JP2010041391A - Wavelength multiplexing optical transmitter - Google Patents

Wavelength multiplexing optical transmitter Download PDF

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JP2010041391A
JP2010041391A JP2008201920A JP2008201920A JP2010041391A JP 2010041391 A JP2010041391 A JP 2010041391A JP 2008201920 A JP2008201920 A JP 2008201920A JP 2008201920 A JP2008201920 A JP 2008201920A JP 2010041391 A JP2010041391 A JP 2010041391A
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optical
wavelength
polarization
injection
carriers
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JP5026366B2 (en
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Tetsuya Suzuki
徹也 鈴木
Hisaya Sakurai
尚也 桜井
Tomohiro Taniguchi
友宏 谷口
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Nippon Telegraph and Telephone Corp
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Abstract

<P>PROBLEM TO BE SOLVED: To provide a wavelength multiplexing optical transmitter, capable of reducing a non-linear crosstalks and linear crosstalks between optical carriers whose frequencies adjoin. <P>SOLUTION: The transmitter comprises a polarization quadrature multiple-wavelength light source 8 for transmitting a plurality of linearly-polarized wave optical carriers, in which polarized waves among optical carriers whose frequencies are adjacent are orthogonal, and a plurality of injection-synchronized optical transmitters 11<SB>1</SB>to 11<SB>N</SB>, by which a plurality of linearly-polarized wave optical carriers are inputted via a linear polarization maintaining optical coupler 10; each of the plurality of injection-synchronized optical transmitters, 11<SB>1</SB>to 11<SB>N</SB>, synchronizes with any one of frequencies and polarized waves of the plurality of linearly-polarized wave optical carriers, and produces modulated optical signals in each of which the frequency spectrum does not overlap; and the linear polarization maintaining optical coupler 10 outputs a plurality of produced modulated optical signals, after multiplexing. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

本発明は、波長多重光伝送システムにおける波長多重光送信器に関する。   The present invention relates to a wavelength division multiplexing optical transmitter in a wavelength division multiplexing optical transmission system.

コアネットワークにおいては、ＷＤＭ（波長多重：Wavelength Division Multiplexing）光伝送システムが広く導入されている。ＷＤＭ光伝送システムは、図１に示されているように、それぞれ異なる信号を複数の波長チャネルに割り当て、単一の光伝送路で複数の光信号を伝送する方式である。一般に複数の光信号は周波数軸上または波長軸上に等間隔で配置され、図１では周波数間隔Δｆで表されている。ここで、ｆは周波数を表し、網掛け部分は各波長チャネルの光信号スペクトルを表す。また、光伝送路中のある直線偏波軸方向を//で表し、これに直交する直線偏波軸方向を⊥で表す。ここでは、便宜上、//および⊥をそれぞれ水平偏波方向および垂直偏波方向と呼ぶこととする。ここでは、ＷＤＭ信号は、全て水平偏波成分を持つとしている。一般に、ＷＤＭ光伝送システムにおいては、複数の波長チャネルに割り当てられた光信号は、波長合分波器を用いて合分波される。また、近年、盛んに検討されているコヒーレント光通信システムにおいては、波長合分波器を用いる他に、受信時の局発光源との周波数ミキシングおよび電気的なフィルタリングにより電気領域で所望の信号成分を取り出すことができる。   In the core network, a WDM (Wavelength Division Multiplexing) optical transmission system is widely introduced. As shown in FIG. 1, the WDM optical transmission system is a system in which different signals are assigned to a plurality of wavelength channels, and a plurality of optical signals are transmitted through a single optical transmission line. In general, a plurality of optical signals are arranged at equal intervals on the frequency axis or the wavelength axis, and are represented by a frequency interval Δf in FIG. Here, f represents the frequency, and the shaded portion represents the optical signal spectrum of each wavelength channel. In addition, a linear polarization axis direction in the optical transmission line is represented by //, and a linear polarization axis direction orthogonal to this is represented by ⊥. Here, for convenience, // and ⊥ will be referred to as a horizontal polarization direction and a vertical polarization direction, respectively. Here, it is assumed that all WDM signals have horizontal polarization components. Generally, in a WDM optical transmission system, optical signals assigned to a plurality of wavelength channels are multiplexed / demultiplexed using a wavelength multiplexer / demultiplexer. In addition, in coherent optical communication systems that have been actively studied in recent years, in addition to using a wavelength multiplexer / demultiplexer, desired signal components in the electrical domain can be obtained by frequency mixing with the local light source during reception and electrical filtering. Can be taken out.

ＷＤＭ光伝送システムにおいては、伝送容量拡大および光帯域利用効率の向上のために信号スペクトルが重なり合わない範囲内で高密度化することが有効である。このとき、まず、システム内の全波長を周波数間隔Δｆで、ある所望の周波数グリッドに安定化することが必要となる。また、全波長チャネルを安定化した上で、所望の波長チャネル以外の波長チャネルとのクロストークによる信号劣化を低減することが重要である。クロストークには、線形クロストークおよび非線形クロストークがある。線形クロストークは、偏波方向に依存しない強度雑音成分と偏波方向に依存するビート雑音成分からなる。ビート雑音成分は、所望の波長チャネルの受信信号帯域内で生じ、所望の波長チャネルとクロストークの原因となる波長チャネルの偏波が一致した場合にビート雑音は最大となる。これらを低減するには、合分波時に所望の波長チャネル以外の波長チャネルを十分に遮断することが必要となる。また、非線形クロストークは、ＦＷＭ（四光波混合：Four Wave Mixing）やＸＰＭ（相互位相変調：Cross Phase Modulation)などからなる。これら非線形クロストークは、所望の光信号の偏波成分に一致する偏波成分を持つ光信号との非線形相互作用によって生じ、周波数間隔が狭いほど信号劣化は大きくなる。   In a WDM optical transmission system, it is effective to increase the density within a range where signal spectra do not overlap in order to increase transmission capacity and improve optical band utilization efficiency. At this time, first, it is necessary to stabilize all wavelengths in the system to a desired frequency grid with a frequency interval Δf. In addition, it is important to reduce signal degradation due to crosstalk with wavelength channels other than the desired wavelength channel after stabilizing all wavelength channels. Crosstalk includes linear crosstalk and non-linear crosstalk. Linear crosstalk consists of an intensity noise component that does not depend on the polarization direction and a beat noise component that depends on the polarization direction. The beat noise component is generated within the received signal band of the desired wavelength channel, and the beat noise becomes maximum when the polarization of the desired wavelength channel and the wavelength channel causing crosstalk coincide. In order to reduce these, it is necessary to sufficiently block wavelength channels other than the desired wavelength channel at the time of multiplexing / demultiplexing. The non-linear crosstalk includes FWM (Four Wave Mixing) and XPM (Cross Phase Modulation). These nonlinear crosstalks are generated by nonlinear interaction with an optical signal having a polarization component that matches the polarization component of the desired optical signal, and the signal degradation increases as the frequency interval decreases.

また、近年、アクセスネットワークにおいても、ＷＤＭ技術の活用が検討されている。アクセスネットワークにおいては、コアネットワークと比較してコスト低減要求が強く、そのためには、部品点数の削減や高価な部品の使用を極力控えることが重要である。   In recent years, the use of WDM technology is also being considered for access networks. In the access network, there is a strong demand for cost reduction as compared with the core network. To that end, it is important to reduce the number of parts and use expensive parts as much as possible.

図２は、非特許文献１に記載の従来技術１を示している。従来技術１は、λ’１，//〜λ’Ｎ，//の等周波数間隔Δｆに配置された複数の光信号を送出するＮ個の光送信器３１〜３Ｎと、Ｎ個の光信号のうち奇数チャネル（λ’１，//、λ’３，//、〜λ’Ｎ−１，//）および偶数チャネル（λ’２，//、λ’４，//、〜λ’Ｎ，//）をそれぞれ合波する２個の波長合分波器２１、２２と、ＰＢＳ（偏波ビームスプリッタ：Polarization Beam Splitter）１からなり、奇数チャネルと偶数チャネルはＰＢＳ １により合波され、周波数が隣接する光信号の偏波が直交した偏波直交多波長光信号が送出される。ここで、λは波長チャネルを表し、添え字の’は変調された信号であることを表す。非特許文献１においては、Δｆ＝５０ＧＨｚ、一波当たり４０Ｇｂｉｔ／ｓのＮＲＺ（非ゼロ復帰：Non Return to Zero）変調方式が用いられている。図３に示されているように、この構成とすることで、隣接波長チャネルと偏波が直交しているため、隣接波長チャネルとの非線形クロストークを抑圧することができる。即ち、奇数チャネル間および偶数チャネル間の周波数間隔２Δｆに応じて生ずる非線形クロストークを考慮すればよい。非特許文献１によると、特にＸＰＭを低減できることが指摘されている。 FIG. 2 shows Prior Art 1 described in Non-Patent Document 1. The prior art 1 includes N optical transmitters 3 1 to 3 N that transmit a plurality of optical signals arranged at equal frequency intervals Δf of λ ′ 1, // to λ ′ N, / , and N Among the optical signals, odd channels (λ ′ 1, // , λ ′ 3, // , ˜λ ′ N−1, // ) and even channels (λ ′ 2, // , λ ′ 4, // , λ ′ N, // ) are combined with two wavelength multiplexers / demultiplexers 2 1 , 2 2 and PBS (Polarization Beam Splitter) 1. The odd and even channels are PBS 1. , And a polarization orthogonal multi-wavelength optical signal in which the polarizations of optical signals having adjacent frequencies are orthogonal to each other are transmitted. Here, λ represents a wavelength channel, and the subscript 'represents a modulated signal. In Non-Patent Document 1, an NRZ (Non Return to Zero) modulation method of Δf = 50 GHz and 40 Gbit / s per wave is used. As shown in FIG. 3, by adopting this configuration, since the adjacent wavelength channel and the polarization are orthogonal, nonlinear crosstalk with the adjacent wavelength channel can be suppressed. That is, the non-linear crosstalk generated according to the frequency interval 2Δf between the odd channels and between the even channels may be considered. According to Non-Patent Document 1, it is pointed out that XPM can be particularly reduced.

図４は、非特許文献２に記載の従来技術２を示している。また、図５は、従来技術２の原理を表している。λ１，//〜λＮ，//の等周波数間隔Δｆに配置された複数の光キャリア（以下、多波長光とする）を送出する多波長光源４と、前記多波長光が入力され、そのうちある１つの光キャリアの周波数に同期した光信号を送出するＮ個の注入同期光送信器５１〜５Ｎが光カプラ６を介して接続される。図５（ａ）は多波長光スペクトル、図５（ｂ）はある１つの注入同期光送信器の送出光スペクトル、図５（ｃ）は複数の注入同期光送信器出力を光カプラにより合波させた後の送出スペクトルの模式図を表す。Ｎ個の注入同期光送信器５１〜５Ｎは、図５（ａ）に示されている多波長光のうち、図５（ｂ）に示されているようにそれぞれ目標とする光キャリアの周波数に重複なく同期した光信号を送出し、それら光信号が光カプラ６により図５（ｃ）に示されているように合波されることで多波長光信号が送出される。ここでは、注入同期光送信器５１〜５Ｎの出力光は、Ｎ個の光送信器全てについて水平偏波//としている。これは、一般に多波長光を生成する際に用いる光部品は直線偏波に対して動作するものが多いため、多波長光の偏波は全て同一の直線偏波であるとともに、注入同期光送信器の入出力光の偏波状態を一致させる必要があるためである。例えば、非特許文献１においては多波長光源としてＭＬ−ＬＤ（モードロックレーザダイオード：Mode-Lock Laser Diode）が用いられている。他にも、光周波数コムなどを用いてもよく、これらは偏波無依存化のためなどの特別の構成としない限り直線偏波光を出力する。また、光送信器として一般に用いられるＦＰ−ＬＤ（ファブリー・ペロー形レーザダイオード：Fabry-Perot LD）やＤＦＢ−ＬＤ（分布帰還形レーザ：Distributed Feed-back LD）などの半導体レーザを注入同期光送信器として用いる場合、これらは単一の直線偏波で発振し、発振偏波に一致した周波数および偏波に対して注入同期される。この構成においては、多波長光源に高価な光部品を必要とするため、多波長光源が大きなコスト要因となるが、これはＮ個の注入同期光送信器を一群として、複数の注入同期光送信器群で共用することによりコストを低減することができる。非特許文献２によると、従来技術２は、周波数間隔が極めて高密度にできることが指摘されており、設計パラメータの一例として、Δｆ＝１０ＧＨｚ、０．１〜１Ｇｂｉｔ／ｓのＤＰＳＫ（差動位相シフトキーイング：Differential Phase Shift Keying）変調方式を適用した場合の実現可能性について言及されている。また、波長チャネルごとに周波数基準を与える光部品や波長合分波器が不要であるため部品点数が少なく単純であること、多波長光の周波数間隔を制御することにより任意の周波数間隔のＷＤＭ信号光の生成が実現できることといった利点がある。
Ｋ．Ｆｕｋｕｃｈｉ ｅｔ．ａｌ．，“１０．９２−Ｔｂ／ｓ（２７３ｘ４０−Ｇｂ／ｓ）ｔｒｉｐｌｅ−ｂａｎｄ／ｕｌｔｒａ−ｄｅｎｓｅ ＷＤＭ ｏｐｔｉｃａｌ−ｒｅｐｅａｔｅｒｅｄ ｔｒａｎｓｍｉｓｓｉｏｎ ｅｘｐｅｒｉｍｅｎｔ”，ＯＦＣ２００１ Ｋ．Ｋｉｋｕｃｈｉ ｅｔ．ａｌ．，“Ａｍｐｌｉｔｕｄｅ−Ｍｏｄｕｌａｔｉｏｎ Ｓｉｄｅｂａｎｄ Ｉｎｊｅｃｔｉｏｎ Ｌｏｃｋｉｎｇ Ｃｈａｒａｃｔｅｒｉｓｔｉｃｓ ｏｆ Ｓｅｍｉｃｏｎｄｕｃｔｏｒ Ｌａｓｅｒｓ ａｎｄ Ｔｈｅｉｒ Ａｐｐｌｉｃａｔｉｏｎ”，ＪＬＴ，Ｖｏｌ．６，Ｎｏ．１２，Ｄｅｃ．，１９８８ Ｋｅｎｔ Ｄ．Ｃｈｏｑｕｅｔｔｅ ｅｔ． ａｌ．， “Ｃｏｎｔｒｏｌ ｏｆ Ｖｅｒｔｉｃａｌ−Ｃａｖｉｔｙ Ｌａｓｅｒ Ｐｏｌａｒｉｚａｔｉｏｎ ｗｉｔｈ Ａｎｉｓｏｔｒｏｐｉｃ Ｔｒａｎｓｖｅｒｓｅ Ｃａｖｉｔｙ Ｇｅｏｍｅｔｒｉｅｓ”， ＩＥＥＥ Ｐｈｏｔｏｎｉｃｓ Ｔｅｃｈｎｏｌｏｇｙ Ｌｅｔｔｅｒｓ，Ｖｏｌ．６，Ｎｏ．１，Ｊａｎ．，１９９４ FIG. 4 shows Prior Art 2 described in Non-Patent Document 2. FIG. 5 shows the principle of the prior art 2. a multi-wavelength light source 4 for transmitting a plurality of optical carriers (hereinafter referred to as multi-wavelength light) arranged at equal frequency intervals Δf of λ 1, // to λ N, // , and the multi-wavelength light is input, of which are one of sending an optical signal in synchronization with the frequency of the optical carrier N number of injection locking optical transmitter 5 1 to 5 N is connected via an optical coupler 6. 5A is a multi-wavelength optical spectrum, FIG. 5B is a transmission optical spectrum of a single injection-locked optical transmitter, and FIG. 5C is a combination of a plurality of injection-locked optical transmitter outputs by an optical coupler. The schematic diagram of the transmission spectrum after making it represent is represented. The N injection-locked optical transmitters 5 1 to 5 N each have a target optical carrier as shown in FIG. 5B among the multi-wavelength light shown in FIG. Multi-wavelength optical signals are transmitted by transmitting optical signals that are synchronized with each other without overlapping, and combining the optical signals by the optical coupler 6 as shown in FIG. 5C. Here, the output light of the injection locking optical transmitters 5 1 to 5 N is set to horizontal polarization // for all the N optical transmitters. This is because, in general, many optical components used for generating multi-wavelength light operate with respect to linearly polarized light. This is because it is necessary to match the polarization states of the input and output light of the detector. For example, in Non-Patent Document 1, ML-LD (Mode-Lock Laser Diode) is used as a multi-wavelength light source. In addition, an optical frequency comb or the like may be used, and these output linearly polarized light unless they have a special configuration such as polarization independence. Also, semiconductor lasers such as FP-LD (Fabry-Perot LD) and DFB-LD (Distributed Feed-back LD), which are generally used as optical transmitters, are injection-locked optically transmitted. When used as a detector, they oscillate with a single linearly polarized wave and are injection-locked with respect to the frequency and polarization matched to the oscillating polarization. In this configuration, an expensive optical component is required for the multi-wavelength light source, so the multi-wavelength light source is a large cost factor. This is because a plurality of injection-locked optical transmitters with N injection-locked optical transmitters as a group. The cost can be reduced by sharing it with a group of containers. According to Non-Patent Document 2, it is pointed out that the prior art 2 can make the frequency interval extremely high. As an example of design parameters, DPSK (differential phase shift) of Δf = 10 GHz and 0.1 to 1 Gbit / s. Reference is made to the feasibility of applying a differential phase shift keying (modulation). Also, there is no need for optical components and wavelength multiplexers / demultiplexers that provide a frequency reference for each wavelength channel, so the number of components is simple, and WDM signals with an arbitrary frequency interval are controlled by controlling the frequency interval of multi-wavelength light. There is an advantage that light generation can be realized.
K. Fukuchi et. al. , “10.92-Tb / s (273 × 40-Gb / s) triple-band / ultra-dense WDM optical-repeated transmission experiment”, OFC 2001 K. Kikuchi et. al. "Amplitude-Modulation Sideband Injection Locking Characteristics of Semiconductor Lasers and Therer Application", JLT, Vol. 6, no. 12, Dec. , 1988 Kent D. Choquette et. al. "Control of Vertical-Cavity Laser Polarization with Anisotropic Transverse Cavity Geometry", IEEE Photonics Technology Letters, Vol. 6, no. 1, Jan. 1994

従来技術１は、複数の波長チャネルをそれぞれ所望の周波数に安定化するために目標周波数に対する周波数基準を与える光部品を別に必要とするとともにそれら所定の周波数と波長合分波器の透過中心周波数を一致させる必要があり、また高密度化するに従い十分な遮断特性を有する波長合分波器を製造するコストが上昇するなど、光伝送システム全体のコストが上昇する課題があった。   Prior art 1 requires separate optical components that provide a frequency reference for the target frequency in order to stabilize each of the plurality of wavelength channels at a desired frequency, and sets the predetermined frequency and the transmission center frequency of the wavelength multiplexer / demultiplexer. There is a problem that the cost of the entire optical transmission system increases, for example, the cost of manufacturing a wavelength multiplexer / demultiplexer having sufficient cutoff characteristics increases as the density increases.

従来技術２においては、従来技術１と比べて、特に波長合分波器を必要としないなど、簡易な構成で極めて高密度な波長多重光送信器を実現することができるが、多波長光と注入同期光送信器の入出力偏波を一致させる必要があるため、波長多重信号光の偏波状態は全波長で一致し、非線形クロストークによる信号劣化が生じる。この課題に対して、従来技術１と同様の構成とすることにより非線形クロストークを低減することが考えられる。図６はその構成の一例を示している。また、図７はその原理を表している。図６においては、多波長光源４が送出する周波数間隔Δｆの多波長光をインタリーバ７に入力し、２Δｆ間隔の多波長光とし、それらをＮ個の注入同期光送信器５１〜５Ｎのうち奇数チャネルおよび偶数チャネルごとに注入同期し、出力光信号をＰＢＳ １で合波するものである。図７（ａ）は、例として水平偏波成分を持つ周波数間隔２Δｆの多波長光スペクトル、図７（ｂ）はある１つの注入同期光送信器の送出光スペクトル、図７（ｃ）はλ’１，//、λ’３，//、〜λ’Ｎ−１，//と、λ’２，//、λ’４，//、〜λ’Ｎ，//をＰＢＳにより合波させた後の送出スペクトルの模式図を表す。このように、従来技術１と同様に偏波が直交した多波長光信号を生成することができる。しかし、この構成においては、多波長光源とインタリーバを複数の注入同期光送信器群で共用したとしても、一群の注入同期光送信器ごとにＰＢＳを必要とし、また多波長光が２系統に分割されるため追加光伝送路が必要になるなど、装置および実装コストが増大する課題がある。 In the prior art 2, compared with the prior art 1, a wavelength multiplexing optical transmitter having a very high density can be realized with a simple configuration, such as not requiring a wavelength multiplexer / demultiplexer. Since it is necessary to match the input / output polarization of the injection locked optical transmitter, the polarization state of the wavelength multiplexed signal light is the same for all wavelengths, and signal degradation due to nonlinear crosstalk occurs. For this problem, it is conceivable to reduce the non-linear crosstalk by adopting the same configuration as that of the prior art 1. FIG. 6 shows an example of the configuration. FIG. 7 shows the principle. In Figure 6, a multi-wavelength optical frequency interval Δf of multi-wavelength light source 4 is transmitted to the input to the interleaver 7, the multi-wavelength light 2Δf spacing them of N injection locking optical transmitter 5 1 to 5 N Of these, injection locking is performed for each of the odd-numbered channel and the even-numbered channel, and the output optical signal is multiplexed by the PBS 1. FIG. 7A shows a multi-wavelength optical spectrum with a frequency interval 2Δf having a horizontal polarization component as an example, FIG. 7B shows a transmission optical spectrum of one injection-locked optical transmitter, and FIG. ' 1, // , λ' 3, // , ~ λ ' N-1, // , and λ' 2, // , λ ' 4, // , ~ λ' N, // are combined by PBS The schematic diagram of the transmission spectrum after making it represent is represented. In this way, a multi-wavelength optical signal whose polarizations are orthogonal to each other can be generated in the same manner as in the prior art 1. However, in this configuration, even if a multi-wavelength light source and an interleaver are shared by a plurality of injection-locking optical transmitter groups, a PBS is required for each group of injection-locking optical transmitters, and the multi-wavelength light is divided into two systems. Therefore, there is a problem that the device and the mounting cost increase, such as the need for an additional optical transmission line.

さらに、各注入同期光送信器における注入同期動作において所望の波長チャネルとそれ以外の波長チャネルとのＳＭＳＲ（サイドモード抑圧比：Side Mode Supression Ratio）が十分確保できない場合には、隣接波長チャネルの残留サイドモードに起因する線形クロストークにより所望の波長チャネルの信号品質が劣化する課題がある。例えば、非特許文献２では、強度変調による多波長光を用いた場合には注入同期光送信器として用いるレーザダイオードの緩和振動周波数よりも大きなΔｆに対してこのようなことが生ずることが指摘されている。図８は、注入同期光送信器としてＦＰ−ＬＤを用い、正弦波強度変調により生成した１２．５ＧＨｚ間隔の多波長光に対して注入同期させた場合の出力スペクトルの一例である。この測定では、１９４．２ＴＨｚを中心とする３波の光パワーを−３０ｄＢｍとした１２．５ＧＨｚ間隔の多波長光を用いている。１９４．２ＴＨｚにある中央の最大ピークが注入同期された所望の波長チャネル、それ以外のピークが残留サイドモードであり、最大ピークに隣接するピークが支配的な線形クロストーク要因となるため、最大ピークと隣接ピークとの光パワー差をＳＭＳＲとしている。この測定例では、最大ピークから低周波側では１０．１ｄＢ、高周波側では１７．４ｄＢのＳＭＳＲしか得られていない。このように、ＳＭＳＲが小さい場合の多波長光信号スペクトルについて図９を用いて説明する。図９（ａ）は多波長光スペクトル、図９（ｂ）はある１つの注入同期光送信器の送出光スペクトル、図９（ｃ）は複数の注入同期光送信器出力を光カプラにより合波させた後の送出スペクトルの模式図を表す。ここで、縦線網掛け以外の網掛けで表されている箇所はクロストーク成分を表す。このとき、ＳＭＳＲが十分に確保できない場合、図３（ｃ）に示されているように、所望の波長チャネルは隣接する注入同期光送信器の残留サイドモードに起因する強度雑音およびビート雑音により信号品質が劣化する。   Furthermore, in the injection locking operation in each injection locking optical transmitter, if a sufficient SMSR (Side Mode Supression Ratio) between the desired wavelength channel and the other wavelength channels cannot be ensured, the residual wavelength channel remains. There is a problem that the signal quality of a desired wavelength channel deteriorates due to linear crosstalk caused by the side mode. For example, in Non-Patent Document 2, it is pointed out that this occurs for Δf which is larger than the relaxation oscillation frequency of a laser diode used as an injection locking optical transmitter when multi-wavelength light by intensity modulation is used. ing. FIG. 8 shows an example of an output spectrum when FP-LD is used as an injection-locking optical transmitter and injection locking is performed on multi-wavelength light with 12.5 GHz intervals generated by sinusoidal intensity modulation. In this measurement, multi-wavelength light at 12.5 GHz intervals in which the optical power of three waves centered at 194.2 THz is set to −30 dBm is used. The center peak at 194.2 THz is the desired wavelength channel that is injection-locked, the other peaks are residual side modes, and the peak adjacent to the peak is the dominant linear crosstalk factor. And the optical power difference between adjacent peaks is SMSR. In this measurement example, only 10.1 dB SMSR is obtained on the low frequency side and 17.4 dB on the high frequency side from the maximum peak. Thus, the multi-wavelength optical signal spectrum when the SMSR is small will be described with reference to FIG. 9A is a multi-wavelength optical spectrum, FIG. 9B is a transmission optical spectrum of a single injection-locked optical transmitter, and FIG. 9C is a combination of outputs of a plurality of injection-locked optical transmitters by an optical coupler. The schematic diagram of the transmission spectrum after making it represent is represented. Here, a portion represented by shading other than vertical shading represents a crosstalk component. At this time, if the SMSR cannot be sufficiently secured, as shown in FIG. 3C, the desired wavelength channel is a signal due to intensity noise and beat noise caused by the residual side mode of the adjacent injection locked optical transmitter. Quality deteriorates.

本発明は、このような問題点に鑑みてなされたものであり、本発明の目的は、周波数が隣接する光キャリア間の非線形クロストークおよび線形クロストークを低減できる波長多重光送信器を提供することにある。   The present invention has been made in view of such problems, and an object of the present invention is to provide a wavelength division multiplexing optical transmitter capable of reducing nonlinear crosstalk and linear crosstalk between optical carriers having adjacent frequencies. There is.

上記目的を達成するため、本発明の波長多重光送信器は、周波数が隣接する光キャリア間の偏波が直交した複数の直線偏波光キャリアを送出する偏波直交多波長光源と、前記複数の直線偏波光キャリアを、直線偏波保持光カプラを介して入力する複数の注入同期光送信器とを備え、前記複数の注入同期光送信器のそれぞれが、前記複数の直線偏波光キャリアのいずれかの周波数および偏波に同期し、かつ互いに周波数スペクトルが重複しない変調光信号を生成し、生成された複数の前記変調光信号を前記直線偏波保持光カプラにより合波して出力することを特徴とする。   In order to achieve the above object, a wavelength division multiplexing optical transmitter according to the present invention includes a polarization orthogonal multi-wavelength light source that transmits a plurality of linearly polarized optical carriers having orthogonal polarizations between adjacent optical carriers, A plurality of injection locking optical transmitters that input linearly polarized optical carriers via linear polarization maintaining optical couplers, and each of the plurality of injection locking optical transmitters is one of the plurality of linearly polarized optical carriers. A modulated optical signal that is synchronized with the frequency and polarization of the optical signal and has a frequency spectrum that does not overlap with each other, and a plurality of the modulated optical signals that are generated are combined and output by the linear polarization maintaining optical coupler. And

本発明の波長多重光送信器は、前記注入同期光送信器として、前記複数の直線偏波光キャリアに対して光利得の偏波依存性を有するレーザダイオードが用いられ、前記複数の直線偏波光キャリアのいずれかの周波数および偏波に重複なく注入同期が達成されるように前記レーザダイオードが配置されていることが好ましい。また、前記レーザダイオードを集積したレーザダイオードアレイを用いることが好ましい。   In the wavelength division multiplexing optical transmitter of the present invention, a laser diode having a polarization dependence of optical gain with respect to the plurality of linearly polarized optical carriers is used as the injection locking optical transmitter, and the plurality of linearly polarized optical carriers are used. It is preferable that the laser diode is arranged so that injection locking is achieved without any overlap in any of the frequencies and polarizations. It is preferable to use a laser diode array in which the laser diodes are integrated.

本発明は、隣接する光キャリア間の偏波が直線偏波直交していることで隣接する光キャリア間の非線形クロストークを低減できるとともに、多波長光に対する注入同期における残留サイドモードによる線形クロストークを低減できる。   The present invention can reduce nonlinear crosstalk between adjacent optical carriers because the polarizations between adjacent optical carriers are orthogonal to each other, and linear crosstalk due to residual side mode in injection locking for multi-wavelength light. Can be reduced.

本発明の実施の形態について図面を参照して説明する。
（第１の実施形態）
図１０は、本発明の波長多重光送信器の第１の実施形態を示している。第１の実施形態の波長多重光送信器は、等周波数間隔に配置され、周波数が隣接する光キャリア間の偏波が直交したλ１，//、λ２，⊥、λ３，//〜λＮ，⊥の複数の直線偏波光キャリア（以下、偏波直交多波長光とする）を送出する偏波直交多波長光源８と、前記偏波直交多波長光を、直線偏波保持光伝送路および直線偏波保持光カプラ１０を介して入力するＮ個（Ｎは任意の自然数）の注入同期光送信器１１１〜１１Ｎを備えている。Ｎ個の注入同期光送信器１１１〜１１Ｎが、λ１，//、λ２，⊥、λ３，//〜λＮ，⊥の光キャリアのうちそれぞれ異なる光キャリアの周波数および偏波状態に同期し、かつ互いに周波数スペクトルが重複しない変調光信号を生成して送出し、それら光信号を直線偏波保持光カプラ１０により合波することで偏波直交多波長光信号λ’１，//、λ’２，⊥、λ’３，//〜λ’Ｎ，⊥を送出する。図１１（ａ）は偏波多波長光スペクトル、図１１（ｂ）はある１つの注入同期光送信器の送出光スペクトル、図１１（ｃ）は複数の注入同期光送信器出を直線偏波保持光カプラにより合波させた後の送出スペクトルの模式図を表す。この構成とすることにより、図１１（ｃ）に示されているように、注入同期光送信器群ごとのＰＢＳや追加光伝送路を必要としない簡易な構成で、偏波直交光信号を生成することができる。 Embodiments of the present invention will be described with reference to the drawings.
(First embodiment)
FIG. 10 shows a first embodiment of the wavelength division multiplexing optical transmitter of the present invention. The wavelength division multiplexing optical transmitter according to the first embodiment is arranged at equal frequency intervals, and λ 1, // , λ 2, ⊥ , λ 3, // . A polarization orthogonal multi-wavelength light source 8 that transmits a plurality of linearly polarized optical carriers of λ N, ⊥ (hereinafter referred to as polarization orthogonal multi-wavelength light), and linear polarization-maintaining optical transmission of the polarization orthogonal multi-wavelength light N (N is an arbitrary natural number) injection-locked optical transmitters 11 1 to 11 N that are input via the path and the linear polarization maintaining optical coupler 10. The N injection-locked optical transmitters 11 1 to 11 N have different optical carrier frequencies and polarizations among the optical carriers of λ 1, // , λ 2 , λ, λ 3, // to λ N, ⊥. A modulated optical signal that is synchronized with the state and has a frequency spectrum that does not overlap with each other is generated and transmitted, and these optical signals are combined by the linearly polarized light maintaining optical coupler 10 so that the polarization orthogonal multi-wavelength optical signal λ ′ 1, // λ ′ 2, 、, λ ′ 3, /// ˜λ ′ N, ⊥ are sent out. 11 (a) is a polarization multi-wavelength optical spectrum, FIG. 11 (b) is a transmission light spectrum of one injection locking optical transmitter, and FIG. 11 (c) is a linear polarization maintaining a plurality of injection locking optical transmitter outputs. The schematic diagram of the transmission spectrum after combining with an optical coupler is represented. With this configuration, as shown in FIG. 11C, a polarization orthogonal optical signal is generated with a simple configuration that does not require a PBS or additional optical transmission line for each injection-locked optical transmitter group. can do.

本発明において用いられている偏波直交多波長光は複数の方法により生成することができる。図１２に本発明において用いられている偏波直交多波長光源の例１を示す。偏波直交多波長光源の例１は、２つの多波長光源４１、４２およびＰＢＳ １からなる。第１の多波長光源４１は第１の多波長光λ１，//、λ３，//、〜λＮ−１，//を出力し、第２の多波長光源４２は第２の多波長光λ２，//、λ４，//、〜λＮ，/を出力する。第１の多波長光の偏波状態と第２の多波長光の偏波状態を直交させた状態でＰＢＳ １により合波することにより偏波直交多波長光を生成することができる。また、ＰＢＳを用いる代わりに、いずれかの多波長光源の出力端にＰＣ（偏波コントローラ：Polarization Controller)を配置し、偏波を直交させた上で直線偏波保持光カプラにより合波してもよい。 The polarization orthogonal multi-wavelength light used in the present invention can be generated by a plurality of methods. FIG. 12 shows Example 1 of the polarization orthogonal multi-wavelength light source used in the present invention. Example 1 of the polarization orthogonal multi-wavelength light source includes two multi-wavelength light sources 4 1 , 4 2 and PBS 1. The first multiple-wavelength light source 4 1 a first multiple wavelength light λ 1, //, λ 3, //, ~λ N-1, and outputs a //, the second multiple-wavelength light source 4 2 second Multi-wavelength light λ 2, // , λ 4, // , to λ N, / is output. By combining the polarization state of the first multi-wavelength light and the polarization state of the second multi-wavelength light orthogonally with the PBS 1, the polarization orthogonal multi-wavelength light can be generated. Also, instead of using PBS, a PC (Polarization Controller) is placed at the output end of one of the multi-wavelength light sources, and the polarization is orthogonalized and combined by a linear polarization maintaining optical coupler. Also good.

図１３に偏波直交多波長光源の例２を示す。偏波直交多波長光源の例２は、多波長光源４、インタリーバ７、ＰＢＳ １からなる。インタリーバ７の２出力について偏波状態を直交させた状態でＰＢＳ １により合波することにより偏波直交多波長光を生成することができる。また、ＰＢＳを用いる代わりに、インタリーバの２出力のうちいずれかの出力端にＰＣを配置し、偏波を直交させた上で直線偏波保持光カプラにより合波してもよい。   FIG. 13 shows Example 2 of the polarization orthogonal multi-wavelength light source. Example 2 of the polarization orthogonal multi-wavelength light source includes a multi-wavelength light source 4, an interleaver 7, and a PBS 1. By combining the two outputs of the interleaver 7 with the PBS 1 in the state where the polarization states are orthogonal, it is possible to generate polarization orthogonal multi-wavelength light. Further, instead of using the PBS, a PC may be arranged at one of the output terminals of the two outputs of the interleaver, and the polarizations may be orthogonalized and then combined by a linear polarization maintaining optical coupler.

なお、ここでは偏波直交多波長光源の例を２つ示したが、偏波直交多波長光は他の方法で生成しても良く、以下の例においても同様である。また、直線偏波保持光伝送路および直線偏波保持光カプラとして直線偏波保持光ファイバ、直線偏波保持光ファイバカプラ、ＰＬＣ（平面光波回路：Planer Lightwave Circuit）を用いてもよい。   Although two examples of polarization orthogonal multiwavelength light sources are shown here, polarization orthogonal multiwavelength light may be generated by other methods, and the same applies to the following examples. Further, as the linear polarization maintaining optical transmission line and the linear polarization maintaining optical coupler, a linear polarization maintaining optical fiber, a linear polarization maintaining optical fiber coupler, or a PLC (Planer Lightwave Circuit) may be used.

（第２の実施形態）
図１４は、本発明の波長多重光送信器の第２の実施形態を示している。第２の実施形態は、注入同期光送信器として、偏波直交多波長光に対しＰＤＧ（偏波依存性利得：Polarization Dependent Gain）を有するレーザダイオードを用いた構成である。等周波数間隔に配置され、周波数が隣接する光キャリア間の偏波が直交したλ１，//、λ２，⊥、λ３，//〜λＮ，⊥の複数の直線偏波光キャリアが入力され、そのうちある１つの光キャリアの周波数および偏波状態に同期した光変調信号を送出する複数個のレーザダイオード１２１〜１２３が直線偏波保持光伝送路および直線偏波保持光カプラ１０を介して接続される。なお、図１４ではレーザダイオードが３個の場合を示している。第２の実施形態では、ＰＤＧを有する複数個のレーザダイオードを、偏波直交多波長光の各光キャリアの周波数および偏波に重複なく注入同期が達成されるように配置することが特徴である。このような構成とすることで、偏波直交光信号が生成されるだけでなく、従来技術２で課題であった残留サイドモードによる信号劣化を大幅に低減することができる。 (Second Embodiment)
FIG. 14 shows a second embodiment of the wavelength division multiplexing optical transmitter of the present invention. In the second embodiment, a laser diode having PDG (Polarization Dependent Gain) with respect to polarization orthogonal multi-wavelength light is used as an injection locking optical transmitter. Arranged at equal frequency intervals, lambda 1 polarization are orthogonal between optical carrier frequencies are adjacent, //, λ 2, ⊥, λ 3, // ~λ N, input a plurality of linearly polarized optical carriers ⊥ A plurality of laser diodes 12 1 to 12 3 for transmitting an optical modulation signal synchronized with the frequency and polarization state of one optical carrier are used as a linearly polarized light maintaining optical transmission line and a linearly polarized light maintaining optical coupler 10. Connected through. FIG. 14 shows a case where there are three laser diodes. The second embodiment is characterized in that a plurality of laser diodes having PDGs are arranged so that injection locking is achieved without overlapping the frequency and polarization of each optical carrier of polarization orthogonal multi-wavelength light. . With such a configuration, not only a polarization orthogonal optical signal is generated, but also signal degradation due to the residual side mode, which was a problem in the related art 2, can be significantly reduced.

ＦＰ−ＬＤやＤＦＢ−ＬＤなどの端面発光型レーザダイオードの光活性層は一般に長方形であり、軸方向に対する光閉じ込めの非対称性から、注入同期状態にない場合、入力光に対する入出力特性はＰＤＧを有する光増幅器のように振る舞う。このことを図１５および図１６を用いて説明する。図１５は、ＦＰ−ＬＤに対して注入同期が生じない状態で多波長光を入力した場合の入出力スペクトル測定結果を表し、図１６は、偏波直交多波長光を入力した場合の入出力スペクトル測定結果を表している。いずれの測定においても１９４．２ＴＨｚを中心とする３波の光パワーを−３０ｄＢｍとし、周波数間隔は１２．５ＧＨｚ間隔としている。図１５からわかるように、多波長光に対する出力光の中心３波の光パワー差は０．１ｄＢ以下であるのに対し、図１６からわかるように、偏波直交多波長光においては１９４．２ＴＨｚの中心波長に対し隣接２波と１３．３±０．１ｄＢ光パワー差が生じていることがわかる。従って、このような特性を示すレーザダイオードを用い、入出力偏波が一致した偏波直交多波長光の所望の光キャリアに注入同期を行うことで線形クロストークの支配的な要因である隣接チャネルのＳＭＳＲを大幅に拡大することができる。偏波直交多波長光に対し注入同期を行った場合の入出力光スペクトル測定結果を図１７に示す。ＰＤＧの効果により、残留サイドモードによるＳＭＳＲが２８．４ｄＢ以上と、図８に示されている従来技術２におけるものに対して大幅に改善していることがわかる。従って、図１４に示されているように、出力光信号の偏波状態が隣接波長チャネル間で直交するように配置することで、隣接波長チャネル間で偏波が直交しているため非線形クロストークを抑圧できることと共に、残留サイドモードによる線形クロストークを大幅に低減した偏波直交多波長光信号を生成することができる。このことを、図１８を用いて説明する。図１８（ａ）は偏波直交多波長光スペクトル、図１８（ｂ）はある１つの注入同期光送信器の送出光スペクトル、図１８（ｃ）は複数の注入同期光送信器出力を光カプラにより合波させた後の送出スペクトルの模式図を表す。図１８（ａ）に示すような偏波直交多波長光をＰＤＧを有するレーザダイオードに入力したとき、図１８（ｂ）に示すような出力が得られる。ここで、中央の最大ピークが所望の波長チャネルであり、それ以外が残留サイドモードである。ＰＤＧの効果により、最大ピークの隣接ピークは十分に抑圧されている。図１８（ｃ）に示すように、これらを多チャネル合波したとき、最大ピークの隣接ピークは隣接チャネルのクロストークとなるが、残留ピークは十分に抑圧されているため、クロストークによる信号劣化は隣接波長チャネルの偏波状態が一致した従来技術に比べて大幅に低減される。なお、端面発光レーザダイオードの例としてここではＦＰ−ＬＤを用いた場合について測定例を示したが、同様の効果が得られる他の注入同期光送信器を用いてもよい。   The photoactive layer of an edge-emitting laser diode such as FP-LD or DFB-LD is generally rectangular, and due to the asymmetry of optical confinement with respect to the axial direction, the input / output characteristics for input light are PDG when not in the injection locked state. It behaves like an optical amplifier. This will be described with reference to FIGS. 15 and 16. FIG. 15 shows the input / output spectrum measurement result when multi-wavelength light is input to the FP-LD without injection locking, and FIG. 16 shows the input / output when polarized orthogonal multi-wavelength light is input. The spectrum measurement result is shown. In any measurement, the optical power of three waves centered at 194.2 THz is set to −30 dBm, and the frequency interval is set to 12.5 GHz. As can be seen from FIG. 15, the optical power difference of the center three waves of the output light with respect to the multi-wavelength light is 0.1 dB or less, whereas as can be seen from FIG. 16, in the polarization orthogonal multi-wavelength light, 194.2 THz. It can be seen that there is a difference between the adjacent two waves and the 13.3 ± 0.1 dB optical power with respect to the center wavelength. Therefore, by using a laser diode exhibiting such characteristics and performing injection locking on a desired optical carrier of polarization orthogonal multiwavelength light whose input and output polarizations coincide with each other, the adjacent channel that is the dominant factor of linear crosstalk is used. The SMSR can be greatly expanded. FIG. 17 shows the input / output optical spectrum measurement result when injection locking is performed on polarization orthogonal multi-wavelength light. It can be seen from the effect of PDG that the SMSR in the residual side mode is 28.4 dB or more, which is a significant improvement over the prior art 2 shown in FIG. Therefore, as shown in FIG. 14, by arranging the polarization state of the output optical signal so as to be orthogonal between adjacent wavelength channels, the polarization is orthogonal between adjacent wavelength channels. Can be suppressed, and a polarization orthogonal multiwavelength optical signal in which linear crosstalk due to the residual side mode is significantly reduced can be generated. This will be described with reference to FIG. 18A is a polarization orthogonal multi-wavelength optical spectrum, FIG. 18B is a transmission optical spectrum of one injection-locked optical transmitter, and FIG. 18C is an optical coupler that outputs a plurality of injection-locked optical transmitters. The schematic diagram of the transmission spectrum after combining by is represented. When polarized orthogonal multi-wavelength light as shown in FIG. 18A is input to a laser diode having a PDG, an output as shown in FIG. 18B is obtained. Here, the central maximum peak is the desired wavelength channel, and the rest is the residual side mode. Due to the effect of PDG, the adjacent peak of the maximum peak is sufficiently suppressed. As shown in FIG. 18C, when these channels are multiplexed, the adjacent peak of the maximum peak becomes the crosstalk of the adjacent channel, but the residual peak is sufficiently suppressed, so that the signal degradation due to the crosstalk is caused. Is significantly reduced compared to the prior art in which the polarization states of adjacent wavelength channels are the same. In addition, although the example of a measurement was shown here about the case where FP-LD is used as an example of an edge-emitting laser diode, you may use the other injection locking optical transmitter with which the same effect is acquired.

（第３の実施形態）
図１９に本発明の波長多重光送信器の第３の実施形態を示す。第３の実施形態は、注入同期光送信器として、ＰＤＧを有するレーザダイオードアレイ１３を用いた構成である。第２の実施形態においては、個別の注入同期光送信器を用いた場合についての構成を示したが、同一基板上に多数のレーザダイオードが集積されたレーザダイオードアレイ１３を用いることでさらに低コスト化することができる。このようなレーザダイオードアレイの例としては、ＶＣＳＥＬ（面発光レーザ：Vertical Cavity Surface Emitting Laser）アレイがある。これは、例えば端面発光レーザダイオードを用いる場合には、特性検査のためにへき開もしくはダイシング工程を必要とするが、ＶＣＳＥＬにおいてはウエハレベルでの検査が可能であることなどによる。しかし、一般にＶＣＳＥＬは円形もしくは方形状の射出面形状を持つと共に、基板面方位の対称性からＰＤＧが小さい。そこで、大きなＰＤＧを有するＶＣＳＥＬアレイを用いることで第２の実施形態と同様の効果を得ることができる。図１９には例として楕円の射出面形状を有するＶＣＳＥＬ（非特許文献３参照）を用いた場合の構成法を示しているが、ＰＤＧを有するレーザアレイであれば他のものを用いてもよい。このようなレーザアレイを用いることで、例えばＮ個の注入同期光送信器を１個のレーザアレイとして大幅な部品点数の削減を達成することができる。 (Third embodiment)
FIG. 19 shows a third embodiment of the wavelength division multiplexing optical transmitter of the present invention. In the third embodiment, a laser diode array 13 having a PDG is used as an injection locking optical transmitter. In the second embodiment, the configuration in which individual injection locking optical transmitters are used has been described. However, the use of a laser diode array 13 in which a large number of laser diodes are integrated on the same substrate further reduces the cost. Can be An example of such a laser diode array is a VCSEL (Vertical Cavity Surface Emitting Laser) array. This is because, for example, when an edge-emitting laser diode is used, a cleaving or dicing process is required for the characteristic inspection, but in the VCSEL, inspection at the wafer level is possible. However, in general, VCSELs have a circular or rectangular exit surface shape and a small PDG due to the symmetry of the substrate surface orientation. Therefore, the same effect as in the second embodiment can be obtained by using a VCSEL array having a large PDG. FIG. 19 shows a configuration method using a VCSEL having an elliptical exit surface shape (see Non-Patent Document 3) as an example. However, other laser arrays having a PDG may be used. . By using such a laser array, for example, N injection-locking optical transmitters can be used as one laser array, and a significant reduction in the number of components can be achieved.

異なる信号が割り当てられる複数の波長チャネルを示す図である。It is a figure which shows the several wavelength channel to which a different signal is allocated. 従来技術１を説明する図である。It is a figure explaining prior art 1. FIG. 奇数チャネルと偶数チャネルの光信号スペクトルを示す図である。It is a figure which shows the optical signal spectrum of an odd-numbered channel and an even-numbered channel. 従来技術２を説明する図である。It is a figure explaining the prior art 2. FIG. 多波長光スペクトル、注入同期光送信器の送出光スペクトル、合波後の送出スペクトル示す図である。It is a figure which shows the multi-wavelength optical spectrum, the transmission optical spectrum of an injection locking optical transmitter, and the transmission spectrum after multiplexing. 従来技術１と従来技術２とを組み合わせた例を説明する図である。It is a figure explaining the example which combined the prior art 1 and the prior art 2. FIG. 多波長光スペクトル、注入同期光送信器の送出光スペクトル、合波後の送出スペクトル示す図である。It is a figure which shows the multi-wavelength optical spectrum, the transmission optical spectrum of an injection locking optical transmitter, and the transmission spectrum after multiplexing. 注入同期光送信器にＦＰ−ＬＤを用い、１２．５ＧＨｚ間隔の多波長光に対して注入同期させた場合の出力スペクトルの一例を示す図である。It is a figure which shows an example of an output spectrum at the time of carrying out injection locking with respect to the multiwavelength light of 12.5 GHz space | interval using FP-LD for an injection locking optical transmitter. 多波長光スペクトル、注入同期光送信器の送出光スペクトル、合波後の送出スペクトル示す図である。It is a figure which shows the multi-wavelength optical spectrum, the transmission optical spectrum of an injection locking optical transmitter, and the transmission spectrum after multiplexing. 本発明の第１の実施形態を示す図である。It is a figure which shows the 1st Embodiment of this invention. 偏波多波長光スペクトル、注入同期光送信器の送出光スペクトル、合波後の送出スペクトル示す図である。It is a figure which shows a polarization | polarized-light multiwavelength optical spectrum, the transmission optical spectrum of an injection locking optical transmitter, and the transmission spectrum after a combination. 偏波直交多波長光源の例１を示す図である。It is a figure which shows Example 1 of a polarization orthogonal multiwavelength light source. 偏波直交多波長光源の例２を示す図である。It is a figure which shows Example 2 of a polarization orthogonal multiwavelength light source. 本発明の第２の実施形態を示す図である。It is a figure which shows the 2nd Embodiment of this invention. ＦＰ−ＬＤに対して注入同期が生じない状態で多波長光を入力した場合の入出力スペクトルの一例を示す図である。It is a figure which shows an example of the input-output spectrum at the time of inputting multiwavelength light in the state which does not produce injection locking with respect to FP-LD. 偏波直交多波長光を入力した場合の入出力スペクトルの一例を示す図である。It is a figure which shows an example of the input-output spectrum at the time of inputting polarization orthogonal multiwavelength light. 偏波直交多波長光に対し注入同期を行った場合の入出力光スペクトルの一例を示す図である。It is a figure which shows an example of the input-output optical spectrum at the time of performing injection locking with respect to polarization orthogonal multi-wavelength light. 偏波多波長光スペクトル、注入同期光送信器の送出光スペクトル、合波後の送出スペクトル示す図である。It is a figure which shows a polarization | polarized-light multiwavelength optical spectrum, the transmission optical spectrum of an injection locking optical transmitter, and the transmission spectrum after a combination. 本発明の第３の実施形態を示す図である。It is a figure which shows the 3rd Embodiment of this invention.

符号の説明Explanation of symbols

１ ＰＢＳ
２１、２２ 波長合分波器
３１〜３Ｎ 光送信器
４、４１、４２多波長光源
５１〜５Ｎ、１１１〜１１Ｎ注入同期光送信器
６ 光カプラ
７ インタリーバ
８ 偏波直交多波長光源
１０ 直線偏波保持光カプラ
１２１〜１２３ レーザダイオード
１３ レーザダイオードアレイ 1 PBS
2 1 , 2 2 wavelength multiplexer / demultiplexer 3 1 to 3 N optical transmitter 4, 4 1 , 4 2 multiwavelength light source 5 1 to 5 N , 11 1 to 11 N injection locking optical transmitter 6 optical coupler 7 interleaver 8 Polarization orthogonal multi-wavelength light source 10 Linear polarization maintaining optical coupler 12 1 to 12 3 Laser diode 13 Laser diode array

Claims (3)

周波数が隣接する光キャリア間の偏波が直交した複数の直線偏波光キャリアを送出する偏波直交多波長光源と、
前記複数の直線偏波光キャリアを、直線偏波保持光カプラを介して入力する複数の注入同期光送信器とを備え、
前記複数の注入同期光送信器のそれぞれが、前記複数の直線偏波光キャリアのいずれかの周波数および偏波に同期し、かつ互いに周波数スペクトルが重複しない変調光信号を生成し、生成された複数の前記変調光信号を前記直線偏波保持光カプラにより合波して出力することを特徴とする波長多重光送信器。 A polarization orthogonal multi-wavelength light source that transmits a plurality of linearly polarized optical carriers having orthogonal polarizations between adjacent optical carriers,
A plurality of injection-locked optical transmitters that input the plurality of linearly polarized light carriers via a linearly polarized light maintaining optical coupler;
Each of the plurality of injection-locked optical transmitters generates a modulated optical signal that is synchronized with the frequency and polarization of any of the plurality of linearly polarized optical carriers and that has a frequency spectrum that does not overlap with each other. 2. A wavelength division multiplexing optical transmitter characterized in that the modulated optical signal is combined and output by the linearly polarized light maintaining optical coupler. 請求項１に記載の波長多重光送信器であって、
前記注入同期光送信器として、前記複数の直線偏波光キャリアに対して光利得の偏波依存性を有するレーザダイオードが用いられ、前記複数の直線偏波光キャリアのいずれかの周波数および偏波に重複なく注入同期が達成されるように前記レーザダイオードが配置されていることを特徴とする波長多重光送信器。 The wavelength division multiplexing optical transmitter according to claim 1,
As the injection-locked optical transmitter, a laser diode having a polarization dependence of optical gain with respect to the plurality of linearly polarized optical carriers is used, and overlaps with any frequency and polarization of the plurality of linearly polarized optical carriers. A wavelength division multiplexing optical transmitter, wherein the laser diode is arranged so that injection locking is achieved without any problem. 請求項２に記載の波長多重光送信器であって、
前記レーザダイオードを集積したレーザダイオードアレイを用いることを特徴とする波長多重光送信器。 The wavelength division multiplexing optical transmitter according to claim 2,
2. A wavelength division multiplexing optical transmitter using a laser diode array in which the laser diodes are integrated.
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CN102237977A (en) * 2011-07-05 2011-11-09 北京大学 Polarized interweaving OFDM (Orthogonal Frequency Division Multiplexing)/SCFDM (Singe Carrier Frequency Division Multiplexing) passive optical network system

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Publication number Priority date Publication date Assignee Title
JPH0462879A (en) * 1990-06-25 1992-02-27 Oki Electric Ind Co Ltd Fdm transmitting device
JP2002270949A (en) * 2001-03-12 2002-09-20 Atr Adaptive Communications Res Lab Optical wavelength splitting multiple signal generator
JP2003004959A (en) * 2001-06-26 2003-01-08 Nippon Telegr & Teleph Corp <Ntt> Waveguide type optical multipexer and multiple wavelength light source using the same

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPH0462879A (en) * 1990-06-25 1992-02-27 Oki Electric Ind Co Ltd Fdm transmitting device
JP2002270949A (en) * 2001-03-12 2002-09-20 Atr Adaptive Communications Res Lab Optical wavelength splitting multiple signal generator
JP2003004959A (en) * 2001-06-26 2003-01-08 Nippon Telegr & Teleph Corp <Ntt> Waveguide type optical multipexer and multiple wavelength light source using the same

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN102237977A (en) * 2011-07-05 2011-11-09 北京大学 Polarized interweaving OFDM (Orthogonal Frequency Division Multiplexing)/SCFDM (Singe Carrier Frequency Division Multiplexing) passive optical network system

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