JP6636884B2 - Optical transmitter, optical transmission system and optical receiver - Google Patents

Optical transmitter, optical transmission system and optical receiver Download PDF

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JP6636884B2
JP6636884B2 JP2016174066A JP2016174066A JP6636884B2 JP 6636884 B2 JP6636884 B2 JP 6636884B2 JP 2016174066 A JP2016174066 A JP 2016174066A JP 2016174066 A JP2016174066 A JP 2016174066A JP 6636884 B2 JP6636884 B2 JP 6636884B2
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政則 中村
政則 中村
福太郎 濱岡
福太郎 濱岡
建吾 堀越
建吾 堀越
明日香 松下
明日香 松下
宗彦 長谷
宗彦 長谷
山崎　裕史
裕史 山崎
佐野　明秀
明秀 佐野
平野　章
章 平野
宮本　裕
宮本　　裕
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Description

本発明は、光送信機、光伝送システム及び光受信機に関する。   The present invention relates to an optical transmitter, an optical transmission system, and an optical receiver.

光通信システムの基幹網において、近年の通信トラヒックの拡大と、４００Ｇｂｐｓ（Gigabits per second）や１Ｔｂｐｓ（Terabits per second）のＥｔｈｅｒｎｅｔ（登録商標）をはじめとするクライアント信号を収容する回線の容量増加により、１チャネルあたりの伝送容量の拡大が求められている。現在の１チャネルあたり１００Ｇｂｐｓを有するシステムでは、変調速度が３２ＧＢａｕｄ（Baud）であり、変調方式としてＤＰ−ＱＰＳＫ(Dual Polarization-Quadrature Phase Shift Keying)を用いるデジタルコヒーレント光伝送方式が採用されている（例えば、非特許文献１参照）。   In the backbone network of the optical communication system, due to the recent expansion of communication traffic and an increase in the capacity of a line for accommodating client signals such as Ethernet (registered trademark) such as 400 Gbps (Gigabits per second) and 1 Tbps (Terabits per second), There is a demand for an increase in transmission capacity per channel. In a current system having 100 Gbps per channel, a modulation rate is 32 GBaud (Baud), and a digital coherent optical transmission method using DP-QPSK (Dual Polarization-Quadrature Phase Shift Keying) as a modulation method is adopted (for example, , Non-Patent Document 1).

１チャネルあたりの伝送容量拡大に向け、次世代の４００Ｇｂｐｓ、１Ｔｂｐｓ級の伝送では、変調速度の向上が検討されている（例えば、非特許文献２参照）。変調速度を向上させる上でＤＡＣ(Digital to Analog Converter)のアナログ帯域の制限が課題となる。ＤＡＣのアナログ帯域を拡大する技術として、複数の低速信号をアナログ的に合成し高速信号を生成する技術が提案されている（例えば、非特許文献３及び４参照）。   To increase the transmission capacity per channel, in next-generation transmission of 400 Gbps and 1 Tbps, improvement of the modulation speed is being studied (for example, see Non-Patent Document 2). In improving the modulation speed, there is a problem of limiting the analog band of a DAC (Digital to Analog Converter). As a technique for expanding the analog band of the DAC, a technique of synthesizing a plurality of low-speed signals in an analog manner to generate a high-speed signal has been proposed (for example, see Non-Patent Documents 3 and 4).

Joe Berthold et.al, ”100G Ultra Long Haul DWDM Framework Document”, OIF(OPTICAL INTERNETWORKING FORUM), June 30, 2009.Joe Berthold et.al, “100G Ultra Long Haul DWDM Framework Document”, OIF (OPTICAL INTERNETWORKING FORUM), June 30, 2009. G. Raybon, A. L. Adamiecki, P. Winzer, C. Xie, A. Konczykowska, F. Jorge, J.-Y. Dupuy, L. L. Buhl, S. Chandrashekhar, S. Draving, M. Grove, and K. Rush, "Single-carrier 400G interface and 10-channel WDM transmission over 4,800 km using all-ETDM 107-Gbaud PDM-QPSK" in Optical Fiber Communication Conference/National Fiber Optic Engineers Conference 2013, OSA Technical Digest (online) (Optical Society of America, 2013), paper PDP5A.5.G. Raybon, AL Adamiecki, P. Winzer, C. Xie, A. Konczykowska, F. Jorge, J.-Y. Dupuy, LL Buhl, S. Chandrashekhar, S. Draving, M. Grove, and K. Rush, "Single-carrier 400G interface and 10-channel WDM transmission over 4,800 km using all-ETDM 107-Gbaud PDM-QPSK" in Optical Fiber Communication Conference / National Fiber Optic Engineers Conference 2013, OSA Technical Digest (online) (Optical Society of America , 2013), paper PDP5A.5. H. Yamazaki et al., “160-Gbps Nyquist PAM4 Transmitter Using a Digital-Preprocessed Analog-Multiplexed DAC” Optical Communication (ECOC), 2015 European Conference on, Valencia, 2015, pp. 1-3.H. Yamazaki et al., “160-Gbps Nyquist PAM4 Transmitter Using a Digital-Preprocessed Analog-Multiplexed DAC” Optical Communication (ECOC), 2015 European Conference on, Valencia, 2015, pp. 1-3. X. Chen, S. Chandrasekhar, S. Randel, G. Raybon, A. Adamiecki, P. Pupalaikis, and P. Winzer, "All-electronic 100-GHz Bandwidth Digital-to-Analog Converter Generating PAM Signals up to 190-GBaud" in Optical Fiber Communication Conference Postdeadline Papers, OSA Technical Digest (online) (Optical Society of America, 2016), paper Th5C.5.X. Chen, S. Chandrasekhar, S. Randel, G. Raybon, A. Adamiecki, P. Pupalaikis, and P. Winzer, "All-electronic 100-GHz Bandwidth Digital-to-Analog Converter Generating PAM Signals up to 190- GBaud "in Optical Fiber Communication Conference Postdeadline Papers, OSA Technical Digest (online) (Optical Society of America, 2016), paper Th5C.5.

しかしながら、非特許文献３及び４に記載された技術では、低速信号に基づいて高速信号を生成する際に複数のＤＡＣが用いられ、合成部にはアナログデバイスが用いられる。そのため、ＤＡＣの個体差や、アナログデバイスの不完全性により、低速信号間の周波数特性が異なることによる信号品質の劣化が発生してしまうという問題があった。   However, in the techniques described in Non-Patent Documents 3 and 4, when generating a high-speed signal based on a low-speed signal, a plurality of DACs are used, and an analog device is used for a synthesis unit. For this reason, there is a problem that signal quality is degraded due to a difference in frequency characteristics between low-speed signals due to individual differences of DACs and imperfections of analog devices.

上記事情に鑑み、本発明は、信号品質の劣化を改善することができる光送信機、光伝送システム及び光受信機の提供を目的としている。   In view of the above circumstances, an object of the present invention is to provide an optical transmitter, an optical transmission system, and an optical receiver that can improve signal quality deterioration.

本発明の一態様は、送信データ系列から複数の低速信号を生成する送信信号生成部と、前記複数の低速信号を、２つ以上の前記低速信号を含む組み合わせに分け、前記複数の低速信号をデジタルアナログ変換して前記組み合わせごとに合成することにより高速信号を生成する高速信号生成部と、生成される前記高速信号と、参照信号とに基づいて伝達関数を算出する伝達関数推定部と、前記送信信号生成部が生成する前記複数の低速信号を、前記伝達関数に基づいて補償して前記高速信号生成部に出力する伝達関数補償部と、を備える光送信機である。   One aspect of the present invention is a transmission signal generation unit that generates a plurality of low-speed signals from a transmission data sequence, and divides the plurality of low-speed signals into a combination including two or more of the low-speed signals. A high-speed signal generation unit that generates a high-speed signal by performing digital-to-analog conversion and combining for each combination; a transfer function estimation unit that calculates a transfer function based on the generated high-speed signal and a reference signal; A transfer function compensator for compensating the plurality of low-speed signals generated by the transmission signal generator based on the transfer function and outputting the compensated low-speed signal to the high-speed signal generator.

本発明の一態様は、上記の光送信機であって、前記伝達関数推定部は、前記送信信号生成部が生成する複数の低速信号を前記参照信号として前記伝達関数を算出するか、または、予め既知信号として定められている前記送信データ系列の一部を前記参照信号として前記伝達関数を算出するか、または、前記高速信号の受信シンボルを判定して得られるシンボル系列から前記低速信号を生成し、生成した前記低速信号を前記参照信号として前記伝達関数を算出する。   One aspect of the present invention is the optical transmitter described above, wherein the transfer function estimating unit calculates the transfer function using a plurality of low-speed signals generated by the transmission signal generating unit as the reference signal, or Either calculate the transfer function using a part of the transmission data sequence previously determined as a known signal as the reference signal, or generate the low-speed signal from a symbol sequence obtained by determining a reception symbol of the high-speed signal. Then, the transfer function is calculated using the generated low-speed signal as the reference signal.

本発明の一態様は、光送信機と、光受信機と、前記光送信機と前記光受信機とに接続される伝送路と、を備える光伝送システムであって、前記光送信機は、送信データ系列から複数の低速信号を生成する送信信号生成部と、前記複数の低速信号を、２つ以上の前記低速信号を含む組み合わせに分け、前記複数の低速信号をデジタルアナログ変換して前記組み合わせごとに合成することにより高速信号を生成する高速信号生成部と、前記高速信号を変調した光信号を前記伝送路に対して送信する光変調器と、を有し、前記光受信機は、前記伝送路から前記光信号を受信し、受信する前記光信号から得られる前記高速信号を出力する受信部と、前記受信部が出力する前記高速信号に基づいて、前記送信データ系列に含まれるバイナリ情報を復調する受信データ復調部と、を有し、前記光送信機は、前記高速信号生成部が生成する前記高速信号と、参照信号とに基づいて伝達関数を算出する伝達関数推定部と、前記送信信号生成部が生成する前記複数の低速信号を、前記伝達関数に基づいて補償し、前記高速信号生成部に出力する伝達関数補償部と、を備える光伝送システムである。
本発明の一態様は、光送信機と、光受信機と、前記光送信機と前記光受信機とに接続される伝送路と、を備える光伝送システムであって、前記光送信機は、送信データ系列から複数の低速信号を生成する送信信号生成部と、前記複数の低速信号を、２つ以上の前記低速信号を含む組み合わせに分け、前記複数の低速信号をデジタルアナログ変換して前記組み合わせごとに合成することにより高速信号を生成する高速信号生成部と、前記高速信号を変調した光信号を前記伝送路に対して送信する光変調器と、を有し、前記光受信機は、前記伝送路から前記光信号を受信し、受信する前記光信号から得られる前記高速信号を出力する受信部と、前記受信部が出力する前記高速信号に基づいて、前記送信データ系列に含まれるバイナリ情報を復調する受信データ復調部と、を有し、前記光受信機は、前記受信部が出力する前記高速信号と、参照信号とに基づいて伝達関数を算出する伝達関数推定部を備え、前記光送信機は、前記送信信号生成部が生成する前記複数の低速信号を、前記伝達関数推定部が算出した前記伝達関数に基づいて補償する伝達関数補償部、を備え、前記伝達関数推定部は、前記送信信号生成部が生成する前記複数の低速信号を前記参照信号として前記伝達関数を算出するか、または、前記高速信号の受信シンボルを判定し、判定によって得られるシンボル系列から前記低速信号を生成し、生成した前記低速信号を前記参照信号として前記伝達関数を算出する光伝送システムである。
本発明の一態様は、光送信機と、光受信機と、前記光送信機と前記光受信機とに接続される伝送路と、を備える光伝送システムであって、前記光送信機は、送信データ系列から複数の低速信号を生成する送信信号生成部と、前記複数の低速信号を、２つ以上の前記低速信号を含む組み合わせに分け、前記複数の低速信号をデジタルアナログ変換して前記組み合わせごとに合成することにより高速信号を生成する高速信号生成部と、前記高速信号を変調した光信号を前記伝送路に対して送信する光変調器と、を有し、前記光受信機は、前記伝送路から前記光信号を受信し、受信する前記光信号から得られる前記高速信号を出力する受信部と、前記受信部が出力する前記高速信号に基づいて、前記送信データ系列に含まれるバイナリ情報を復調する受信データ復調部と、を有し、前記光受信機は、前記受信部が出力する前記高速信号と、参照信号とに基づいて伝達関数を算出する伝達関数推定部と、前記受信部が受信する前記光信号から得られる前記複数の低速信号を、前記伝達関数に基づいて補償する伝達関数補償部と、を備える光伝送システムである。 One embodiment of the present invention is an optical transmission system including an optical transmitter, an optical receiver, and a transmission line connected to the optical transmitter and the optical receiver, wherein the optical transmitter is A transmission signal generation unit that generates a plurality of low-speed signals from a transmission data sequence, and divides the plurality of low-speed signals into a combination including two or more low-speed signals; A high-speed signal generation unit that generates a high-speed signal by synthesizing each, and an optical modulator that transmits an optical signal obtained by modulating the high-speed signal to the transmission line, and the optical receiver includes: A receiving unit that receives the optical signal from a transmission line and outputs the high-speed signal obtained from the received optical signal; and, based on the high-speed signal output by the receiving unit, binary information included in the transmission data sequence. Demodulate Includes a reception data demodulation portion, said optical transmitter, said high-speed signals to the high-speed signal generating unit generates a transfer function estimating unit that calculates a transfer function based on the reference signal, the transmission signal A transfer function compensating unit that compensates the plurality of low-speed signals generated by the generating unit based on the transfer function and outputs the compensated low-speed signal to the high-speed signal generating unit .
One embodiment of the present invention is an optical transmission system including an optical transmitter, an optical receiver, and a transmission line connected to the optical transmitter and the optical receiver, wherein the optical transmitter is A transmission signal generation unit that generates a plurality of low-speed signals from a transmission data sequence, and divides the plurality of low-speed signals into a combination including two or more low-speed signals; A high-speed signal generation unit that generates a high-speed signal by synthesizing each, and an optical modulator that transmits an optical signal obtained by modulating the high-speed signal to the transmission line, and the optical receiver includes: A receiving unit that receives the optical signal from a transmission line and outputs the high-speed signal obtained from the received optical signal; and, based on the high-speed signal output by the receiving unit, binary information included in the transmission data sequence. Demodulate A reception data demodulation unit, the optical receiver includes a transfer function estimating unit that calculates a transfer function based on the high-speed signal output by the reception unit and a reference signal, and the optical transmitter includes: A transfer function compensator for compensating the plurality of low-speed signals generated by the transmission signal generator based on the transfer function calculated by the transfer function estimator; and the transfer function estimator includes: The transfer function is calculated using the plurality of low-speed signals generated by the generation unit as the reference signal, or a received symbol of the high-speed signal is determined, and the low-speed signal is generated from a symbol sequence obtained by the determination. An optical transmission system that calculates the transfer function using the obtained low-speed signal as the reference signal.
One embodiment of the present invention is an optical transmission system including an optical transmitter, an optical receiver, and a transmission line connected to the optical transmitter and the optical receiver, wherein the optical transmitter is A transmission signal generation unit that generates a plurality of low-speed signals from a transmission data sequence, and divides the plurality of low-speed signals into a combination including two or more low-speed signals; A high-speed signal generation unit that generates a high-speed signal by synthesizing each, and an optical modulator that transmits an optical signal obtained by modulating the high-speed signal to the transmission line, and the optical receiver includes: A receiving unit that receives the optical signal from a transmission line and outputs the high-speed signal obtained from the received optical signal; and, based on the high-speed signal output by the receiving unit, binary information included in the transmission data sequence. Demodulate A reception data demodulation unit, wherein the optical receiver receives the high-speed signal output by the reception unit, a transfer function estimation unit that calculates a transfer function based on a reference signal, and the reception unit receives A transfer function compensator for compensating the plurality of low-speed signals obtained from the optical signal based on the transfer function.

本発明の一態様は、上記の光伝送システムであって、前記伝達関数推定部は、前記送信信号生成部が生成する前記複数の低速信号を前記参照信号として前記伝達関数を算出するか、または、予め既知信号として定められている前記送信データ系列の一部を前記参照信号として前記伝達関数を算出するか、または、前記高速信号の受信シンボルを判定し、判定によって得られるシンボル系列から前記低速信号を生成し、生成した前記低速信号を前記参照信号として前記伝達関数を算出する。   One aspect of the present invention is the above-described optical transmission system, wherein the transfer function estimating unit calculates the transfer function using the plurality of low-speed signals generated by the transmission signal generating unit as the reference signal, or Calculating the transfer function using a part of the transmission data sequence previously determined as a known signal as the reference signal, or determining a received symbol of the high-speed signal, and determining the low-speed signal from the symbol sequence obtained by the determination. A signal is generated, and the transfer function is calculated using the generated low-speed signal as the reference signal.

本発明の一態様は、上記の光伝送システムであって、前記伝達関数推定部は、前記送信信号生成部が、前記伝送路における波形歪を補償する波形整形を行っている場合、前記波形整形が行われていない前記複数の低速信号を前記参照信号として用いるか、または、前記高速信号に対して同一の前記波形整形を行ってから前記伝達関数の算出を行う。   One embodiment of the present invention is the above-described optical transmission system, wherein the transfer function estimating unit is configured to perform the waveform shaping when the transmission signal generating unit performs waveform shaping to compensate for waveform distortion in the transmission path. The transfer function is calculated after using the plurality of low-speed signals for which the processing has not been performed as the reference signal, or after performing the same waveform shaping on the high-speed signal.

本発明の一態様は、複数の低速信号を、２つ以上の前記低速信号を含む組み合わせに分け、前記複数の低速信号をデジタルアナログ変換して前記組み合わせごとに合成することにより高速信号を生成する光送信機が送信する光信号を受信する光受信機であって、前記光信号を受信する受信部と、前記受信部が受信する前記光信号から得られる前記高速信号と、参照信号とに基づいて伝達関数を算出する伝達関数推定部と、前記受信部が受信する前記光信号から得られる前記複数の低速信号を、前記伝達関数に基づいて補償する伝達関数補償部と、前記伝達関数補償部が補償する前記複数の低速信号を合成して前記高速信号を生成する信号合成部と、生成される前記高速信号に基づいて、送信データ系列に含まれるバイナリ情報を復調する受信データ復調部と、を備える光受信機である。   One embodiment of the present invention generates a high-speed signal by dividing a plurality of low-speed signals into a combination including two or more of the low-speed signals, and performing digital-to-analog conversion on the plurality of low-speed signals and synthesizing each of the combinations. An optical receiver that receives an optical signal transmitted by an optical transmitter, a receiving unit that receives the optical signal, the high-speed signal obtained from the optical signal received by the receiving unit, and a reference signal. A transfer function estimating unit that calculates a transfer function, a transfer function compensating unit that compensates the plurality of low-speed signals obtained from the optical signal received by the receiving unit based on the transfer function, and a transfer function compensating unit. A signal combining unit that combines the plurality of low-speed signals to compensate to generate the high-speed signal; and a reception unit that demodulates binary information included in a transmission data sequence based on the generated high-speed signal. And over data demodulator, an optical receiver comprising a.

本発明の一態様は、上記の光受信機であって、前記伝達関数推定部は、前記光送信機から前記複数の低速信号を受信し、受信した前記複数の低速信号を前記参照信号として前記伝達関数を算出するか、または、予め既知信号として定められている前記送信データ系列の一部を前記参照信号として前記伝達関数を算出するか、または、受信した前記光信号から得られる前記高速信号の受信シンボルを判定し、判定によって得られるシンボル系列から前記低速信号を生成し、生成した前記低速信号を前記参照信号として前記伝達関数を算出する。   One aspect of the present invention is the optical receiver, wherein the transfer function estimating unit receives the plurality of low-speed signals from the optical transmitter, and uses the received plurality of low-speed signals as the reference signal. Either calculating a transfer function, or calculating the transfer function using a part of the transmission data sequence previously determined as a known signal as the reference signal, or the high-speed signal obtained from the received optical signal , The low-speed signal is generated from the symbol sequence obtained by the determination, and the transfer function is calculated using the generated low-speed signal as the reference signal.

本発明の一態様は、上記の光受信機であって、前記受信部が受信する前記光信号から得られる前記高速信号を分離して前記複数の低速信号を生成する高速信号分離部を備えており、前記伝達関数補償部は、前記高速信号分離部が生成する前記複数の低速信号を、前記伝達関数に基づいて補償する。   One aspect of the present invention is the optical receiver described above, further comprising a high-speed signal separation unit that generates the plurality of low-speed signals by separating the high-speed signal obtained from the optical signal received by the reception unit. The transfer function compensator compensates the plurality of low-speed signals generated by the high-speed signal separator based on the transfer function.

この発明によれば、信号品質の劣化を改善することが可能となる。   According to the present invention, it is possible to improve signal quality deterioration.

第１実施形態における光送信機の構成を示すブロック図である。FIG. 2 is a block diagram illustrating a configuration of an optical transmitter according to the first embodiment. 送信信号生成部の構成を示すブロック図である。FIG. 3 is a block diagram illustrating a configuration of a transmission signal generation unit. 高速信号生成部の構成を示すブロック図である。FIG. 3 is a block diagram illustrating a configuration of a high-speed signal generation unit. 伝達関数推定部の構成を示すブロック図である。FIG. 3 is a block diagram illustrating a configuration of a transfer function estimating unit. 光送信機の他の構成例を示すブロック図である。It is a block diagram showing another example of composition of an optical transmitter. 第２実施形態における光伝送システムの構成を示すブロック図である。It is a block diagram showing the composition of the optical transmission system in a 2nd embodiment. 第３実施形態における光伝送システムの構成を示すブロック図である。It is a block diagram showing the composition of the optical transmission system in a 3rd embodiment. 光受信機に適用される伝達関数推定部の構成を示すブロック図（その１）である。It is a block diagram (the 1) showing the composition of the transfer function estimation part applied to an optical receiver. 光受信機に適用される伝達関数推定部の構成を示すブロック図（その２）である。It is a block diagram (the 2) showing the composition of the transfer function estimation part applied to an optical receiver. 第２実施形態の光伝送システムを用いた実験結果を示すグラフである。9 is a graph illustrating an experimental result using the optical transmission system according to the second embodiment.

（第１実施形態）
以下、本発明の実施形態について図面を参照して説明する。図１は、第１実施形態における光送信機の構成を示すブロック図である。光送信機１０は、送信信号生成部１１、伝達関数補償部１２、高速信号生成部１３−１〜１３−４、光変調器１４及び伝達関数推定部１５を備える。なお、以下の記載において、低速信号及び高速信号の用語における低速と高速の意味は、アナログ帯域の帯域幅の狭さと広さを示しており、例えば、高速信号の帯域幅がｆｃ［ＧＨｚ］である場合、低速信号の帯域幅はｆｃ［ＧＨｚ］より小さい値となる。本実施形態では、高速信号≒低速信号×Ｎ（Ｎは整数でＤＡＣの個数）程度の帯域幅とする。 (1st Embodiment)
Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a block diagram illustrating a configuration of the optical transmitter according to the first embodiment. The optical transmitter 10 includes a transmission signal generator 11, a transfer function compensator 12, high-speed signal generators 13-1 to 13-4, an optical modulator 14, and a transfer function estimator 15. In the following description, the meaning of low speed and high speed in the terms of low speed signal and high speed signal indicates the narrowness and width of the bandwidth of the analog band. For example, when the bandwidth of the high speed signal is fc [GHz]. In some cases, the bandwidth of the low-speed signal is smaller than fc [GHz]. In the present embodiment, the bandwidth is about high-speed signal / low-speed signal × N (N is an integer and the number of DACs).

送信信号生成部１１は、図２に示す内部構成を有しており、ビットマッピング部１１１、波形整形部１１２及び高速信号生成部用前置信号処理部１１３を備える。ビットマッピング部１１１は、外部から供給されるバイナリ情報である送信データ系列に対して、ＱＰＳＫ（Quadrature Phase Shift Keying）や１６ＱＡＭ（Quadrature Amplitude Modulation）等のシンボル点に対する送信ビットの割り当てを行い、高速信号である変調信号系列（ＸＩ，ＸＱ，ＹＩ，ＹＱ）を生成する。波形整形部１１２は、ビットマッピング部１１１が出力する変調信号系列に対してＲａｉｓｅｄ Ｃｏｓｉｎｅ ＦｉｌｔｅｒやＲｏｏｔ Ｒａｉｓｅｄ Ｃｏｓｉｎｅ Ｆｉｌｔｅｒ等のフィルタリング処理を行う。なお、波形整形部１１２において、伝送路での波形歪を補償する前置波長分散補償や前置非線形光学効果補償等の任意の信号処理を行うようにしてもよい。   The transmission signal generation unit 11 has the internal configuration shown in FIG. 2 and includes a bit mapping unit 111, a waveform shaping unit 112, and a high-speed signal generation unit front signal processing unit 113. The bit mapping section 111 allocates transmission bits to symbol points such as QPSK (Quadrature Phase Shift Keying) and 16QAM (Quadrature Amplitude Modulation) to a transmission data sequence that is binary information supplied from the outside, and The modulated signal sequence (XI, XQ, YI, YQ) is generated. The waveform shaping unit 112 performs a filtering process such as a raised cosine filter or a root raised cosine filter on the modulated signal sequence output from the bit mapping unit 111. The waveform shaping section 112 may perform any signal processing such as a pre-wavelength dispersion compensation or a pre-linear optical effect compensation for compensating for waveform distortion in a transmission path.

高速信号生成部用前置信号処理部１１３は、出力する低速信号が高速信号生成部１３−１〜１３−４により合成された際に、所望の信号が生成されるように信号処理を行って低速信号を生成する。低速信号の生成の手法としては、例えば、非特許文献３に示す手法がある。非特許文献３に示す手法では、波形整形部１１２によってフィルタリング処理された高速信号である変調信号系列（ＸＩ，ＸＱ，ＹＩ，ＹＱ）を周波数領域で分割し、高周波成分を折り返し、低周波成分と加算した信号と、低周波成分から減算した信号とをそれぞれ低速信号として出力する。また、高速信号生成部用前置信号処理部１１３は、非特許文献３に示す手法以外の任意の手法を用いて低速信号を生成してもよい。   The high-speed signal generation unit front signal processing unit 113 performs signal processing so that a desired signal is generated when the low-speed signals to be output are combined by the high-speed signal generation units 13-1 to 13-4. Generate a low-speed signal. As a method of generating a low-speed signal, for example, there is a method disclosed in Non-Patent Document 3. According to the technique disclosed in Non-Patent Document 3, a modulated signal sequence (XI, XQ, YI, YQ), which is a high-speed signal filtered by the waveform shaping unit 112, is divided in a frequency domain, a high-frequency component is folded, and a low-frequency component is The added signal and the signal subtracted from the low-frequency component are output as low-speed signals. Also, the high-speed signal generation unit front signal processing unit 113 may generate the low-speed signal using any method other than the method described in Non-Patent Document 3.

伝達関数補償部１２は、伝達関数推定部１５が算出する伝達関数に基づいて、高速信号生成部１３−１〜１３−４内における周波数特性の補償を行う。ここで、伝達関数に基づく周波数特性の補償の方式としては、任意の方式を適用することができ、例えば、ＦＩＲ（Finite Impulse Response）フィルタやＩＩＲ（Infinite Impulse Response）フィルタ等を使ったデジタル信号処理方式、または、位相器や遅延線等のアナログフィルタを用いたアナログ方式が適用される。   The transfer function compensator 12 compensates for frequency characteristics in the high-speed signal generators 13-1 to 13-4 based on the transfer function calculated by the transfer function estimator 15. Here, any method can be applied as a method of compensating the frequency characteristics based on the transfer function. For example, digital signal processing using an FIR (Finite Impulse Response) filter, an IIR (Infinite Impulse Response) filter, or the like can be used. An analog method using an analog filter such as a phase shifter or a delay line is applied.

高速信号生成部１３−１〜１３−４は、同一の内部構成を有しており、一例として、図３に、高速信号生成部１３−１の内部構成を示す。高速信号生成部１３−１は、２つのＳｕｂ−ＤＡＣ１３１−１及び１３２−１と、アナログ多重器１３３−１を備える。２つのＳｕｂ−ＤＡＣ１３１−１及び１３２−１は、デジタル信号である低速信号をアナログ信号に変換する。アナログ多重器１３３−１は、２つのＳｕｂ−ＤＡＣ１３１−１及び１３２−１それぞれによって変換されたアナログ信号を合成して高速信号を生成する。このように、２つのＳｕｂ−ＤＡＣ１３１−１及び１３２−１を用いることで、単一のＤＡＣにより高速信号を生成する場合に対して、２つのＳｕｂ−ＤＡＣ１３１−１及び１３２−１の各々に要求される帯域を大幅に低減することができる。   The high-speed signal generators 13-1 to 13-4 have the same internal configuration. As an example, FIG. 3 shows the internal configuration of the high-speed signal generator 13-1. The high-speed signal generator 13-1 includes two sub-DACs 131-1 and 132-1 and an analog multiplexer 133-1. The two Sub-DACs 131-1 and 132-1 convert a low-speed signal, which is a digital signal, into an analog signal. The analog multiplexer 133-1 combines the analog signals converted by the two Sub-DACs 131-1 and 132-1 to generate a high-speed signal. As described above, by using the two Sub-DACs 131-1 and 132-1, each of the two Sub-DACs 131-1 and 132-1 is required to generate a high-speed signal using a single DAC. Band to be performed can be significantly reduced.

光変調器１４は、偏波多重型マッハツェンダ型ベクトル変調器、ドライバアンプ、レーザモジュールを備える偏波多重ＩＱ変調器である。また、光変調器１４において、高速信号生成部１３−１〜１３−４が出力する４レーンの高速信号（ＸＩ，ＸＱ，ＹＩ，ＹＱ）に対して、各々のレーンに設置されるドライバアンプが増幅を行い、増幅した高速信号を偏波多重型マッハツェンダ型ベクトル変調器に変調信号として出力する。偏波多重型マッハツェンダ型ベクトル変調器は、当該変調信号に基づいてレーザモジュールからの光信号を変調し、変調した光信号を伝送路に対して出力する。   The optical modulator 14 is a polarization multiplexing IQ modulator including a polarization multiplexing type Mach-Zehnder type vector modulator, a driver amplifier, and a laser module. In the optical modulator 14, a driver amplifier installed in each lane is provided for four lanes of high-speed signals (XI, XQ, YI, YQ) output from the high-speed signal generators 13-1 to 13-4. Amplification is performed, and the amplified high-speed signal is output as a modulation signal to a polarization multiplexing type Mach-Zehnder type vector modulator. The polarization multiplexing type Mach-Zehnder type vector modulator modulates an optical signal from a laser module based on the modulated signal, and outputs the modulated optical signal to a transmission line.

伝達関数推定部１５は、図４に示す内部構成を有しており、高速信号（ＸＩ，ＸＱ，ＹＩ，ＹＱ）の４つのレーンごとの伝達関数推定部１５−１〜１５−４を備えている。伝達関数推定部１５−１〜１５−４の各々は、同一の内部構成を有しており、一例として、図４に伝達関数推定部１５−１の内部構成を示す。伝達関数推定部１５−１は、高速信号生成部用前置信号処理部１５１−１と、２つの伝達関数推定回路１５２−１，１５３−１を備える。   The transfer function estimating unit 15 has an internal configuration shown in FIG. 4, and includes transfer function estimating units 15-1 to 15-4 for high speed signals (XI, XQ, YI, YQ) for each of four lanes. I have. Each of transfer function estimating units 15-1 to 15-4 has the same internal configuration, and FIG. 4 shows an internal configuration of transfer function estimating unit 15-1 as an example. The transfer function estimating unit 15-1 includes a pre-signal processing unit 151-1 for a high-speed signal generating unit, and two transfer function estimating circuits 152-1 and 153-1.

高速信号生成部用前置信号処理部１５１−１は、前述した送信信号生成部１１が備える高速信号生成部用前置信号処理部１１３の１レーン分の高速信号を処理する機能を有している。高速信号生成部用前置信号処理部１５１−１は、高速信号（ＸＩ）から低速信号（ＸＩ１，ＸＩ２）を生成する。また、高速信号生成部用前置信号処理部１５１−１は、低速信号（ＸＩ１）を伝達関数推定回路１５２−１に出力し、低速信号（ＸＩ２）を伝達関数推定回路１５３−１に出力する。 The high-speed signal generation unit front signal processing unit 151-1 has a function of processing a high-speed signal for one lane of the high-speed signal generation unit front signal processing unit 113 included in the transmission signal generation unit 11 described above. I have. The high-speed signal generation unit front signal processing unit 151-1 generates low-speed signals (XI 1 , XI 2 ) from the high-speed signal (XI). Also, the high-speed signal generation unit front signal processing unit 151-1 outputs the low-speed signal (XI 1 ) to the transfer function estimation circuit 152-1 and outputs the low-speed signal (XI 2 ) to the transfer function estimation circuit 153-1. Output.

伝達関数推定回路１５２−１は、送信信号生成部１１が出力する低速信号（ＸＩ１）を参照用の信号として取得し、高速信号生成部用前置信号処理部１５１−１が出力する低速信号（ＸＩ１）と、参照用の低速信号（ＸＩ１）（以下「参照信号」という。）とを同期して周波数応答を算出する。ここで、周波数応答の算出手法としては、高速信号生成部用前置信号処理部１５１−１が出力する低速信号（ＸＩ１）と、参照信号（ＸＩ１）との誤差を最小化するようにデジタルフィルタのタップ係数を最適化するＬＭＳ(Least Mean Square)アルゴリズムやＲＬＳ（Recursive Least Square）アルゴリズムを用いる適用フィルタを利用する手法がある。また、これら以外の手法として、ＺＦ（Zero-Forcing）法や、ＭＭＳＥ（Minimum Mean Square Error）法等を適用してもよい。 The transfer function estimating circuit 152-1 acquires the low-speed signal (XI 1 ) output from the transmission signal generation unit 11 as a reference signal, and outputs the low-speed signal output from the high-speed signal generation unit front signal processing unit 151-1. (XI 1 ) and a reference low-speed signal (XI 1 ) (hereinafter referred to as “reference signal”) are synchronized to calculate a frequency response. Here, the method of calculating the frequency response is such that an error between the low-speed signal (XI 1 ) output from the pre-signal processing unit 151-1 for the high-speed signal generation unit and the reference signal (XI 1 ) is minimized. There is a method using an applied filter using an LMS (Least Mean Square) algorithm or an RLS (Recursive Least Square) algorithm for optimizing tap coefficients of a digital filter. Further, as a method other than these, a ZF (Zero-Forcing) method, an MMSE (Minimum Mean Square Error) method, or the like may be applied.

伝達関数推定回路１５３−１も同様に、送信信号生成部１１が出力する低速信号（ＸＩ２）を参照用信号として取得し、高速信号生成部用前置信号処理部１５１−１が出力する低速信号（ＸＩ２）と、参照信号（ＸＩ２）とを同期して周波数応答を算出する。このようにして、伝達関数推定部１５−２，１５−３，１５−４の各々において、高速信号（ＸＱ）と参照信号（ＸＱ１，ＸＱ２）、高速信号（ＹＩ）と参照信号（ＹＩ１，ＹＩ２）、及び高速信号（ＹＱ）と参照信号（ＹＱ１，ＹＱ２）における周波数応答を算出することにより伝達関数を算出する。 Similarly, the transfer function estimating circuit 153-1 acquires the low-speed signal (XI 2 ) output from the transmission signal generation unit 11 as a reference signal, and outputs the low-speed signal (XI 2 ) output from the high-speed signal generation unit front signal processing unit 151-1. The frequency response is calculated by synchronizing the signal (XI 2 ) and the reference signal (XI 2 ). Thus, in each of the transfer function estimator 15-2,15-3,15-4, high-speed signal (XQ) and the reference signal (XQ 1, XQ 2), high-speed signal (YI) and the reference signal (YI 1 , YI 2 ) and the frequency response of the high-speed signal (YQ) and the reference signal (YQ 1 , YQ 2 ) to calculate the transfer function.

なお、光変調器１４と伝達関数推定部１５における高速信号（ＸＩ，ＸＱ，ＹＩ，ＹＱ）の受信方式については、例えば、高速のＡＤＣ（Analog Digital Converter）を用いる方式や、低速のＡＤＣを用いて、高速信号の周期と相対位相を変化させ、繰り返しデータを受信することで、高速信号を受信する方式がある。また、高速信号の受信方式として、これら以外の任意の方式を適用してもよい。   The high-speed signals (XI, XQ, YI, YQ) received by the optical modulator 14 and the transfer function estimating unit 15 are received, for example, using a high-speed ADC (Analog Digital Converter) or a low-speed ADC. There is a method of receiving a high-speed signal by changing the cycle and relative phase of the high-speed signal and repeatedly receiving data. In addition, as a high-speed signal receiving method, any other method may be applied.

上記の第１実施形態の構成では、送信信号生成部１１が出力する低速信号（ＸＩ１，ＸＩ２，ＸＱ１，ＸＱ２，ＹＩ１，ＹＩ２，ＹＱ１，ＹＱ２）を参照信号とし、高速信号生成部１３−１〜１３−４が出力する高速信号（ＸＩ，ＸＱ，ＹＩ，ＹＱ）から伝達関数推定部１５が伝達関数を算出する。伝達関数補償部１２は、算出された伝達関数に基づいて、送信信号生成部１１が出力する低速信号（ＸＩ１，ＸＩ２，ＸＱ１，ＸＱ２，ＹＩ１，ＹＩ２，ＹＱ１，ＹＱ２）に対して補償する演算を行う。これにより、高速信号生成部１３−１〜１３−４において複数のＤＡＣ（例えば、Ｓｕｂ−ＤＡＣ１３１−１，１３２−１）を用いることで発生する低速信号間の周波数特性の差と、高速信号生成部１３−１〜１３−４内でのアナログデバイスの不完全性とを補償することができ、信号品質の改善が可能となる。 In the configuration of the first embodiment, the low-speed signals (XI 1 , XI 2 , XQ 1 , XQ 2 , YI 1 , YI 2 , YQ 1 , YQ 2 ) output by the transmission signal generation unit 11 are used as reference signals, The transfer function estimator 15 calculates a transfer function from the high-speed signals (XI, XQ, YI, YQ) output from the high-speed signal generators 13-1 to 13-4. The transfer function compensator 12 is configured to output the low-speed signals (XI 1 , XI 2 , XQ 1 , XQ 2 , YI 1 , YI 2 , YQ 1 , YQ 2) output from the transmission signal generator 11 based on the calculated transfer function. ) Is performed. Thereby, the difference in frequency characteristics between low-speed signals generated by using a plurality of DACs (for example, Sub-DACs 131-1 and 132-1) in the high-speed signal generation units 13-1 to 13-4, and the high-speed signal generation It is possible to compensate for imperfections of analog devices in the units 13-1 to 13-4, and to improve signal quality.

また、上記の第１実施形態では、送信信号生成部１１が出力する低速信号（ＸＩ１，ＸＩ２，ＸＱ１，ＸＱ２，ＹＩ１，ＹＩ２，ＹＱ１，ＹＱ２）を参照信号としているが、本発明の実施の形態は、当該実施の形態に限られない。例えば、送信データ系列の一部を既知の信号とし、伝達関数推定部１５において当該既知の信号を予め記憶させておき、当該既知の信号が送信される際に伝達関数の算出を行うことで、送信信号生成部１１が出力する低速信号を用いることなく伝達関数の算出を行うことができる。また、伝達関数推定部１５において、高速信号生成部１３−１〜１３−４が出力する高速信号（ＸＩ，ＸＱ，ＹＩ，ＹＱ）から高速信号の受信シンボルを判定し、判定によって得られたシンボル系列から低速信号を生成し、生成した低速信号を参照信号としてもよい。このように、送信信号生成部１１が出力する低速信号（ＸＩ１，ＸＩ２，ＸＱ１，ＸＱ２，ＹＩ１，ＹＩ２，ＹＱ１，ＹＱ２）を参照信号として用いない場合、伝達関数推定部１５に替えて、図５に示す伝達関数推定部１５ａを適用して、伝達関数推定部１５ａと送信信号生成部１１の出力端とが接続しない構成とすることができる。 In the first embodiment, the low-speed signals (XI 1 , XI 2 , XQ 1 , XQ 2 , YI 1 , YI 2 , YQ 1 , YQ 2 ) output by the transmission signal generation unit 11 are used as reference signals. However, the embodiment of the present invention is not limited to the embodiment. For example, by making a part of the transmission data sequence a known signal, storing the known signal in the transfer function estimating unit 15 in advance, and calculating the transfer function when the known signal is transmitted, The transfer function can be calculated without using the low-speed signal output by the transmission signal generation unit 11. Further, the transfer function estimator 15 determines a received symbol of the high-speed signal from the high-speed signals (XI, XQ, YI, YQ) output from the high-speed signal generators 13-1 to 13-4, and determines the symbol obtained by the determination. A low-speed signal may be generated from a sequence, and the generated low-speed signal may be used as a reference signal. As described above, when the low-speed signals (XI 1 , XI 2 , XQ 1 , XQ 2 , YI 1 , YI 2 , YQ 1 , YQ 2 ) output from the transmission signal generation unit 11 are not used as the reference signals, the transfer function estimation is performed. A transfer function estimating unit 15a shown in FIG. 5 may be applied in place of the unit 15 so that the transfer function estimating unit 15a and the output terminal of the transmission signal generating unit 11 are not connected.

（第２実施形態）
図６は、第２実施形態における光伝送システムの構成を示すブロック図である。第１実施形態の光送信機１０，１０ａと同一の構成については同一の符号を付し、説明を省略する。光伝送システム１は、光送信機１０ｂ、光受信機２０、光送信機１０ｂと光受信機２０とに接続される伝送路４、及び光送信機１０ｂと光受信機２０とに接続される通信回線５を備える。光送信機１０ｂは、送信信号生成部１１、伝達関数補償部１２、高速信号生成部１３−１〜１３−４、光変調器１４を備え、第１実施形態の光送信機１０と異なり、伝達関数推定部１５を備えない。 (2nd Embodiment)
FIG. 6 is a block diagram illustrating a configuration of the optical transmission system according to the second embodiment. The same components as those of the optical transmitters 10 and 10a according to the first embodiment are denoted by the same reference numerals, and description thereof will be omitted. The optical transmission system 1 includes an optical transmitter 10b, an optical receiver 20, a transmission path 4 connected to the optical transmitter 10b and the optical receiver 20, and a communication connected to the optical transmitter 10b and the optical receiver 20. A line 5 is provided. The optical transmitter 10b includes a transmission signal generator 11, a transfer function compensator 12, high-speed signal generators 13-1 to 13-4, and an optical modulator 14. Unlike the optical transmitter 10 of the first embodiment, the optical transmitter 10b transmits The function estimating unit 15 is not provided.

伝送路４は、光ファイバ４−１と光増幅器４−２とを有し、光送信機１０ｂから出力される光信号は、光ファイバ４−１により伝送され、光増幅器４−２により増幅されて、光受信機２０が受信する。通信回線５は、例えば、下記の参考文献１に示されるコミュニケーションチャネルや、ＮＥ−Ｏｐｓ（Network Element Operation System）やＮＷ−Ｏｐｓ（Network Operation System）等の制御チャネルである（参考文献１：S. Okamoto, M. Yoshida, K. Yonenaga, and T. Kataoka. “Adaptive Pre-equalization using Bidirectional Pilot Sequences to Estimate and Feed Back Amplitude Transfer Function and Chromatic Dispersion”, OFC2015 Th2A.29）。   The transmission line 4 has an optical fiber 4-1 and an optical amplifier 4-2, and an optical signal output from the optical transmitter 10b is transmitted by the optical fiber 4-1 and amplified by the optical amplifier 4-2. Then, the optical receiver 20 receives the signal. The communication line 5 is, for example, a communication channel shown in Reference 1 below, or a control channel such as NE-Ops (Network Element Operation System) or NW-Ops (Network Operation System) (Reference 1: S.A. Okamoto, M. Yoshida, K. Yonenaga, and T. Kataoka. “Adaptive Pre-equalization using Bidirectional Pilot Sequences to Estimate and Feed Back Amplitude Transfer Function and Chromatic Dispersion”, OFC2015 Th2A.29).

通信回線５は、光送信機１０ｂの送信信号生成部１１の出力端と光受信機２０の伝達関数推定部１５とに接続され、また、当該伝達関数推定部１５と光送信機１０ｂの伝達関数補償部１２とに接続される。また、通信回線５は、送信信号生成部１１が出力する低速信号（ＸＩ１，ＸＩ２，ＸＱ１，ＸＱ２，ＹＩ１，ＹＩ２，ＹＱ１，ＹＱ２）を光受信機２０の伝達関数推定部１５に送信される際、また、伝達関数推定部１５が算出した伝達関数が光送信機１０ｂの伝達関数補償部１２に送信される際に用いられる。 The communication line 5 is connected to the output terminal of the transmission signal generator 11 of the optical transmitter 10b and the transfer function estimator 15 of the optical receiver 20, and the transfer function estimator 15 and the transfer function of the optical transmitter 10b. It is connected to the compensator 12. Further, the communication line 5 transmits the low-speed signals (XI 1 , XI 2 , XQ 1 , XQ 2 , YI 1 , YI 2 , YQ 1 , YQ 2 ) output from the transmission signal generation unit 11 to the transfer function of the optical receiver 20. It is used when transmitted to the estimator 15 and when the transfer function calculated by the transfer function estimator 15 is transmitted to the transfer function compensator 12 of the optical transmitter 10b.

光受信機２０は、受信部２１、受信データ復調部２５、及び第１実施形態の光送信機１０に備えられる伝達関数推定部１５を備える。受信部２１は、光コヒーレント受信部２２、ＡＤＣ（Analog to Digital Converter）２３−１〜２３−４、デジタル信号処理部２４を備える。光コヒーレント受信部２２は、内部にレーザモジュールを有しており、伝送路４から受信した光信号を、レーザモジュールからの局発光によりベースバンド信号に変換して電気信号として出力する。ＡＤＣ２３−１〜２３−４は、アナログの電気信号をデジタルの電気信号に変換して出力する。   The optical receiver 20 includes a receiving unit 21, a received data demodulating unit 25, and a transfer function estimating unit 15 included in the optical transmitter 10 according to the first embodiment. The receiving unit 21 includes an optical coherent receiving unit 22, ADCs (Analog to Digital Converter) 23-1 to 23-4, and a digital signal processing unit 24. The optical coherent receiving unit 22 has a laser module inside, converts an optical signal received from the transmission line 4 into a baseband signal by local light emission from the laser module, and outputs it as an electric signal. The ADCs 23-1 to 23-4 convert analog electric signals into digital electric signals and output the digital electric signals.

デジタル信号処理部２４は、伝送路４において発生する波長分散、偏波変動、非線形光学効果による波形劣化を補償する。また、デジタル信号処理部２４は、光送信機１０ｂ側のレーザと光受信機２０側のレーザの周波数誤差と各々のレーザが有する線幅による位相雑音の補償を行って高速信号（ＸＩ，ＸＱ，ＹＩ，ＹＱ）を伝達関数推定部１５と、受信データ復調部２５とに出力する。受信データ復調部２５は、デジタル信号処理部２４が出力する高速信号（ＸＩ，ＸＱ，ＹＩ，ＹＱ）を判定して光送信機１０ｂが送信したバイナリ情報を復調する。   The digital signal processing unit 24 compensates for chromatic dispersion and polarization fluctuation occurring in the transmission path 4 and waveform deterioration due to the nonlinear optical effect. Further, the digital signal processing unit 24 compensates for phase noise due to the frequency error between the laser on the optical transmitter 10b side and the laser on the optical receiver 20 side and the line width of each laser, and performs high-speed signals (XI, XQ, YI, YQ) are output to the transfer function estimator 15 and the received data demodulator 25. The reception data demodulation unit 25 determines the high-speed signals (XI, XQ, YI, YQ) output from the digital signal processing unit 24 and demodulates the binary information transmitted by the optical transmitter 10b.

伝達関数推定部１５は、通信回線５を通じて受信する光送信機１０ｂの送信信号生成部１１が生成する低速信号（ＸＩ１，ＸＩ２，ＸＱ１，ＸＱ２，ＹＩ１，ＹＩ２，ＹＱ１，ＹＱ２）を参照信号として、デジタル信号処理部２４が出力する高速信号（ＸＩ，ＸＱ，ＹＩ，ＹＱ）に基づいて伝達関数の算出を行う。また、伝達関数推定部１５は、算出した伝達関数を通信回線５を通じて光送信機１０ｂの伝達関数補償部１２に送信する。 The transfer function estimating unit 15 receives the low-speed signals (XI 1 , XI 2 , XQ 1 , XQ 2 , YI 1 , YI 2 , YQ 1) generated by the transmission signal generating unit 11 of the optical transmitter 10 b which receives through the communication line 5. The transfer function is calculated based on the high-speed signals (XI, XQ, YI, YQ) output from the digital signal processing unit 24 using YQ 2 ) as a reference signal. Further, the transfer function estimating unit 15 transmits the calculated transfer function to the transfer function compensating unit 12 of the optical transmitter 10b through the communication line 5.

上記の第２実施形態の構成では、光送信機１０ｂが出力した光信号が伝送路４によって伝送され、光受信機２０が当該光信号を受信し、受信部２１が受信した光信号から高速信号（ＸＩ，ＸＱ，ＹＩ，ＹＱ）を生成する。光受信機２０が備える伝達関数推定部１５は、送信信号生成部１１が出力する低速信号（ＸＩ１，ＸＩ２，ＸＱ１，ＸＱ２，ＹＩ１，ＹＩ２，ＹＱ１，ＹＱ２）を通信回線５を通じて受信し、当該低速信号を参照信号とし、受信部２１が出力する高速信号（ＸＩ，ＸＱ，ＹＩ，ＹＱ）に基づいて伝達関数の算出を行う。伝達関数推定部１５は、算出した伝達関数を通信回線５を通じて光送信機１０ｂの伝達関数補償部１２に送信する。伝達関数補償部１２は、受信した伝達関数に基づいて、送信信号生成部１１が出力する低速信号（ＸＩ１，ＸＩ２，ＸＱ１，ＸＱ２，ＹＩ１，ＹＩ２，ＹＱ１，ＹＱ２）に対して補償する演算を行う。これにより、光送信機１０ｂの高速信号生成部１３−１〜１３−４及び光変調器１４において生じる低速信号間や高速信号間の周波数特性差やアナログデバイスの不完全性を補償する伝達関数を算出することができ、算出した伝達関数による補償を行うことで信号品質の改善を行うことが可能となる。 In the configuration of the second embodiment, the optical signal output from the optical transmitter 10b is transmitted through the transmission path 4, the optical receiver 20 receives the optical signal, and the receiving unit 21 converts the optical signal received from the optical signal into a high-speed signal. (XI, XQ, YI, YQ) are generated. The transfer function estimator 15 included in the optical receiver 20 communicates the low-speed signals (XI 1 , XI 2 , XQ 1 , XQ 2 , YI 1 , YI 2 , YQ 1 , YQ 2 ) output from the transmission signal generator 11. The transfer function is received based on the high-speed signals (XI, XQ, YI, YQ) output from the receiving unit 21 using the low-speed signal as a reference signal. The transfer function estimating unit 15 transmits the calculated transfer function to the transfer function compensating unit 12 of the optical transmitter 10b through the communication line 5. The transfer function compensator 12 is configured to output the low-speed signals (XI 1 , XI 2 , XQ 1 , XQ 2 , YI 1 , YI 2 , YQ 1 , YQ 2 ) output from the transmission signal generator 11 based on the received transfer function. Is performed for the compensation. Accordingly, a transfer function for compensating for a frequency characteristic difference between low-speed signals and high-speed signals and imperfections of analog devices generated in the high-speed signal generation units 13-1 to 13-4 and the optical modulator 14 of the optical transmitter 10b can be obtained. The signal quality can be calculated, and the signal quality can be improved by performing compensation using the calculated transfer function.

（第３実施形態）
図７は、第３実施形態における光伝送システムの構成を示すブロック図である。第１実施形態の光送信機１０，１０ａ及び第２実施形態の光伝送システム１と同一の構成については同一の符号を付し、以下、異なる構成について説明する。光伝送システム２は、光送信機１０ｃ、光受信機２０ｃ、光送信機１０ｃと光受信機２０ｃとに接続される伝送路４、及び光送信機１０ｃと光受信機２０ｃとに接続される通信回線５ｃを備える。光送信機１０ｃは、送信信号生成部１１、高速信号生成部１３−１〜１３−４、光変調器１４を備え、第２実施形態の光送信機１０ｂと異なり、伝達関数補償部１２を備えない。 (Third embodiment)
FIG. 7 is a block diagram illustrating a configuration of an optical transmission system according to the third embodiment. The same components as those of the optical transmitters 10 and 10a of the first embodiment and the optical transmission system 1 of the second embodiment are denoted by the same reference numerals, and different configurations will be described below. The optical transmission system 2 includes an optical transmitter 10c, an optical receiver 20c, a transmission line 4 connected to the optical transmitter 10c and the optical receiver 20c, and a communication connected to the optical transmitter 10c and the optical receiver 20c. A line 5c is provided. The optical transmitter 10c includes a transmission signal generator 11, high-speed signal generators 13-1 to 13-4, and an optical modulator 14, and includes a transfer function compensator 12 unlike the optical transmitter 10b of the second embodiment. Absent.

光受信機２０ｃは、受信部２１、高速信号分離部２６、第１及び第２実施形態の光送信機１０，１０ａ，１０ｂに備えられる伝達関数補償部１２、信号合成部２８−１〜２８−４、受信データ復調部２５、伝達関数推定部１５を備える。伝達関数推定部１５は、通信回線５ｃを通じて受信する光送信機１０ｃの送信信号生成部１１が生成する低速信号（ＸＩ１，ＸＩ２，ＸＱ１，ＸＱ２，ＹＩ１，ＹＩ２，ＹＱ１，ＹＱ２）を参照信号として、デジタル信号処理部２４が出力する高速信号（ＸＩ，ＸＱ，ＹＩ，ＹＱ）に基づいて伝達関数の算出を行う。また、伝達関数推定部１５は、算出した伝達関数を伝達関数補償部１２に送信する。 The optical receiver 20c includes a receiving unit 21, a high-speed signal separating unit 26, a transfer function compensating unit 12 provided in the optical transmitters 10, 10a, and 10b of the first and second embodiments, and signal combining units 28-1 to 28-. 4, a reception data demodulation unit 25 and a transfer function estimation unit 15 The transfer function estimating unit 15 receives the low-speed signals (XI 1 , XI 2 , XQ 1 , XQ 2 , YI 1 , YI 2 , YQ 1 , and the like) generated by the transmission signal generating unit 11 of the optical transmitter 10c that receives the signals via the communication line 5c. The transfer function is calculated based on the high-speed signals (XI, XQ, YI, YQ) output from the digital signal processing unit 24 using YQ 2 ) as a reference signal. Further, the transfer function estimating unit 15 transmits the calculated transfer function to the transfer function compensating unit 12.

高速信号分離部２６は、送信信号生成部１１の高速信号生成部用前置信号処理部１１３と同一の処理を行い、デジタル信号処理部２４が出力する高速信号（ＸＩ，ＸＱ，ＹＩ，ＹＱ）から低速信号（ＸＩ１，ＸＩ２，ＸＱ１，ＸＱ２，ＹＩ１，ＹＩ２，ＹＱ１，ＹＱ２）を生成する。 The high-speed signal separation section 26 performs the same processing as the high-speed signal generation section front signal processing section 113 of the transmission signal generation section 11 and outputs the high-speed signals (XI, XQ, YI, YQ) output by the digital signal processing section 24. To generate low-speed signals (XI 1 , XI 2 , XQ 1 , XQ 2 , YI 1 , YI 2 , YQ 1 , YQ 2 ).

伝達関数補償部１２は、生成された低速信号（ＸＩ１，ＸＩ２，ＸＱ１，ＸＱ２，ＹＩ１，ＹＩ２，ＹＱ１，ＹＱ２）に対して、伝達関数推定部１５が算出した伝達関数に基づく補償する処理を行う。信号合成部２８−１〜２８−４の各々は、伝達関数補償部１２によって補償の処理がされた低速信号（ＸＩ１，ＸＩ２）、低速信号（ＸＱ１，ＸＱ２）、低速信号（ＹＩ１，ＹＩ２）、及び低速信号（ＹＱ１，ＹＱ２）の各々に基づいて高速信号（ＸＩ，ＸＱ，ＹＩ，ＹＱ）を生成する。受信データ復調部２５は、信号合成部２８−１〜２８−４が生成した高速信号（ＸＩ，ＸＱ，ＹＩ，ＹＱ）からバイナリ情報を復調する。なお、信号合成部２８−１〜２８−４は、高速信号生成部１３−１〜１３−４と同様にアナログ部品で構成してもよいし、同様の回路構成をデジタル的に再現して構成してもよい。 The transfer function compensator 12 calculates the transfer calculated by the transfer function estimator 15 for the generated low-speed signals (XI 1 , XI 2 , XQ 1 , XQ 2 , YI 1 , YI 2 , YQ 1 , YQ 2 ). Perform compensation processing based on the function. Each of the signal synthesizing units 28-1 to 28-4 is a low-speed signal (XI 1 , XI 2 ), a low-speed signal (XQ 1 , XQ 2 ), and a low-speed signal (YI) compensated by the transfer function compensating unit 12. 1 , YI 2 ) and the low-speed signals (YQ 1 , YQ 2 ) to generate high-speed signals (XI, XQ, YI, YQ). The reception data demodulation unit 25 demodulates binary information from the high-speed signals (XI, XQ, YI, YQ) generated by the signal combining units 28-1 to 28-4. The signal synthesizing units 28-1 to 28-4 may be configured by analog components as in the high-speed signal generating units 13-1 to 13-4, or may be configured by digitally reproducing the same circuit configuration. May be.

上記の第３実施形態の構成では、光送信機１０ｃが出力した光信号が伝送路４によって伝送され、光受信機２０ｃが当該光信号を受信し、受信部２１が受信した光信号から高速信号（ＸＩ，ＸＱ，ＹＩ，ＹＱ）を生成する。光受信機２０ｃが備える伝達関数推定部１５は、送信信号生成部１１が出力する低速信号（ＸＩ１，ＸＩ２，ＸＱ１，ＸＱ２，ＹＩ１，ＹＩ２，ＹＱ１，ＹＱ２）を通信回線５ｃを通じて受信し、当該低速信号を参照信号とし、受信部２１が出力する高速信号（ＸＩ，ＸＱ，ＹＩ，ＹＱ）に基づいて伝達関数の算出を行う。伝達関数推定部１５は、算出した伝達関数を伝達関数補償部１２に出力する。高速信号分離部２６は、デジタル信号処理部２４が出力する高速信号（ＸＩ，ＸＱ，ＹＩ，ＹＱ）から低速信号（ＸＩ１，ＸＩ２，ＸＱ１，ＸＱ２，ＹＩ１，ＹＩ２，ＹＱ１，ＹＱ２）を生成する。伝達関数補償部１２は、当該伝達関数に基づいて、高速信号分離部２６が出力する低速信号（ＸＩ１，ＸＩ２，ＸＱ１，ＸＱ２，ＹＩ１，ＹＩ２，ＹＱ１，ＹＱ２）に対して補償を行う。これにより、光送信機１０ｃの高速信号生成部１３−１〜１３−４及び光変調器１４において生じる低速信号間や高速信号間の周波数特性差やアナログデバイスの不完全性を補償する伝達関数を算出することができ、算出した伝達関数による補償を行うことで信号品質の改善を行うことが可能となる。 In the configuration of the third embodiment, the optical signal output from the optical transmitter 10c is transmitted through the transmission line 4, the optical receiver 20c receives the optical signal, and the receiving unit 21 converts the optical signal received from the optical signal into a high-speed signal. (XI, XQ, YI, YQ) are generated. The transfer function estimator 15 included in the optical receiver 20c communicates the low-speed signals (XI 1 , XI 2 , XQ 1 , XQ 2 , YI 1 , YI 2 , YQ 1 , YQ 2 ) output from the transmission signal generator 11. The transfer function is calculated based on the high-speed signals (XI, XQ, YI, YQ) output from the receiving unit 21 while receiving the signals via the line 5c and using the low-speed signals as reference signals. The transfer function estimator 15 outputs the calculated transfer function to the transfer function compensator 12. The high-speed signal separation unit 26 converts the high-speed signals (XI, XQ, YI, YQ) output from the digital signal processing unit 24 into low-speed signals (XI 1 , XI 2 , XQ 1 , XQ 2 , YI 1 , YI 2 , YQ 1). , YQ 2 ). The transfer function compensator 12 converts the low-speed signals (XI 1 , XI 2 , XQ 1 , XQ 2 , YI 1 , YI 2 , YQ 1 , YQ 2 ) output from the high-speed signal separator 26 based on the transfer function. Compensation for Thereby, a transfer function for compensating for the frequency characteristic difference between the low-speed signals and the high-speed signals and the imperfections of the analog device generated in the high-speed signal generators 13-1 to 13-4 and the optical modulator 14 of the optical transmitter 10 c is obtained. The signal quality can be calculated, and the signal quality can be improved by performing compensation using the calculated transfer function.

なお、上記の第３実施形態において、高速信号分離部２６は、デジタル信号処理部２４が生成して出力する高速信号（ＸＩ，ＸＱ，ＹＩ，ＹＱ）に基づいて、低速信号（ＸＩ１，ＸＩ２，ＸＱ１，ＸＱ２，ＹＩ１，ＹＩ２，ＹＱ１，ＹＱ２）を生成するようになっているが、本発明の構成は、当該実施の形態に限られない。例えば、伝達関数推定部１５が生成する高速信号（ＸＩ，ＸＱ，ＹＩ，ＹＱ）に基づいて、低速信号（ＸＩ１，ＸＩ２，ＸＱ１，ＸＱ２，ＹＩ１，ＹＩ２，ＹＱ１，ＹＱ２）を生成し、伝達関数補償部１２が当該低速信号に対して補償を行うようにしてもよい。 In the above-described third embodiment, the high-speed signal separation unit 26 generates the low-speed signals (XI 1 , XI) based on the high-speed signals (XI, XQ, YI, YQ) generated and output by the digital signal processing unit 24. 2 , XQ 1 , XQ 2 , YI 1 , YI 2 , YQ 1 , YQ 2 ), but the configuration of the present invention is not limited to this embodiment. For example, high-speed signal transfer function estimator 15 generates (XI, XQ, YI, YQ ) on the basis of the low-speed signal (XI 1, XI 2, XQ 1, XQ 2, YI 1, YI 2, YQ 1, YQ 2 ), and the transfer function compensator 12 may compensate for the low-speed signal.

なお、上記の第２、第３実施形態の構成において、伝達関数推定部１５は、通信回線５，５ｃを通じて受信する送信信号生成部１１が生成する低速信号（ＸＩ１，ＸＩ２，ＸＱ１，ＸＱ２，ＹＩ１，ＹＩ２，ＹＱ１，ＹＱ２）を参照信号としているが、本発明の構成は当該実施の形態に限られない。例えば、送信データ系列の一部を既知の信号とし、伝達関数推定部１５において当該既知の信号を予め記憶させておき、当該既知の信号が送信される際に伝達関数の算出を行うことで、送信信号生成部１１が出力する低速信号を用いることなく伝達関数の算出を行うことができる。また、伝達関数推定部１５において、デジタル信号処理部２４が出力する高速信号（ＸＩ，ＸＱ，ＹＩ，ＹＱ）から高速信号の受信シンボルを判定し、判定によって得られたシンボル系列から低速信号を生成し、生成した低速信号を参照信号としてもよい。このように、送信信号生成部１１が出力する低速信号（ＸＩ１，ＸＩ２，ＸＱ１，ＸＱ２，ＹＩ１，ＹＩ２，ＹＱ１，ＹＱ２）を参照信号として用いない場合、送信信号生成部１１の出力端と伝達関数推定部１５とを接続する通信回線５，５ｃを備えなくてもよく、また、伝達関数推定部１５に替えて、図５に示す伝達関数推定部１５ａが適用されることになる。 In the configurations of the second and third embodiments, the transfer function estimating unit 15 generates the low-speed signals (XI 1 , XI 2 , XQ 1 , XQ 2 , YI 1 , YI 2 , YQ 1 , YQ 2 ) are used as reference signals, but the configuration of the present invention is not limited to this embodiment. For example, by making a part of the transmission data sequence a known signal, storing the known signal in the transfer function estimating unit 15 in advance, and calculating the transfer function when the known signal is transmitted, The transfer function can be calculated without using the low-speed signal output by the transmission signal generation unit 11. Further, the transfer function estimating unit 15 determines a received symbol of a high-speed signal from the high-speed signal (XI, XQ, YI, YQ) output from the digital signal processing unit 24, and generates a low-speed signal from a symbol sequence obtained by the determination. Then, the generated low-speed signal may be used as the reference signal. As described above, when the low-speed signals (XI 1 , XI 2 , XQ 1 , XQ 2 , YI 1 , YI 2 , YQ 1 , YQ 2 ) output from the transmission signal generation unit 11 are not used as reference signals, It is not necessary to provide the communication lines 5 and 5c for connecting the output end of the unit 11 and the transfer function estimating unit 15, and a transfer function estimating unit 15a shown in FIG. Will be.

また、上記の第２、第３実施形態において、光送信機１０ｂ，１０ｃの送信信号生成部１１の波形整形部１１２において、伝送路４の波形歪を補償する前置分散補償や前置非線形光学効果補償を行う場合、送信信号生成部１１が出力する低速信号（ＸＩ１，ＸＩ２，ＸＱ１，ＸＱ２，ＹＩ１，ＹＩ２，ＹＱ１，ＹＱ２）に伝送路４において生じる波形歪が内在することになる。光受信機２０，２０ｃでは、デジタル信号処理部２４において伝送路４において生じる波形歪を補償してしまうため、伝達関数推定部１５が、伝送路４において生じる波形歪が内在した低速信号（ＸＩ１，ＸＩ２，ＸＱ１，ＸＱ２，ＹＩ１，ＹＩ２，ＹＱ１，ＹＱ２）を用いて、伝達関数を算出しようとしても光送信機１０ｂ，１０ｃ内の伝達関数のみを推定することができない。 In the second and third embodiments, the waveform shaping unit 112 of the transmission signal generation unit 11 of the optical transmitters 10b and 10c compensates for the waveform distortion of the transmission path 4 by the dispersion compensation or the nonlinear optical. When effect compensation is performed, waveform distortion generated in the transmission path 4 is generated in the low-speed signals (XI 1 , XI 2 , XQ 1 , XQ 2 , YI 1 , YI 2 , YQ 1 , YQ 2 ) output from the transmission signal generation unit 11. Will be inherent. In the optical receivers 20 and 20c, the digital signal processing unit 24 compensates for the waveform distortion generated in the transmission path 4. Therefore, the transfer function estimating unit 15 outputs the low-speed signal (XI 1) including the waveform distortion generated in the transmission path 4. , XI 2 , XQ 1 , XQ 2 , YI 1 , YI 2 , YQ 1 , YQ 2 ), it is not possible to estimate only the transfer functions in the optical transmitters 10 b and 10 c even when trying to calculate the transfer functions. .

この場合、送信信号生成部１１の波形整形部１１２において前置分散補償や前置非線形光学効果補償を行う信号を出力させるとともに、前置分散補償や前置非線形光学効果補償を行わない信号を出力させる。前置分散補償や前置非線形光学効果補償を行った信号に基づいて高速信号生成部用前置信号処理部１１３が低速信号を生成して光送信機１０ｂの伝達関数補償部１２、または、光送信機１０ｃの高速信号生成部１３−１〜１３−４に出力する。一方、前置分散補償や前置非線形光学効果補償を行わない信号に基づいて高速信号生成部用前置信号処理部１１３が低速信号を生成し、生成した低速信号を、例えば、通信回線５，５ｃを通じて伝達関数推定部１５に送信する。伝達関数推定部１５は、受信した低速信号を伝達関数の算出の際の参照信号として用いることで、前置分散補償や前置非線形光学効果補償を行いつつ、光送信機１０ｂ，１０ｃ内の伝達関数のみを算出することが可能となる。   In this case, the waveform shaping unit 112 of the transmission signal generating unit 11 outputs a signal for performing the pre-dispersion compensation or the pre-linear optical effect compensation, and outputs a signal for which the pre-dispersion compensation or the pre-linear optical effect compensation is not performed. Let it. The pre-signal processing unit 113 for the high-speed signal generation unit generates a low-speed signal based on the signal on which the pre-dispersion compensation or the pre-linear optical effect compensation has been performed, and the transfer function compensating unit 12 of the optical transmitter 10b or the optical signal The signal is output to the high-speed signal generators 13-1 to 13-4 of the transmitter 10c. On the other hand, the high-speed signal generation unit front signal processing unit 113 generates a low-speed signal based on a signal that does not perform front-end dispersion compensation or front-end non-linear optical effect compensation. 5c to the transfer function estimator 15. The transfer function estimating unit 15 uses the received low-speed signal as a reference signal when calculating the transfer function, thereby performing the dispersion compensation and the nonlinear optical effect compensation while transmitting the signals in the optical transmitters 10b and 10c. Only the function can be calculated.

また、他の手法として、伝達関数推定部１５に替えて、図８に示す伝達関数推定部１５ｄを用いる手法がある。伝達関数推定部１５ｄは、高速信号のレーンに対応する伝達関数推定部１５ｄ−１〜１５ｄ−４を備えている。伝達関数推定部１５ｄ−１〜１５ｄ−４は、同一の内部構成を有しており、図８では、一例として、伝達関数推定部１５ｅ−１の内部構成を示している。各々の伝達関数推定部１５ｄ−１〜１５ｄ−４は、各々が備える高速信号生成部用前置信号処理部１５１−１〜１５１−４の前段に波形整形部１５４−１〜１５４−４を備えている。当該波形整形部１５４−１〜１５４−４は、送信信号生成部１１の波形整形部１１２と同一の波形整形を行う。波形整形部１５４−１〜１５４−４による波形整形後の信号に基づいて、高速信号生成部用前置信号処理部１５１−１〜１５１−４が低速信号を生成する。これにより、送信信号生成部１１の波形整形部１１２において前置分散補償や前置非線形光学効果補償が行われていたとしても、伝達関数推定部１５ｄにおいても、同様の補償処理を行うため、送信信号生成部１１が生成する低速信号（ＸＩ１，ＸＩ２，ＸＱ１，ＸＱ２，ＹＩ１，ＹＩ２，ＹＱ１，ＹＱ２）を用いて、光送信機１０ｂ，１０ｃ内の伝達関数のみを算出することが可能となる。 As another method, there is a method using a transfer function estimating unit 15d shown in FIG. The transfer function estimator 15d includes transfer function estimators 15d-1 to 15d-4 corresponding to the high-speed signal lanes. Transfer function estimating units 15d-1 to 15d-4 have the same internal configuration, and FIG. 8 shows an internal configuration of transfer function estimating unit 15e-1 as an example. Each of the transfer function estimating units 15d-1 to 15d-4 includes a waveform shaping unit 154-1 to 154-4 in a stage preceding the high-speed signal generating unit pre-signal processing units 151-1 to 151-4 provided in each. ing. The waveform shaping units 154-1 to 154-4 perform the same waveform shaping as the waveform shaping unit 112 of the transmission signal generation unit 11. The high-speed signal generator front signal processing units 151-1 to 151-4 generate low-speed signals based on the signals after the waveform shaping by the waveform shaping units 154-1 to 154-4. Accordingly, even if the pre-dispersion compensation and the pre-linear optical effect compensation are performed in the waveform shaping unit 112 of the transmission signal generation unit 11, the transfer function estimating unit 15d performs the same compensation processing. Using the low-speed signals (XI 1 , XI 2 , XQ 1 , XQ 2 , YI 1 , YI 2 , YQ 1 , YQ 2 ) generated by the signal generation unit 11, only transfer functions in the optical transmitters 10 b and 10 c are used. It can be calculated.

また、更に、他の手法として、伝達関数推定部１５に替えて、図９に示す伝達関数推定部１５ｅを用いる手法がある。伝達関数推定部１５ｅは、高速信号のレーンに対応する伝達関数推定部１５ｅ−１〜１５ｅ−４を備えている。伝達関数推定部１５ｅ−１〜１５ｅ−４は、同一の内部構成を有しており、図９では、一例として、伝達関数推定部１５ｅ−１の内部構成について説明する。伝達関数推定部１５ｅ−１は、シンボル同期部１５５−１、波形整形部１５４−１、高速信号生成部用前置信号処理部１５１−１、伝達関数推定回路１５２ｅ−１，１５３ｅ−１を備える。波形整形部１５４−１については、前述した伝達関数推定部１５ｄが備えるものと同一の構成であり、高速信号生成部用前置信号処理部１５１−１も伝達関数推定部１５、１５ａ、１５ｄが備えるものと同一の構成である。   Further, as another method, there is a method in which the transfer function estimating unit 15e shown in FIG. The transfer function estimating unit 15e includes transfer function estimating units 15e-1 to 15e-4 corresponding to the high-speed signal lanes. The transfer function estimating units 15e-1 to 15e-4 have the same internal configuration, and FIG. 9 illustrates the internal configuration of the transfer function estimating unit 15e-1 as an example. The transfer function estimating unit 15e-1 includes a symbol synchronizing unit 155-1, a waveform shaping unit 154-1, a high-speed signal generating unit front signal processing unit 151-1, and transfer function estimating circuits 152e-1 and 153e-1. . The waveform shaping unit 154-1 has the same configuration as that of the transfer function estimating unit 15d described above. The pre-signal processing unit 151-1 for the high-speed signal generating unit also includes the transfer function estimating units 15, 15a, and 15d. The configuration is the same as that provided.

伝達関数推定部１５ｅを適用する前提として、図６及び図７に示す通信回線５，５ｃのうち伝達関数推定部１５と送信信号生成部１１の出力端を接続する回線の一端が、送信信号生成部１１の出力端に替えて、送信信号生成部１１のビットマッピング部１１１の出力端に接続されているものとする。シンボル同期部１５５−１は、ビットマッピング部１１１から受信するシンボル情報を参照信号として、デジタル信号処理部２４が出力する高速信号（ＸＩ）とシンボル同期を行う。シンボル同期部１５５−１は、デジタル信号処理部２４が出力した高速信号（ＸＩ）と、シンボル同期を行った高速信号（ｓＸＩ）とを波形整形部１５４−１に出力する。   As a premise of applying the transfer function estimating unit 15e, one end of a line connecting the transfer function estimating unit 15 and the output terminal of the transmission signal generation unit 11 among the communication lines 5 and 5c shown in FIGS. It is assumed that it is connected to the output terminal of the bit mapping unit 111 of the transmission signal generation unit 11 instead of the output terminal of the unit 11. The symbol synchronization section 155-1 performs symbol synchronization with the high-speed signal (XI) output from the digital signal processing section 24 using the symbol information received from the bit mapping section 111 as a reference signal. The symbol synchronization section 155-1 outputs the high-speed signal (XI) output from the digital signal processing section 24 and the high-speed signal (sXI) on which symbol synchronization has been performed to the waveform shaping section 154-1.

波形整形部１５４−１は、高速信号（ＸＩ）と高速信号（ｓＸＩ）に対して、送信信号生成部１１の波形整形部１１２と同一の波形整形を行う。波形整形部１５４−１による波形整形後の信号に基づいて高速信号生成部用前置信号処理部１５１−１が４つの低速信号（ＸＩ１，ｓＸＩ１，ＸＩ２，ｓＸＩ２）を生成する。伝達関数推定回路１５２ｃ−１，１５３ｃ−１の各々は、低速信号（ＸＩ１，ｓＸＩ１）と低速信号（ＸＩ２，ｓＸＩ２）とに基づいて伝達関数の算出を行う。伝達関数推定部１５ｅ−２〜１５ｅ−４も同様に伝達関数の算出を行う。これにより、送信信号生成部１１の波形整形部１１２において前置分散補償や前置非線形光学効果補償が行われていたとしても、これらの補償処理が施される前のビットマッピング部１１１が出力するシンボル情報を用いることで、送信信号生成部１１の波形整形部１１２において前置分散補償や前置非線形光学効果補償を行いつつ、伝達関数推定部１５ｅにおいて、光送信機１０ｂ，１０ｃ内の伝達関数のみを算出することが可能となる。 The waveform shaping unit 154-1 performs the same waveform shaping on the high-speed signal (XI) and the high-speed signal (sXI) as the waveform shaping unit 112 of the transmission signal generation unit 11. High-speed signal generating unit for pre置信No. processor 151-1 based on the signal after the waveform shaping by the waveform shaping unit 154-1 generates four low-speed signals (XI 1, sXI 1, XI 2, sXI 2). Each of the transfer function estimating circuits 152c- 1 and 153c- 1 calculates a transfer function based on the low-speed signals (XI 1 , sXI 1 ) and the low-speed signals (XI 2 , sXI 2 ). The transfer function estimating units 15e-2 to 15e-4 similarly calculate transfer functions. Thereby, even if the pre-dispersion compensation and the pre-linear optical effect compensation are performed in the waveform shaping section 112 of the transmission signal generating section 11, the bit mapping section 111 outputs before the compensation processing is performed. By using the symbol information, the waveform shaping unit 112 of the transmission signal generating unit 11 performs the dispersion compensation and the nonlinear optical effect compensation, and the transfer function estimating unit 15e transmits the transfer function in the optical transmitters 10b and 10c. Can be calculated.

なお、上記の第２、第３実施形態において、デジタル信号処理部２４が、波形等化前のデジタル信号を伝達関数推定部１５に出力し、伝達関数推定部１５において伝送路４において生じる波形歪を補償した後に伝達関数の算出を行うようにしてもよい。
また、上記の第２、第３実施形態において、伝送路４において、経路切り替え機を設置しても良い。 In the second and third embodiments, the digital signal processing unit 24 outputs the digital signal before the waveform equalization to the transfer function estimating unit 15, and the transfer function estimating unit 15 generates the waveform distortion generated in the transmission path 4. , The transfer function may be calculated.
In the second and third embodiments, a path switching device may be provided in the transmission path 4.

（実験結果）
図１０に第２実施形態の光伝送システム１を用いた実験による効果を示す。変調方式として偏波多重１６ＱＡＭ（ＤＰ−１６ＱＡＭ）を用い、変調速度は９６ＧＢａｕｄとした。伝送路４は、Ｂａｃｋ−ｔｏ−Ｂａｃｋ条件として実験を行った。この場合、高速信号生成部１３−１〜１３−４において、低速信号が、９６ＧＳａｍｐｌｅ／ｓｅｃのサンプリングレートでＳｕｂ−ＤＡＣ１３１−１〜１３１−４，１３２−１〜１３２−４に与えられる。アナログ多重器１３３−１〜１３３−４は、Ｓｕｂ−ＤＡＣ１３１−１〜１３１−４，１３２−１〜１３２−４からの出力を合成して９６ＧＢａｕｄの高速信号として出力する。 (Experimental result)
FIG. 10 shows an effect obtained by an experiment using the optical transmission system 1 according to the second embodiment. Polarization multiplexing 16QAM (DP-16QAM) was used as the modulation method, and the modulation speed was 96 GBaud. The experiment was performed on the transmission line 4 under the back-to-back condition. In this case, in the high-speed signal generators 13-1 to 13-4, the low-speed signal is provided to the Sub-DACs 131-1 to 131-4 and 132-1 to 132-4 at a sampling rate of 96 GSample / sec. The analog multiplexers 133-1 to 133-4 combine the outputs from the Sub-DACs 131-1 to 131-4 and 132-1 to 132-4 and output them as high-speed signals of 96 GBaud.

図１０において、横軸は、光信号対雑音電力（OSNR: Optical Signal to Noise Ratio）であり、縦軸は、受信Ｑ値である。図１０において、実線は、９６ＧＢａｕｄ−ＤＰ−１６ＱＡＭの理論値の線である。四角のプロットが伝達関数補償無しの実験結果で、丸のプロットが第２実施形態の光伝送システム１において伝達関数補償を行った際の実験結果である。伝達関数補償により、ＯＳＮＲ４０ｄＢの場合、受信Ｑ値で約２．５ｄＢ改善し、受信Ｑ値５ｄＢ付近においてＯＳＮＲ耐力が約２ｄＢ改善していることが分かる。   In FIG. 10, the horizontal axis represents optical signal-to-noise ratio (OSNR), and the vertical axis represents received Q value. In FIG. 10, the solid line is a line of theoretical values of 96 GBaud-DP-16QAM. The square plot is an experimental result without transfer function compensation, and the circular plot is an experimental result when transfer function compensation is performed in the optical transmission system 1 of the second embodiment. It can be seen that the transfer function compensation improves the received Q value by about 2.5 dB when the OSNR is 40 dB, and improves the OSNR tolerance by about 2 dB near the received Q value of 5 dB.

また、上記の第１、第２、及び第３実施形態では、非特許文献３に示される例と同様に、２つのＳｕｂ−ＤＡＣ１３１−１，１３２−１と１つのアナログ多重器１３３−１により高速信号を生成しているが、本発明の実施の形態は、当該実施の形態に限られない。例えば、非特許文献４に示す例のように３つのＤＡＣと、１つのアナログ多重器によって高速信号を生成するようにしてもよいし、４つ以上のＤＡＣを用いるようにしてもよい。また、２つの低速信号から１つの高速信号を生成する構成と、３つ以上の低速信号から１つの高速信号を生成する構成とが混在していてもよい。   In the first, second, and third embodiments described above, similarly to the example shown in Non-Patent Document 3, two Sub-DACs 131-1 and 132-1 and one analog multiplexer 133-1 are used. Although the high-speed signal is generated, the embodiment of the present invention is not limited to the embodiment. For example, three DACs and one analog multiplexer may be used to generate a high-speed signal as in the example shown in Non-Patent Document 4, or four or more DACs may be used. Further, a configuration for generating one high-speed signal from two low-speed signals and a configuration for generating one high-speed signal from three or more low-speed signals may be mixed.

なお、上記の第１、第２、及び第３実施形態の構成では、偏波多重信号を対象としているが、単一偏波信号でもよい。また、上記の第１、第２、及び第３実施形態の構成では、ＩＱ変調信号を対象としているが、強度変調信号でもよく、この場合、光変調器１４は、前述した偏波多重型マッハツェンダ型ベクトル変調器ではなく、強度変調器タイプのものや、レーザモジュールに直接変調光源を用いるものが適用される。   Although the configurations of the first, second, and third embodiments are directed to the polarization multiplexed signal, the configuration may be a single polarization signal. Further, in the configurations of the first, second, and third embodiments, the IQ modulation signal is targeted, but the intensity modulation signal may be used. In this case, the optical modulator 14 is the polarization multiplexing type Mach-Zehnder type. Instead of the vector modulator, an intensity modulator type or a laser module using a modulation light source directly is applied.

また、上記の第１、第２、及び第３実施形態の構成では、ビットマッピング部１１１が割り当てるシンボル点として、ＱＰＳＫや１６ＱＡＭのシンボル点を適用しているが、これら以外の変調フォーマットを適用してもよい。   In the configurations of the first, second, and third embodiments, symbol points of QPSK or 16QAM are applied as symbol points assigned by the bit mapping section 111, but modulation formats other than these are applied. You may.

また、上記の第１、第２、及び第３実施形態において、周波数特性による波形歪が大きい際は、信号品質が劣化により、伝達関数推定部１５，１５ａ，１５ｄ，１５ｅにおいて正確な推定ができない場合が考えられる。その場合、算出した伝達関数を伝達関数補償部１２にフィードバックして、伝達関数の算出を繰り返していくことで、より高い精度での伝達関数による補償が可能となる。   In the first, second, and third embodiments, when waveform distortion due to frequency characteristics is large, the transfer function estimating units 15, 15a, 15d, and 15e cannot perform accurate estimation due to signal quality deterioration. Case is conceivable. In that case, the calculated transfer function is fed back to the transfer function compensator 12 and the calculation of the transfer function is repeated, so that the transfer function can be compensated with higher accuracy.

また、上記の第１実施形態の光送信機１０において、図４に示す伝達関数推定部１５に替えて、図８や図９に示す伝達関数推定部１５ｄや伝達関数推定部１５ｅを適用するようにしてもよい。図９に示す伝達関数推定部１５ｅを光送信機１０に適用する場合、送信信号生成部１１の出力端から低速信号（ＸＩ１，ＸＩ２，ＸＱ１，ＸＱ２，ＹＩ１，ＹＩ２，ＹＱ１，ＹＱ２）を受信する構成ではなく、送信信号生成部１１のビットマッピング部１１１の出力端からシンボル情報を参照信号として受信することになる。 Further, in the optical transmitter 10 of the first embodiment, instead of the transfer function estimating unit 15 shown in FIG. 4, a transfer function estimating unit 15d or a transfer function estimating unit 15e shown in FIGS. It may be. When the transfer function estimator 15 e shown in FIG. 9 is applied to the optical transmitter 10, low-speed signals (XI 1 , XI 2 , XQ 1 , XQ 2 , YI 1 , YI 2 , YQ) are output from the output end of the transmission signal generator 11. 1 , YQ 2 ), but receives symbol information as a reference signal from the output end of the bit mapping section 111 of the transmission signal generation section 11.

上述した第１、第２、及び第３実施形態における光送信機１０，１０ａ，１０ｂ，１０ｃ、光受信機２０，２０ｃをコンピュータで実現するようにしてもよい。その場合、この機能を実現するためのプログラムをコンピュータ読み取り可能な記録媒体に記録して、この記録媒体に記録されたプログラムをコンピュータシステムに読み込ませ、実行することによって実現してもよい。なお、ここでいう「コンピュータシステム」とは、ＯＳや周辺機器等のハードウェアを含むものとする。また、「コンピュータ読み取り可能な記録媒体」とは、フレキシブルディスク、光磁気ディスク、ＲＯＭ、ＣＤ−ＲＯＭ等の可搬媒体、コンピュータシステムに内蔵されるハードディスク等の記憶装置のことをいう。さらに「コンピュータ読み取り可能な記録媒体」とは、インターネット等のネットワークや電話回線等の通信回線を介してプログラムを送信する場合の通信線のように、短時間の間、動的にプログラムを保持するもの、その場合のサーバやクライアントとなるコンピュータシステム内部の揮発性メモリのように、一定時間プログラムを保持しているものも含んでもよい。また上記プログラムは、前述した機能の一部を実現するためのものであってもよく、さらに前述した機能をコンピュータシステムにすでに記録されているプログラムとの組み合わせで実現できるものであってもよく、ＦＰＧＡ（Field Programmable Gate Array）等のプログラマブルロジックデバイスを用いて実現されるものであってもよい。   The optical transmitters 10, 10a, 10b, 10c and the optical receivers 20, 20c in the first, second, and third embodiments described above may be realized by a computer. In that case, a program for realizing this function may be recorded on a computer-readable recording medium, and the program recorded on this recording medium may be read and executed by a computer system. Here, the “computer system” includes an OS and hardware such as peripheral devices. The “computer-readable recording medium” refers to a portable medium such as a flexible disk, a magneto-optical disk, a ROM, and a CD-ROM, and a storage device such as a hard disk built in a computer system. Further, the “computer-readable recording medium” refers to a communication line for transmitting a program via a network such as the Internet or a communication line such as a telephone line. Such a program may include a program that holds a program for a certain period of time, such as a volatile memory in a computer system serving as a server or a client in that case. The program may be for realizing a part of the functions described above, or may be a program that can realize the functions described above in combination with a program already recorded in a computer system. It may be realized using a programmable logic device such as an FPGA (Field Programmable Gate Array).

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。   As described above, the embodiments of the present invention have been described in detail with reference to the drawings. However, the specific configuration is not limited to the embodiments and includes a design and the like within a range not departing from the gist of the present invention.

１０…光送信機， １１…送信信号生成部， １２…伝達関数補償部， １３−１〜１３−４…高速信号生成部， １４…光変調器， １５…伝達関数推定部， ２０…光受信機， ２１…受信部， ２２…光コヒーレント受信部， ２３−１〜２３−４…ＡＤＣ， ２４…デジタル信号処理部， ２５…受信データ復調部 Reference Signs List 10 optical transmitter, 11 transmission signal generator, 12 transfer function compensator, 13-1 to 13-4 high-speed signal generator, 14 optical modulator, 15 transfer function estimator, 20 optical reception Machine 21 receiving unit 22 optical coherent receiving unit 23-1 to 23-4 ADC 24 digital signal processing unit 25 received data demodulating unit

Claims (10)

送信データ系列から複数の低速信号を生成する送信信号生成部と、
前記複数の低速信号を、２つ以上の前記低速信号を含む組み合わせに分け、前記複数の低速信号をデジタルアナログ変換して前記組み合わせごとに合成することにより高速信号を生成する高速信号生成部と、
生成される前記高速信号と、参照信号とに基づいて伝達関数を算出する伝達関数推定部と、
前記送信信号生成部が生成する前記複数の低速信号を、前記伝達関数に基づいて補償して前記高速信号生成部に出力する伝達関数補償部と、
を備える光送信機。 A transmission signal generation unit that generates a plurality of low-speed signals from a transmission data sequence;
A high-speed signal generation unit that divides the plurality of low-speed signals into a combination including two or more low-speed signals, and generates a high-speed signal by performing digital-to-analog conversion on the plurality of low-speed signals and synthesizing each combination;
The generated high-speed signal, a transfer function estimating unit that calculates a transfer function based on the reference signal,
A transfer function compensating unit that compensates the plurality of low-speed signals generated by the transmission signal generating unit based on the transfer function and outputs the compensated low-speed signal to the high-speed signal generating unit;
An optical transmitter comprising: 前記伝達関数推定部は、
前記送信信号生成部が生成する複数の低速信号を前記参照信号として前記伝達関数を算出するか、または、予め既知信号として定められている前記送信データ系列の一部を前記参照信号として前記伝達関数を算出するか、または、前記高速信号の受信シンボルを判定して得られるシンボル系列から前記低速信号を生成し、生成した前記低速信号を前記参照信号として前記伝達関数を算出する、請求項１に記載の光送信機。 The transfer function estimator,
Either calculate the transfer function using the plurality of low-speed signals generated by the transmission signal generation unit as the reference signal, or use the transfer function as a part of the transmission data sequence previously determined as a known signal as the reference signal. Or calculating the transfer function by generating the low-speed signal from a symbol sequence obtained by determining a received symbol of the high-speed signal, and using the generated low-speed signal as the reference signal, The optical transmitter as described. 光送信機と、光受信機と、前記光送信機と前記光受信機とに接続される伝送路と、を備える光伝送システムであって、
前記光送信機は、
送信データ系列から複数の低速信号を生成する送信信号生成部と、
前記複数の低速信号を、２つ以上の前記低速信号を含む組み合わせに分け、前記複数の低速信号をデジタルアナログ変換して前記組み合わせごとに合成することにより高速信号を生成する高速信号生成部と、
前記高速信号を変調した光信号を前記伝送路に対して送信する光変調器と、を有し、
前記光受信機は、
前記伝送路から前記光信号を受信し、受信する前記光信号から得られる前記高速信号を出力する受信部と、
前記受信部が出力する前記高速信号に基づいて、前記送信データ系列に含まれるバイナリ情報を復調する受信データ復調部と、
を有し、
前記光送信機は、
前記高速信号生成部が生成する前記高速信号と、参照信号とに基づいて伝達関数を算出する伝達関数推定部と、
前記送信信号生成部が生成する前記複数の低速信号を、前記伝達関数に基づいて補償し、前記高速信号生成部に出力する伝達関数補償部と、
を備える光伝送システム。 An optical transmission system including an optical transmitter, an optical receiver, and a transmission line connected to the optical transmitter and the optical receiver,
The optical transmitter,
A transmission signal generation unit that generates a plurality of low-speed signals from a transmission data sequence;
A high-speed signal generation unit that divides the plurality of low-speed signals into a combination including two or more low-speed signals, and generates a high-speed signal by performing digital-to-analog conversion on the plurality of low-speed signals and synthesizing each combination;
An optical modulator that transmits an optical signal obtained by modulating the high-speed signal to the transmission line,
The optical receiver,
A receiving unit that receives the optical signal from the transmission line and outputs the high-speed signal obtained from the received optical signal;
Based on the high-speed signal output by the reception unit, a reception data demodulation unit that demodulates binary information included in the transmission data sequence,
Has,
The optical transmitter ,
A transfer function estimator for calculating said high-speed signals to the high-speed signal generator generates the transfer function based on the reference signal,
A transfer function compensating unit that compensates the plurality of low-speed signals generated by the transmission signal generating unit based on the transfer function and outputs the low-speed signal to the high-speed signal generating unit .
An optical transmission system comprising: 光送信機と、光受信機と、前記光送信機と前記光受信機とに接続される伝送路と、を備える光伝送システムであって、
前記光送信機は、
送信データ系列から複数の低速信号を生成する送信信号生成部と、
前記複数の低速信号を、２つ以上の前記低速信号を含む組み合わせに分け、前記複数の低速信号をデジタルアナログ変換して前記組み合わせごとに合成することにより高速信号を生成する高速信号生成部と、
前記高速信号を変調した光信号を前記伝送路に対して送信する光変調器と、を有し、
前記光受信機は、
前記伝送路から前記光信号を受信し、受信する前記光信号から得られる前記高速信号を出力する受信部と、
前記受信部が出力する前記高速信号に基づいて、前記送信データ系列に含まれるバイナリ情報を復調する受信データ復調部と、
を有し、
前記光受信機は、
前記受信部が出力する前記高速信号と、参照信号とに基づいて伝達関数を算出する伝達関数推定部を備え、
前記光送信機は、
前記送信信号生成部が生成する前記複数の低速信号を、前記伝達関数推定部が算出した前記伝達関数に基づいて補償する伝達関数補償部、
を備え、
前記伝達関数推定部は、
前記送信信号生成部が生成する前記複数の低速信号を前記参照信号として前記伝達関数を算出するか、または、前記高速信号の受信シンボルを判定し、判定によって得られるシンボル系列から前記低速信号を生成し、生成した前記低速信号を前記参照信号として前記伝達関数を算出する光伝送システム。 An optical transmission system including an optical transmitter, an optical receiver, and a transmission line connected to the optical transmitter and the optical receiver,
The optical transmitter,
A transmission signal generation unit that generates a plurality of low-speed signals from a transmission data sequence;
A high-speed signal generation unit that divides the plurality of low-speed signals into a combination including two or more low-speed signals, and generates a high-speed signal by performing digital-to-analog conversion on the plurality of low-speed signals and synthesizing each combination;
An optical modulator that transmits an optical signal obtained by modulating the high-speed signal to the transmission line,
The optical receiver,
A receiving unit that receives the optical signal from the transmission line and outputs the high-speed signal obtained from the received optical signal;
Based on the high-speed signal output by the reception unit, a reception data demodulation unit that demodulates binary information included in the transmission data sequence,
Has,
Before Symbol optical receiver,
The high-speed signal output by the receiving unit, a transfer function estimating unit that calculates a transfer function based on the reference signal,
The optical transmitter ,
A transfer function compensator that compensates the plurality of low-speed signals generated by the transmission signal generator based on the transfer function calculated by the transfer function estimator .
Equipped with a,
The transfer function estimator,
The transfer function is calculated using the plurality of low-speed signals generated by the transmission signal generation unit as the reference signal, or a received symbol of the high-speed signal is determined, and the low-speed signal is generated from a symbol sequence obtained by the determination. An optical transmission system that calculates the transfer function using the generated low-speed signal as the reference signal . 光送信機と、光受信機と、前記光送信機と前記光受信機とに接続される伝送路と、を備える光伝送システムであって、
前記光送信機は、
送信データ系列から複数の低速信号を生成する送信信号生成部と、
前記複数の低速信号を、２つ以上の前記低速信号を含む組み合わせに分け、前記複数の低速信号をデジタルアナログ変換して前記組み合わせごとに合成することにより高速信号を生成する高速信号生成部と、
前記高速信号を変調した光信号を前記伝送路に対して送信する光変調器と、を有し、
前記光受信機は、
前記伝送路から前記光信号を受信し、受信する前記光信号から得られる前記高速信号を出力する受信部と、
前記受信部が出力する前記高速信号に基づいて、前記送信データ系列に含まれるバイナリ情報を復調する受信データ復調部と、
を有し、
前記光受信機は、
前記受信部が出力する前記高速信号と、参照信号とに基づいて伝達関数を算出する伝達関数推定部と、
前記受信部が受信する前記光信号から得られる前記複数の低速信号を、前記伝達関数に基づいて補償する伝達関数補償部と、
を備える光伝送システム。 An optical transmission system comprising an optical transmitter, an optical receiver, and a transmission line connected to the optical transmitter and the optical receiver,
The optical transmitter,
A transmission signal generation unit that generates a plurality of low-speed signals from a transmission data sequence;
A high-speed signal generation unit that divides the plurality of low-speed signals into a combination including two or more low-speed signals, generates a high-speed signal by digital-to-analog converting the plurality of low-speed signals, and synthesizes each of the combinations;
An optical modulator that transmits an optical signal obtained by modulating the high-speed signal to the transmission line,
The optical receiver,
A receiving unit that receives the optical signal from the transmission line and outputs the high-speed signal obtained from the received optical signal;
Based on the high-speed signal output by the receiving unit, a reception data demodulation unit that demodulates binary information included in the transmission data sequence,
Has ,
Before Symbol optical receiver,
The high-speed signal output by the receiving unit, a transfer function estimating unit that calculates a transfer function based on the reference signal,
The plurality of low-speed signals obtained from the optical signal received by the receiving unit, a transfer function compensation unit that compensates based on the transfer function,
An optical transmission system comprising: 前記伝達関数推定部は、
前記送信信号生成部が生成する前記複数の低速信号を前記参照信号として前記伝達関数を算出するか、または、予め既知信号として定められている前記送信データ系列の一部を前記参照信号として前記伝達関数を算出するか、または、前記高速信号の受信シンボルを判定し、判定によって得られるシンボル系列から前記低速信号を生成し、生成した前記低速信号を前記参照信号として前記伝達関数を算出する、請求項３又は５に記載の光伝送システム。 The transfer function estimator,
The transfer function is calculated using the plurality of low-speed signals generated by the transmission signal generation unit as the reference signal, or a part of the transmission data sequence previously determined as a known signal is transmitted as the reference signal. Calculating a function or determining a received symbol of the high-speed signal, generating the low-speed signal from a symbol sequence obtained by the determination, calculating the transfer function using the generated low-speed signal as the reference signal, Item 6. The optical transmission system according to item 3 or 5 . 前記伝達関数推定部は、
前記送信信号生成部が、前記伝送路における波形歪を補償する波形整形を行っている場合、前記波形整形が行われていない前記複数の低速信号を前記参照信号として用いるか、または、前記高速信号に対して同一の前記波形整形を行ってから前記伝達関数の算出を行う、請求項４又は５に記載の光伝送システム。 The transfer function estimator,
When the transmission signal generation unit is performing waveform shaping to compensate for waveform distortion in the transmission path, the plurality of low-speed signals that have not been subjected to the waveform shaping may be used as the reference signal, or the high-speed signal 6. The optical transmission system according to claim 4 , wherein the transfer function is calculated after performing the same waveform shaping with respect to. 複数の低速信号を、２つ以上の前記低速信号を含む組み合わせに分け、前記複数の低速信号をデジタルアナログ変換して前記組み合わせごとに合成することにより高速信号を生成する光送信機が送信する光信号を受信する光受信機であって、
前記光信号を受信する受信部と、
前記受信部が受信する前記光信号から得られる前記高速信号と、参照信号とに基づいて伝達関数を算出する伝達関数推定部と、
前記受信部が受信する前記光信号から得られる前記複数の低速信号を、前記伝達関数に基づいて補償する伝達関数補償部と、
前記伝達関数補償部が補償する前記複数の低速信号を合成して前記高速信号を生成する信号合成部と、
生成される前記高速信号に基づいて、送信データ系列に含まれるバイナリ情報を復調する受信データ復調部と、
を備える光受信機。 Light transmitted by an optical transmitter that generates a high-speed signal by dividing a plurality of low-speed signals into a combination including two or more low-speed signals, converting the plurality of low-speed signals from digital to analog, and synthesizing each combination. An optical receiver for receiving a signal,
A receiving unit that receives the optical signal,
The high-speed signal obtained from the optical signal received by the receiving unit, a transfer function estimating unit that calculates a transfer function based on the reference signal,
A transfer function compensator that compensates the plurality of low-speed signals obtained from the optical signal received by the receiver based on the transfer function,
A signal combining unit that combines the plurality of low-speed signals compensated by the transfer function compensating unit to generate the high-speed signal;
Based on the generated high-speed signal, a reception data demodulation unit that demodulates binary information included in a transmission data sequence,
An optical receiver comprising: 前記伝達関数推定部は、
前記光送信機から前記複数の低速信号を受信し、受信した前記複数の低速信号を前記参照信号として前記伝達関数を算出するか、または、予め既知信号として定められている前記送信データ系列の一部を前記参照信号として前記伝達関数を算出するか、または、受信した前記光信号から得られる前記高速信号の受信シンボルを判定し、判定によって得られるシンボル系列から前記低速信号を生成し、生成した前記低速信号を前記参照信号として前記伝達関数を算出する、請求項８に記載の光受信機。 The transfer function estimator,
The plurality of low-speed signals are received from the optical transmitter, and the transfer function is calculated using the received plurality of low-speed signals as the reference signal, or one of the transmission data sequences predetermined as a known signal. Calculating the transfer function using the reference signal as the reference, or determining the received symbol of the high-speed signal obtained from the received optical signal, generating the low-speed signal from a symbol sequence obtained by the determination, generated The optical receiver according to claim 8 , wherein the transfer function is calculated using the low-speed signal as the reference signal. 前記受信部が受信する前記光信号から得られる前記高速信号を分離して前記複数の低速信号を生成する高速信号分離部を備えており、
前記伝達関数補償部は、
前記高速信号分離部が生成する前記複数の低速信号を、前記伝達関数に基づいて補償する、請求項８又は９に記載の光受信機。 The high-speed signal separation unit that generates the plurality of low-speed signals by separating the high-speed signal obtained from the optical signal received by the reception unit,
The transfer function compensator is:
The high-speed signal the plurality of low-speed signals separating unit is generated and compensation based on the transfer function, the optical receiver according to claim 8 or 9.
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