JP2006286918A - Optical amplifier - Google Patents

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JP2006286918A
JP2006286918A JP2005104629A JP2005104629A JP2006286918A JP 2006286918 A JP2006286918 A JP 2006286918A JP 2005104629 A JP2005104629 A JP 2005104629A JP 2005104629 A JP2005104629 A JP 2005104629A JP 2006286918 A JP2006286918 A JP 2006286918A
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optical
control circuit
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optical waveguide
excitation light
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Nobuyuki Kagi
信行 加木
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Furukawa Electric Co Ltd
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Abstract

<P>PROBLEM TO BE SOLVED: To provide an optical amplifier used for a WDM (Wavelength Division Multiplex) transmission system, which amplifier controls signal light of multiple wavelengths transmitted through a WDM transmission path for each wavelength and improves transmission quality. <P>SOLUTION: The optical amplifier comprises a first photoelectric conversion element 8 which is connected to an amplifying optical waveguide 2 via a first optical directional coupler 3, and receives signal light of multiple wavelengths; an excitation light source 9 which emits excited light onto the optical waveguide 2 in a location closer to the signal output side than the first optical directional coupler 3 in the optical waveguide 2; a second photoelectric conversion element 10 which is connected to the optical waveguide 2 via a second optical directional coupler 4 in a location closer to the signal output side than an excited light exposure field in the optical waveguide 2, and receives signal light of multiple wavelengths; an optical attenuator 7 which is connected to an area between the first and second optical directional couplers 3, 4 in the optical waveguide 2, and is capable of setting the amount of attenuation for each wavelength; a first control circuit 11 which controls light output from the excitation light source 9 unitl a comparison value based on output from the first and second photoelectric convesion elements 8, 10 come to coincide with or come close to an externally set target gain; and a second control circuit 14 which sets output from the optical attenuator 7 to a target spectrum. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

本発明は、光増幅装置に関し、より詳しくは、波長多重光伝送システムに適用される光増幅装置に関する。   The present invention relates to an optical amplifying device, and more particularly to an optical amplifying device applied to a wavelength division multiplexing optical transmission system.

インターネット、画像伝送等のネットワークサービスが拡大するにつれてネットワークを伝送する情報量は増加し、これに対応する通信方法として、複数波長の信号光を１本の光ファイバで伝送する波長多重（ＷＤＭ：Wavelength Division Multiplex）光通信方式が有効である。ＷＤＭ光信号路では、複数波長の信号光をエルビウム（Er）添加光ファイバ（増幅用光導波路）に伝搬させてそこに励起光を照射することにより複数波長の信号光を一括して増幅することが行われる。   As network services such as the Internet and image transmission expand, the amount of information transmitted over the network increases. As a communication method corresponding to this, wavelength multiplexing (WDM: Wavelength) that transmits signal light of a plurality of wavelengths through a single optical fiber. Division Multiplex) optical communication system is effective. In a WDM optical signal path, signal light of a plurality of wavelengths is propagated to an erbium (Er) -doped optical fiber (amplification optical waveguide) and irradiated with pumping light to amplify the signal light of a plurality of wavelengths collectively. Is done.

そのような光増幅装置では、Er添加光ファイバ内を伝搬する信号光の波長数の増加、減少（Add/drop）に対応させて励起光のエネルギーを制御することにより、Er添加光ファイバから出力される１信号光当たりのパワーレベルが変動しないようにしている。   In such an optical amplifying device, output from the Er-doped optical fiber is controlled by controlling the energy of the pumping light in response to the increase / decrease (Add / drop) of the wavelength of the signal light propagating in the Er-doped optical fiber. The power level per one signal light is not changed.

例えば、下記の特許文献１では、複数のファイバーグレーティングを用いることにより、Er添加光ファイバ内を伝搬する信号光の波長数をカウントしてそのカウント数に応じて励起光の照射エネルギーを調整することが記載されている。   For example, in Patent Document 1 below, by using a plurality of fiber gratings, the number of wavelengths of signal light propagating in an Er-doped optical fiber is counted, and the irradiation energy of excitation light is adjusted according to the number of counts. Is described.

また、下記の特許文献２では、一定の波長範囲を掃引する掃引回路を用いることにより、Er添加光ファイバから出力される信号光の波長数をカウントし、そのカウント数に応じて励起光エネルギーの目標値を設定するとともに、その目標値となるように励起光の照射エネルギーを制御することが記載されている。   Further, in Patent Document 2 below, the number of wavelengths of signal light output from the Er-doped optical fiber is counted by using a sweep circuit that sweeps a certain wavelength range, and the excitation light energy is determined according to the counted number. It describes that the target value is set and the irradiation energy of the excitation light is controlled so as to be the target value.

また、下記の特許文献３では、Er添加光ファイバの入力と出力の比を一定に保つための自動利得制御回路（ＡＧＣ）を設けることにより、信号光の波長数のAdd/dropに応じてEr添加光ファイバの入出力比が一定になるように励起光のエネルギーを制御することが記載されている。また、特許文献３には、Er添加光ファイバの信号光の出力レベルを光伝送系全体に対応させる大きさに保持するために、Er添加光ファイバの出力端寄りに可変光減衰器を接続することが記載されている。その可変減衰器における損失は、Er添加光ファイバの出力レベルに基づいて自動レベル制御回路により制御される。また、その自動レベル制御回路の時定数は、励起光のエネルギーを制御する信号が励起光源に通知されるまでの時間に比べて長くなっている。
特開平９−８３４８９号公報 特開平１０−５１３９６号公報 特開２００３−１７４４２１号公報 Further, in Patent Document 3 below, an automatic gain control circuit (AGC) for keeping the ratio of input to output of an Er-doped optical fiber constant is provided, so that Er according to Add / drop of the number of wavelengths of signal light. It is described that the energy of pumping light is controlled so that the input / output ratio of the doped optical fiber is constant. In Patent Document 3, a variable optical attenuator is connected near the output end of the Er-doped optical fiber in order to maintain the output level of the signal light of the Er-doped optical fiber so as to correspond to the entire optical transmission system. It is described. The loss in the variable attenuator is controlled by an automatic level control circuit based on the output level of the Er-doped optical fiber. The time constant of the automatic level control circuit is longer than the time until the signal for controlling the energy of the excitation light is notified to the excitation light source.
Japanese Patent Laid-Open No. 9-83489 Japanese Patent Laid-Open No. 10-51396 JP 2003-174421 A

しかし、特許文献１〜３によれば各波長数のエネルギーを一括して制御しているために、特定の波長のパワーに不足が生じてもこれを補正することができず、信号光伝送に支障をきたすおそれがある。   However, according to Patent Documents 1 to 3, since the energy of each wavelength is collectively controlled, even if the power of a specific wavelength is insufficient, this cannot be corrected, and signal light transmission is not possible. May cause trouble.

本発明の目的は、ＷＤＭ伝送路に伝搬される複数波長の信号光を波長毎に制御するとともに、伝搬品質を向上することができる光増幅装置を提供することにある。   An object of the present invention is to provide an optical amplifying device capable of controlling signal light of a plurality of wavelengths propagated to a WDM transmission line for each wavelength and improving propagation quality.

上記の課題を解決するための本発明の第１の態様に係る光増幅装置は、増幅用光導波路に第１光分岐器を介して接続されて複数波長の信号光を受光する第１の光電変換素子と、前記増幅用光導波路のうち前記第１光分岐器よりも信号光出力側で前記増幅用光導波路に励起光を照射する励起光源と、前記増幅用光導波路のうち前記励起光の照射領域よりも信号光出力側で第２光分岐器を介して接続されて前記複数波長の信号光を受光する第２の光電変換素子と、前記増幅用光導波路のうち前記第１光分岐器と前記第２光分岐器の間の領域に接続されて波長毎に減衰量の設定が可能な光減衰器と、前記第１の光電変換素子の出力と前記第２の光電変換素子の出力に基づく比較値が、外部から設定される目標利得値に一致し又は近づく状態になるまで前記励起光源の光出力を制御する第１制御回路と、前記光減衰器の出力を目標となるスペクトラムに設定させる第２制御回路とを有することを特徴とする。   An optical amplifying device according to a first aspect of the present invention for solving the above-described problems is a first photoelectric device that receives signal light having a plurality of wavelengths and is connected to an amplifying optical waveguide via a first optical splitter. A conversion element; an excitation light source for irradiating the amplification optical waveguide with the excitation light on the signal light output side of the first optical splitter of the amplification optical waveguide; and an excitation light source of the amplification optical waveguide. A second photoelectric conversion element connected via a second optical splitter on the signal light output side of the irradiation region and receiving the signal light of the plurality of wavelengths; and the first optical splitter of the amplification optical waveguide And an optical attenuator connected to a region between the second optical branching device and capable of setting an attenuation amount for each wavelength, an output of the first photoelectric conversion element, and an output of the second photoelectric conversion element The comparison value based on this value matches or approaches the target gain value set externally. And having a first control circuit for controlling the light output of the excitation light source, and a second control circuit for setting to a spectrum as a target output of the optical attenuator.

本発明の第２の態様は、第１の態様に係る光増幅装置において、前記増幅用光導波路のうち前記励起光の前記照射領域及び前記第２の光分岐器よりも信号光出力側で前記信号光の波長毎の光パワーを測定するモニタが接続され、前記第２制御回路は前記モニタの出力に基づいて前記光減衰器のスペクトラムを制御することを特徴とする。   According to a second aspect of the present invention, in the optical amplifying device according to the first aspect, the irradiation region of the excitation light in the optical waveguide for amplification and the signal light output side from the second optical branching device A monitor for measuring the optical power for each wavelength of the signal light is connected, and the second control circuit controls the spectrum of the optical attenuator based on the output of the monitor.

本発明の第３の態様は、第１又は第２の態様に係る光増幅装置において、前記第１制御回路により前記励起光源を制御するための第１の制御周期は、前記第２制御回路により前記光減衰器を制御するための第２の制御周期よりも短く、かつ前記目標利得値の前記第１制御回路への設定周期は前記第２の制御周期よりも長くする構成を有することを特徴とする。   According to a third aspect of the present invention, in the optical amplifying device according to the first or second aspect, the first control cycle for controlling the pumping light source by the first control circuit is performed by the second control circuit. It is shorter than a second control period for controlling the optical attenuator, and has a configuration in which a set period of the target gain value in the first control circuit is longer than the second control period. And

本発明の第４の態様は、第１乃至第３の態様のいずれかに係る光増幅装置において、前記第２制御回路は、前記目標利得値に応じて予め設定された減衰スペクトラムに一致させるか近づくように前記光減衰器を制御する構成を有することを特徴とする。   According to a fourth aspect of the present invention, in the optical amplifying device according to any one of the first to third aspects, is the second control circuit configured to match an attenuation spectrum set in advance according to the target gain value? It has the structure which controls the said optical attenuator so that it may approach.

本発明によれば、Er添加光ファイバ等の増幅用光導波路のうち入力パワーをモニタする第１の光電変換素子と出力パワーをモニタする第２の光電変換素子の間の領域に、波長毎に減衰量の設定が可能な光減衰器を設けているので、複数波長の信号光を増幅する場合に波長毎に出力パワーを調整することができ、信号光伝送を正常に保持することができる。
また、本発明によれば、増幅用光導波路に励起光を照射する励起光源の出力を調整するための制御周期１と、光減衰器の目標スペクトラムを調整するための制御周期２と、励起光源の目標利得を再設定するための制御周期３との関係を、制御周期１＜制御周期２＜制御周期３としている。
従って、励起光源による目標利得を制御パラメータに入れる場合に、上記の関係を保持することにより、発振しない安定な制御が可能になる。 According to the present invention, the region between the first photoelectric conversion element that monitors the input power and the second photoelectric conversion element that monitors the output power of the amplification optical waveguide such as an Er-doped optical fiber is provided for each wavelength. Since an optical attenuator capable of setting the attenuation amount is provided, the output power can be adjusted for each wavelength when amplifying signal light of a plurality of wavelengths, and signal light transmission can be normally maintained.
Further, according to the present invention, the control cycle 1 for adjusting the output of the excitation light source that irradiates the amplification optical waveguide with the excitation light, the control cycle 2 for adjusting the target spectrum of the optical attenuator, and the excitation light source The relationship with the control cycle 3 for resetting the target gain is set as control cycle 1 <control cycle 2 <control cycle 3.
Therefore, when the target gain by the excitation light source is included in the control parameters, stable control without oscillation is possible by maintaining the above relationship.

以下に本発明の実施の形態を図面に基づいて詳細に説明する。
（第１の実施の形態）
図１は、本発明の第１実施形態に係る光増幅装置を示す回路図である。 Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
(First embodiment)
FIG. 1 is a circuit diagram showing an optical amplifying device according to the first embodiment of the present invention.

光増幅装置１は、増幅用光導波路としてEr添加光ファイバ（ＥＤＦ：Er Doped Fiber）２を有しており、このＥＤＦ２には入力端から出力端にかけて第１、第２及び第３の光分岐器３，４，５が順に取り付けられ、さらに第１の光分岐器３と第２の光分岐器４の間の領域には光合波器６とダイナミックゲインイコライザ（ＤＧＥ：Dynamic Gain Equalizer）７が接続されている。   The optical amplifying apparatus 1 has an Er-doped optical fiber (EDF) 2 as an amplification optical waveguide. The EDF 2 includes first, second, and third optical branches from the input end to the output end. Units 3, 4, and 5 are attached in order, and an optical multiplexer 6 and a dynamic gain equalizer (DGE) 7 are provided in a region between the first optical splitter 3 and the second optical splitter 4. It is connected.

第１の光分岐器３の分岐路には第１の光電変換素子８、例えばフォトダイオードの受光部が接続されており、これによりＥＤＦ２の入力端から入力される複数波長の全ての信号光をモニタするように構成されている。   A first photoelectric conversion element 8, for example, a light receiving portion of a photodiode, is connected to the branch path of the first optical branching device 3, and thereby, all signal lights of a plurality of wavelengths input from the input end of the EDF 2 are received. It is configured to monitor.

また、光合波器６の入光ポートには励起光源９、例えばレーザダイオードの光出射部が接続され、この励起光源９からＥＤＦ２に励起光を照射してＥＤＦ２内を通る複数波長の信号光を一括で励起して増幅するように構成されている。ＥＤＦ２を伝搬する複数波長の信号光が例えば１５３０μｍ〜１６１０μｍの波長帯に存在する場合に、励起光源９として信号光よりも短波長、例えば９８０μｍ、１４８０μｍの波長であって１００ｍＷ〜１Ｗ程度のエネルギーを出射する構造を有するレーザダイオードが用いられる。   In addition, a pumping light source 9, for example, a light emitting part of a laser diode, is connected to the light incident port of the optical multiplexer 6. The pumping light source 9 irradiates the EDF 2 with pumping light and emits signal light having a plurality of wavelengths passing through the EDF 2. It is configured to amplify by exciting all at once. When signal light having a plurality of wavelengths propagating through the EDF 2 exists in a wavelength band of 1530 μm to 1610 μm, for example, the excitation light source 9 has a shorter wavelength than the signal light, for example, wavelengths of 980 μm and 1480 μm, and energy of about 100 mW to 1 W A laser diode having a structure for emitting light is used.

第２の光分岐器４の分岐路には第２の光電変換素子１０、例えばフォトダイオードの受光部が接続されていて、励起光源９により増幅された全ての複数波長の信号光のパワーをモニタするように構成されている。   The branch path of the second optical branching device 4 is connected to a second photoelectric conversion element 10, for example, a light receiving portion of a photodiode, and monitors the power of all the multiple wavelength signal lights amplified by the excitation light source 9. Is configured to do.

第１、第２の光電変換素子８，１０のそれぞれの出力信号は第１制御回路１１の２つの入力端に入力され、また、励起光源９の駆動制御信号は第１制御回路１１から出力される。
第１制御回路１１は、第１の光電変換素子８の出力の補正値Ｗ1に対する第２の光電変換素子１０の出力の補正値Ｗ2の比較値（Ｗ2 ／Ｗ1 ）が目標利得Ｇ又はその許容範囲となるように励起光源９の駆動電流を調整してその励起光源９の出力光のパワーを制御する。目標利得Ｇは、例えば光伝送係全体を制御する制御回路（不図示）から所定の周期で第１制御回路１１に出力される値である。また、第１、第２の光電変換素子８，１０の出力はそれぞれ図示しないモニタ回路を介して第１制御回路１４に入力されて比較されており、モニタ回路では光電変換素子の感度や分岐比などの補正を行って真の光パワーを算出し、その算出値を出力する構成を有している。 The output signals of the first and second photoelectric conversion elements 8 and 10 are input to two input terminals of the first control circuit 11, and the drive control signal of the excitation light source 9 is output from the first control circuit 11. The
In the first control circuit 11, the comparison value (W 2 / W 1 ) of the correction value W 2 of the output of the second photoelectric conversion element 10 with respect to the correction value W 1 of the output of the first photoelectric conversion element 8 is the target gain G. Alternatively, the drive current of the excitation light source 9 is adjusted so as to be within the allowable range, and the power of the output light of the excitation light source 9 is controlled. The target gain G is, for example, a value output to the first control circuit 11 at a predetermined cycle from a control circuit (not shown) that controls the entire optical transmission unit. The outputs of the first and second photoelectric conversion elements 8 and 10 are respectively input to the first control circuit 14 via a monitor circuit (not shown) and compared. The monitor circuit compares the sensitivity and branching ratio of the photoelectric conversion elements. The true optical power is calculated by performing such corrections, and the calculated value is output.

第３の光分岐器５の分岐路には、光チャンネルモニター（ＯＣＭ：Optical Channel Monitor）１３が接続されている。ＯＣＭ１３は、励起光源９により励起された信号光のパワーを波長毎に測定する構造を有する光パワー測定モニタで、例えば波長可変フィルタとフォトダイオードから構成される。   An optical channel monitor (OCM) 13 is connected to the branch path of the third optical splitter 5. The OCM 13 is an optical power measurement monitor having a structure for measuring the power of signal light excited by the excitation light source 9 for each wavelength, and is composed of, for example, a wavelength variable filter and a photodiode.

ＤＧＥ７は、波長毎に個別に減衰量を設定して所望のスペクトラムに合わせる又は近づける光減衰器である。ＤＧＥ７として、例えば特開平１１−３３７７５０号公報に記載されているように、グレーティング周期の異なる複数種類のグレーティングデバイスをＥＤＦ２上に配置するとともに、グレーティングのＥＤＦ２への押圧力をピエゾ素子によって変化させることにより各波長の信号光のパワーを変化させる構造のものがある。また、ＤＧＥ７として、その他に、特開２００３−６６３０９５号公報に記載のように可変分岐比スプリッタと複数の光フィルタを用いた構造の可変光利得化装置などを用いてもよい。   The DGE 7 is an optical attenuator that sets an attenuation amount individually for each wavelength and matches or approaches a desired spectrum. As DGE7, for example, as described in Japanese Patent Application Laid-Open No. 11-337750, a plurality of types of grating devices having different grating periods are arranged on the EDF 2 and the pressing force of the grating on the EDF 2 is changed by a piezo element. There is a structure that changes the power of signal light of each wavelength. In addition, as the DGE 7, a variable optical gain increasing device having a structure using a variable branching ratio splitter and a plurality of optical filters as described in JP-A-2003-663095 may be used.

上記のＯＣＭ１３の出力信号は第２制御回路１４に出力され、第２制御回路１４はＯＣＭ１３の出力信号のスペクトラムが所望のスペクトラム、例えばフラットに近づくようにＤＧＥ７を制御する。   The output signal of the OCM 13 is output to the second control circuit 14, and the second control circuit 14 controls the DGE 7 so that the spectrum of the output signal of the OCM 13 approaches a desired spectrum, for example, flat.

ここで、励起光源９の光出力パワー、ＤＧＥ７の損失スペクトラム、及び第１制御回路１１への目標利得Ｇという３つのパラメータを変化させることについて検討する。   Here, consideration will be given to changing three parameters of the optical output power of the pumping light source 9, the loss spectrum of the DGE 7, and the target gain G to the first control circuit 11.

まず、励起光源９の光出力パワーは波長数が変化したときに変える必要がある。励起光源９の出力パワーの制御は第１制御回路１１により行われる。   First, it is necessary to change the optical output power of the excitation light source 9 when the number of wavelengths changes. The output power of the excitation light source 9 is controlled by the first control circuit 11.

また、ＤＧＥ７の損失スペクトルは、例えば環境温度に依存してＥＤＦ２の利得スペクトラムが変化したときに変える必要がある。この場合、ＤＧＥ７からの総出力パワーが変化することもあるので励起光源９による励起パワーも合わせて調整する必要がる。ＤＧＥ７の出力制御は第２制御回路１４により行われる。   Further, the loss spectrum of the DGE 7 needs to be changed when the gain spectrum of the EDF 2 changes depending on the environmental temperature, for example. In this case, since the total output power from the DGE 7 may change, it is necessary to adjust the excitation power from the excitation light source 9 as well. The output control of the DGE 7 is performed by the second control circuit 14.

さらに、目標利得Ｇは、線路の損失が変化したとき、あるいは光信号発生用光源のパワーが変化したときにそれを補うために変化させる必要がある。このとき、ＥＤＦ２の利得スペクトルも変化するのでＤＧＥ７の損失スペクトルも併せて変化させ、さらに、ＤＧＥ７の損失スペクトルを変化させるときには、それを補償するために励起光源９の出力パワーも変化させる必要がある。目標利得Ｇの制御は光伝送システム系の制御回路（不図示）によって行われる。   Furthermore, the target gain G needs to be changed in order to compensate for a change in the line loss or a change in the power of the optical signal generating light source. At this time, since the gain spectrum of the EDF 2 also changes, the loss spectrum of the DGE 7 is also changed. Further, when the loss spectrum of the DGE 7 is changed, the output power of the excitation light source 9 needs to be changed to compensate for it. . The target gain G is controlled by a control circuit (not shown) of the optical transmission system system.

このように考えると光増幅装置１の動作点を変化させる事象としては下記の表１に示すような３種類があって、それぞれ変化させたいパラメータが異なることがわかる。

Figure 2006286918
Considering this, there are three types of events that change the operating point of the optical amplifying apparatus 1 as shown in Table 1 below, and it can be seen that the parameters to be changed are different.
Figure 2006286918

例えば、励起光源９の駆動電流を変化させると、ＥＤＦ２の増幅波長特性が変わってＯＣＭ１３で測定されるスペクトラムが変化する。これにより、第２制御回路１４はＤＧＥ７の減衰スペクトラムを目標スペクトラムになるように制御するとすれば、これに伴って第２の光電変換素子１０に入力する光パワーが変化する。従って、第１制御回路１１は、補正された光信号の入出力パワー比が目標利得Ｇとなるように励起光源９を制御する必要が生じる。   For example, when the drive current of the excitation light source 9 is changed, the amplification wavelength characteristic of the EDF 2 changes and the spectrum measured by the OCM 13 changes. Accordingly, if the second control circuit 14 controls the attenuation spectrum of the DGE 7 so as to become the target spectrum, the optical power input to the second photoelectric conversion element 10 changes accordingly. Therefore, the first control circuit 11 needs to control the pumping light source 9 so that the input / output power ratio of the corrected optical signal becomes the target gain G.

第２制御回路１４によりＤＧＥ７を変化させる周期を第１制御回路１１により励起光源９を変化させる周期よりも短くしてしまうと、第１制御回路１１の励起光源９への制御値が定まらずに系全体が発振するおそれがあるので、第２制御回路１４がＤＧＥ７の出力を変更する制御周期を第１制御回路１１が励起光源９の出力を変更する制御周期よりも十分長くする必要がある。   If the cycle of changing the DGE 7 by the second control circuit 14 is shorter than the cycle of changing the excitation light source 9 by the first control circuit 11, the control value for the excitation light source 9 of the first control circuit 11 is not fixed. Since the entire system may oscillate, the control cycle in which the second control circuit 14 changes the output of the DGE 7 needs to be sufficiently longer than the control cycle in which the first control circuit 11 changes the output of the excitation light source 9.

同様に、第１制御回路１１の制御の基準となる目標利得Ｇを変化させる周期を、第２制御回路１４がＤＧＥ７の制御を変更する制御周期よりも短くすると、ＯＣＭ１３で測定されるスペクトラム、ひいてはＤＧＥ７の減衰スペクトラムも安定しない。従って、目標利得Ｇを変更する周期を第２制御回路１４の制御周期よりも長くする必要がある。第１、第２制御回路１１，１４の制御周期についてはクロックなどを用いて設定する。また、目標利得Ｇを変更する設定周期については伝送システム全体を管理するコンピュータなどにより設定する。   Similarly, if the period for changing the target gain G that is the reference for control of the first control circuit 11 is shorter than the control period for the second control circuit 14 to change the control of the DGE 7, the spectrum measured by the OCM 13, and consequently The attenuation spectrum of DGE7 is not stable. Therefore, it is necessary to make the cycle for changing the target gain G longer than the control cycle of the second control circuit 14. The control periods of the first and second control circuits 11 and 14 are set using a clock or the like. The setting cycle for changing the target gain G is set by a computer or the like that manages the entire transmission system.

以上を考慮すると次の関係が成り立つ。
第１制御回路の制御周期＜第２制御回路の制御周期＜Ｇの設定周期
それらの周期の具体的な範囲については例えば次のような値が採用される。 Considering the above, the following relationship holds.
The control period of the first control circuit <the control period of the second control circuit <the set period of G For the specific range of these periods, for example, the following values are adopted.

第１制御回路１１については、励起光源９により励起されるＥＤＦ２の利得緩和時間よりも十分に短い周期である必要があり、１μ秒以下の制御周期である。また、第２制御回路１４については、時定数の長い事象、例えば温度変化に対応できればよいので、１ｍ秒〜６００秒の制御周期である。これは、温度の変化について１０分毎でも十分に追従できるからである。さらに、目標利得Ｇの設定周期については、光伝送系全体からみた変化は長く、第２制御回路１４の制御周期の１０倍以上あれば十分である。   The first control circuit 11 needs to have a cycle sufficiently shorter than the gain relaxation time of the EDF 2 excited by the excitation light source 9, and is a control cycle of 1 μsec or less. Further, the second control circuit 14 has a control cycle of 1 msec to 600 sec, as long as it can cope with an event having a long time constant, for example, a temperature change. This is because the temperature change can be sufficiently followed even every 10 minutes. Further, the setting cycle of the target gain G has a long change as viewed from the entire optical transmission system, and it is sufficient that it is not less than 10 times the control cycle of the second control circuit 14.

以上のような光増幅制御装置１において、ＥＤＦ２に入力する信号光の波長数が増加又は減少すると、第１、第２の光電変換素子８，１０に入力する波長数も増加又は減少する。従って、第１の光電変換素子８の光入力パワーの補正値に対する第２の光電変換素子１０の光入力パワーの補正値の割合が目標利得Ｇに一致する又はその許容範囲に収まるようにＥＤＦ２への励起パワーを調整する。励起パワーの調整は、第１制御回路１１による励起光源９の制御によって行われる。   In the optical amplification control apparatus 1 as described above, when the number of wavelengths of signal light input to the EDF 2 increases or decreases, the number of wavelengths input to the first and second photoelectric conversion elements 8 and 10 also increases or decreases. Therefore, the ratio of the correction value of the optical input power of the second photoelectric conversion element 10 to the correction value of the optical input power of the first photoelectric conversion element 8 matches the target gain G or falls within the allowable range. Adjust the excitation power. The adjustment of the excitation power is performed by controlling the excitation light source 9 by the first control circuit 11.

これにより第１の光電変換素子８の光入力パワーに対する第２の光電変換素子１０の光入力パワーの割合が安定した後に、第２制御回路１４は次の制御周期でＯＣＭ１３の出力値に基づいて目標となるスペクトラムを得るためにＤＧＥ７を制御する。その目標となるスペクトラムは、例えば環境温度の違いなどによってあらかじめ第２制御回路１４に定められる。第２制御回路１４によるＤＧＥ７の制御周期は、温度の変化の追従に十分な時間、例えば１０分毎に制御することで十分である。そのスペクトラムの目標が変化すると、ＥＤＦ２による増幅波長特性も変化するので、第１制御回路１１の次の制御周期において励起光源９の励起条件が変更される。この場合、光伝送系全体の特性も変化するので、例えば１時間毎に第１制御回路１１に設定される目標利得Ｇも再設定され、これにより、第１、第２制御回路１１，１４による制御も上記と同様に行われる。   Thus, after the ratio of the optical input power of the second photoelectric conversion element 10 to the optical input power of the first photoelectric conversion element 8 is stabilized, the second control circuit 14 is based on the output value of the OCM 13 in the next control cycle. The DGE 7 is controlled to obtain a target spectrum. The target spectrum is determined in advance in the second control circuit 14 by, for example, the difference in environmental temperature. It is sufficient that the control cycle of the DGE 7 by the second control circuit 14 is controlled every time sufficient for tracking the temperature change, for example, every 10 minutes. When the target of the spectrum changes, the amplification wavelength characteristic by the EDF 2 also changes, so that the excitation condition of the excitation light source 9 is changed in the next control cycle of the first control circuit 11. In this case, since the characteristics of the entire optical transmission system also change, for example, the target gain G set in the first control circuit 11 is reset every hour, whereby the first and second control circuits 11 and 14 Control is performed in the same manner as described above.

以上のように光増幅装置１は、いろいろな事象の変化に応じて制御パラメータを変化させる必要があり、事象の種類によって変化させるべきパラメータは異なるが、本実施形態では、各種周期の関係を調整して所定のパラメータのみを制御しているので安定な信号光の増幅が可能となる。   As described above, the optical amplifying apparatus 1 needs to change the control parameters in accordance with changes in various events, and the parameters to be changed differ depending on the types of events, but in this embodiment, the relationship between various cycles is adjusted. Since only predetermined parameters are controlled, stable signal light amplification is possible.

（第２の実施の形態）
図２は、本発明の第２実施形態に係る光増幅装置の回路図であり、図１と同じ符号は同じ要素を示している。
図２において、第３の光分岐器５に接続されているＯＣＭ１３の出力は第２制御回路１４に出力されるとともに、目標利得調整回路１５にも入力される。 (Second Embodiment)
FIG. 2 is a circuit diagram of an optical amplifying device according to the second embodiment of the present invention. The same reference numerals as those in FIG. 1 denote the same elements.
In FIG. 2, the output of the OCM 13 connected to the third optical branching device 5 is output to the second control circuit 14 and also to the target gain adjustment circuit 15.

目標利得調整回路１５は、ＯＣＭ１３から出力される情報に基づいて所望のチャネルが許容範囲の出力パワーになるように目標利得Ｇを調整するものである。なお、所望のチャネルあたりの出力パワーの目標値Ｇ０はシステム系全体を制御する制御回路から設定され、目標値Ｇ０の設定周期は、第１制御回路への目標利得Ｇの設定周期となる。   The target gain adjustment circuit 15 adjusts the target gain G so that a desired channel has an allowable output power based on information output from the OCM 13. The target value G0 of the desired output power per channel is set by a control circuit that controls the entire system system, and the setting cycle of the target value G0 is the setting cycle of the target gain G for the first control circuit.

従って、第１、第２制御回路１１，１４の制御周期及び目標利得Ｇの設定周期は、第１実施形態と同様に次のような関係となる。   Accordingly, the control cycle of the first and second control circuits 11 and 14 and the set cycle of the target gain G have the following relationship as in the first embodiment.

第１制御回路の制御周期＜第２制御回路の制御周期＜目標利得制御回路の目標利得Ｇ０の設定周期   Control cycle of first control circuit <Control cycle of second control circuit <Set cycle of target gain G0 of target gain control circuit

（第３の実施の形態）
図３は、本発明の第３実施形態に係る光増幅装置の回路図であり、図１と同じ符号は同じ要素を示している。
図３において、第２制御回路１４には第１制御回路１１と同じ目標利得Ｇのデータを入力するとともに、メモリ１６から目標となるスペクトラムのデータを入力する。メモリ１６は、目標利得Ｇの違いに応じてあらかじめ決められた図４に示すようなスペクトラムのデータを複数持つ。 (Third embodiment)
FIG. 3 is a circuit diagram of an optical amplifying device according to the third embodiment of the present invention. The same reference numerals as those in FIG. 1 denote the same elements.
In FIG. 3, the same target gain G data as that of the first control circuit 11 is input to the second control circuit 14 and the target spectrum data is input from the memory 16. The memory 16 has a plurality of spectrum data as shown in FIG. 4 determined in advance according to the difference in the target gain G.

そして目標利得Ｇの変更に伴って、第２制御回路１４は、目標利得Ｇに対応したスペクトラムのデータをメモリ１６から入力して、そのメモリに示すスペクトラムが得られるようにＤＧＥ７を制御する。   As the target gain G is changed, the second control circuit 14 inputs spectrum data corresponding to the target gain G from the memory 16 and controls the DGE 7 so that the spectrum shown in the memory is obtained.

これにより、目標利得Ｇの変化に対応してＥＤＦ２の駆動電流の制御とＤＧＥ７の制御を行うことが可能になる。   Thereby, it becomes possible to control the drive current of the EDF 2 and the control of the DGE 7 in response to the change of the target gain G.

（その他の実施形態）
上述した実施形態では光増幅用光導波路２としてEr添加光ファイバを用いたが、他の希土類、例えばネオジウム（Nd）、イットリウム（Yb）を添加した光ファイバを使用してもよい。 (Other embodiments)
In the embodiment described above, an Er-doped optical fiber is used as the optical amplification optical waveguide 2, but an optical fiber doped with another rare earth, for example, neodymium (Nd) or yttrium (Yb) may be used.

また、光増幅方法としてラマン散乱を発生させるタイプの増幅用光導波路と励起光源を用いてもよい。さらに、上記したＤＧＥ７は、増幅用光導波路２のうち図１に示すように光合波器６と第２の光分岐器７の間の領域ではなく、第１の光分岐器３と光合波器６の間の領域に挿入してもよい。   Further, as an optical amplification method, an amplification optical waveguide that generates Raman scattering and an excitation light source may be used. Further, the DGE 7 described above is not the region between the optical multiplexer 6 and the second optical splitter 7 as shown in FIG. 1 in the amplification optical waveguide 2, but the first optical splitter 3 and the optical multiplexer. You may insert in the area between 6.

ところで、図５に示すように、光増幅装置１内に分散補償ファイバ２０を増幅用光導波路２に接続する場合に、分散補償ファイバ２０はパワー損失が大きいので、入力端寄りに別の光増幅回路２１を接続してもよい。その第２の光増幅回路２１は、図５に例示するように分散補償ファイバ２０を挟むように信号光の入力側に接続する。   By the way, as shown in FIG. 5, when the dispersion compensating fiber 20 is connected to the amplification optical waveguide 2 in the optical amplifying apparatus 1, the dispersion compensating fiber 20 has a large power loss. The circuit 21 may be connected. The second optical amplifier circuit 21 is connected to the input side of the signal light so as to sandwich the dispersion compensating fiber 20 as illustrated in FIG.

図５において、光増幅用光導波路２には第４、第５の光分岐器２２，２３が接続され、それらの光分岐器２２，２３の分岐路にはそれぞれ第３、第４の光電変換素子２４，２５の受光部が接続されている。また、光増幅用光導波路２のうち第４、第５の光分岐器２２，２３の間には光合波器２６が接続され、その光合波器２６には第２の励起光源２７が接続されている。また、第３、第４の光電変換素子２４，２５の出力は第３制御回路２８の入力端に入力され、第３の光電変換素子２４の出力に対する第４の光電変換素子２５の出力の比が目標利得Ｇ１に達成するように第３制御回路２８は励起光源２７の光出力を制御する。   In FIG. 5, fourth and fifth optical branching units 22 and 23 are connected to the optical amplification optical waveguide 2, and third and fourth photoelectric conversions are respectively connected to the branching paths of these optical branching units 22 and 23. The light receiving portions of the elements 24 and 25 are connected. An optical multiplexer 26 is connected between the fourth and fifth optical splitters 22 and 23 in the optical amplification optical waveguide 2, and a second excitation light source 27 is connected to the optical multiplexer 26. ing. The outputs of the third and fourth photoelectric conversion elements 24 and 25 are input to the input terminal of the third control circuit 28, and the ratio of the output of the fourth photoelectric conversion element 25 to the output of the third photoelectric conversion element 24. The third control circuit 28 controls the light output of the pump light source 27 so that the target gain G1 is achieved.

図１は、本発明の第１実施形態に係る光増幅装置を示す回路図である。FIG. 1 is a circuit diagram showing an optical amplifying device according to the first embodiment of the present invention. 図２は、本発明の第２実施形態に係る光増幅装置を示す回路図である。FIG. 2 is a circuit diagram showing an optical amplifying device according to the second embodiment of the present invention. 図３は、本発明の第３実施形態に係る光増幅装置を示す回路図である。FIG. 3 is a circuit diagram showing an optical amplifying device according to the third embodiment of the present invention. 図４は、本発明の第３実施形態に係る光増幅装置内のＤＧＥを制御する目標となるスペクトラムのデータの一例を示す特性図である。FIG. 4 is a characteristic diagram showing an example of spectrum data as a target for controlling DGE in the optical amplifying apparatus according to the third embodiment of the present invention. 図５は、本発明のその他の実施形態に係る光増幅装置を示す回路図である。FIG. 5 is a circuit diagram showing an optical amplifying device according to another embodiment of the present invention.

符号の説明Explanation of symbols

１：光増幅装置
２：増幅用光導波路
３，４，５：光分岐器
６：光合波器
７：ＤＧＥ
８、１０：光電変換素子
１１：第１制御回路
１３：ＯＣＭ
１４：第２制御回路
１５：目標利得調整回路
１６：メモリ 1: Optical amplification device 2: Optical waveguide for amplification 3, 4, 5: Optical branching device 6: Optical multiplexer 7: DGE
8, 10: Photoelectric conversion element 11: First control circuit 13: OCM
14: Second control circuit 15: Target gain adjustment circuit 16: Memory

Claims (4)

増幅用光導波路に第１光分岐器を介して接続されて複数波長の信号光を受光する第１の光電変換素子と、
前記増幅用光導波路のうち前記第１光分岐器よりも信号光出力側で前記増幅用光導波路に励起光を照射する励起光源と、
前記増幅用光導波路のうち前記励起光の照射領域よりも信号光出力側で第２光分岐器を介して接続されて前記複数波長の信号光を受光する第２の光電変換素子と、
前記増幅用光導波路のうち前記第１光分岐器と前記第２光分岐器の間の領域に接続されて波長毎に減衰量の設定が可能な光減衰器と、
前記第１の光電変換素子の出力と前記第２の光電変換素子の出力に基づく比較値が、外部から設定される目標利得値に一致し又は近づく状態になるまで前記励起光源の光出力を制御する第１制御回路と、
前記光減衰器の出力を目標となるスペクトラムに設定させる第２制御回路とを有することを特徴とする光増幅装置。 A first photoelectric conversion element connected to the amplification optical waveguide via a first optical splitter and receiving signal light of a plurality of wavelengths;
An excitation light source for irradiating the amplification optical waveguide with excitation light on the signal light output side of the first optical splitter in the amplification optical waveguide;
A second photoelectric conversion element connected to the signal light output side of the amplification optical waveguide from the excitation light irradiation region via a second optical splitter and receiving the signal light having the plurality of wavelengths;
An optical attenuator connected to a region between the first optical splitter and the second optical splitter in the optical waveguide for amplification and capable of setting an attenuation amount for each wavelength;
The light output of the excitation light source is controlled until a comparison value based on the output of the first photoelectric conversion element and the output of the second photoelectric conversion element matches or approaches a target gain value set from the outside. A first control circuit that
And a second control circuit for setting the output of the optical attenuator to a target spectrum. 前記増幅用光導波路のうち前記励起光の前記照射領域及び前記第２の光分岐器よりも信号光出力側で前記信号光の波長毎の光パワーを測定するモニタが接続され、
前記第２制御回路は前記モニタの出力に基づいて前記光減衰器のスペクトラムを制御することを特徴とする請求項１に記載の光増幅装置。 A monitor for measuring the optical power for each wavelength of the signal light is connected to the signal light output side from the irradiation region of the excitation light and the second optical splitter in the optical waveguide for amplification,
The optical amplifying apparatus according to claim 1, wherein the second control circuit controls a spectrum of the optical attenuator based on an output of the monitor. 前記第１制御回路により前記励起光源を制御するための第１の制御周期は、前記第２制御回路により前記光減衰器を制御するための第２の制御周期よりも短く、
かつ前記目標利得値の前記第１制御回路への設定周期は前記第２の制御周期よりも長くする構成を有することを特徴とする請求項１又は請求項２に記載の光増幅装置。 The first control cycle for controlling the excitation light source by the first control circuit is shorter than the second control cycle for controlling the optical attenuator by the second control circuit,
3. The optical amplifying apparatus according to claim 1, wherein a setting cycle of the target gain value in the first control circuit is longer than the second control cycle. 前記第２制御回路は、前記目標利得値に応じて予め設定された減衰スペクトラムに一致させるか近づくように前記光減衰器を制御する構成を有することを特徴とする請求項１乃至請求項３のいずれか１つに記載の光増幅装置。 The said 2nd control circuit has a structure which controls the said optical attenuator so that it may be made to correspond to the attenuation spectrum preset according to the said target gain value, or it approaches. The optical amplifying device according to any one of the above.
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