JP6295689B2

JP6295689B2 - Wavelength control apparatus and wavelength control method

Info

Publication number: JP6295689B2
Application number: JP2014019530A
Authority: JP
Inventors: 岳人大沼
Original assignee: NEC Corp
Current assignee: NEC Corp
Priority date: 2014-02-04
Filing date: 2014-02-04
Publication date: 2018-03-20
Anticipated expiration: 2034-02-04
Also published as: JP2015146559A

Description

本発明は、波長制御装置及び波長制御方法に関し、特に、コヒーレント光受信方式を用いた光受信器で用いられる波長制御装置及び波長制御方法に関する。 The present invention relates to a wavelength control device and a wavelength control method, and more particularly to a wavelength control device and a wavelength control method used in an optical receiver using a coherent light reception method.

近年のデータ通信サービスの需要の増加に伴い、デジタルコヒーレント受信方式が採用された、高密度に波長が多重された大容量の光ファイバ通信システムの導入が進んでいる。このため、既存の光ファイバ通信システムにおいても、波長多重される信号光の波長の再割り当てを行う（再構成する）ことによる、信号光の波長密度のさらなる向上が求められている。 With the increase in demand for data communication services in recent years, introduction of a large-capacity optical fiber communication system in which wavelengths are multiplexed at a high density using a digital coherent reception method is progressing. For this reason, even in the existing optical fiber communication system, further improvement in the wavelength density of the signal light is required by reassigning (reconfiguring) the wavelength of the signal light to be wavelength multiplexed.

図１１は、波長多重光通信システムにおける、一般的な波長の再割り当てを説明するための図である。図１１の（Ａ）、（Ｂ）の縦軸は信号光の光パワー、横軸は信号光の波長を示す。図１１の（Ａ）は、波長多重光通信システムにおいて、信号光ａ１０１、ａ１０２、ａ１０３、ａ１０４が、Ａ（ＧＨｚ）間隔の波長で割り当てられた状態を示す。図１１では、（Ａ）のように波長が割り当てられた信号光が、再割り当てによって、（Ｂ）に示すように、Ｂ（ＧＨｚ）の間隔の信号光ａ２０１、ａ２０２、ａ２０３、ａ２０４に再割り当てされる。その結果、図１１の（Ｂ）に示されるように、波長チャネルが増設可能な領域Ｃが確保される。また、再割り当てによって、信号光ａ１０１〜ａ１０４の波長間隔が小さくなり、信号光ａ２０１〜ａ２０４のように波長配置が高密度化される。 FIG. 11 is a diagram for explaining general wavelength reassignment in a wavelength division multiplexing optical communication system. 11A and 11B, the vertical axis represents the optical power of the signal light, and the horizontal axis represents the wavelength of the signal light. FIG. 11A shows a state in which signal lights a101, a102, a103, and a104 are assigned at wavelengths of A (GHz) in the wavelength division multiplexing optical communication system. In FIG. 11, the signal light to which the wavelength is assigned as shown in (A) is reassigned to the signal lights a201, a202, a203, and a204 at intervals of B (GHz) as shown in (B) by reassignment. Is done. As a result, as shown in FIG. 11B, a region C in which wavelength channels can be added is secured. Further, the reassignment reduces the wavelength interval of the signal lights a101 to a104, and the wavelength arrangement is increased in density as in the signal lights a201 to a204.

本発明に関連して、特許文献１〜５には、信号光をコヒーレント検波するための構成が記載されている。 In relation to the present invention, Patent Documents 1 to 5 describe configurations for coherent detection of signal light.

特開昭６３−０５２５２８号公報（２ページ右下−４ページ右下）JP-A-63-052528 (Page 2 lower right-page 4 lower right) 特開平０２−００２７２８号公報（３ページ左上−４ページ左上）Japanese Patent Laid-Open No. 02-002728 (3 pages upper left-4 pages upper left) 特開平０５−１９１３５１号公報（［００１５］−［００１８］段落）JP 05-191351 A (paragraphs [0015]-[0018]) 特開平１０−１７８３９４号公報（［００２９］−［００３６］段落）JP 10-178394 A (paragraphs [0029]-[0036]) 特開２００１−２８１１０４号公報（［００２３］−［００２９］段落）JP 2001-281104 A (paragraphs [0023]-[0029])

コヒーレント光受信装置においては、信号光の波長が再割り当てによって変化すると、局部発振光の波長も受信信号光の波長に追従させて変化させる必要がある。例えば、特許文献１〜４は、信号光と局部発振光とのビート信号に基づいて局部発振光の波長が制御される構成を記載している。しかしながら、ビート信号を用いた局部発振光の制御にはビート信号を処理するための高周波回路が必要なため、特許文献１〜４に記載された技術には、光受信装置の構成が複雑になるとともに光受信装置のコストが上昇する、という課題がある。また、特許文献５には、信号光の波長変化に対して局部発振光の波長が制御される構成について記載されていない。
（発明の目的）
本発明は、局部発振光の波長を信号光の波長に追従させる機能を簡単な構成で実現することを目的とする。 In the coherent optical receiver, when the wavelength of the signal light changes due to reassignment, the wavelength of the local oscillation light needs to be changed to follow the wavelength of the received signal light. For example, Patent Documents 1 to 4 describe a configuration in which the wavelength of the local oscillation light is controlled based on the beat signal of the signal light and the local oscillation light. However, since control of local oscillation light using a beat signal requires a high-frequency circuit for processing the beat signal, the techniques described in Patent Documents 1 to 4 complicate the configuration of the optical receiver. At the same time, there is a problem that the cost of the optical receiving device increases. Further, Patent Document 5 does not describe a configuration in which the wavelength of the local oscillation light is controlled with respect to the wavelength change of the signal light.
(Object of invention)
An object of this invention is to implement | achieve the function to make the wavelength of local oscillation light track the wavelength of signal light with a simple structure.

本発明の波長制御装置は、局部発振光を出力する局部発振光源と、信号光が入力される、第１の波長特性を持つ第１の光フィルタと、前記第１の光フィルタを透過した前記信号光の強度の増加に対して振幅が単調に増加する第１の電流を出力する第１の受光部と、前記局部発振光が入力される、第２の波長特性を持つ第２の光フィルタと、前記第２の光フィルタを透過した前記局部発振光の強度の増加に対して振幅が単調に増加する第２の電流を出力する第２の受光部と、前記第１の電流が極大となるように前記第１の波長特性を制御し、前記第１の電流が極大となるように制御された前記第１の波長特性と前記第２の波長特性とが一致するように前記第２の波長特性を制御し、前記第２の電流が極大となるように前記局部発振光の波長を制御する制御部と、を備える。 The wavelength control device of the present invention includes a local oscillation light source that outputs local oscillation light, a first optical filter having a first wavelength characteristic to which signal light is input, and the first optical filter that has passed through the first optical filter. A first light receiving unit that outputs a first current whose amplitude monotonously increases with an increase in the intensity of the signal light; and a second optical filter having a second wavelength characteristic to which the local oscillation light is input. A second light receiving unit that outputs a second current whose amplitude monotonously increases with an increase in the intensity of the local oscillation light that has passed through the second optical filter, and the first current is a maximum. The first wavelength characteristic is controlled so that the first wavelength characteristic and the second wavelength characteristic are controlled so that the first current is maximized so that the second wavelength characteristic coincides with the second wavelength characteristic. The wavelength characteristics are controlled, and the wavelength of the local oscillation light is controlled so that the second current is maximized. And a control unit for, a.

本発明の波長制御方法は、第１の波長特性を持つ第１の光フィルタを透過した信号光の強度の増加に対して振幅が単調に増加する第１の電流を出力し、第２の波長特性を持つ第２の光フィルタを透過した局部発振光の強度の増加に対して振幅が単調に増加する振幅の第２の電流を出力し、前記第１の電流が極大となるように前記第１の波長特性を制御し、前記第１の電流が極大となるように制御された前記第１の波長特性と前記第２の波長特性とが一致するように前記第２の波長特性を制御し、前記第２の電流が極大となるように前記局部発振光の波長を制御する、ことを特徴とする。 The wavelength control method of the present invention outputs a first current whose amplitude monotonously increases with an increase in the intensity of the signal light transmitted through the first optical filter having the first wavelength characteristic, and the second wavelength. A second current having an amplitude that monotonously increases with an increase in the intensity of the local oscillation light that has passed through the second optical filter having characteristics is output, and the first current is maximized so that the first current becomes a maximum. The second wavelength characteristic is controlled so that the first wavelength characteristic and the second wavelength characteristic, which are controlled so as to maximize the first current, coincide with each other. The wavelength of the local oscillation light is controlled so that the second current becomes a maximum.

本発明は、局部発振光の波長を信号光の波長に追従させる機能を簡単な構成で実現できるという効果を奏する。 The present invention has an effect that the function of causing the wavelength of the local oscillation light to follow the wavelength of the signal light can be realized with a simple configuration.

第１の実施形態の光受信器の構成を示すブロック図である。It is a block diagram which shows the structure of the optical receiver of 1st Embodiment. 可変波長フィルタ（ＦＩＬ１）の構成を示す図である。It is a figure which shows the structure of a variable wavelength filter (FIL1). 可変波長フィルタ（ＦＩＬ２）の構成を示す図である。It is a figure which shows the structure of a variable wavelength filter (FIL2). 信号光の波長が変化した場合のスペクトルを示す図である。It is a figure which shows a spectrum when the wavelength of signal light changes. 可変波長フィルタ（ＦＩＬ１）の透過帯域の制御を示す図である。It is a figure which shows control of the transmission band of a variable wavelength filter (FIL1). 可変波長フィルタ（ＦＩＬ２）の透過帯域の制御を示す図である。It is a figure which shows control of the transmission band of a variable wavelength filter (FIL2). 波長制御部の制御手順を示すフローチャートである。It is a flowchart which shows the control procedure of a wavelength control part. 第２の実施形態の波長制御装置の構成を示すブロック図である。It is a block diagram which shows the structure of the wavelength control apparatus of 2nd Embodiment. 第３の実施形態の光受信器の構成を示すブロック図である。It is a block diagram which shows the structure of the optical receiver of 3rd Embodiment. 第４の実施形態の可変波長フィルタの構成を示すブロック図である。It is a block diagram which shows the structure of the variable wavelength filter of 4th Embodiment. 波長の再割り当てを説明するための図である。It is a figure for demonstrating the reallocation of a wavelength.

本発明の実施形態について以下に説明する。各実施形態で説明されるように、信号光の波長は光フィルタで検出される。そして、検出された信号光の波長に基づいて、局部発振光の波長が制御される。 Embodiments of the present invention will be described below. As described in each embodiment, the wavelength of the signal light is detected by an optical filter. Then, the wavelength of the local oscillation light is controlled based on the detected wavelength of the signal light.

以下の実施形態では、透過帯域の波長が可変である可変波長フィルタを透過した信号光の強度を検出することにより、信号光の波長変化が検出される。そして、検出された波長の変化と連動して、局部発振光の光路上に挿入された他の可変波長フィルタの透過帯域が変更される。さらに、他の可変波長フィルタの、変更された透過帯域を局部発振光が透過するように、局部発振光源の波長が制御される。その結果、信号光の波長変化に対して局部発振光の波長を追従させることが可能となる。
（第１の実施形態）
図１は、本発明の第１の実施形態の光受信器１の構成を示すブロック図である。光受信器１は、デジタルコヒーレント変調された信号光１０を復調して、復調された信号を復調信号１１として出力する。光受信器１は、局部発振光源（local oscillator、ＬＯ）１０２、可変波長フィルタ（ＦＩＬ１）１０１、可変波長フィルタ（ＦＩＬ２）１０３、及び波長制御部１０４を備える。光受信器１は、さらに、９０度ハイブリッド回路１０５、ＰＤ（photo diode、フォトダイオード）１０６、ＴＩＡ（trans-impedance amplifier、トランスインピーダンス増幅器）１０７及びＤＳＰ（digital signal processor、デジタル信号処理装置）１０８を備える。 In the following embodiments, the wavelength change of the signal light is detected by detecting the intensity of the signal light transmitted through the variable wavelength filter whose transmission band wavelength is variable. Then, in conjunction with the detected change in wavelength, the transmission band of another variable wavelength filter inserted on the optical path of the local oscillation light is changed. Further, the wavelength of the local oscillation light source is controlled so that the local oscillation light is transmitted through the changed transmission band of the other variable wavelength filter. As a result, the wavelength of the local oscillation light can be made to follow the wavelength change of the signal light.
(First embodiment)
FIG. 1 is a block diagram showing a configuration of an optical receiver 1 according to the first embodiment of the present invention. The optical receiver 1 demodulates the signal light 10 subjected to digital coherent modulation and outputs the demodulated signal as a demodulated signal 11. The optical receiver 1 includes a local oscillator (LO) 102, a variable wavelength filter (FIL1) 101, a variable wavelength filter (FIL2) 103, and a wavelength control unit 104. The optical receiver 1 further includes a 90-degree hybrid circuit 105, a PD (photo diode) 106, a TIA (trans-impedance amplifier) 107, and a DSP (digital signal processor) 108. Prepare.

可変波長フィルタ１０１、１０３は、入力された光を透過する波長帯域（以下、「透過帯域」という。）を外部から制御可能な光バンドパスフィルタである。可変波長フィルタ１０１、１０３は、入力された光の波長を検出するために用いられる。透過帯域を連続的に変化させることが可能な光フィルタは、例えば、誘電体多層膜を用いた光フィルタを用いて実現されている。 The variable wavelength filters 101 and 103 are optical bandpass filters that can control a wavelength band (hereinafter referred to as “transmission band”) that transmits input light from the outside. The variable wavelength filters 101 and 103 are used to detect the wavelength of the input light. An optical filter capable of continuously changing the transmission band is realized by using, for example, an optical filter using a dielectric multilayer film.

局部発振光源１０２は、信号光１０のコヒーレント検波に用いられる、信号光と等しいか接近した波長の局部発振光（以下、「ＬＯ光」という。）１２を出力するための光源である。波長制御部１０４は、可変波長フィルタ１０１、１０３及び局部発振光源１０２を制御する。波長制御部１０４の制御機能については後述する。 The local oscillation light source 102 is a light source for use in coherent detection of the signal light 10 to output local oscillation light (hereinafter referred to as “LO light”) 12 having a wavelength equal to or close to that of the signal light. The wavelength control unit 104 controls the variable wavelength filters 101 and 103 and the local oscillation light source 102. The control function of the wavelength control unit 104 will be described later.

９０度ハイブリッド回路１０５は、可変波長フィルタ１０１を透過した変調信号１０と、可変波長フィルタ１０３を透過したＬＯ光１２と、を干渉させ、干渉させた信号をＰＤ１０６へ出力する。信号光１０とＬＯ光１２とを９０度ハイブリッド回路１０５で干渉させるために、信号光１０の波長とＬＯ光１２の波長とは同一であるか、あるいは接近している。 The 90-degree hybrid circuit 105 causes the modulated signal 10 that has passed through the variable wavelength filter 101 to interfere with the LO light 12 that has passed through the variable wavelength filter 103, and outputs the interfered signal to the PD 106. In order to cause the signal light 10 and the LO light 12 to interfere with each other by the 90-degree hybrid circuit 105, the wavelength of the signal light 10 and the wavelength of the LO light 12 are the same or close to each other.

ＰＤ１０６は、９０度ハイブリッド回路１０５で干渉させた信号光をコヒーレント検波して検波された信号をアナログ電気信号に変換する、受光素子である。ＴＩＡ１０７はアナログ増幅回路であり、ＰＤ１０６から出力されたアナログ電気信号を、所定の振幅を持つように増幅する。ＤＳＰ１０８は、ＴＩＡ１０７で増幅された信号をデジタル信号に変換して復調処理を行い、復調信号１１を生成する。ＤＳＰ１０８は、プログラムによって動作する信号処理装置である。なお、９０度ハイブリッド回路１０５、ＰＤ１０６、ＴＩＡ１０７及びＤＳＰ１０８の構成及び動作は一般的なデジタルコヒーレント光受信器と同様であるので、これらの詳細な説明は省略する。 The PD 106 is a light receiving element that converts the detected signal light coherently detected by the 90-degree hybrid circuit 105 into an analog electric signal. The TIA 107 is an analog amplification circuit, and amplifies the analog electric signal output from the PD 106 so as to have a predetermined amplitude. The DSP 108 converts the signal amplified by the TIA 107 into a digital signal, performs demodulation processing, and generates a demodulated signal 11. The DSP 108 is a signal processing device that operates according to a program. The configurations and operations of the 90-degree hybrid circuit 105, the PD 106, the TIA 107, and the DSP 108 are the same as those of a general digital coherent optical receiver, and thus detailed description thereof is omitted.

図２は、可変波長フィルタ１０１（ＦＩＬ１）の構成を示す図である。可変波長フィルタ１０１は、光分岐器１０１１、フィルタＡ１０１２、フィルタＢ１０１３、フィルタＣ１０１４及びＰＤ−Ａ１０１５、ＰＤ−Ｂ１０１６、ＰＤ−Ｃ１０１７を備える。フィルタＡ１０１２、フィルタＢ１０１３及びフィルタＣ１０１４は、いずれも特定の透過帯域の光のみを透過する光バンドパスフィルタである。ＰＤ−Ａ１０１５、ＰＤ−Ｂ１０１６及びＰＤ−Ｃ１０１７は、フォトダイオードである。ＰＤ−Ａ１０１５、ＰＤ−Ｂ１０１６及びＰＤ−Ｃ１０１７は、それぞれ、フィルタＡ１０１２、フィルタＢ１０１３及びフィルタＣ１０１４を透過した光を受光して、受光した光のパワーに比例したモニタ電流を出力する。 FIG. 2 is a diagram illustrating a configuration of the variable wavelength filter 101 (FIL1). The variable wavelength filter 101 includes an optical splitter 1011, a filter A 1012, a filter B 1013, a filter C 1014, a PD-A 1015, a PD-B 1016, and a PD-C 1017. Each of the filter A 1012, the filter B 1013, and the filter C 1014 is an optical bandpass filter that transmits only light in a specific transmission band. PD-A 1015, PD-B 1016, and PD-C 1017 are photodiodes. The PD-A 1015, PD-B 1016, and PD-C 1017 receive the light transmitted through the filter A 1012, the filter B 1013, and the filter C 1014, respectively, and output a monitor current that is proportional to the power of the received light.

光分岐器１０１１は、入力された信号光１０を、４本の経路に分岐して出力する。分岐された経路のうち１本は９０度ハイブリッド回路１０５の入力の一方に接続されており、残りの３本はフィルタＡ１０１２〜フィルタＣ１０１４に接続されている。光分岐器１０１１のフィルタＡ１０１２〜フィルタＣ１０１４に接続されている光路への分岐比は一定でなくともよい。しかし、フィルタＡ１０１２〜フィルタＣ１０１４の透過帯域において、光分岐器１０１１に入力される光パワーに対する、ＰＤ−Ａ１０１５〜ＰＤ−Ｃ１０１７のモニタ電流の振幅は同一であることが好ましい。 The optical branching device 1011 branches the inputted signal light 10 into four paths and outputs it. One of the branched paths is connected to one of the inputs of the 90-degree hybrid circuit 105, and the remaining three are connected to the filters A1012 to C1014. The branching ratio to the optical path connected to the filter A 1012 to the filter C 1014 of the optical splitter 1011 may not be constant. However, in the transmission band of the filter A 1012 to the filter C 1014, the amplitude of the monitor current of the PD-A 1015 to PD-C 1017 with respect to the optical power input to the optical branching device 1011 is preferably the same.

フィルタＡ１０１２〜フィルタＣ１０１４は、光分岐器１０１１で分岐された信号光１０の、特定の透過帯域の光のみを透過させる。フィルタＡ１０１２、フィルタＢ１０１３、フィルタＣ１０１４の透過帯域をそれぞれ透過帯域Ａ、Ｂ、Ｃと呼ぶ。すなわち、ＰＤ−Ａ１０１５、ＰＤ−Ｂ１０１６及びＰＤ−Ｃ１０１７には、それぞれ、透過帯域Ａ、Ｂ、Ｃの波長範囲の光が入力される。そして、ＰＤ−Ａ１０１５〜ＰＤ−Ｃ１０１７は、入力された光のパワーに比例した振幅のモニタ電流を波長制御部１０４に出力する。 The filters A 1012 to C 1014 transmit only the light in a specific transmission band of the signal light 10 branched by the optical splitter 1011. The transmission bands of the filter A 1012, the filter B 1013, and the filter C 1014 are referred to as transmission bands A, B, and C, respectively. That is, light in the wavelength ranges of the transmission bands A, B, and C is input to the PD-A 1015, PD-B 1016, and PD-C 1017, respectively. Then, the PD-A 1015 to PD-C 1017 outputs to the wavelength control unit 104 a monitor current having an amplitude proportional to the power of the input light.

図３は、可変波長フィルタ１０３の構成を示す図である。可変波長フィルタ１０３は、光分岐器１０３１、フィルタＤ１０３２、フィルタＥ１０３３、フィルタＦ１０３４及びＰＤ−Ｄ１０３５、ＰＤ−Ｅ１０３６、ＰＤ−Ｆ１０３７を備える。フィルタＤ１０３２、フィルタＥ１０３３及びフィルタＦ１０３４は、いずれも特定の透過帯域の光のみを透過する光バンドパスフィルタである。ＰＤ−Ｄ１０３５、ＰＤ−Ｅ１０３６及びＰＤ−Ｆ１０３７は、フォトダイオードであり、それぞれ、フィルタＤ１０３２、フィルタＥ１０３３及びフィルタＦ１０３４を透過した光を受光する。 FIG. 3 is a diagram illustrating a configuration of the variable wavelength filter 103. The variable wavelength filter 103 includes an optical splitter 1031, a filter D1032, a filter E1033, a filter F1034, a PD-D1035, a PD-E1036, and a PD-F1037. Each of the filter D1032, the filter E1033, and the filter F1034 is an optical bandpass filter that transmits only light in a specific transmission band. PD-D 1035, PD-E 1036, and PD-F 1037 are photodiodes, and receive light transmitted through the filter D1032, the filter E1033, and the filter F1034, respectively.

可変波長フィルタ１０１と同様に、光分岐器１０３１は、ＬＯ光１２を、４本の経路に分岐して出力する。分岐された経路のうち１本は９０度ハイブリッド回路１０５の入力の他方に接続されており、残りの３本はフィルタＤ１０３２、フィルタＥ１０３３、フィルタＦ１０３４にそれぞれ接続されている。光分岐器１０３３のフィルタＤ１０３２〜フィルタＦ１０３４に接続されている光路への分岐比は一定でなくともよい。しかし、フィルタＤ１０３２〜フィルタＦ１０３４の透過帯域において、光分岐器１０３１に入力される光パワーに対する、ＰＤ−Ｄ１０３５〜ＰＤ−Ｆ１０３７のモニタ電流の振幅は同一であることが好ましい。 Similar to the variable wavelength filter 101, the optical branching device 1031 branches the LO light 12 into four paths and outputs it. One of the branched paths is connected to the other input of the 90-degree hybrid circuit 105, and the remaining three are connected to the filter D1032, the filter E1033, and the filter F1034, respectively. The branching ratio to the optical path connected to the filter D1032 to the filter F1034 of the optical splitter 1033 may not be constant. However, in the transmission band of the filter D1032 to the filter F1034, the amplitude of the monitor current of the PD-D 1035 to PD-F 1037 with respect to the optical power input to the optical splitter 1031 is preferably the same.

フィルタＤ１０３２〜フィルタＦ１０３４は、光分波器１０３１で分岐されたＬＯ光１２の、特定の透過帯域の光のみを透過させる。フィルタＤ１０３２、フィルタＥ１０３３、フィルタＦ１０３４が透過させる透過帯域を、それぞれ透過帯域Ｄ、Ｅ、Ｆと呼ぶ。すなわち、ＰＤ−Ｄ１０３５、ＰＤ−Ｅ１０３６及びＰＤ−Ｆ１０３７には、それぞれ、透過帯域Ｄ、Ｅ、Ｆの波長範囲の光が入力される。そして、ＰＤ−Ｄ１０３５〜ＰＤ−Ｆ１０３７は、入力された光のパワーに比例した振幅のモニタ電流を波長制御部１０４に出力する。 The filters D1032 to F1034 transmit only light in a specific transmission band of the LO light 12 branched by the optical demultiplexer 1031. The transmission bands transmitted by the filter D1032, the filter E1033, and the filter F1034 are referred to as transmission bands D, E, and F, respectively. That is, light in the wavelength ranges of the transmission bands D, E, and F is input to the PD-D 1035, PD-E 1036, and PD-F 1037, respectively. Then, the PD-D 1035 to the PD-F 1037 output a monitor current having an amplitude proportional to the power of the input light to the wavelength control unit 104.

続いて、信号光１０の波長が変化した際の動作について説明する。図４は、信号光１０の波長が変化した場合のスペクトルを示す図である。図４に示すように、本実施形態では、透過帯域Ａの波長帯は、透過帯域Ｂよりも長波長側にあり、かつ、透過帯域Ｃよりも短波長側にある。すなわち、透過帯域Ａは、透過帯域Ａ〜Ｃのうち波長帯が中央にある透過帯域である。信号光１０の波長が短波長側に移動した場合（図４の破線（ａ））には、透過帯域Ｂを透過する光パワーが増加し、透過帯域Ａ、Ｃを透過する光パワーが減少する。逆に、信号光の波長が長波長側に移動した場合（図４の破線（ｂ））には、透過帯域Ｃを透過する光パワーが増加し、透過帯域Ａ、Ｂを透過する光パワーが減少する。従って、ＰＤ−Ａ１０１５〜ＰＤ−Ｃ１０１７から出力されるモニタ電流の変化を監視することにより、波長制御部１０４は、信号光１０の波長が変化した際に、信号光１０の波長が短波長側及び長波長側のいずれの側にあるかを検出できる。そして、波長制御部１０４は、透過帯域Ａの光パワーに対応するＰＤ−Ａ１０１５のモニタ電流が極大値となるようにフィルタＡの透過帯域Ａの波長帯を制御することで、信号光１０の波長が透過帯域Ａ内にあることを知ることができる。 Next, an operation when the wavelength of the signal light 10 is changed will be described. FIG. 4 is a diagram illustrating a spectrum when the wavelength of the signal light 10 is changed. As shown in FIG. 4, in the present embodiment, the wavelength band of the transmission band A is on the longer wavelength side than the transmission band B and is on the shorter wavelength side than the transmission band C. That is, the transmission band A is a transmission band having a wavelength band in the center among the transmission bands A to C. When the wavelength of the signal light 10 moves to the short wavelength side (broken line (a) in FIG. 4), the optical power transmitted through the transmission band B increases and the optical power transmitted through the transmission bands A and C decreases. . Conversely, when the wavelength of the signal light moves to the longer wavelength side (broken line (b) in FIG. 4), the optical power transmitted through the transmission band C increases and the optical power transmitted through the transmission bands A and B increases. Decrease. Therefore, by monitoring the change in the monitor current output from the PD-A 1015 to PD-C 1017, the wavelength control unit 104 can change the wavelength of the signal light 10 to the short wavelength side when the wavelength of the signal light 10 changes. It is possible to detect which side is on the long wavelength side. Then, the wavelength control unit 104 controls the wavelength band of the transmission band A of the filter A so that the monitor current of the PD-A 1015 corresponding to the optical power of the transmission band A becomes a maximum value. Can be found in the transmission band A.

また、同様の手順により、ＰＤ−Ｄ１０３５〜ＰＤ−Ｆ１０３７から出力されるモニタ電流を監視することにより、波長制御部１０４は、現在のＬＯ光１２の波長が透過帯域Ｄに対して短波長側にあるか長波長側にあるかを知ることができる。そして、波長制御部１０４は、透過帯域Ｄの光パワーに対応するＰＤ−Ｄ１０３５のモニタ電流が極大値となるようにＬＯ光１２の波長を制御することで、ＬＯ光１２の波長が透過帯域Ｄに入るように、局部発振光源１０２を制御する。 Further, by monitoring the monitor current output from the PD-D 1035 to PD-F 1037 according to the same procedure, the wavelength control unit 104 causes the current wavelength of the LO light 12 to be shorter than the transmission band D. You can know if it is on the long wavelength side. Then, the wavelength control unit 104 controls the wavelength of the LO light 12 so that the monitor current of the PD-D 1035 corresponding to the optical power in the transmission band D becomes a maximum value, so that the wavelength of the LO light 12 becomes the transmission band D. The local oscillation light source 102 is controlled to enter.

図５及び図６は、可変波長フィルタ１０１及び１０３の透過帯域の制御を示す図である。図５に示す透過帯域Ａ〜Ｃのそれぞれの帯域幅及び各透過帯域の間隔と、図６に示す透過帯域Ｄ〜Ｆのそれぞれの帯域幅及び各透過帯域の間隔とは同一である。 5 and 6 are diagrams showing control of the transmission band of the variable wavelength filters 101 and 103. FIG. The bandwidths of the transmission bands A to C and the intervals between the transmission bands shown in FIG. 5 are the same as the bandwidths of the transmission bands D to F and the intervals of the transmission bands shown in FIG.

図５に示すように、可変波長フィルタ１０１は、波長制御部１０４によって、透過帯域Ａ〜Ｃ間の波長間隔を一定に保ったまま、図５の波長軸上を平行移動するように制御される。 As shown in FIG. 5, the variable wavelength filter 101 is controlled by the wavelength control unit 104 so as to translate on the wavelength axis of FIG. 5 while keeping the wavelength interval between the transmission bands A to C constant. .

波長制御部１０４は、信号光１０の波長を検出するために、透過帯域Ａの透過光を受光するＰＤ−Ａ１０１から出力されるモニタ電流が最大になるように、可変波長フィルタ１０１の透過帯域を移動させる。例えば、図５に示すように、信号光１０の波長がフィルタＢ１０１３の透過帯域Ｂよりも短波長側に移動した場合（図５の（Ａ））を考える。波長制御部１０４が可変波長フィルタ１０１の透過帯域Ａ〜Ｃを短波長側に移動させると、まず、透過帯域Ｂと信号光１０のスペクトルとが重なる。その結果、ＰＤ−Ｂ１０１６のみにモニタ電流が生じる。すなわち、透過帯域を短波長側に移動させた結果、ＰＤ−Ｂ１０１６のみにモニタ電流が生じた場合には、信号光１０の波長は透過帯域Ａ〜Ｃよりも短波長側にあることがわかる。 In order to detect the wavelength of the signal light 10, the wavelength control unit 104 sets the transmission band of the variable wavelength filter 101 so that the monitor current output from the PD-A 101 that receives the transmission light in the transmission band A is maximized. Move. For example, as shown in FIG. 5, consider a case where the wavelength of the signal light 10 moves to a shorter wavelength side than the transmission band B of the filter B 1013 (FIG. 5A). When the wavelength control unit 104 moves the transmission bands A to C of the variable wavelength filter 101 to the short wavelength side, first, the transmission band B and the spectrum of the signal light 10 overlap. As a result, a monitor current is generated only in the PD-B 1016. That is, when the monitor band is generated only in the PD-B 1016 as a result of moving the transmission band to the short wavelength side, it can be seen that the wavelength of the signal light 10 is on the shorter wavelength side than the transmission bands A to C.

波長制御部１０４が、可変波長フィルタ１０１の透過帯域Ａ〜Ｃをさらに短波長側に移動させると、信号光１０のスペクトルのピークが透過帯域Ｂ内を通過する。透過帯域Ａ〜Ｃをさらに短波長側に移動させると、図４で説明した手順によって、信号光１０のスペクトルのピークが透過帯域Ａ内に入るように、透過帯域Ａの波長を制御することができる（図５の（Ｂ））。この点においては、ＰＤ−Ａ１０１５が出力するモニタ電流は極大値となり、可変波長フィルタ１０１の透過帯域Ａを短波長側及び長波長側のいずれに移動させても、ＰＤ−Ａ１０１５のモニタ電流は減少する。従って、ＰＤ−Ａ１０１５が出力するモニタ電流が極大となった場合には、信号光１０の波長は透過帯域Ａにあると判断できる。 When the wavelength control unit 104 moves the transmission bands A to C of the variable wavelength filter 101 to the shorter wavelength side, the spectrum peak of the signal light 10 passes through the transmission band B. When the transmission bands A to C are further moved to the short wavelength side, the wavelength of the transmission band A can be controlled so that the spectrum peak of the signal light 10 falls within the transmission band A by the procedure described in FIG. (B in FIG. 5). At this point, the monitor current output from the PD-A 1015 has a maximum value, and the monitor current of the PD-A 1015 decreases regardless of whether the transmission band A of the variable wavelength filter 101 is moved to the short wavelength side or the long wavelength side. To do. Therefore, when the monitor current output from the PD-A 1015 becomes maximum, it can be determined that the wavelength of the signal light 10 is in the transmission band A.

なお、図５は信号光１０の波長が透過帯域Ｂよりも短波長側にある場合について説明したが、信号光１０の波長が透過帯域Ｃよりも長波長側にある場合にも、透過帯域Ａ〜Ｃを長波長側に移動させることで、同様に信号光１０の波長を検出できる。 5 illustrates the case where the wavelength of the signal light 10 is on the shorter wavelength side than the transmission band B, but the transmission band A can also be obtained when the wavelength of the signal light 10 is on the longer wavelength side than the transmission band C. The wavelength of the signal light 10 can be similarly detected by moving ~ C to the long wavelength side.

上述の手順により、信号光１０の有無を調査できる波長範囲が拡大される。その結果、透過帯域Ｂ、Ｃにおけるモニタ電流を監視することによって、透過帯域Ａのみのモニタ電流を監視する場合と比較して、信号光１０の波長が移動した方向を、より容易に検出することができる。 By the above procedure, the wavelength range in which the presence or absence of the signal light 10 can be investigated is expanded. As a result, by monitoring the monitor currents in the transmission bands B and C, the direction in which the wavelength of the signal light 10 has moved can be detected more easily than in the case of monitoring the monitor current only in the transmission band A. Can do.

なお、透過帯域を移動させた結果、ＰＤ−Ａ１０１５が出力するモニタ電流が極大となる波長帯が複数存在した場合には、信号光１０の波長はモニタ電流のピーク値が高い方の波長帯にあると判断してもよい。 As a result of shifting the transmission band, when there are a plurality of wavelength bands in which the monitor current output from the PD-A 1015 is maximized, the wavelength of the signal light 10 is set to the wavelength band with the higher peak value of the monitor current. You may judge that there is.

次に、ＬＯ光１２の波長の制御について説明する。波長制御部１０４は、可変波長フィルタ１０３の透過帯域Ｄ〜Ｆのうち、中央の透過帯域である透過帯域Ｄが、信号光１０の波長を透過するように設定された透過帯域Ａと同一となるように、可変波長フィルタ１０３の透過帯域Ｄ〜Ｆを移動させる。例えば、波長制御部１０４は、透過帯域Ａの中心の波長と透過帯域Ｄの中心の波長とが一致するように、フィルタＤ１０３２の透過帯域を移動させる。可変波長フィルタ１０３の透過帯域Ｅ、Ｆは、可変波長フィルタ１０１と同様に、波長制御部１０４の制御によって、透過帯域Ｄとの波長間隔を一定に保ったまま波長軸上を移動する。 Next, control of the wavelength of the LO light 12 will be described. In the wavelength control unit 104, the transmission band D that is the central transmission band among the transmission bands D to F of the variable wavelength filter 103 is the same as the transmission band A that is set to transmit the wavelength of the signal light 10. As described above, the transmission bands D to F of the variable wavelength filter 103 are moved. For example, the wavelength control unit 104 moves the transmission band of the filter D1032 so that the center wavelength of the transmission band A matches the center wavelength of the transmission band D. Similarly to the variable wavelength filter 101, the transmission bands E and F of the variable wavelength filter 103 move on the wavelength axis while keeping the wavelength interval with the transmission band D constant under the control of the wavelength control unit 104.

波長制御部１０４は、図６の（ａ）に示すように、ＬＯ光１２の波長を長波長方向あるいは短波長方向に移動するように制御する。そして、波長制御部１０４は、図６の（ｂ）に示すように、透過帯域Ｄの透過光を受光したＰＤ−Ｄ１０３５のモニタ電流が最大になるように、ＬＯ光１２の波長を移動させる。このような制御により、ＬＯ光１２の波長を、可変波長フィルタ１０１で検出された信号光１０の波長と一致させることができる。 The wavelength control unit 104 controls the wavelength of the LO light 12 so as to move in the long wavelength direction or the short wavelength direction, as shown in FIG. Then, as shown in FIG. 6B, the wavelength control unit 104 moves the wavelength of the LO light 12 so that the monitor current of the PD-D 1035 that receives the transmitted light in the transmission band D is maximized. By such control, the wavelength of the LO light 12 can be matched with the wavelength of the signal light 10 detected by the variable wavelength filter 101.

図７は、以上で説明した波長制御部１０４の制御手順を示すフローチャートである。波長の再割り当てなどの理由により信号光１０の波長が変化すると、波長制御部１０４は、フィルタＡ１０１２〜フィルタＣ１０１４の透過帯域を制御して、波長の変化した方向を検出する（図７のステップＳ１１）。図５を参照して説明したように、信号光１０の波長が変化した方向は、透過帯域Ｂ、Ｃにおけるモニタ電流の有無によって検出される。そして、波長制御部１０４は、ＰＤ−Ａ１０１５のモニタ電流が極大となるように、フィルタＡ１０１２の透過帯域Ａの波長を制御する（ステップＳ１２）。 FIG. 7 is a flowchart showing a control procedure of the wavelength control unit 104 described above. When the wavelength of the signal light 10 changes due to reasons such as wavelength reassignment, the wavelength control unit 104 controls the transmission band of the filters A 1012 to C 1014 to detect the direction in which the wavelength has changed (step S11 in FIG. 7). ). As described with reference to FIG. 5, the direction in which the wavelength of the signal light 10 has changed is detected by the presence or absence of the monitor current in the transmission bands B and C. Then, the wavelength control unit 104 controls the wavelength of the transmission band A of the filter A 1012 so that the monitor current of the PD-A 1015 is maximized (step S12).

次に、波長制御部１０４は、フィルタＤ１０３２の透過帯域Ｄの中心波長が、フィルタＡ１０１２の透過帯域Ａの中心波長と一致するように、透過帯域Ｄの波長を制御する（ステップＳ１３）。さらに、波長制御部１０４は、ＰＤ−Ｄ１０３５のモニタ電流が極大となるように、局部発振光源１０２の発振波長を制御する（ステップＳ１４）。 Next, the wavelength control unit 104 controls the wavelength of the transmission band D so that the center wavelength of the transmission band D of the filter D1032 matches the center wavelength of the transmission band A of the filter A1012 (step S13). Further, the wavelength control unit 104 controls the oscillation wavelength of the local oscillation light source 102 so that the monitor current of the PD-D 1035 is maximized (step S14).

図７のステップＳ１４までの制御が終了して信号光１０の波長とＬＯ光１２の波長とが一致する状態（定常状態）となった後も、環境条件の変化によって信号光１０あるいはＬＯ光１２の波長が変動する場合がある。ステップＳ１３の処理が終了した後に制御フローをステップＳ１２に戻すことで、定常状態において信号光１０あるいはＬＯ光１２の波長が変動した場合にも、信号光１０及びＬＯ光１２の波長を一致させるように制御することができる。 Even after the control up to step S14 in FIG. 7 is completed and the wavelength of the signal light 10 and the wavelength of the LO light 12 coincide with each other (steady state), the signal light 10 or the LO light 12 is changed depending on the environmental conditions. The wavelength of may vary. By returning the control flow to step S12 after the processing of step S13 is completed, even when the wavelength of the signal light 10 or the LO light 12 varies in a steady state, the wavelengths of the signal light 10 and the LO light 12 are matched. Can be controlled.

このように、波長制御部１０４は、可変波長フィルタ１０１の透過帯域Ａを信号光１０の波長に追従するように制御し、可変波長フィルタ１０３の透過帯域Ｄを、可変波長フィルタ１０１の透過帯域Ａと同一となるように制御する。このため、信号光１０の波長の変化に伴って可変波長フィルタ１０３の透過帯域Ｄの波長も移動する。そして、波長制御部１０４は、透過帯域Ｄを透過する光によるモニタ電流が最大になるように、ＬＯ光１２の波長を制御することで、ＬＯ光１２の波長を信号光１０の波長変化に追従させることができる。 Thus, the wavelength control unit 104 controls the transmission band A of the variable wavelength filter 101 so as to follow the wavelength of the signal light 10, and changes the transmission band D of the variable wavelength filter 103 to the transmission band A of the variable wavelength filter 101. Control to be the same. For this reason, as the wavelength of the signal light 10 changes, the wavelength of the transmission band D of the variable wavelength filter 103 also moves. Then, the wavelength control unit 104 follows the wavelength change of the LO light 12 by controlling the wavelength of the LO light 12 so that the monitor current due to the light passing through the transmission band D is maximized. Can be made.

光受信器１は、さらに、ＣＰＵ（central processing unit、中央処理装置）１０９及びメモリ１１０を備えていてもよい。メモリ１１０は、例えば半導体の不揮発性メモリである。ＣＰＵ１０９は、メモリ１１０に記憶されたプログラムを実行することにより、上に述べた波長制御部１０４を含む光受信器１の機能を実現してもよい。 The optical receiver 1 may further include a CPU (central processing unit) 109 and a memory 110. The memory 110 is, for example, a semiconductor nonvolatile memory. The CPU 109 may realize the function of the optical receiver 1 including the wavelength control unit 104 described above by executing a program stored in the memory 110.

このようにして、第１の実施形態の光受信装置は、図１１で説明したような波長再割り当てが行われた際にも、簡単な構成によってＬＯ光１２の波長を信号光１０に追従させることができる。 In this way, the optical receiver of the first embodiment allows the wavelength of the LO light 12 to follow the signal light 10 with a simple configuration even when the wavelength reassignment as described with reference to FIG. 11 is performed. be able to.

以上説明したように、第１の実施形態の光受信装置は、信号光から分岐された信号光の波長を検出する。そして、第１の実施形態の光受信装置は、ＬＯ光を透過させる可変波長フィルタの透過帯域の中心を当該ピーク波長と一致させ、これに基づいて局部発振光源の波長を制御する。その結果、第１の実施形態の光受信装置は、主信号の波長変化に局部発振光源を追従させることができる。 As described above, the optical receiver according to the first embodiment detects the wavelength of the signal light branched from the signal light. Then, the optical receiver of the first embodiment matches the center of the transmission band of the variable wavelength filter that transmits LO light with the peak wavelength, and controls the wavelength of the local oscillation light source based on this. As a result, the optical receiver of the first embodiment can cause the local oscillation light source to follow the wavelength change of the main signal.

また、第１の実施形態の光受信装置は、透過帯域Ａの他に透過帯域Ｂ、Ｃにおけるモニタ電流をも監視することによって、透過帯域Ａのみのモニタ電流を監視する場合と比較して、信号光の波長が移動した方向を、より容易に検出することができる。
（第１の実施形態の第１の変形例）
上述した第１の実施形態では、波長制御部１０４の制御により、可変波長フィルタ１０１の透過帯域Ａ〜Ｃは、各々の透過帯域の幅及び透過帯域の間隔を一定に保ったまま波長軸上を移動する。フィルタＤ１０３２〜Ｆ１０３４の透過帯域Ｄ〜Ｆも同様に制御される。しかしながら、可変波長フィルタ１０１及び１０３の制御の際には、各々の透過帯域の間隔は一定でなくともよい。例えば、信号光１０の波長を検出する際に、透過帯域Ａ〜Ｃのいずれにおいてもモニタ電流が発生していない場合には、透過帯域Ａ〜Ｃの各帯域の間隔を広げるようにフィルタＡ１０１２〜フィルタＣ１０１４を制御してもよい。その結果、波長の検出範囲が広がるため、信号光１０の波長が大きく変化した場合でも、信号光１０の波長の変化した方向の検出が容易になる。また、透過帯域Ａ〜Ｃの間隔を狭めるように制御することで、例えば信号光１０のスペクトル幅が比較的狭い場合でも、信号光１０の検出が容易になる。 In addition, the optical receiver of the first embodiment monitors the monitor currents in the transmission bands B and C in addition to the transmission band A, as compared with the case of monitoring the monitor current only in the transmission band A, The direction in which the wavelength of the signal light has moved can be detected more easily.
(First modification of the first embodiment)
In the first embodiment described above, the transmission band A to C of the variable wavelength filter 101 is controlled on the wavelength axis while keeping the width of each transmission band and the interval between the transmission bands constant under the control of the wavelength control unit 104. Moving. The transmission bands D to F of the filters D1032 to F1034 are similarly controlled. However, when the variable wavelength filters 101 and 103 are controlled, the intervals between the respective transmission bands may not be constant. For example, when the wavelength of the signal light 10 is detected and the monitor current is not generated in any of the transmission bands A to C, the filters A 1012 to increase the interval between the transmission bands A to C. The filter C1014 may be controlled. As a result, the wavelength detection range is widened, so that the direction in which the wavelength of the signal light 10 has changed can be easily detected even when the wavelength of the signal light 10 has changed significantly. Further, by controlling the interval between the transmission bands A to C to be narrow, for example, even when the spectrum width of the signal light 10 is relatively narrow, the signal light 10 can be easily detected.

ＬＯ光１２の制御においても、例えば、信号光１０の波長が大きく変化した場合には、現在のＬＯ光１２に対応する透過帯域Ｄの波長と、新しい信号光１０の波長に対応する透過帯域Ｄの波長とは大きく離れる。透過帯域Ｄ〜Ｆの帯域の間隔を広げるようにフィルタＤ１０３２〜フィルタＦ１０３４を制御することで、信号光１０の波長が大きく変化した場合でも、ＬＯ光１２の波長が透過帯域Ｄに対して短波長側及び長波長側のいずれにあるかの検出が容易になる。また、透過帯域Ｄ〜Ｆの間隔を狭めるように制御することで、例えばＬＯ光１２のスペクトルが比較的狭い場合でも、ＬＯ光１２の検出が容易になる。
（第１の実施形態の第２の変形例）
また、フィルタＡ１０１２〜フィルタＣ１０１４、フィルタＤ１０３２〜フィルタＦ１０３４の透過帯域Ａ〜Ｆの帯域幅は、全てが同一でなくてもよい。例えば、図５において、透過帯域Ａの帯域幅をより狭くすることで、信号光１０の波長の検出精度を向上させることができる。同様に、図６において、透過帯域Ｄの帯域幅をより狭くすることで、ＬＯ光１２の波長の設定精度を向上させることができる。 Also in the control of the LO light 12, for example, when the wavelength of the signal light 10 changes greatly, the wavelength of the transmission band D corresponding to the current LO light 12 and the transmission band D corresponding to the wavelength of the new signal light 10. It is far from the wavelength of. Even when the wavelength of the signal light 10 is greatly changed by controlling the filters D1032 to F1034 so as to widen the interval between the transmission bands D to F, the wavelength of the LO light 12 is shorter than the transmission band D. It is easy to detect which side is on the long wavelength side or the long wavelength side. Further, by controlling so that the interval between the transmission bands D to F is narrowed, for example, even when the spectrum of the LO light 12 is relatively narrow, the detection of the LO light 12 becomes easy.
(Second modification of the first embodiment)
Further, the bandwidths of the transmission bands A to F of the filter A 1012 to the filter C 1014 and the filter D 1032 to the filter F 1034 may not all be the same. For example, in FIG. 5, the detection accuracy of the wavelength of the signal light 10 can be improved by narrowing the bandwidth of the transmission band A. Similarly, in FIG. 6, the setting accuracy of the wavelength of the LO light 12 can be improved by narrowing the bandwidth of the transmission band D.

さらに、図５において、透過帯域Ｂ、Ｃの帯域幅を広くすることで、波長が変化した後の信号光１０を検出できる波長範囲が拡大される。その結果、透過帯域Ａの波長を制御する方向の決定が容易になる。また、図６においても、透過帯域Ｅ、Ｆの帯域幅を広くすることで、ＬＯ光１２を検出できる波長範囲が拡大される。その結果、ＬＯ光１２の波長を制御する方向の決定が容易になる。
（第１の実施形態の第３の変形例）
図２、図３に示したように、第１の実施形態の可変波長フィルタ１０１及び１０３は、フィルタＡ１０１２〜フィルタＣ１０１４及びフィルタＤ１０３２〜フィルタＦ１０３４をそれぞれ備える。しかし、可変波長フィルタ１０１及び１０３が内部に備えるフィルタの数、及び、可変波長フィルタ１０１及び１０３が内部に備えるＰＤの数は、それぞれ３個に限られない。フィルタＡ〜フィルタＦに対応するフィルタの数、及び、対応するＰＤの数を増加させることで、検出可能な波長の範囲の拡大や、波長及び波長の変化量の検出精度の向上が可能である。
（第２の実施形態）
主信号の波長変更に局部発振光源を追従させるという第１の実施形態の効果は、以下の構成を備える波長制御装置２００によっても得られる。 Further, in FIG. 5, by widening the bandwidths of the transmission bands B and C, the wavelength range in which the signal light 10 after the wavelength change can be detected is expanded. As a result, the direction for controlling the wavelength of the transmission band A can be easily determined. Also in FIG. 6, by increasing the bandwidths of the transmission bands E and F, the wavelength range in which the LO light 12 can be detected is expanded. As a result, the direction in which the wavelength of the LO light 12 is controlled can be easily determined.
(Third Modification of First Embodiment)
As shown in FIGS. 2 and 3, the variable wavelength filters 101 and 103 of the first embodiment include a filter A 1012 to a filter C 1014 and a filter D 1032 to a filter F 1034, respectively. However, the number of filters included in the variable wavelength filters 101 and 103 and the number of PDs included in the variable wavelength filters 101 and 103 are not limited to three. By increasing the number of filters corresponding to the filters A to F and the number of corresponding PDs, it is possible to expand the range of detectable wavelengths and improve the detection accuracy of the wavelength and the amount of change in wavelength. .
(Second Embodiment)
The effect of the first embodiment of causing the local oscillation light source to follow the wavelength change of the main signal can also be obtained by the wavelength control device 200 having the following configuration.

図８は、第２の実施形態の波長制御装置２００の構成を示すブロック図である。すなわち、波長制御装置２００は、第１のフィルタ２０１、第１の受光部２１１、第２のフィルタ２０２、第２の受光部２１２、局部発振光源２２１、制御部２２２を備える。 FIG. 8 is a block diagram illustrating a configuration of the wavelength control device 200 according to the second embodiment. That is, the wavelength control apparatus 200 includes a first filter 201, a first light receiving unit 211, a second filter 202, a second light receiving unit 212, a local oscillation light source 221, and a control unit 222.

局部発振光源２２１は、局部発振光（ＬＯ光）を出力する、外部から発振波長を制御可能な光源である。第１の光フィルタ２０１は第１の波長特性を持ち、信号光２３１が入力される。第１の受光部２０２は、第１の光フィルタ２０１を透過した信号光２３１の強度に対応する振幅の第１の電流を出力する。第２の光フィルタ２０２は、第２の波長特性を持ち、ＬＯ光が入力される。ＬＯ光は、波長制御装置２００の外部にも出力される。第２の受光部２１２は、第２の光フィルタ２０２を透過したＬＯ光の強度に対応する振幅の電流を出力する。 The local oscillation light source 221 is a light source that outputs local oscillation light (LO light) and that can control the oscillation wavelength from the outside. The first optical filter 201 has a first wavelength characteristic, and the signal light 231 is input thereto. The first light receiving unit 202 outputs a first current having an amplitude corresponding to the intensity of the signal light 231 that has passed through the first optical filter 201. The second optical filter 202 has a second wavelength characteristic and receives LO light. The LO light is also output to the outside of the wavelength control apparatus 200. The second light receiving unit 212 outputs a current having an amplitude corresponding to the intensity of the LO light transmitted through the second optical filter 202.

制御部２２２は、第１の電流が極大となるように第１の波長特性を制御する。そして、制御部は、第１の電流が極大となるように制御された第１の波長特性と、第２の波長特性と、が一致するように第２の波長特性を制御する。さらに、制御部は、第２の電流が極大となるようにＬＯ光の波長を制御する。 The controller 222 controls the first wavelength characteristic so that the first current becomes a maximum. And a control part controls the 2nd wavelength characteristic so that the 1st wavelength characteristic controlled so that the 1st current may become maximum may coincide with the 2nd wavelength characteristic. Further, the control unit controls the wavelength of the LO light so that the second current becomes a maximum.

このような制御により、制御部２２１は、第１の光フィルタ２０１の波長特性と第２の光フィルタ２０２との波長特性を一致させる。そして、制御部２２１は、第２の光フィルタ２０２のモニタ電流である第２の電流が極大となるようにＬＯ光の波長を制御することにより、ＬＯ光の波長を信号光の波長と一致させることができる。その結果、第２の実施形態の波長制御装置２００は、局部発振光の波長を信号光の波長に追従させる機能を簡単な構成で実現できるという効果を奏する。
（第３の実施形態）
図９は、本発明の第３の実施形態の光受信器１ａの構成を示すブロック図である。光受信器１ａは、図１に示した光受信器１と比較して、可変波長フィルタ１０３を備えていない点で相違している。以下の説明では、第１の実施形態と同一の要素には同一の参照符号が付されている。 By such control, the control unit 221 matches the wavelength characteristics of the first optical filter 201 with the wavelength characteristics of the second optical filter 202. Then, the control unit 221 controls the wavelength of the LO light so that the second current that is the monitor current of the second optical filter 202 is maximized, thereby matching the wavelength of the LO light with the wavelength of the signal light. be able to. As a result, the wavelength control device 200 of the second embodiment has an effect that the function of causing the wavelength of the local oscillation light to follow the wavelength of the signal light can be realized with a simple configuration.
(Third embodiment)
FIG. 9 is a block diagram showing a configuration of an optical receiver 1a according to the third embodiment of the present invention. The optical receiver 1a is different from the optical receiver 1 shown in FIG. 1 in that the variable wavelength filter 103 is not provided. In the following description, the same reference numerals are given to the same elements as those in the first embodiment.

第３の実施形態では、波長制御部１０４は、可変波長フィルタ１０１の透過帯域Ａ〜Ｃを制御するとともに、可変フィルタ１０１の制御結果に基づいて、透過帯域Ａの中心の波長を求める。波長制御部１０４は、さらに、局部発振光源１０２に対して、ＬＯ光１２の発振波長を直接指示する。局部発振光源１０２は、波長制御部１０４から指示された波長のＬＯ光１２を出力する。 In the third embodiment, the wavelength control unit 104 controls the transmission bands A to C of the variable wavelength filter 101 and obtains the center wavelength of the transmission band A based on the control result of the variable filter 101. Further, the wavelength control unit 104 directly instructs the oscillation wavelength of the LO light 12 to the local oscillation light source 102. The local oscillation light source 102 outputs the LO light 12 having the wavelength designated by the wavelength control unit 104.

波長制御部１０４は、可変波長フィルタ１０１の制御結果から透過帯域Ａの中心の波長を求め、求められた波長と同一の波長のＬＯ光１２が出力されるように局部発振光源１０２を制御する。その結果、第３の実施形態の光受信器１ａも第１の実施形態の光受信器１と同様の効果を奏する。さらに、第３の実施形態の光受信器１ａは、可変波長フィルタ１０３が不要となり、光受信器の構成がより簡単になる。 The wavelength control unit 104 obtains the center wavelength of the transmission band A from the control result of the variable wavelength filter 101, and controls the local oscillation light source 102 so that the LO light 12 having the same wavelength as the obtained wavelength is output. As a result, the optical receiver 1a of the third embodiment has the same effects as the optical receiver 1 of the first embodiment. Furthermore, the optical receiver 1a of the third embodiment does not require the variable wavelength filter 103, and the configuration of the optical receiver is simplified.

なお、可変波長フィルタ１０３は、透過帯域Ａの中心の波長を、局部発振光源１０２に直接通知し、局部発振光源１０２は通知された波長と同一の波長のＬＯ光１２を出力してもよい。
（第４の実施形態）
図１０は、本発明の第３の実施形態の可変波長フィルタ１０１ａの構成を示すブロック図である。可変波長フィルタ１０１ａは、光分岐器１０１１、フィルタ１０１２ａ〜１０１４ａ、光スイッチ１０１８、ＰＤ１０１９を備える。 Note that the variable wavelength filter 103 may directly notify the local oscillation light source 102 of the center wavelength of the transmission band A, and the local oscillation light source 102 may output the LO light 12 having the same wavelength as the notified wavelength.
(Fourth embodiment)
FIG. 10 is a block diagram showing a configuration of a variable wavelength filter 101a according to the third embodiment of the present invention. The variable wavelength filter 101a includes an optical splitter 1011, filters 1012a to 1014a, an optical switch 1018, and a PD 1019.

図１０に示す可変波長フィルタ１０１ａは、図２に示した可変波長フィルタ１０１と比較して、光スイッチ１０１８を備える一方、１個のみのＰＤ１０１９を備える。図１０に示した光分岐器１０１１及びフィルタ１０１２ａ〜１０１４ａの機能は、図２に示した可変波長フィルタ１０１の光分岐器１０１１及びフィルタＡ１０１２〜フィルタＣ１０１４と同様である。 A variable wavelength filter 101a illustrated in FIG. 10 includes an optical switch 1018 and includes only one PD 1019, as compared with the variable wavelength filter 101 illustrated in FIG. Functions of the optical branching unit 1011 and the filters 1012a to 1014a illustrated in FIG. 10 are the same as those of the optical branching unit 1011 and the filters A 1012 to C 1014 of the variable wavelength filter 101 illustrated in FIG.

光スイッチ１０１８は、フィルタ１０１２ａ〜１０１４ａのいずれかを透過した光がＰＤ１０１９で受光されるように、フィルタ１０１２ａ〜１０１４ａとＰＤ１０１９との間の光路を切り替える。ＰＤ１０１９は、フィルタ１０１２ａ〜１０１４ａのモニタ電流を光スイッチ１０１８によって切り替えながら出力する。可変波長フィルタ１０１ａは、ＰＤ１０１９のモニタ電流、及び、光スイッチ１０１８によって選択されているフィルタ（フィルタ１０１２ａ〜１０１４ａのいずれか）の情報を出力する。 The optical switch 1018 switches the optical path between the filters 1012a to 1014a and the PD 1019 so that light transmitted through any of the filters 1012a to 1014a is received by the PD 1019. The PD 1019 outputs the monitor currents of the filters 1012a to 1014a while being switched by the optical switch 1018. The variable wavelength filter 101a outputs the monitor current of the PD 1019 and information on the filter (one of the filters 1012a to 1014a) selected by the optical switch 1018.

図１に示された可変波長フィルタ１０１に代えて本実施形態の可変波長フィルタ１０１ａを用いることにより、第１の実施形態の光受信器１は、その効果を減じることなく、ＰＤ−Ａ１０１５〜ＰＤ−Ｃ１０１５の数を減らすことができる。波長制御部１０４は、光スイッチ１０１８によって選択されているフィルタの情報に基づいて、可変波長フィルタ１０１ａから入力されているモニタ電流がフィルタ１０１２ａ〜１０１４ａのいずれのモニタ電流であるかを知ることができる。 By using the variable wavelength filter 101a of this embodiment in place of the variable wavelength filter 101 shown in FIG. 1, the optical receiver 1 of the first embodiment can reduce the effect without reducing the effect. -The number of C1015 can be reduced. Based on the information on the filter selected by the optical switch 1018, the wavelength control unit 104 can know which of the filters 1012a to 1014a is the monitor current input from the variable wavelength filter 101a. .

また、可変波長フィルタ１０１ａの構成が可変波長フィルタ１０３にも適用可能であることは明らかである。従って、第１の実施形態において、可変波長フィルタ１０３に代えて本実施形態の可変波長フィルタ１０１ａが用いられてもよい。 In addition, it is obvious that the configuration of the variable wavelength filter 101 a can be applied to the variable wavelength filter 103. Therefore, in the first embodiment, the variable wavelength filter 101 a of this embodiment may be used instead of the variable wavelength filter 103.

以上、実施形態を参照して本願発明を説明したが、本願発明は上記の実施形態に限定されない。本願発明の構成や詳細には、本願発明のスコープ内で当業者が理解し得る様々な変更をすることができる。 Although the present invention has been described with reference to the embodiments, the present invention is not limited to the above embodiments. Various changes that can be understood by those skilled in the art can be made to the configuration and details of the present invention within the scope of the present invention.

また、それぞれの実施形態に記載された構成は、必ずしも互いに排他的なものではない。本発明の作用及び効果は、上述の実施形態の全部又は一部を組み合わせた構成によって実現されてもよい。 Further, the configurations described in the respective embodiments are not necessarily mutually exclusive. The operation and effect of the present invention may be realized by a configuration in which all or part of the above-described embodiments are combined.

なお、本発明の実施形態は以下の付記のようにも記載されうるが、これらには限定されない。 In addition, although embodiment of this invention can be described also as the following additional remarks, it is not limited to these.

（付記１）
局部発振光を出力する局部発振光源と、
信号光が入力される、第１の波長特性を持つ第１の光フィルタと、
前記第１の光フィルタを透過した前記信号光の強度の増加に対して振幅が単調に増加する第１の電流を出力する第１の受光部と、
前記局部発振光が入力される、第２の波長特性を持つ第２の光フィルタと、
前記第２の光フィルタを透過した前記局部発振光の強度の増加に対して振幅が単調に増加する第２の電流を出力する第２の受光部と、
前記第１の電流が極大となるように前記第１の波長特性を制御し、前記第２の波長特性と前記第１の電流が極大となるように制御された前記第１の波長特性とが一致するように前記第２の波長特性を制御し、前記第２の電流が極大となるように前記局部発振光の波長を制御する制御部と、
を備える波長制御装置。 (Appendix 1)
A local oscillation light source that outputs local oscillation light;
A first optical filter having a first wavelength characteristic to which signal light is input;
A first light receiving unit that outputs a first current whose amplitude monotonously increases with an increase in the intensity of the signal light transmitted through the first optical filter;
A second optical filter having a second wavelength characteristic to which the local oscillation light is input;
A second light-receiving unit that outputs a second current whose amplitude monotonously increases with an increase in intensity of the local oscillation light transmitted through the second optical filter;
The first wavelength characteristic is controlled so that the first current becomes maximum, and the second wavelength characteristic and the first wavelength characteristic controlled so that the first current becomes maximum are obtained. A control unit that controls the second wavelength characteristic so as to match, and controls the wavelength of the local oscillation light so that the second current becomes maximum;
A wavelength control device comprising:

（付記２）
前記第１の光フィルタは、相異なる透過帯域を持つ複数のバンドパスフィルタで構成され、前記第１の受光部は、前記第１の光フィルタが備える前記複数のバンドパスフィルタのうち一のバンドパスフィルタを透過した前記信号光を受光することを特徴とする、付記１に記載された波長制御装置。 (Appendix 2)
The first optical filter includes a plurality of bandpass filters having different transmission bands, and the first light receiving unit is one band of the plurality of bandpass filters included in the first optical filter. The wavelength control device according to appendix 1, wherein the signal light transmitted through the pass filter is received.

（付記３）
前記第１の光フィルタは、互いに重複しない３個の透過帯域を持つバンドパスフィルタで構成され、前記第１の受光部は、前記第１の光フィルタが備える前記バンドパスフィルタの透過帯域のうち、中央の波長帯の透過帯域を持つ前記第１の光フィルタが備える前記バンドパスフィルタを透過した前記信号光を受光することを特徴とする、付記１に記載された波長制御装置。 (Appendix 3)
The first optical filter is composed of a band-pass filter having three transmission bands that do not overlap with each other, and the first light-receiving unit includes a transmission band of the band-pass filter included in the first optical filter. The wavelength control device according to appendix 1, wherein the signal light transmitted through the bandpass filter included in the first optical filter having a transmission band of a central wavelength band is received.

（付記４）
前記第１の光フィルタが備える前記バンドパスフィルタの前記透過帯域の帯域幅及び前記透過帯域の間隔が固定されていることを特徴とする、付記２又は３に記載された波長制御装置。 (Appendix 4)
The wavelength control device according to appendix 2 or 3, wherein a bandwidth of the transmission band and an interval of the transmission band of the band-pass filter included in the first optical filter are fixed.

（付記５）
前記第１の光フィルタが備える前記バンドパスフィルタの前記透過帯域の帯域幅及び前記透過帯域の間隔の少なくとも一方が前記制御部により制御されることを特徴とする、付記２又は３に記載された波長制御装置。 (Appendix 5)
The supplementary note 2 or 3, wherein at least one of a bandwidth of the transmission band and an interval of the transmission band of the band-pass filter included in the first optical filter is controlled by the control unit. Wavelength control device.

（付記６）
前記第２の光フィルタは、相異なる透過帯域を持つ複数のバンドパスフィルタで構成され、前記第２の受光部は、前記第２の光フィルタが備える前記複数のバンドパスフィルタのうち一のバンドパスフィルタを透過した前記局部発振光を受光することを特徴とする、付記１乃至５のいずれかに記載された波長制御装置。 (Appendix 6)
The second optical filter is composed of a plurality of bandpass filters having different transmission bands, and the second light receiving unit is one band of the plurality of bandpass filters included in the second optical filter. 6. The wavelength control device according to any one of appendices 1 to 5, wherein the local oscillation light transmitted through a pass filter is received.

（付記７）
前記第２の光フィルタは、互いに重複しない３個の透過帯域を持つバンドパスフィルタで構成され、前記第２の受光部は、前記第２の光フィルタが備える前記バンドパスフィルタの透過帯域のうち、中央の波長帯の透過帯域を持つ前記第２の光フィルタが備える前記バンドパスフィルタを透過した前記局部発振光を受光することを特徴とする、付記１乃至５のいずれかに記載された波長制御装置。 (Appendix 7)
The second optical filter is configured by a bandpass filter having three transmission bands that do not overlap with each other, and the second light receiving unit includes a transmission band of the bandpass filter included in the second optical filter. The wavelength according to any one of appendices 1 to 5, wherein the local oscillation light transmitted through the bandpass filter included in the second optical filter having a transmission band of a central wavelength band is received. Control device.

（付記８）
前記第２の光フィルタが備える前記バンドパスフィルタの前記透過帯域の帯域幅及び前記透過帯域の間隔が固定されていることを特徴とする、付記６又は７に記載された波長制御装置。 (Appendix 8)
The wavelength control device according to appendix 6 or 7, wherein a bandwidth of the transmission band and an interval of the transmission band of the bandpass filter provided in the second optical filter are fixed.

（付記９）
前記第２の光フィルタが備える前記バンドパスフィルタの前記透過帯域の帯域幅及び前記透過帯域の間隔の少なくとも一方が前記制御部により制御されることを特徴とする、付記６又は７に記載された波長制御装置。 (Appendix 9)
The supplementary note 6 or 7, wherein at least one of a bandwidth of the transmission band and an interval of the transmission band of the band-pass filter included in the second optical filter is controlled by the control unit. Wavelength control device.

（付記１０）
前記第１の光フィルタが備える前記複数のバンドパスフィルタのうち一のバンドパスフィルタを選択して、前記選択されたバンドパスフィルタと前記第１の受光部との光路を接続する第１の光スイッチをさらに備える、付記２乃至５のいずれかに記載された波長制御装置。 (Appendix 10)
A first light that selects one of the plurality of bandpass filters included in the first optical filter and connects an optical path between the selected bandpass filter and the first light receiving unit. The wavelength control device according to any one of appendices 2 to 5, further comprising a switch.

（付記１１）
前記第２の光フィルタが備える前記複数のバンドパスフィルタのうち一のバンドパスフィルタを選択して、前記選択されたバンドパスフィルタと前記第２の受光部との光路を接続する第２の光スイッチをさらに備える、付記６乃至９のいずれかに記載された波長制御装置。 (Appendix 11)
Second light that selects one bandpass filter from among the plurality of bandpass filters included in the second optical filter and connects an optical path between the selected bandpass filter and the second light receiving unit. The wavelength control device according to any one of appendices 6 to 9, further comprising a switch.

（付記１２）
付記１０に記載された第１の光スイッチ及び付記１１に記載された第２の光スイッチを備える、波長制御装置。 (Appendix 12)
A wavelength control apparatus comprising the first optical switch described in appendix 10 and the second optical switch described in appendix 11.

（付記１３）
第１の波長特性を持つ第１の光フィルタを透過した信号光の強度の増加に対して振幅が単調に増加する第１の電流を出力し、
第２の波長特性を持つ第２の光フィルタを透過した局部発振光の強度の増加に対して振幅が単調に増加する振幅の第２の電流を出力し、
前記第１の電流が極大となるように前記第１の波長特性を制御し、
前記第１の電流が極大となるように制御された前記第１の波長特性と前記第２の波長特性とが一致するように前記第２の波長特性を制御し、
前記第２の電流が極大となるように前記局部発振光の波長を制御する、
ことを特徴とする波長制御方法。 (Appendix 13)
Outputting a first current whose amplitude monotonously increases with an increase in the intensity of the signal light transmitted through the first optical filter having the first wavelength characteristic;
A second current having an amplitude that monotonously increases with respect to an increase in the intensity of the local oscillation light transmitted through the second optical filter having the second wavelength characteristic;
Controlling the first wavelength characteristic so that the first current is maximized;
Controlling the second wavelength characteristic so that the first wavelength characteristic and the second wavelength characteristic, which are controlled so that the first current is maximized, coincide with each other;
Controlling the wavelength of the local oscillation light so that the second current is maximized;
And a wavelength control method.

（付記１４）
波長制御装置のコンピュータに、
第１の波長特性を持つ第１の光フィルタを透過した信号光の強度の増加に対して振幅が単調に増加する第１の電流を出力する手順、
第２の波長特性を持つ第２の光フィルタを透過した局部発振光の強度の増加に対して振幅が単調に増加する振幅の第２の電流を出力する手順、
前記第１の電流が極大となるように前記第１の波長特性を制御する手順、
前記第１の電流が極大となるように制御された前記第１の波長特性と前記第２の波長特性とが一致するように前記第２の波長特性を制御する手順、
前記第２の電流が極大となるように前記局部発振光の波長を制御する手順、
を実行させるための波長制御装置の制御プログラム。 (Appendix 14)
In the computer of the wavelength control device,
A procedure of outputting a first current whose amplitude monotonously increases with an increase in intensity of signal light transmitted through a first optical filter having a first wavelength characteristic;
A procedure for outputting a second current having an amplitude that monotonically increases with respect to an increase in intensity of the local oscillation light transmitted through the second optical filter having the second wavelength characteristic;
A procedure for controlling the first wavelength characteristic so that the first current is maximized;
A procedure for controlling the second wavelength characteristic so that the first wavelength characteristic and the second wavelength characteristic, which are controlled so that the first current is maximized, coincide with each other;
A procedure for controlling the wavelength of the local oscillation light so that the second current is maximized;
A control program for a wavelength control device for executing

（付記１５）
局部発振光を出力する局部発振光源と、
信号光が入力される、第１の波長特性を持つ第１の光フィルタと、
前記第１の光フィルタを透過した前記信号光の強度の増加に対して振幅が単調に増加する第１の電流を出力する第１の受光部と、
前記第１の電流が極大となるように前記第１の波長特性を制御し、前記局部発振光の波長を、前記第１の電流が極大となるように制御された前記第１の波長特性が示す波長と一致するように前記局部発振光源を制御する制御部と、
を備える波長制御装置。 (Appendix 15)
A local oscillation light source that outputs local oscillation light;
A first optical filter having a first wavelength characteristic to which signal light is input;
A first light receiving unit that outputs a first current whose amplitude monotonously increases with an increase in the intensity of the signal light transmitted through the first optical filter;
The first wavelength characteristic is controlled so that the first current is maximized, and the wavelength of the local oscillation light is controlled such that the first wavelength characteristic is controlled so that the first current is maximized. A control unit for controlling the local oscillation light source so as to match the wavelength shown;
A wavelength control device comprising:

（付記１６）
第１の波長特性を持つ第１の光フィルタを透過した信号光の強度の増加に対して振幅が単調に増加する第１の電流を出力し、
前記第１の電流が極大となるように前記第１の波長特性を制御し、
局部発振光の波長を、前記第１の電流が極大となるように制御された前記第１の波長特性が示す波長と一致するように制御する、
ことを特徴とする波長制御方法。 (Appendix 16)
Outputting a first current whose amplitude monotonously increases with an increase in the intensity of the signal light transmitted through the first optical filter having the first wavelength characteristic;
Controlling the first wavelength characteristic so that the first current is maximized;
Controlling the wavelength of the local oscillation light so as to coincide with the wavelength indicated by the first wavelength characteristic controlled so that the first current is maximized;
And a wavelength control method.

（付記１７）
波長制御装置のコンピュータに、
第１の波長特性を持つ第１の光フィルタを透過した信号光の強度の増加に対して振幅が単調に増加する第１の電流を出力する手順、
前記第１の電流が極大となるように前記第１の波長特性を制御する手順、
局部発振光の波長を、前記第１の電流が極大となるように制御された前記第１の波長特性が示す波長と一致するように制御する手順、
を実行させるための波長制御装置の制御プログラム。 (Appendix 17)
In the computer of the wavelength control device,
A procedure of outputting a first current whose amplitude monotonously increases with an increase in intensity of signal light transmitted through a first optical filter having a first wavelength characteristic;
A procedure for controlling the first wavelength characteristic so that the first current is maximized;
A procedure for controlling the wavelength of the local oscillation light so as to coincide with the wavelength indicated by the first wavelength characteristic controlled so that the first current is maximized;
A control program for a wavelength control device for executing

（付記１８）
付記１乃至１１及び付記１５のいずれかに記載された波長制御装置と、
前記信号光と前記局部発振光とを干渉させ、干渉させた信号を出力する９０度ハイブリッド回路と、
前記９０度ハイブリッド回路が干渉させた信号をコヒーレント検波して検波された信号をアナログ電気信号に変換する受光部と、
前記受光部から出力された前記アナログ電気信号を、所定の振幅を持つように増幅する増幅回路と、
前記増幅回路で増幅された信号をデジタル信号に変換して復調処理を行い、復調信号を生成するデジタル信号処理部と、
を備える光受信器。 (Appendix 18)
The wavelength control device according to any one of supplementary notes 1 to 11 and supplementary note 15,
A 90-degree hybrid circuit that causes the signal light and the local oscillation light to interfere with each other and outputs the interfered signal;
A light receiving unit for coherently detecting the signal interfered by the 90-degree hybrid circuit and converting the detected signal into an analog electric signal;
An amplification circuit that amplifies the analog electrical signal output from the light receiving unit to have a predetermined amplitude;
A digital signal processing unit that converts the signal amplified by the amplifier circuit into a digital signal, performs a demodulation process, and generates a demodulated signal;
An optical receiver comprising:

１、１ａ光受信器
１０信号光
１１復調信号
１２局部発振光
１０１、１０１ａ、１０３可変波長フィルタ
１０２局部発振光源
１０４波長制御部
１０５９０度ハイブリッド回路
１０６、１０１９ＰＤ
１０７ＴＩＡ
１０８ＤＳＰ
１０９ＣＰＵ
１１０メモリ
１０１１、１０３１光分岐器
１０１２〜１０１４フィルタＡ〜Ｃ
１０１２ａ〜１０４２ａフィルタ
１０１５〜１０１７ＰＤ−Ａ〜ＰＤ−Ｃ
１０１８光スイッチ
１０３２〜１０３４フィルタＤ〜Ｆ
１０３５〜１０３７ＰＤ−Ｄ〜ＰＤ−Ｆ
２００波長制御装置
２０１第１のフィルタ
２０２第２のフィルタ
２１１第１の受光部
２１２第２の受光部
２２１局部発振光源
２２２制御部 DESCRIPTION OF SYMBOLS 1, 1a Optical receiver 10 Signal light 11 Demodulated signal 12 Local oscillation light 101, 101a, 103 Variable wavelength filter 102 Local oscillation light source 104 Wavelength control part 105 90 degree hybrid circuit 106, 1019 PD
107 TIA
108 DSP
109 CPU
110 Memory 1011, 1031 Optical splitter 1012-1014 Filter A-C
1012a to 1042a Filter 1015 to 1017 PD-A to PD-C
1018 Optical switch 1032 to 1034 Filter D to F
1035-1037 PD-D-PD-F
200 Wavelength Control Device 201 First Filter 202 Second Filter 211 First Light Receiving Unit 212 Second Light Receiving Unit 221 Local Oscillating Light Source 222 Control Unit

Claims

A local oscillation light source that outputs local oscillation light;
A first optical filter having a first wavelength characteristic to which signal light is input;
A first light receiving unit that outputs a first current whose amplitude monotonously increases with an increase in the intensity of the signal light transmitted through the first optical filter;
A second optical filter having a second wavelength characteristic to which the local oscillation light is input;
A second light-receiving unit that outputs a second current whose amplitude monotonously increases with an increase in intensity of the local oscillation light transmitted through the second optical filter;
The first wavelength characteristic is controlled so that the first current becomes maximum, and the first wavelength characteristic and the second wavelength characteristic controlled so that the first current becomes maximum are obtained. A control unit that controls the second wavelength characteristic so as to match, and controls the wavelength of the local oscillation light so that the second current becomes maximum;
A wavelength control device comprising:

The first optical filter includes a plurality of bandpass filters having different transmission bands, and the first light receiving unit is one band of the plurality of bandpass filters included in the first optical filter. The wavelength control device according to claim 1, wherein the signal light transmitted through a pass filter is received.

The first optical filter is composed of a band-pass filter having three transmission bands that do not overlap with each other, and the first light-receiving unit includes a transmission band of the band-pass filter included in the first optical filter. The wavelength control device according to claim 1, wherein the signal light transmitted through the bandpass filter included in the first optical filter having a transmission band of a central wavelength band is received.

4. The wavelength control device according to claim 2, wherein a bandwidth of the transmission band and an interval between the transmission bands of the band-pass filter included in the first optical filter are fixed. 5.

4. The method according to claim 2, wherein at least one of a bandwidth of the transmission band and an interval of the transmission band of the band-pass filter included in the first optical filter is controlled by the control unit. 5. Wavelength control device.

The second optical filter is composed of a plurality of bandpass filters having different transmission bands, and the second light receiving unit is one band of the plurality of bandpass filters included in the second optical filter. 6. The wavelength control apparatus according to claim 1, wherein the local oscillation light transmitted through a pass filter is received.

The second optical filter is configured by a bandpass filter having three transmission bands that do not overlap with each other, and the second light receiving unit includes a transmission band of the bandpass filter included in the second optical filter. 6. The local oscillation light transmitted through the bandpass filter included in the second optical filter having a transmission band of a central wavelength band is received, according to any one of claims 1 to 5. Wavelength control device.

The wavelength control according to claim 6 or 7, wherein a bandwidth of each of the transmission bands and an interval of the transmission bands of the band-pass filter included in the second optical filter are fixed. apparatus.

Outputting a first current whose amplitude monotonously increases with an increase in the intensity of the signal light transmitted through the first optical filter having the first wavelength characteristic;
A second current having an amplitude that monotonously increases with respect to an increase in the intensity of the local oscillation light transmitted through the second optical filter having the second wavelength characteristic;
Controlling the first wavelength characteristic so that the first current is maximized;
Controlling the second wavelength characteristic so that the first wavelength characteristic and the second wavelength characteristic, which are controlled so that the first current is maximized, coincide with each other;
Controlling the wavelength of the local oscillation light so that the second current is maximized;
And a wavelength control method.

A wavelength control device according to any one of claims 1 to 8,
A 90-degree hybrid circuit that causes the signal light and the local oscillation light to interfere with each other and outputs the interfered signal;
A light receiving unit for coherently detecting the signal interfered by the 90-degree hybrid circuit and converting the detected signal into an analog electric signal;
An amplification circuit that amplifies the analog electrical signal output from the light receiving unit to have a predetermined amplitude;
A digital signal processing unit that converts the signal amplified by the amplifier circuit into a digital signal, performs a demodulation process, and generates a demodulated signal;
An optical receiver comprising: