light from the second light source is obtained.
  • the light intensity modulator modulates the intensity of the output light from the third light source using the FM signal and outputs the modulated light. Since this method converts the input signal into a wideband FM signal all at once, it has excellent noise tolerance of the transmission path.
  • ITU-T J.185 Transmission equipment for transferring multi-channel television signals over optical access networks by frequency modulation conversion
  • International Telecommunication Union June 2012.
  • Toshiaki Shimoha Tomoaki Yoshida, Jun Terada, “Optical video distribution technology using FM batch conversion method”
  • Institute of Electronics, Information and Communication Engineers IEICE Technical Report CS2019-84, IE2019-64 (2019- 12), p.97-101
  • R. Miyatake, T. Shitaba, A. Tanabe, Y. Fukada, T. Yoshida "Optical transmission experiment on FM conversion method with wideband phase modulation," IEICE Communications Express, Vol.10, No.12, p.967- 972, 2021.
  • the above-mentioned FM batch conversion method requires two light sources to generate FM signals.
  • the oscillation frequencies of these light sources fluctuate randomly over time. Therefore, a certain phase noise occurs in the FM signal output from the light receiving section. As a result, the possible transmission distance is limited.
  • an object of the present invention is to provide an optical transmitter and an optical signal generation method that can perform FM conversion with low noise.
  • An optical transmission device includes an optical comb generator that generates an optical signal in which optical combs are arranged at equal frequency intervals using output light from a first light source and a frequency from a signal source; an extraction unit that extracts a first optical comb and a second optical comb from the optical signal generated by the optical comb generator; and a phase modulation unit that generates a modulation signal by phase modulating the first optical comb with an input signal.
  • an adjustment unit that adjusts the delay amount of the second optical comb; a multiplexing unit that multiplexes the modulated signal and the second optical comb whose delay amount has been adjusted; It includes a light receiving section that performs square law detection of the combined light to generate an FM (Frequency Modulation) signal, and a light intensity modulation section that intensity modulates the output light of the second light source using the FM signal.
  • FM Frequency Modulation
  • An optical signal generation method includes an optical comb generation step of generating an optical signal in which optical combs are arranged at equal frequency intervals using output light from a first light source and a frequency from a signal source; an extraction step of extracting a first optical comb and a second optical comb from the optical signal generated in the optical comb generation step; and a phase modulation step of generating a modulation signal by phase-modulating the first optical comb with an input signal.
  • the method includes a signal generation step of square-law detection of the light multiplexed in the step to generate an FM (Frequency Modulation) signal, and a light intensity modulation step of intensity modulating the output light of the second light source using the FM signal.
  • FM Frequency Modulation
  • the present invention enables FM conversion with low noise.
  • FIG. 1 is a block diagram showing the configuration of an optical transmitter according to an embodiment of the present invention.
  • 1 is a diagram showing a conventional optical video distribution system.
  • FIG. 1 is a block diagram showing the configuration of a conventional optical transmitter.
  • the present embodiment relates to an optical transmitter of an optical transmission system that employs an FM batch conversion method.
  • the FM batch conversion method input signals are collectively converted into a wideband FM signal, and then the optical signal is intensity-modulated using the wideband FM signal and output. Since the optical transmitter of this embodiment requires only one light source to generate the FM signal, it is possible to suppress the phase noise of the FM signal to a level lower than that of the prior art. Therefore, it is possible to realize a low-noise optical transmitter.
  • FIG. 1 is a functional block diagram of an optical transmitter 1 according to an embodiment of the present invention.
  • the optical transmitter 1 includes a first light source 11, an optical comb generator 12, a signal source 13, a distribution section 14, a first band limiter 15, a phase modulator 16, a second band limiter 17, and a second band limiter 17. , an optical path length adjustment section 18, a multiplexing section 19, a light receiving section 20, a light intensity modulation section 21, and a second light source 22.
  • the optical path including the first band limiting section 15 and the phase modulating section 16 is referred to as the first optical path
  • the optical path including the second band limiting section 17 and the optical path length adjusting section is referred to as the first optical path.
  • the optical path including 18 will be referred to as a second optical path.
  • the first light source 11 outputs light of a single frequency.
  • the output light from the first light source 11 is input to the optical comb generator 12 .
  • the optical comb generator 12 converts the light input from the first light source 11 into an optical signal in which optical spectra are arranged at equal intervals at the frequency output from the signal source 13.
  • the optical comb is an optical spectrum of each frequency arranged at equal intervals.
  • the optical comb generator 12 generally has a structure in which an optical modulator is inserted into an optical resonator, and generates a plurality of sideband waves with a frequency interval equal to the frequency of a modulation signal input to the optical modulator. It is a device that generates The modulated signal input to the optical modulator corresponds to the signal output from the signal source 13.
  • the distribution unit 14 inputs the optical signal converted by the optical comb generator 12.
  • the distribution unit 14 divides the input optical signal into two, outputs one optical signal to the first band limiting unit 15 on the first optical path, and outputs the other optical signal to the second band limiting unit 17 on the second optical path. Output.
  • the first band limiting unit 15 receives the optical signal from the distribution unit 14 and extracts a specific optical comb from the plurality of optical combs included in the input optical signal. That is, the first band limiting section 15 extracts one optical comb of a predetermined frequency. The first band limiting section 15 outputs the extracted optical comb to the phase modulation section 16 and does not output other optical combs.
  • the phase modulation unit 16 phase-modulates the optical comb input from the first band limiting unit 15 using an input electrical signal.
  • the input signal may be a signal at one frequency or may include multiple signals at different frequencies.
  • the input signal may be a signal obtained by combining a frequency multiplexed signal of 90 to 770 Hz and a frequency multiplexed signal of 1.0 to 2.1 GHz.
  • the second band limiter 17 receives the optical signal from the distributor 14 and extracts a specific optical comb different from the first band limiter 15 from the plurality of optical combs included in the input optical signal. That is, the second band limiter 17 extracts one optical comb having a predetermined frequency different from the frequency of the optical comb extracted by the first band limiter 15. The second band limiting section 17 outputs the extracted optical comb to the optical path length adjusting section 18 and does not output other optical combs.
  • the optical path length adjustment unit 18 has a predetermined optical path length, and the second band limiter 17 outputs an output so that the amount of delay of the optical signal on the second optical path is equal to the amount of delay of the optical signal on the first optical path. Adjust the delay amount of the optical comb. This is mainly because a delay occurs due to the optical path length of the phase modulation section 16. A value measured in advance can be used as the amount of delay to be adjusted.
  • the optical path length adjustment section 18 outputs the optical comb whose delay amount has been adjusted to the multiplexing section 19 .
  • the multiplexer 19 multiplexes the optical signal phase-modulated by the phase modulator 16 and the optical signal input from the optical path length adjuster 18, and outputs the optical signal obtained by the multiplexer to the light receiver 20.
  • the optical signal input from the optical path length adjustment section 18 is an optical comb whose delay amount has been adjusted.
  • the light receiving unit 20 performs square law detection of the optical signal input from the multiplexing unit 19, and detects a frequency centered at a frequency equal to the frequency difference between the two combined optical signals, that is, the frequency difference between the first optical comb and the second optical comb. It is converted into a wideband FM signal.
  • the light receiving section 20 outputs a wideband FM signal to the optical intensity modulating section 21 .
  • the light intensity modulation section 21 intensity-modulates the output light from the second light source 22 using the broadband FM signal input from the light receiving section 20.
  • the optical intensity modulator 21 outputs an intensity-modulated optical signal to a transmission path.
  • the optical transmitter 1 described above reduces the number of light sources conventionally required for FM signal generation from two to one. Since one light source is used, phase noise degradation due to temporal fluctuations in the oscillation frequency of the light source is extremely small. Therefore, it is possible to suppress the phase noise of the FM signal at the output of the light receiving section to be lower than before, and to realize an optical transmitter with lower noise than the conventional system. Because the noise is low, optical signals can be transmitted over longer distances than conventional systems.
  • the optical transmission device includes an optical comb generator, an extraction section, a phase modulation section, an adjustment section, a multiplexing section, a light receiving section, and a light intensity modulation section.
  • the optical comb generator generates an optical signal in which optical combs are arranged at equal frequency intervals using the output light from the first light source and the frequency from the signal source.
  • the extractor extracts the first optical comb and the second optical comb from the optical signal generated by the optical comb generator.
  • the phase modulation section generates a modulation signal by phase modulating the first optical comb with an input signal.
  • the input signal may be a non-multiplexed signal or a frequency multiplexed signal.
  • the adjustment unit adjusts the amount of delay of the second optical comb.
  • the adjustment section corresponds to, for example, the optical path length adjustment section 18 of the embodiment.
  • the multiplexing unit multiplexes the modulated signal and the second optical comb whose delay amount has been adjusted.
  • the light receiving section performs square law detection of the light multiplexed by the multiplexing section to generate an FM (Frequency Modulation) signal.
  • the light intensity modulation section intensity-modulates the output light of the second light source using the FM signal.
  • the extraction section may include a distribution section, a first extraction section, and a second extraction section.
  • the distribution section divides the optical signal generated by the optical comb generator into two parts.
  • the first extraction section extracts the first optical comb from one of the optical signals distributed by the distribution section.
  • the second extraction section extracts a second optical comb from the other optical signal distributed by the distribution section.
  • the first extractor corresponds to the first band limiter 15 of the embodiment
  • the second extractor corresponds to the second band limiter 17 of the embodiment.
  • Optical transmitter 11 First light source 12
  • Optical comb generator 13 Signal source 14
  • Distribution section 15 First band limiter 16
  • Second band limiter 18 Optical path length adjuster 19
  • Multiplexer 20 Light receiver 21
  • Light intensity Modulation section 22 Second light source

Abstract

According to the present invention, an optical comb generator uses output light from a first light source and a frequency from a signal source and generates an optical signal in which optical combs are aligned side by side at equal frequency intervals therebetween. An extracting unit extracts a first optical comb and a second optical comb from an optical signal generated by the optical comb generator. A phase modulating unit generates a modulated signal obtained by phase-modulating the first optical comb in response to an input signal. An adjusting unit adjusts the delay amount of the second optical comb. A multiplexing unit multiplexes the modulated signal and the second optical comb the delay amount of which has been adjusted. A light-receiving unit performs square-law detection on the light multiplexed by the multiplexing unit and generates a frequency modulation (FM) signal. An optical intensity modulating unit modulates the intensity of output light of a second light source in response to the FM signal.

Description

光送信装置及び光信号生成方法Optical transmitter and optical signal generation method
　本発明は、光送信装置及び光信号生成方法に関する。 The present invention relates to an optical transmitter and an optical signal generation method.
　ＦＭ（Frequency Modulation）一括変換方式（例えば、非特許文献１、非特許文献２参照）を採用した光映像配信システムが導入されている。図２は、光映像配信システムの概略を示す図である。図２に示す光映像配信システムは、光送信装置と光受信装置とを有する。光送信装置と光受信装置とは光ネットワークにより接続される。 An optical video distribution system that employs an FM (Frequency Modulation) batch conversion method (see, for example, Non-Patent Document 1 and Non-Patent Document 2) has been introduced. FIG. 2 is a diagram schematically showing an optical video distribution system. The optical video distribution system shown in FIG. 2 includes an optical transmitter and an optical receiver. The optical transmitter and the optical receiver are connected by an optical network.
　光送信装置は、ＦＭ一括変換部と、電気／光変換部とを有する。ＦＭ一括変換部は、周波数多重された映像信号等の入力信号を、３ＧＨｚを中心とする広帯域なＦＭ信号に一括して変換する。電気／光変換部は、広帯域ＦＭ信号を光強度変調信号に変換して出力する。出力された光強度変調信号は、光ネットワークを伝送する。光ネットワークは、ＥＤＦＡ（エルビウム添加ファイバー増幅器）等の光増幅器と光分配器とを多段接続することで、広域な光伝送を可能とする。光受信装置は、光ネットワークを伝送した光強度変調信号を受信する。 The optical transmitter includes an FM batch conversion section and an electrical/optical conversion section. The FM batch conversion unit batch converts input signals such as frequency-multiplexed video signals into wideband FM signals centered around 3 GHz. The electrical/optical converter converts the broadband FM signal into a light intensity modulation signal and outputs the signal. The output optical intensity modulated signal is transmitted through the optical network. Optical networks enable wide-area optical transmission by connecting optical amplifiers such as EDFAs (erbium-doped fiber amplifiers) and optical distributors in multiple stages. The optical receiver receives the optical intensity modulated signal transmitted through the optical network.
　光受信装置は、光／電気変換部と、遅延検波部と、増幅部とを有する。光／電気変換部は、受信した光強度変調信号を広帯域ＦＭ信号に変換する。遅延検波部は、広帯域ＦＭ信号を元の信号に復調する。増幅部は、復調信号をシステムに適切なレベルに増幅した後、出力する。 The optical receiving device includes an optical/electrical conversion section, a delay detection section, and an amplification section. The optical/electrical converter converts the received optical intensity modulation signal into a wideband FM signal. The delay detection section demodulates the wideband FM signal into the original signal. The amplification section amplifies the demodulated signal to a level suitable for the system, and then outputs the amplified signal.
　図３は、ＦＭ一括変換方式における光送信装置の機能ブロックの一例を示す図である（例えば、非特許文献３参照）。図３に示す光送信装置は、第一光源と、光位相変調部と、合波部と、第二光源と、受光部と、光強度変調部と、第三光源とを有する。 FIG. 3 is a diagram illustrating an example of functional blocks of an optical transmitter in the FM batch conversion method (see, for example, Non-Patent Document 3). The optical transmitter shown in FIG. 3 includes a first light source, an optical phase modulation section, a multiplexing section, a second light source, a light receiving section, a light intensity modulation section, and a third light source.
　第一光源からの出力光は、後段の光位相変調部に入力される。光位相変調部は、第一入力信号及び第二入力信号により、第一光源からの出力光を位相変調する。例えば、第一入力信号は、９０～７７０ＭＨｚの周波数多重信号であり、第二入力信号は、１．０～２．１ＧＨｚの周波数多重信号である。合波部は、光位相変調部が位相変調した光と、第二光源の出力光とを合波する。受光部は、合波部が合波した出力光を、光ヘテロダイン受信する。これにより、第一光源の光と第二光源の光との周波数差に等しい周波数を中心とする広帯域なＦＭ信号が得られる。光強度変調部は、第三光源からの出力光を、このＦＭ信号により強度変調して出力する。本方式は、入力信号を一括して広帯域なＦＭ信号に変換するため、伝送路の雑音耐力に優れる。 The output light from the first light source is input to the subsequent optical phase modulation section. The optical phase modulation section phase modulates the output light from the first light source using the first input signal and the second input signal. For example, the first input signal is a frequency multiplexed signal from 90 to 770 MHz, and the second input signal is a frequency multiplexed signal from 1.0 to 2.1 GHz. The multiplexer multiplexes the light phase-modulated by the optical phase modulator and the output light from the second light source. The light receiving section optically heterodyne receives the output light multiplexed by the multiplexing section. As a result, a broadband FM signal centered at a frequency equal to the frequency difference between the light from the first light source and the light from the second light source is obtained. The light intensity modulator modulates the intensity of the output light from the third light source using the FM signal and outputs the modulated light. Since this method converts the input signal into a wideband FM signal all at once, it has excellent noise tolerance of the transmission path.
　上述したＦＭ一括変換方式では、ＦＭ信号生成のために二つの光源が必要である。これらの光源の発振周波数は、時間的にランダムに揺らぐ。そのため、受光部から出力されるＦＭ信号には一定の位相雑音が発生する。その結果、伝送可能距離が制限される。 The above-mentioned FM batch conversion method requires two light sources to generate FM signals. The oscillation frequencies of these light sources fluctuate randomly over time. Therefore, a certain phase noise occurs in the FM signal output from the light receiving section. As a result, the possible transmission distance is limited.
　上記事情に鑑み、本発明は、雑音を低く抑えたＦＭ変換を行うことができる光送信装置及び光信号生成方法を提供することを目的としている。 In view of the above circumstances, an object of the present invention is to provide an optical transmitter and an optical signal generation method that can perform FM conversion with low noise.
　本発明の一態様の光送信装置は、第一の光源からの出力光と信号源からの周波数とを用いて等しい周波数間隔で光コムが並んだ光信号を発生する光コム発生器と、前記光コム発生器が発生した前記光信号から第一の光コム及び第二の光コムを抜きだす抽出部と、前記第一の光コムを入力信号により位相変調した変調信号を生成する位相変調部と、前記第二の光コムの遅延量を調整する調整部と、前記変調信号と、遅延量が調整された前記第二の光コムとを合波する合波部と、前記合波部により合波された光を二乗検波してＦＭ（Frequency Modulation）信号を生成する受光部と、前記ＦＭ信号により第二の光源の出力光を強度変調する光強度変調部と、を備える。 An optical transmission device according to one aspect of the present invention includes an optical comb generator that generates an optical signal in which optical combs are arranged at equal frequency intervals using output light from a first light source and a frequency from a signal source; an extraction unit that extracts a first optical comb and a second optical comb from the optical signal generated by the optical comb generator; and a phase modulation unit that generates a modulation signal by phase modulating the first optical comb with an input signal. an adjustment unit that adjusts the delay amount of the second optical comb; a multiplexing unit that multiplexes the modulated signal and the second optical comb whose delay amount has been adjusted; It includes a light receiving section that performs square law detection of the combined light to generate an FM (Frequency Modulation) signal, and a light intensity modulation section that intensity modulates the output light of the second light source using the FM signal.
　本発明の一態様の光信号生成方法は、第一の光源からの出力光と信号源からの周波数とを用いて等しい周波数間隔で光コムが並んだ光信号を発生する光コム発生ステップと、前記光コム発生ステップにおいて発生させた前記光信号から第一の光コム及び第二の光コムを抜きだす抽出ステップと、前記第一の光コムを入力信号により位相変調した変調信号を生成する位相変調ステップと、前記第二の光コムの遅延量を調整する調整ステップと、前記変調信号と、遅延量が調整された前記第二の光コムとを合波する合波ステップと、前記合波ステップにおいて合波された光を二乗検波してＦＭ（Frequency Modulation）信号を生成する信号生成ステップと、前記ＦＭ信号により第二の光源の出力光を強度変調する光強度変調ステップと、を有する。 An optical signal generation method according to one aspect of the present invention includes an optical comb generation step of generating an optical signal in which optical combs are arranged at equal frequency intervals using output light from a first light source and a frequency from a signal source; an extraction step of extracting a first optical comb and a second optical comb from the optical signal generated in the optical comb generation step; and a phase modulation step of generating a modulation signal by phase-modulating the first optical comb with an input signal. a modulation step, an adjustment step of adjusting the delay amount of the second optical comb, a combining step of multiplexing the modulated signal and the second optical comb with the adjusted delay amount, and the multiplexing step. The method includes a signal generation step of square-law detection of the light multiplexed in the step to generate an FM (Frequency Modulation) signal, and a light intensity modulation step of intensity modulating the output light of the second light source using the FM signal.
　本発明により、雑音を低く抑えたＦＭ変換が可能となる。 The present invention enables FM conversion with low noise.
本発明の実施形態による光送信装置の構成を示すブロック図である。FIG. 1 is a block diagram showing the configuration of an optical transmitter according to an embodiment of the present invention. 従来の光映像配信システムを示す図である。1 is a diagram showing a conventional optical video distribution system. 従来の光送信装置の構成を示すブロック図である。FIG. 1 is a block diagram showing the configuration of a conventional optical transmitter.
　以下、図面を参照しながら本発明の実施形態を詳細に説明する。本実施形態は、ＦＭ一括変換方式を採用する光伝送システムの光送信装置に関する。ＦＭ一括変換方式は、入力信号を一括して広帯域なＦＭ信号に変換した後、さらに広帯域ＦＭ信号により光信号を強度変調して出力する。本実施形態の光送信装置は、ＦＭ信号を生成するために必要な光源が一つであるため、ＦＭ信号の位相雑音を従来よりも低く抑えることができる。よって、低雑音な光送信装置を実現することが可能である。 Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. The present embodiment relates to an optical transmitter of an optical transmission system that employs an FM batch conversion method. In the FM batch conversion method, input signals are collectively converted into a wideband FM signal, and then the optical signal is intensity-modulated using the wideband FM signal and output. Since the optical transmitter of this embodiment requires only one light source to generate the FM signal, it is possible to suppress the phase noise of the FM signal to a level lower than that of the prior art. Therefore, it is possible to realize a low-noise optical transmitter.
　図１は、本発明の実施形態による光送信装置１の機能ブロック図である。光送信装置１は、第一光源１１と、光コム発生器１２と、信号源１３と、分配部１４と、第一帯域制限部１５と、位相変調部１６と、第二帯域制限部１７と、光路長調整部１８と、合波部１９と、受光部２０と、光強度変調部２１と、第二光源２２とを備える。分配部１４と合波部１９の間の２つの光路のうち、第一帯域制限部１５及び位相変調部１６を含む光路を第一光路と記載し、第二帯域制限部１７及び光路長調整部１８を含む光路を第二光路と記載する。 FIG. 1 is a functional block diagram of an optical transmitter 1 according to an embodiment of the present invention. The optical transmitter 1 includes a first light source 11, an optical comb generator 12, a signal source 13, a distribution section 14, a first band limiter 15, a phase modulator 16, a second band limiter 17, and a second band limiter 17. , an optical path length adjustment section 18, a multiplexing section 19, a light receiving section 20, a light intensity modulation section 21, and a second light source 22. Of the two optical paths between the distribution section 14 and the multiplexing section 19, the optical path including the first band limiting section 15 and the phase modulating section 16 is referred to as the first optical path, and the optical path including the second band limiting section 17 and the optical path length adjusting section is referred to as the first optical path. The optical path including 18 will be referred to as a second optical path.
　第一光源１１は、単一周波数の光を出力する。第一光源１１からの出力光は、光コム発生器１２に入力される。光コム発生器１２は、第一光源１１から入力した光を、信号源１３から出力される周波数で等間隔に光スぺクトルが並んだ光信号に変換する。光コムは、この等間隔に並んだ各周波数の光スぺクトルである。ここで、光コム発生器１２とは、一般的に、光変調器を光共振器中に挿入した構造により、光変調器に入力される変調信号の周波数に等しい周波数間隔の複数の側帯波を発生させる装置である。光変調器に入力される変調信号は、信号源１３が出力する信号に相当する。 The first light source 11 outputs light of a single frequency. The output light from the first light source 11 is input to the optical comb generator 12 . The optical comb generator 12 converts the light input from the first light source 11 into an optical signal in which optical spectra are arranged at equal intervals at the frequency output from the signal source 13. The optical comb is an optical spectrum of each frequency arranged at equal intervals. Here, the optical comb generator 12 generally has a structure in which an optical modulator is inserted into an optical resonator, and generates a plurality of sideband waves with a frequency interval equal to the frequency of a modulation signal input to the optical modulator. It is a device that generates The modulated signal input to the optical modulator corresponds to the signal output from the signal source 13.
　分配部１４は、光コム発生器１２が変換した光信号を入力する。分配部１４は、入力した光信号を２分配し、一方の光信号を第一光路の第一帯域制限部１５に出力し、もう一方の光信号を第二光路の第二帯域制限部１７に出力する。 The distribution unit 14 inputs the optical signal converted by the optical comb generator 12. The distribution unit 14 divides the input optical signal into two, outputs one optical signal to the first band limiting unit 15 on the first optical path, and outputs the other optical signal to the second band limiting unit 17 on the second optical path. Output.
　第一帯域制限部１５は、分配部１４から光信号を入力し、入力した光信号に含まれる複数の光コムから、特定の光コムを抜き出す。すなわち、第一帯域制限部１５は、所定の周波数の一つの光コムを抜き出す。第一帯域制限部１５は、抜き出した光コムを位相変調部１６に出力し、他の光コムを出力しない。 The first band limiting unit 15 receives the optical signal from the distribution unit 14 and extracts a specific optical comb from the plurality of optical combs included in the input optical signal. That is, the first band limiting section 15 extracts one optical comb of a predetermined frequency. The first band limiting section 15 outputs the extracted optical comb to the phase modulation section 16 and does not output other optical combs.
　位相変調部１６は、第一帯域制限部１５から入力した光コムを、電気信号の入力信号によって位相変調する。例えば、入力信号は、一つの周波数の信号でもよく、異なる周波数の複数の信号を含んでもよい。例えば、入力信号は、９０～７７０Ｈｚの周波数多重信号と、１．０～２．１ＧＨｚの周波数多重信号とが合波された信号でもよい。 The phase modulation unit 16 phase-modulates the optical comb input from the first band limiting unit 15 using an input electrical signal. For example, the input signal may be a signal at one frequency or may include multiple signals at different frequencies. For example, the input signal may be a signal obtained by combining a frequency multiplexed signal of 90 to 770 Hz and a frequency multiplexed signal of 1.0 to 2.1 GHz.
　一方、第二帯域制限部１７は、分配部１４から光信号を入力し、入力した光信号に含まれる複数の光コムから第一帯域制限部１５とは異なる特定の光コムを抜き出す。すなわち、第二帯域制限部１７は、第一帯域制限部１５が抜き出す光コムの周波数とは異なる所定の周波数の一つの光コムを抜き出す。第二帯域制限部１７は、抜き出した光コムを光路長調整部１８に出力し、他の光コムを出力しない。 On the other hand, the second band limiter 17 receives the optical signal from the distributor 14 and extracts a specific optical comb different from the first band limiter 15 from the plurality of optical combs included in the input optical signal. That is, the second band limiter 17 extracts one optical comb having a predetermined frequency different from the frequency of the optical comb extracted by the first band limiter 15. The second band limiting section 17 outputs the extracted optical comb to the optical path length adjusting section 18 and does not output other optical combs.
　光路長調整部１８は、所定の光路長を有しており、第二光路の光信号の遅延量と第一光路の光信号の遅延量と等しくなるように、第二帯域制限部１７が出力した光コムの遅延量を調整する。これは、主に、位相変調部１６の光路長によって遅延が生じるためである。調整する遅延量には、予め計測した値を用いることができる。光路長調整部１８は、遅延量が調整された光コムを合波部１９に出力する。 The optical path length adjustment unit 18 has a predetermined optical path length, and the second band limiter 17 outputs an output so that the amount of delay of the optical signal on the second optical path is equal to the amount of delay of the optical signal on the first optical path. Adjust the delay amount of the optical comb. This is mainly because a delay occurs due to the optical path length of the phase modulation section 16. A value measured in advance can be used as the amount of delay to be adjusted. The optical path length adjustment section 18 outputs the optical comb whose delay amount has been adjusted to the multiplexing section 19 .
　合波部１９は、位相変調部１６により位相変調された光信号と、光路長調整部１８から入力した光信号とを合波し、合波により得られた光信号を受光部２０に出力する。光路長調整部１８から入力した光信号は、遅延量が調整された光コムである。受光部２０は、合波部１９から入力した光信号を二乗検波し、合波された二つの光信号の周波数差、すなわち、第一光コム及び第二光コムの周波数差に等しい周波数を中心とする、広帯域ＦＭ信号に変換する。受光部２０は、広帯域ＦＭ信号を光強度変調部２１に出力する。 The multiplexer 19 multiplexes the optical signal phase-modulated by the phase modulator 16 and the optical signal input from the optical path length adjuster 18, and outputs the optical signal obtained by the multiplexer to the light receiver 20. . The optical signal input from the optical path length adjustment section 18 is an optical comb whose delay amount has been adjusted. The light receiving unit 20 performs square law detection of the optical signal input from the multiplexing unit 19, and detects a frequency centered at a frequency equal to the frequency difference between the two combined optical signals, that is, the frequency difference between the first optical comb and the second optical comb. It is converted into a wideband FM signal. The light receiving section 20 outputs a wideband FM signal to the optical intensity modulating section 21 .
　光強度変調部２１は、第二光源２２からの出力光を、受光部２０から入力した広帯域ＦＭ信号により強度変調する。光強度変調部２１は、強度変調された光信号を伝送路に出力する。 The light intensity modulation section 21 intensity-modulates the output light from the second light source 22 using the broadband FM signal input from the light receiving section 20. The optical intensity modulator 21 outputs an intensity-modulated optical signal to a transmission path.
　上述の光送信装置１は、従来ＦＭ信号生成のために必要な光源を二つから一つに削減する。一つの光源を用いるため、光源の発振周波数の時間的な揺らぎによる、位相雑音の劣化が極めて小さい。従って、受光部出力におけるＦＭ信号の位相雑音を従来よりも低く抑え、従来方式よりも低雑音の光送信装置を実現できる。雑音が小さいため、従来システムと比較して、より長距離に光信号を送信可能である。 The optical transmitter 1 described above reduces the number of light sources conventionally required for FM signal generation from two to one. Since one light source is used, phase noise degradation due to temporal fluctuations in the oscillation frequency of the light source is extremely small. Therefore, it is possible to suppress the phase noise of the FM signal at the output of the light receiving section to be lower than before, and to realize an optical transmitter with lower noise than the conventional system. Because the noise is low, optical signals can be transmitted over longer distances than conventional systems.
　以上説明した実施形態によれば、光送信装置は、光コム発生器と、抽出部と、位相変調部と、調整部と、合波部と、受光部と、光強度変調部とを備える。光コム発生器は、第一の光源からの出力光と信号源からの周波数とを用いて等しい周波数間隔で光コムが並んだ光信号を発生する。抽出部は、光コム発生器が発生した光信号から第一の光コム及び第二の光コムを抜きだす。位相変調部は、第一の光コムを入力信号により位相変調した変調信号を生成する。入力信号は、多重されていない信号でもよく、周波数多重信号でもよい。調整部は、第二の光コムの遅延量を調整する。調整部は、例えば、実施形態の光路長調整部１８に対応する。合波部は、変調信号と、遅延量が調整された第二の光コムとを合波する。受光部は、合波部により合波された光を二乗検波してＦＭ（Frequency Modulation）信号を生成する。光強度変調部は、ＦＭ信号により第二の光源の出力光を強度変調する。 According to the embodiment described above, the optical transmission device includes an optical comb generator, an extraction section, a phase modulation section, an adjustment section, a multiplexing section, a light receiving section, and a light intensity modulation section. The optical comb generator generates an optical signal in which optical combs are arranged at equal frequency intervals using the output light from the first light source and the frequency from the signal source. The extractor extracts the first optical comb and the second optical comb from the optical signal generated by the optical comb generator. The phase modulation section generates a modulation signal by phase modulating the first optical comb with an input signal. The input signal may be a non-multiplexed signal or a frequency multiplexed signal. The adjustment unit adjusts the amount of delay of the second optical comb. The adjustment section corresponds to, for example, the optical path length adjustment section 18 of the embodiment. The multiplexing unit multiplexes the modulated signal and the second optical comb whose delay amount has been adjusted. The light receiving section performs square law detection of the light multiplexed by the multiplexing section to generate an FM (Frequency Modulation) signal. The light intensity modulation section intensity-modulates the output light of the second light source using the FM signal.
　抽出部は、分配部と、第一抽出部と、第二抽出部とを備えてもよい。分配部は、光コム発生器が発生した光信号を２分配する。第一抽出部は、分配部が分配した一方の光信号から第一の光コムを抽出する。第二抽出部は、分配部が分配したもう一方の光信号から第二の光コムを抽出する。例えば、第一抽出部は、実施形態の第一帯域制限部１５に対応し、第二抽出部は、実施形態の第二帯域制限部１７に対応する。 The extraction section may include a distribution section, a first extraction section, and a second extraction section. The distribution section divides the optical signal generated by the optical comb generator into two parts. The first extraction section extracts the first optical comb from one of the optical signals distributed by the distribution section. The second extraction section extracts a second optical comb from the other optical signal distributed by the distribution section. For example, the first extractor corresponds to the first band limiter 15 of the embodiment, and the second extractor corresponds to the second band limiter 17 of the embodiment.
　以上、この発明の実施形態について図面を参照して詳述してきたが、具体的な構成はこの実施形態に限られるものではなく、この発明の要旨を逸脱しない範囲の設計等も含まれる。 Although the embodiments of the present invention have been described above in detail with reference to the drawings, the specific configuration is not limited to these embodiments, and includes designs within the scope of the gist of the present invention.
１　光送信装置
１１　第一光源
１２　光コム発生器
１３　信号源
１４　分配部
１５　第一帯域制限部
１６　位相変調部
１７　第二帯域制限部
１８　光路長調整部
１９　合波部
２０　受光部
２１　光強度変調部
２２　第二光源 1 Optical transmitter 11 First light source 12 Optical comb generator 13 Signal source 14 Distribution section 15 First band limiter 16 Phase modulator 17 Second band limiter 18 Optical path length adjuster 19 Multiplexer 20 Light receiver 21 Light intensity Modulation section 22 Second light source

Claims (4)

  1. 　第一の光源からの出力光と信号源からの周波数とを用いて等しい周波数間隔で光コムが並んだ光信号を発生する光コム発生器と、
    　前記光コム発生器が発生した前記光信号から第一の光コム及び第二の光コムを抜きだす抽出部と、
    　前記第一の光コムを入力信号により位相変調した変調信号を生成する位相変調部と、
    　前記第二の光コムの遅延量を調整する調整部と、
    　前記変調信号と、遅延量が調整された前記第二の光コムとを合波する合波部と、
    　前記合波部により合波された光を二乗検波してＦＭ（Frequency Modulation）信号を生成する受光部と、
    　前記ＦＭ信号により第二の光源の出力光を強度変調する光強度変調部と、
    　を備える光送信装置。     an optical comb generator that generates an optical signal in which optical combs are arranged at equal frequency intervals using the output light from the first light source and the frequency from the signal source;
    an extraction unit that extracts a first optical comb and a second optical comb from the optical signal generated by the optical comb generator;
    a phase modulation unit that generates a modulation signal by phase modulating the first optical comb with an input signal;
    an adjustment unit that adjusts the amount of delay of the second optical comb;
    a multiplexing unit that multiplexes the modulated signal and the second optical comb with an adjusted delay amount;
    a light receiving unit that generates an FM (Frequency Modulation) signal by performing square law detection of the light multiplexed by the multiplexing unit;
    a light intensity modulator that intensity-modulates the output light of the second light source using the FM signal;
    An optical transmitter comprising:
  2. 　前記抽出部は、
    　前記光コム発生器が発生した前記光信号を２分配する分配部と、
    　前記分配部が分配した一方の前記光信号から前記第一の光コムを抽出する第一抽出部と、
    　前記分配部が分配したもう一方の前記光信号から前記第二の光コムを抽出する第二抽出部とを備える、
    　請求項１に記載の光送信装置。     The extraction section is
    a distribution unit that divides the optical signal generated by the optical comb generator into two;
    a first extraction unit that extracts the first optical comb from one of the optical signals distributed by the distribution unit;
    a second extraction unit that extracts the second optical comb from the other optical signal distributed by the distribution unit;
    The optical transmitter according to claim 1.
  3. 　前記入力信号は、多重されていない信号、又は、周波数多重された信号である、
    　請求項１又は請求項２に記載の光送信装置。     the input signal is a non-multiplexed signal or a frequency-multiplexed signal;
    The optical transmitter according to claim 1 or claim 2.
  4. 　第一の光源からの出力光と信号源からの周波数とを用いて等しい周波数間隔で光コムが並んだ光信号を発生する光コム発生ステップと、
    　前記光コム発生ステップにおいて発生させた前記光信号から第一の光コム及び第二の光コムを抜きだす抽出ステップと、
    　前記第一の光コムを入力信号により位相変調した変調信号を生成する位相変調ステップと、
    　前記第二の光コムの遅延量を調整する調整ステップと、
    　前記変調信号と、遅延量が調整された前記第二の光コムとを合波する合波ステップと、
    　前記合波ステップにおいて合波された光を二乗検波してＦＭ（Frequency Modulation）信号を生成する信号生成ステップと、
    　前記ＦＭ信号により第二の光源の出力光を強度変調する光強度変調ステップと、
    　を有する光信号生成方法。     an optical comb generation step of generating an optical signal in which optical combs are arranged at equal frequency intervals using the output light from the first light source and the frequency from the signal source;
    an extraction step of extracting a first optical comb and a second optical comb from the optical signal generated in the optical comb generation step;
    a phase modulation step of generating a modulation signal by phase modulating the first optical comb with an input signal;
    an adjusting step of adjusting the delay amount of the second optical comb;
    a combining step of combining the modulated signal and the second optical comb with an adjusted delay amount;
    a signal generation step of generating a frequency modulation (FM) signal by square law detection of the light multiplexed in the multiplexing step;
    a light intensity modulation step of intensity modulating the output light of the second light source using the FM signal;
    An optical signal generation method comprising:
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