JP4079424B2 - Optical fiber amplifier and optical transmission system - Google Patents

Description

本発明の第１の実施の形態である光ファイバ増幅器の実施例５を、表１と図９を用いて説明する。表１は市販されている１４ピン励起レーザモジュールのピンの配置である。Ａ、Ｂ、Ｃ、Ｄ型と４種類に大別される。励起レーザのピンはＴＥＣ（ペルチェ素子）の正と負の極（ＴＥＣ＋、ＴＥＣ−）、レーザダイオードの駆動のアノードとカソード（ＬＤ＿Ａ、ＬＤ＿Ｃ）、モニタ用フォトダイオードのアノードとカソード（ＰＡ、ＰＣ）、温度モニタ用サーミスタ（ＴＲ、ＴＲ）からなる。図９は基板６４０の配線パタンの励起レーザモジュール部と励起レーザ６００のＡのピン配置の関係を示した図である。 基板パタンでは、ＴＥＣ＋制御端６１１、ＴＥＣ−制御端６１２、ＰＤカソード制御端６１５、レーザダイオードアノード制御端６１６、サーミスタ制御端６１７、接地端６１８、ＰＤカソード制御端６１９、ＰＤアノード端６２０、ＴＥＣ−回路端６２１、レーザダイオード制御端６２２、サーミスタ制御端６２３、サーミスタ接続端６２５、接地６２７、レーザダイオードカソード制御端６２８、ＰＤアノード端６２９を図９のように配置する。０オームチップ抵抗の利用により、４種類の励起レーザのピン接続に対応できる。内側に示した表記は励起レーザ６００のＡのピン配置である。サーミスタ回路入力（ＴＲ）６１３とレーザモジュールの２番ピン６０２、モニタＰＤのアノード回路入力（ＰＤ＿Ａ）６１４とレーザモジュールの３番ピン６０３、レーザダイオードのアノード制御回路入力（ＬＤ＿Ａ）６２６とレーザモジュールの１０番ピン６０９、レーザダイオードのカソード制御回路入力（ＬＤ＿Ｃ）６２４とレーザモジュールの１１番ピン６０８のパッド間、総計４個の０オームのチップ抵抗を入れることでA型のレーザモジュールに対応した接続が行える。本実施例では、ＬＤ＿ＡとＰＤ＿Ｃとサーミスタの片方（ＴＲ（Ｇ））は常にグランドに接続する回路を想定している。他の型のレーザモジュールに対しても５個以内の０オームのチップ抵抗の接続で対応できる。
【００８２】
本実施例では０オームのチップ抵抗を使用する例を挙げた。これはバッドの変わりにピンを立て、ジャンパ線におきかえてもよい。
【００８３】
さらに、チップ抵抗用のパッドをレーザモジュールのピンが立つ穴パッドにしてそのピンのさし込みをピン配置に対応した機能の穴に選択してさすようにすることでも可能である。
【００８４】
［実施例６］
本発明の第２の実施の形態である光伝送システムの実施例６を、図１０を用いて説明する。
【００８５】
図１０は、１６波長多重まで可能な光中継ファイバ増幅器を用いた光伝送システムの構成である。
【００８６】
送信側のｎまでの波長と１６番目の波長チャネルで多重化した場合について説明する。送信器（Ｔｘ）７０１−７１６が設定されると、監視系（ＳＶ）７１８に送信器設定の情報７１７があがる。例えば、ｎ番目の送信器７０ｎがセットされるとそれまでのｎ−１までの送信チャネルと１６番目のチャネル７１６のトータルｎ波長数の情報がｎ＋１にあらためられる。この情報は直ちに光学的な監視信号系（Ｌ−ＳＶ）７２１に伝えられる。信号光は光ファイバ伝送路７２３の波長多重信号光合波系結合器７１９により信号波長多重化され、送信用光増幅器７２０で一括増幅される。
【００８７】
監視信号は別の波長の監視信号光として監視光／信号光結合器７２２により重畳される。重畳された波長数情報は各中継ファイバ増幅器（ＬＡ）７２４、７２６および受信光ファイバ増幅器（ＲＡ）７２９で検出される。多重化主信号光は各光ファイバ増幅器７２４、７２６、７２９で分散量を補償しながら増幅される、受信部では波長分離器７３１で各波長に信号が分離された後、各波長の信号は光信号受信器７５１−７６６で電気信号に変換される。監視信号により波長数情報が伝達された後に各光ファイバ増幅器がチャネル数変化に応じた光出力ならびに内部の設定を数ｍｓから数百ｍｓの特定の時間で緩やかに設定を変えていく。これにより、光伝送システムの波長多重数の変化に伴う、各チャネル信号の状態の変化を抑え、システム全体の伝送品質を保つ。
【００８８】
また、波長数情報については、光学的な監視信号系のみによらず、別の監視信号伝達系７７１−７７４を利用することもできる。
【００８９】
光ファイバ増幅器の早い応答を利得一定制御することで、仮に波長数変動が急激に生じても、チャネル毎の出力変動は少なく、またリップルを持つような変動がないため、伝送時の障害を発生しないシステムが構成できる。
【００９０】
異常な光入力の低下からの回復、あるいは分散補償光ファイバ（ＤＣＦ）のような分散補償器７２５、７２７、７３０の挿抜時などに発生する光の異常ピーク出力を抑える機能を有する光ファイバ増幅器を光伝送システムに使用することで光サージが抑制されるため、信号の上流で発生する光サージの伝達に伴う、下流の光中継器や受信装置の光学部品７５１−７６６等の破壊を防ぐ。
【００９１】
さらに波長平坦化のための光ファイバ増幅器に挿入した光減衰器周波数帯域を１ｋＨｚ以下に抑えることにより、６００Ｍｂｉｔ／ｓの伝送速度における信号においても、低域の波形歪みの発生がなく、光伝送システムの品質を保つことができる。特に、中継器を光ファイバ増幅器で構成する場合には、光ファイバ増幅器が１Ｒ（Ｒｅｓｈａｐｅ）中継であるため、周波数特性は累積される、ここで周波数域が広いことは、中継数の増加に対しても波形劣化が低い光伝送システムが構成できる。
【００９２】
また、各光ファイバ増幅器７２０、７２４、７２６、７２９には、他の実施例で記載したいずれの光ファイバ増幅器であっても良い。
【００９３】
【発明の効果】
本発明によれば、伝送区間損失や波長数に依存しない、利得の波長依存性の少ない汎用的な波長多重光伝送用ファイバ増幅器できる。光伝送システム運用時に波長数増減が可能となり、システムに柔軟性をもたらす。光サージを抑え、光ファイバ増幅器を使用する光伝送システムの信頼性を高める。光部品の挿入の有無を知らせて使い勝手をよくする。光部品の高密度実装により、小型化が図れる。多種のレーザが一つの基板パタンで使い分けられ、コストの低減ができる。
【図面の簡単な説明】
【図１】本発明の実施例１の光ファイバ増幅器の２段２励起光ファイバ増幅器の構成を示す図である。
【図２】本発明の実施例１の光ファイバ増幅器の前段増幅部可変光減衰器周辺の制御構成を示す図である。
【図３】本発明の実施例１の光ファイバ増幅器の後段増幅部光出力制御構成を示す図である。
【図４】本発明の実施例２の光ファイバ増幅器の中間光挿入部制御構成を示す図である。
【図５】本発明の実施例３の光ファイバ増幅器の残留前段励起光の後段利用型光ファイバ増幅器の構成を示す図である。
【図６】本発明の実施例１の光ファイバ増幅器の伝送区間損失が異なる場合の光レベルダイヤグラムを示す図である。
【図７】総出力一定制御時の光出力の波長依存性を説明する図である。
【図８】本発明の実施例４の光ファイバ増幅器のファイバ型光学部品の収納例を示す図である。
【図９】本発明の実施例５の光ファイバ増幅器の市販励起レーザのＡ型を接続する例を示す図である。
【図１０】本発明の実施例６の波長多重光伝送システムの構成例を示す図である。
【符号の説明】
１…光信号入力、２…光信号出力、３…前段光増幅部、４…後段光増幅部、５…２段光ファイバ増幅器、１０…前段入力部可変光減衰器、１１…後段入力部光減衰器、２０…前段入力モニタ用光分岐カプラ、２１…前段光出力モニタ用光分岐カプラ、２２…後段光入力モニタ用光分岐カプラ、２３…後段光出力モニタ用光分岐カプラ、３０…前段前方励起用励起光／信号光結合器、３１…後段後方励起用励起光／信号光結合器、３３…０．９８μｍ励起光／信号光分離器、３４…０．９８μｍ励起光／信号光合波結合器、３５…前段の０．９８μｍ残留励起光、４０…前段増幅用光ファイバ、４１…後段増幅用光ファイバ、５０…中間挿入光部品、１００…前段光増幅部制御回路、１５０…後段光増幅部制御回路、２００…監視制御回路、２０１…波長数情報を含む監視情報、２０２…２段光ファイバ増幅器の監視情報、１１０…可変減衰器駆動回路、１１１…可変減衰器駆動値モニタ、１１２…Ａ／Ｄ変換器、１１３…減衰量演算器、１１４…減衰量補正データ、１１５… Ｄ／Ａ変換器、１１６…低速フィルタ、１２０…入力モニタＰＤ、１２１…演算導出光入力モニタ値、１２２…加算器、１２３…平均化回路、１２４…相対判定基準値、１２５…減算器、１２６…相対値入力判定、１２７…絶対値入力判定値、１２８…絶対値入力判定、１２９…ＯＲ論理回路、１３０…前段励起用励起ＬＤ、１３１…励起ＬＤ駆動回路、１３２…励起抑制信号、１３３…前段光出力制御回路からの制御信号、１７０…後段光出力モニタ、１７１…基準値／モニタ値差分、１７２…低周波フィルタ、１７３…利得一定制御、１７４…利得演算回路、１７５…出力基準値、１７６…出力異常検出閾値、１７７…出力異常判定、１７８…出力異常信号、１８０…後段励起ＬＤ、１８１…励起ＬＤ駆動回路、２１０…波長数情報、２１１…波長数情報比較、２１２…前波長数情報、２１３…波長数対応出力、２１４…波長数対応出力データ、２１５…Ｄ／Ａ変換器、２１６…波長数対応入力データ、２１７…後段光増幅部波長数対応光入力基準値、２１８…波長数対応光入力基準値、３００…前段の光ファイバ増幅器、３０１…１２０ｋｍの光ファイバ伝送、３０２…８２ｋｍの光ファイバ伝送路、３０３…４７ｋｍの光ファイバ伝送路、４２０…前段光増幅部光出力モニタＰＤ、４２１…レベル判定、４２２…光部品抜去判定、４２３…後段光増幅部光入力モニタＰＤ、４２４…レベル判定、４２５…励起抑制信号、４２６…光部品抜去情報、４２７…AND論理、４２８…出力異常低下信号、４２９…ＯＲ論理、５００…光学系収納箱、２０３０…（光分岐＋励起光／信号光合波結合＋光アイソレータ＋モニタＰＤ）複合光モジュール、２１３２…（光分岐＋利得平坦化フィルタ＋光アイソレータ＋モニタＰＤ）複合光モジュール、１１２２…（光分岐＋光アイソレータ＋モニタＰＤ）複合光モジュール、２３３１…（励起光／信号光結合＋光アイソレータ＋光分岐＋モニタＰＤ）複合光モジュール、６００…励起レーザモジュール、６０１…レーザペルチェ正極ピン、６０２…サーミスタピン、６０３…ＰＤアノードピン、６０４…ＰＤカソードピン、６０５…サーミスタピン、６０６…レーザペルチェ負極ピン、６０７…接地ピン、６０８…ＬＤカソードピン、６０９…レーザアノードピン、６１１…レーザペルチェ駆動正極出力端、６１２…レーザペルチェ駆動負極出力端、６１３…サーミスタ接続端、６１４…ＰＤアノード制御端、６１５…ＰＤカソード制御端、６１６…ＬＤアノード制御端、６１７…サーミスタ接地側接続端、６１８…ＰＤカソード制御端、６２０…ＰＤアノード制御端、６２１…レーザペルチェ駆動負極出力端、６２２…ＬＤアノード制御端、６２３…サーミスタ接地側接続端、６２４…レーザカソード制御端、６２５…サーミスタ接続端、６２６…レーザアノード制御端、６２７…サーミスタ接地側接続端、６２８…レーザカソード制御端、ＰＤアノード制御端、７０１…光信号送信器１（波長１）、７０２…光信号送信器２（波長２）、７０ｎ…光信号送信器ｎ（波長ｎ）、７１６…光信号送信器１６（波長１６）、７１７…送信器動作情報、７１８…監視信号系、７１９…波長多重合波結合器、７２０…一括増幅送信用光ファイバ増幅器、７２１…監視信号送信器、７２２…監視信号光／多重信号光合波結合器、７２３…光ファイバ伝送路、７２４…光中継増幅器、７２５…分散報償器、７２６…光中継増幅器、７２７…分散補償器、７２９…一括増幅受信用光ファイバ増幅器、７３０…分散補償器、７３１…多重波長信号分離器、７５１…光信号受信器１（波長１）、７５２…光信号受信器２（波長２）、７５ｎ…光波長受信器ｎ（波長ｎ）、７６６…光信号受信器１６（波長１６）、７７１−７７４…管理信号系、Ａ…１２０ｋｍの光ファイバ伝送路３０１伝送後の光入力レベル、Ｂ…８２ｋｍの光ファイバ伝送路３０２伝送後の光入力レベル、Ｃ…４７ｋｍの光ファイバ伝送路３０３伝送後の光入力レベル。３−１…可変光減衰器制御経路、３−２…光減衰量情報経路、３−３…相対的光レベル低下判定経路、３−４…絶対光レベル低下判定経路、４−１…利得一定制御経路、４−２…光出力一定制御経路。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an optical fiber amplifier for an optical transmission system and an optical transmission system using the optical fiber amplifier, and more particularly to an optical fiber amplifier for wavelength multiplexing and a wavelength multiplexing optical transmission system.
[0002]
[Prior art]
With the advent of optical fiber amplifiers, it has become possible to amplify optical signals with low light intensity to high output with low noise and light. As a result, the optical transmission distance can be greatly increased.
[0003]
Further, since the optical fiber amplifier has a wide gain wavelength range from 1530 nm to 1565 nm, wavelength multiplexed optical transmission in which a plurality of signal lights within the amplified wavelength range are simultaneously amplified and transmitted is possible. For example, according to “2.6 Terabit / s WDM Transmission Exponential using Optical Dual Coding” (22nd European Conferencing on Optical Communication-GPC'96 h. It is possible to arrange 120 wavelengths from 1529 nm to 1564 nm and transmit 120 km at the same time. In this announcement, the transmitting optical fiber amplifier functions to compensate for optical loss that occurs in the multiplexed portion when wavelength multiplexing is performed, and to increase the output in order to extend the transmission distance. The optical output of the optical fiber amplifier on the transmission side has an output of 21 dBm with a simultaneous output of 132 wavelengths.
[0004]
In wavelength division multiplexing transmission, the optical output of each signal wavelength is a value between the lower limit optical output that maintains the required signal-to-noise ratio and the upper limit optical output that does not cause waveform distortion due to nonlinear effects in the transmission path. It is necessary to fit in. On the other hand, an optical fiber amplifier usually has a wavelength dependency (gain deviation) in gain, and an output range between wavelengths is accumulated every time relay amplification is performed. Since a signal error occurs when the difference exceeds the allowable width of the optical output, it is necessary to suppress a gain deviation between wavelengths in the optical fiber amplifier.
[0005]
As a method of controlling the optical output of an optical fiber amplifier at the time of wavelength multiplexing, “flattening of multi-wavelength collective amplification characteristics of an optical fiber amplifier using fiber gain control” (Technical Report of IEICE Technical Report OCS94-66 p.31) As described above, there is a method in which the constant gain control is performed so that the optical output for each wavelength becomes constant regardless of the multiplicity, and the optical output is adjusted by an optical attenuator on the output side. However, in order to satisfy the constant gain condition, when the optical input becomes large, a large optical output from the amplification optical fiber is required, and a strong pumping light power is required. Further, in order to keep the light output within the determined light output, the increased light output is lowered to the light output equivalent to that at the low input level by the optical attenuator, so that the efficiency is poor.
[0006]
“Examination of configuration method of wavelength-multiplexed Er-doped fiber optical amplifier” (Technical Report OCS95-36 p.21 of IEICE) shows another configuration method of wavelength-multiplexed Er-doped fiber optical amplifier. In the configuration of the two-stage amplification unit, the front-stage amplification unit performs constant gain control and keeps the gain constant regardless of the optical input. In an optical fiber amplifier, the wavelength dependence of gain strongly depends on the gain, so that the gain dependence on wavelength can be controlled independent of the optical input by controlling the gain constant. In the latter stage amplification unit, an optical attenuator is installed in the input unit, and the value of the optical input to the amplification unit is controlled to be constant. As a result, the optical output is controlled to be constant while keeping the overall optical gain constant. Furthermore, the overall gain flatness can be obtained without using an optical filter by designing so as to cancel the gain gradient in the front stage and the rear stage. The optical output is set so that the total optical output of all wavelengths is constant by lowering the output of each wavelength to 1 dBm from the output of 7 dBm at each wavelength when multiplexing 4 wavelengths to 16 dBm.
[0007]
The use of the optical fiber amplifier is not limited to the amplification of the optical output at the time of wavelength multiplexing, but is also used as loss compensation for functional optical components. The dispersion value increases as the distance of the optical fiber transmission line having chromatic dispersion increases. In order to eliminate the influence of this dispersion, it is necessary to compensate for the chromatic dispersion. “Dispersion-Compensator-Incorporated Er-Doped Fiber Amplifier” (1 Optical Amplifiers and Thirr Applications, Compensator 994 Technical Diens. It is described to do. At this time, if an optical component that generates a loss is arranged in the center of the optical fiber amplifier divided into two, the loss of the optical functional component is apparently reduced and the pumping efficiency is increased while maintaining the low noise property of the optical amplifier. Can do.
[0008]
Japanese Patent Application Laid-Open No. 7-281219 discloses an optical amplifier in which a variable optical attenuator is inserted in the preceding stage to reduce output distortion of the optical fiber amplifier.
[0009]
Furthermore, JP-A-5-244098 and JP-A-5-292040 disclose monitoring light control.
[0010]
[Problems to be solved by the invention]
When light of many wavelengths is incident on one optical fiber amplifier and constant optical output control is performed, the optical gain expressed by the ratio of the optical output to the optical input changes when the optical input changes. Since the wavelength dependence of the gain of the optical fiber amplifier changes as the gain changes, the wavelength dependence of the gain changes as the optical input changes. There is no problem if the section lengths of the transmission lines, which are the intervals at which the optical fiber amplifiers are provided, are the same and a constant light input is provided to each optical fiber amplifier, but in reality there are various section lengths and the optical input levels are various. Therefore, there is a need for an optical fiber amplifier that does not change the wavelength dependency of gain even when the optical input level changes. For example, a receiving optical fiber amplifier having a maximum gain of 30 dB and an optical output of 0 dBm needs to support a dynamic range of -30 dBm to -9 dBm. The repeater optical fiber amplifier requires a gain up to about 40 dB, and the silica-based erbium-doped optical fiber amplifier has a very large gain deviation between 1535 nm and 1542 nm, and a gain difference of about 6 dB between the minimum and maximum optical input. Changes.
[0011]
The problem of wavelength dependence will be described with reference to FIG. FIG. 7 shows the wavelength dependence of the optical output of an EDFA (erbium-doped optical fiber amplifier) when the total output constant control is performed. In the figure, A, B, and C are in order of increasing light input. As the light input increases, the light output decreases remarkably near 1530 nm, and the light output increases near 1560 nm. Even if an optical filter for correction is inserted so that the wavelength dependence of the optical output becomes flat at a specific light input, the wavelength dependence characteristics of the gain change as the light input changes. Appears. When this is connected in multiple stages, deviations corresponding to the number of stages are accumulated. For long distance transmission of 600 km or more, 4 to 7 repeater optical fiber amplifiers are required, and the output wavelength deviation of the optical fiber amplifier per unit is required to be suppressed to 1 dB or less.
[0012]
In the present invention, as a method for overcoming the above problem, a variable light source attenuator is inserted at the input end of the optical fiber amplifier to keep the optical input level to the amplification optical fiber constant. When a variable attenuator is inserted to control the optical input level to the EDF (erbium-doped optical fiber) to be constant, if the feedback control is too early, the signal becomes 0 in the low frequency region (near 10 kHz) of the digital transmission signal. This is a control that equalizes the output of 1 and degrades the frequency characteristics of the transmission signal. The optical fiber amplifier is a regenerator with a 1R (Reshape) function and should not limit the signal band. For this reason, it is necessary to control so as not to limit the low-frequency band of the amplification optical fiber.
[0013]
Furthermore, when a variable optical attenuator is inserted on the input side of the optical fiber amplifier and control is performed to keep the input level to the EDF constant, a monitor is installed behind the variable optical attenuator. In this configuration, since the input to the EDF is controlled to a constant value by the variable optical attenuator, the true optical input to the optical fiber amplifier cannot be directly monitored. However, it is necessary to monitor the optical input level even when the level of the input light is controlled by the variable optical attenuator.
[0014]
In wavelength division multiplexing optical transmission, it is desirable that the number of wavelengths used can be changed arbitrarily in the operating state. Even if the number of transmission channels changes, it is necessary that the optical output per channel in the wavelength division multiplexing optical transmission always keeps the output level of the optical transmission system within an allowable range.
[0015]
In the conventional technique described above, when the wavelength division multiplexing optical fiber amplifier has all the wavelengths, the optical output for each wavelength is controlled to be the same. However, in actual operation, there are not necessarily all wavelengths, and there are cases where the number of wavelengths is initially used with a small number of wavelengths and the number of wavelengths is increased as necessary. As the light input changes, it is desired to change the overall light output to ensure a minimum light output.
[0016]
Not only in a wavelength multiplexing system, in an optical fiber amplifier, when a high level light input suddenly rises in a short time of about μs from a low light input state, an optical surge is generated on the light output side. This is a phenomenon peculiar to the optical fiber amplifier, and is caused by the property of keeping the optical gain constant. The light output with high light surge is expensive and damages important photo detectors. For this reason, it is necessary to suppress optical surges. When performing control to maintain the optical output at a specified value, the potential gain of the optical fiber amplifier increases when the optical input is small, and an optical surge peculiar to the optical fiber amplifier is generated if a high optical input is suddenly input at that time. To do. In order to suppress the optical surge, it is necessary to suppress an increase in the latent gain, and it is necessary to suppress the optical excitation that causes this latent gain and to suppress it to a low level. Until now, as described in Japanese Patent Laid-Open No. 5-130043, there is an example in which the optical excitation is completely stopped when the absolute value of the light input falls below a specific light input.
[0017]
However, in an optical fiber amplifier that operates with a wide optical input width, a specific optical input value that is determined to suppress excitation is set to a low value. At this time, when there is an optical input directly above the specific optical input (that is, the lowest optical input in the operating range), the pump is in a high excitation state, and when the optical input returns to a high optical input in this state, an optical surge is generated. Light output. For this reason, it is desired to further suppress the optical output like a light surge.
[0018]
When an optical component is inserted in the middle of an optical fiber amplifier composed of a plurality of stages of optical amplifiers, there is another cause of optical surge. When an optical component is inserted in the middle of an optical fiber amplifier, there is a risk of generating an optical surge when the optical component is inserted or removed and then reinserted. For example, in “Dispersion-Compensator-Incorporated Fiber-Amplified Amplifier” described in the conventional example, a description will be given using a case where the amplification optical fibers of the front and rear stages are excited by one pump light source. Even if the optical input as the optical amplifier has a predetermined value, it is in an optically disconnected state when the intermediate insertion optical component is removed. Since there is no light input to the amplification fiber at the subsequent stage, the excited state becomes high. When the optical component is reinserted in this state, the signal light amplified in the previous stage is incident on the amplification optical fiber in the subsequent stage of the high excitation state, so that an optical surge is generated on the optical output side. It is necessary to suppress the optical surge at the time of inserting / removing the optical component in the middle.
[0019]
In addition, when the optical functional part can be inserted into and removed from the center of the optical fiber amplifier, it cannot be distinguished whether the optical output of the amplification optical fiber in the subsequent stage is due to a failure or due to a missing optical part. There is a need for a method for distinguishing between these two states, ie, a decrease in optical output due to removal of an optical functional component, or a failure of an optical fiber amplifier due to other reasons.
[0020]
Further, the configuration of the optical system box that houses the optical system is necessary to eliminate the exposure of the optical fiber and to eliminate the accident of the optical fiber disconnection due to the handling failure. However, it is necessary to secure the required optical fiber bend diameter for the storage of optical fibers, and this requires space, creating a vacant space when storing multiple optical components and increasing the size of the device. It was the cause. A technique for reducing the empty space as much as possible is necessary for miniaturization of the optical fiber amplifier.
[0021]
On the other hand, semiconductor laser modules have different pin functional arrangements depending on the manufacturer. Depending on the application and price, it is necessary to reduce costs by using different types of semiconductor laser pump modules of various manufacturers on the same substrate. Substrate patterns corresponding to various pin arrangements are effective in suppressing the stock quantity of substrate types and eliminating waste of cost.
[0022]
In an optical transmission system, an inexpensive and small-sized optical fiber amplification transmission system that always maintains the optical output level for each wavelength at an arbitrary wavelength multiplicity and does not have a destructive element such as an optical surge is reliable, popular, and transmission quality. Desired from the viewpoint.
[0023]
[Means for Solving the Problems]
A variable optical attenuator is inserted into the optical input section of the optical fiber amplifier to adjust the optical input level to the amplification optical fiber to be constant. To adjust the amount of light attenuation, the level of light immediately after light attenuation is monitored, and feedback control is performed on the variable optical attenuator so that the monitored value is always constant.
[0024]
The principle will be described. The gain wavelength dependence of the optical fiber amplifier strongly depends on the gain of the optical fiber amplifier. This will be described again with reference to FIG. FIG. 7 shows the wavelength dependence of the gain when the wavelength multiplexed optical input is controlled so that the collective optical output becomes constant by the collective amplification. The total optical input is increased by adding the optical input of each wavelength in the order of A, B, and C. The optical gain is represented by the ratio between the optical output and the optical input. In the constant optical output control, the gain decreases by 10 dB in order of A, B, C from the order of decreasing optical input. When the optical input is small and the optical gain is large, the optical gain in the vicinity of 1530 nm rises significantly higher than other wavelengths. When the optical input is high and the optical gain is small, the gain in the short wavelength region as in C can be suppressed, and the gain decrease is reduced on the long wavelength side.
[0025]
Now, in an optical transmission system, an optical fiber amplifier defines an optical output to a specific narrow width, for example, about ± 1 dB in operation. Since the section loss of the actual transmission path is not always constant, the optical input changes by about 20 dB depending on the section loss installed. When a wavelength range of 1530 nm to 1560 nm is used for wavelength optical multiplexing optical transmission and light in that wavelength range is uniformly amplified collectively, the optical gain changes when the optical input level changes. Sex changes.
[0026]
In the present invention, the attenuation amount of the optical attenuator is adjusted in accordance with the optical input of the optical fiber amplifier so that the optical input to the amplification optical fiber is constant. Since the optical amplification amount in the amplification optical fiber is kept constant, the wavelength dependency of gain does not change. In FIG. 7, the optical attenuator of the input unit is adjusted so as to always match A having the largest gain (smallest optical input). The wavelength characteristic of the gain is corrected by an optical filter or the like so that the wavelength dependency becomes flat so that the gain peak at 1535 nm and the gain around 1550 nm coincide with the gain at 1540 nm. A wavelength division multiplexing optical fiber amplifier having a flat gain wavelength dependency corresponding to a wide dynamic range of optical input can be configured.
[0027]
In this method, the optical input to the amplification optical fiber is adjusted by increasing the loss on the input side. The light input to the amplification optical fiber is always set to the minimum light input. In this control, when the optical signal input is large, the noise characteristic is deteriorated by attenuation on the input side. A method for improving this defect will be described. The dependence of the wavelength dependence of the gain of an actual amplification optical fiber on the optical input is not extremely large. The light input serving as the reference for adjustment is set to a point 5 dB higher than the minimum light input, for example. This point can be improved by minimizing the attenuation of the optical attenuator between the light input 5 dB higher than the minimum light input and the minimum light input. During the 5 dB period, the optical input to the amplification optical fiber changes, and a small wavelength dependence of about 1 dB occurs.
[0028]
A method for controlling the optical output in accordance with the number of wavelengths during wavelength multiplexing will be described. The number of channels on the transmission side is sent to the optical fiber amplifier by the monitoring signal. The optical fiber amplifier receives channel number information, sets a signal voltage for controlling optical input / output corresponding to the wavelength number information, and controls optical input and output to the amplification optical fiber.
[0029]
In order to ensure the minimum light output per wavelength, the total light output is adjusted according to the number of wavelengths. Not only does the optical input level change due to transmission section loss, but the total optical input changes when the previous repeater transmission output changes according to the number of wavelengths. Since the wavelength dependency of the gain depends on the gain of the optical fiber for amplification, it is also necessary to adjust the attenuation amount of the optical input in accordance with the wavelength number information so that the gain is constant. For example, when information of two wavelengths comes at 10 dBm (10 mW) at one wavelength, it is increased by 3 dB (doubled) to 13 dBm (20 mW). The optical input is also increased by 3 dB (double) to -17 dBm (20 μW) when the optical input at one wavelength is −20 dBm (10 μW). By doing so, the optical output per wavelength is made the same with respect to the change in the number of wavelengths, and at the same time, the change in gain of the amplification optical fiber is eliminated, and the wavelength flatness is ensured.
[0030]
Next, means for preventing light surge will be described. The optical signal fluctuation time of the system using the optical fiber amplifier is 1 ms or less (necessary band> 1 kHz), and the fluctuation amount is 3 dB or less up to the frequency range of 1 MHz. If the optical input over a period of two orders of magnitude longer than the time required for optical signal transmission is averaged, the average optical input level in the system in which the optical fiber amplifier is installed can be regarded as constant in a stable state. If the value rapidly decreases (relative value) by, for example, 6 dB in 1 ms or less than the averaged light input, it is considered to be an abnormal input decrease. When optical output constant control is performed by an optical fiber amplifier, excitation is increased to maintain the optical output when the optical input is reduced. When there is a rapid recovery of light input of 100 μs or less in a high excitation state, an optical surge is generated on the output side. In order to avoid the occurrence of this optical surge, the excitation is suppressed to a level at which no optical surge is generated when the abnormal light input is reduced to a relative value.
[0031]
In the present invention, the optical input averaging process is monitored through a very slow filter of several Hz in an analog circuit, and in digital control, a sample value in the order of ms is memorized for about 1 s. This is realized by performing the conversion process. Data is replaced with new data for 1s before sampling.
[0032]
Even when the input is abnormally lower than the minimum light input value of the system, a high excitation state is obtained. It is necessary to avoid a highly excited state that cannot be considered as a normal use state. In the case of a gradual decrease in light input, an abnormal decrease in light input due to the relative value cannot be detected. Therefore, LOSS OF SIGNAL (LOS) is detected by the absolute value of the optical input, and photoexcitation is stopped. LOS can be directly monitored when there is no variable optical attenuator, but is detected by both the control signal of the variable optical attenuator and the optical monitor when there is a variable optical attenuator. Suppression of the occurrence of an optical surge is performed by performing excitation reduction control based on the OR theory value of the relative LOS and the absolute LOS detection value.
[0033]
As for the optical input monitor used for determining the optical input, when the variable optical attenuator is inserted on the input side, the optical input monitor value cannot be monitored. As a countermeasure, there can be considered a method of directly monitoring by installing an optical branch for optical input monitoring in front of the variable optical attenuator. However, there is a problem that optical signal input is deteriorated due to the branch insertion of the optical input monitor. Another method for monitoring the optical input while avoiding this problem is to obtain the actual optical input by adding the attenuation obtained from the control signal of the variable optical attenuator and the optical monitor value immediately after the variable optical attenuator. is there.
[0034]
A method for suppressing the occurrence of optical surge due to component insertion / removal when an optical functional component is inserted in the middle of an optical fiber amplifier composed of a plurality of stages of optical amplifiers will be described. An optical monitor is inserted on the input side of the subsequent optical amplification unit. When the optical monitor detects a value lower than a predetermined value, it is determined that the optical component is not connected and the excitation intensity is reduced. As a result, the abnormally excited state of the subsequent amplification unit is suppressed, and the occurrence of optical surges when optical components are connected is suppressed. When the pump control at the front stage and the rear stage are independent, when the optical component is not connected, the optical output reduction control of the pump light source at the rear stage is applied.
[0035]
In the configuration of an optical fiber amplifier including a plurality of stages of optical amplifying units, there is a one-pumping two-stage amplification configuration in which residual pumping light pumped from the front optical amplifying unit is used as the subsequent optical amplifying unit. At this time, the optical output of the optical amplifier of the preceding stage is monitored together with the optical output of the optical amplifier of the subsequent stage, and when the optical input of the subsequent stage is present, excitation control is performed so that the optical monitor of the subsequent stage is constant. When there is no light input, the control is switched so that the light output monitor in the previous stage becomes constant with low excitation that does not cause an optical surge when the optical component is connected. Using weak light amplified by the preceding optical amplifier when connecting the optical component, the input to the subsequent optical amplifier when the optical component is connected is detected, and the latter optical input automatically detects the light and detects the subsequent light. Performs constant light output control.
[0036]
The optical component insertion, non-insertion detection, information transmission, and processing will be described. In the monitor system, if the optical output monitor at the front stage shows a predetermined value and the optical input monitor at the rear stage does not detect the optical input, the central optical component is not inserted. At this time, uninserted information is transmitted. When this signal is output, even if information on an optical output drop abnormality of the optical amplifier is output, it is not a decrease in optical output due to the failure of the optical amplifier, so the output abnormality is masked.
[0037]
The control frequency characteristics will be described. When controlling optical input, for example, a magneto-optical variable optical attenuator as described in the 1996 Society of Electronics, Information and Communication Engineers Electronics Society Conference C-128 may be used, but the response speed is about 300 μs. When this response speed is utilized to the maximum, a band of about 3 kHz is obtained. Alternatively, sub-ns can be controlled using an electroabsorption modulator, and μs or less can be controlled using an acousto-optic modulator. By making the low frequency side of the output constant control band of the variable optical attenuator control slower than the modulation band originally possessed by the optical fiber amplifier, it is possible to suppress band degradation when the variable optical attenuator is used. The band of an optical fiber amplifier is usually several kHz or less, and is a sub-kHz at a slow speed, and even if a magneto-optic variable optical attenuator is used, band control by electric control is required. When adjusting the optical input with the variable optical attenuator, the optical input level is controlled at a low speed so as not to destroy the bandwidth of the amplification optical fiber.
[0038]
Next, implementation will be described. The optical fiber amplifier is composed of a plurality of fiber-type optical components such as an amplification optical fiber, a pump light / signal light combiner, an optical isolator, and an optical monitor. In order to increase the mounting density, the present invention is to obliquely arrange the optical components in a box for storing optical components. The optical fiber is required to have a bending radius R> 30 mm in order to ensure reliability for bending. That is, a bending space of at least 60 mm is required to place the optical fiber. When an elongated optical component is placed along the flow of the optical fiber, it is necessary to add a bending space of the optical fiber to the length of the optical component. For example, in an optical component having a length of 70 mm in the fiber coupling direction, a fiber bend R = 30 mm on both sides is added to the length of the main body, and a minimum length of 130 mm is required. When placed diagonally, the part length looks short when viewed from one side of the rectangle. For example, when tilted to 30 °, 70 * cos (30 °) = 60.6 mm, and the required length of 9.4 mm is shortened to 120.6 mm by adding a fiber bending space of 60 mm. When tilted by 45 °, it becomes 109.5 mm and becomes 20.5 mm shorter. Further, by mounting the bending space of the optical fiber, it becomes possible to mount the high density mounting in a more realistic space.
[0039]
The wiring corresponding to the pin arrangement of various types of excitation lasers will be described. First, wiring corresponding to the pin arrangement of the available semiconductor laser module for excitation is put in the substrate pattern. To the pins that are connected in common, connect the wiring to the pad holes into which the pins are inserted. Wiring is terminated with an open pad so that connection can be selected by connecting to a pin having a different pin arrangement among various types of excitation lasers by connecting with a 0 ohm chip resistor or a short-circuit jumper to the pad. The opposing pad pad also terminates with an open pad at a position opposite the open pad.
[0040]
In this way, all the possible wirings for the pins that can have different functions depending on the difference of the excitation lasers are preliminarily included in the open pad. In actual use, the open pads corresponding to the functions are connected by a 0 ohm chip resistor or jumper wiring by the excitation laser to be used. Or, instead of an open pad, connect wires corresponding to a variety of possible functions to the hole pad, and adjust the length of the semiconductor laser module pin until it is bent, so that it can be inserted into a pad with a suitable pattern It corresponds to different pin arrangement by doing.
[0041]
In this way, by using a common substrate pattern so that it can be handled at the time of manufacture, the laser module can be switched to a low-cost and easy-to-use laser module.
[0042]
By using an optical fiber amplifier as described above in a wavelength division multiplexing optical transmission system, the minimum optical output per wavelength channel can be maintained even if the number of wavelengths changes, optical functional components can be inserted in the middle, and optical surges can be suppressed. It is possible to build a low-priced and small-sized system, maintain transmission quality, improve the chromatic dispersion compensation function, and improve the reliability of the transmission system.
[0043]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention will be described below with reference to the drawings.
[0044]
[Example 1]
Example 1 of the optical fiber amplifier according to the first embodiment of the present invention will be described with reference to FIGS. 1 to 3, 7 and 10. FIG.
[0045]
FIG. 1 shows a configuration of an optical fiber amplifier 5 for wavelength multiplexing comprising a two-stage optical amplifying unit including a front-stage optical amplifying unit 3 and a rear-stage optical amplifying unit 4 including an optical component 50 in the middle. The optical level of the signal light 1 incident on the input end optical connector is adjusted by the variable optical attenuator 10. A part of light is separated by the next optical branching coupler 20 and used for monitoring input light. The excitation light and the signal light combiner 30 superimpose the excitation light on the signal light. In the amplification optical fiber 40, the signal light is amplified when passing through the optical fiber excited by the excitation light. A part of the light to be amplified is separated by the optical branching coupler 21 and used for an optical output monitor. In the pre-stage optical amplifying unit control circuit 100, negative feedback is applied to the variable optical attenuator 10 so that the optical level branched by the incident input optical branch 20 is constant, and further branched by the output-side optical coupler 21 to be light. The pump light incident on the amplification optical fiber 40 is negatively fed back by the combiner 30 of the pump light and the signal light so that the level of the light becomes constant.
[0046]
Light emitted from the optical amplification unit 3 in the previous stage is coupled to an optical component 50, for example, a dispersion compensating optical fiber via an optical connector. Thereafter, the light enters the optical amplification unit 4 at the subsequent stage through the optical connector. The fixed attenuator 11 is inserted so that the loss of the optical component 50 and the total loss of the fixed attenuator 11 are within a shift of, for example, 5 dB. The fixed optical attenuator 11 can adjust the light input to the optical fiber for amplification in the subsequent stage in a fixed manner regardless of the loss of the optical components. In the post-stage optical amplifying unit 4, a part of the light is branched and monitored by the optical branching coupler 22. Main signal light enters the amplification optical fiber 41. For example, the branching ratio is 95: 5. Excitation light is superimposed on the amplification optical fiber 41 from behind via the excitation light / signal optical coupler 31 to excite the amplification optical fiber 41 from behind. The signal light is amplified when passing through the excited optical fiber for amplification. A part of the amplified signal light is separated by the optical branching coupler 23 and monitored as an optical output. The post-stage optical amplifier control circuit 150 performs negative feedback control of the pumping light so that the monitored optical signal becomes constant. Main signal light is emitted.
[0047]
The wavelength number information and the external management control signal are input / output 201 and 202 to / from the monitoring control circuit 200, and signals are transmitted to and received from the post-stage optical amplifier control circuit 150 and the pre-stage optical amplifier control circuit 100.
[0048]
Next, control for adjusting the light level by the variable optical attenuator 10 on the input side of the pre-stage optical amplifying unit 3 will be described with reference to FIG. FIG. 6 is a diagram illustrating an optical level diagram when transmission section losses are different. FIG. 6 shows the total light levels in the three cases where the section lengths of the transmission line optical fibers are different from the optical output before the optical fiber amplifier of this embodiment. The section length is long in the order of A, B, and C. A is the optical level when the optical fiber transmission line 301 is 120 km, B is the optical fiber transmission line of 83.5 km, and C is the optical fiber transmission line of 47 km. Even if the transmission output to the transmission line is constant at 5 dBm per wavelength, the section loss is different, so the optical input level at the optical fiber amplifier is -28 dBm for A, -18 dBm for B, and -8 dBm for C. In this embodiment, the optical input level is controlled so that the level of the optical monitor immediately after the variable optical attenuator 10 becomes constant. Therefore, at the entrance of the amplification optical fiber 40, the light level is always constant regardless of the section loss.
[0049]
Now, the optical output wavelength dependency at the time of the output constant control of the amplification optical fiber 40 corresponding to the wavelength multiplexing when the light input of this embodiment is directly input to the amplification optical fiber 40 without applying the control where the light input is constant is shown. Let us explain again with FIG. The wavelength dependence of the gain of the silica-based erbium-doped optical fiber 40 depends on the magnitude of the gain (ratio of optical input to optical output). For this reason, if the level of the input light by the variable optical attenuator 10 is not adjusted, the gain depending on the optical input level corresponding to the magnitude of the section loss changes as shown in A, B, and C of FIG. Have sex. For example, in the vicinity of 1533 nm, the change in output with respect to the change in light input is 3 dB (output change) / 10 dB (input change). From the section loss range, the dynamic range of the optical input is about 20 dB. For this reason, when the optical input is incident on the erbium-doped amplification optical fiber 40 as it is, an output change of 6 dB occurs for the signal light having a wavelength of 1533 nm.
[0050]
In the present embodiment, the dependency of the gain wavelength deviation on the optical input level with respect to the wavelengths of 1533 nm and 1541 nm is made constant by adjusting the attenuation amount of the optical attenuator on the optical input side.
[0051]
For example, when the section loss is 10 dB or 20 dB lower C and B, the input side optical attenuator is adjusted so that the optical input is always equivalent to 22 dB A, which is the largest section loss in the transmission path design. The loss is adjusted by an optical attenuator. This adjustment is automatically performed by feedback control from an optical monitor immediately after the variable optical attenuator 10. Thus, for example, in the case of C and B section loss, the attenuation of the variable optical attenuator 10 is adjusted to 13 dB and 3 dB. The total loss is 23 dB because the minimum attenuation of the variable optical attenuator 10 is 1 dB. By keeping the optical input level to the amplifying optical fiber 40 constant, there is no change in the optical input to the EDF with respect to the change in the transmission line section loss due to the section loss or the connection loss of the optical connector. Thus, it is possible to perform control without causing a gain wavelength deviation due to a difference in the light level 1 in FIG. Since the wavelength dependency of the gain at the low input A is particularly large at the wavelengths of 1533 nm and 1541 nm, the gain flattening filter 32 is inserted into the pre-stage optical amplifying unit 3 as an optical filter for flattening the wavelength dependency.
[0052]
Next, referring to FIG. 2, the variable optical attenuator 10 is controlled, the optical input monitor when the variable optical attenuator 10 is used, the optical input fluctuation detection for optical surge countermeasures, the optical input signal interruption detection, and the optical surge countermeasures. A function for performing the control will be described. FIG. 2 is a diagram illustrating a control configuration around the pre-amplifier variable optical attenuator.
[0053]
First, control of the variable optical attenuator 10 will be described. After the optical input passes through the variable optical attenuator 10, it enters the monitoring optical branching coupler 20 having a branching ratio of 95: 5, and part of the light is also branched for monitoring. The main signal light travels to the pump light / signal light combiner 30. The pumping light / signal light coupler 30 is superposed with the pumping light controlled by the pumping laser diode (LD) 130 and proceeds to the amplification optical fiber 40. For example, there is a multiplexer of 0.98 μm wavelength excitation light and 1.55 μm signal light. In the control of the optical input level, a signal obtained by converting the optical level received by the monitor photodiode (PD) 120 into an electrical signal is transmitted to the optical attenuator driving circuit 110 via the low-speed filter 116. The band on the low speed side of the optical amplification characteristic of fiber amplification is about 3 kHz. If the adjustment speed of the variable optical attenuator 10 is fast, there is a risk of narrowing the band on the low speed side and changing the level of the transmission waveform. Therefore, a low-speed filter of 1 kHz or less is set so as not to narrow the original low-speed band of the optical fiber amplifier. Thereby, 3 kHz which is a low-speed side band inherent in the amplification optical fiber 40 is not impaired by the control. The drive circuit 110 amplifies the difference compared with a predetermined optical input monitor value 111 and feeds it back to the variable optical attenuator 10. By performing control along the negative feedback route 3-1, the optical input becomes constant. The variable optical attenuator 10 and the optical branching coupler 20 have almost no wavelength dependency of loss in a necessary wavelength range, and for example, use a total of 0.5 dB or less.
[0054]
Next, an optical input monitor when the variable optical attenuator 10 is used will be described. Since the optical signal input 1 is adjusted by the variable optical attenuator 10, the monitor PD 20 cannot monitor the correct value. However, if the optical input monitor is placed in front of the variable optical attenuator 10, the optical loss increases, which is not desirable. In this embodiment, the optical attenuation amount of the variable optical attenuator 10 is obtained by converting from the drive current along the route 3-2.
[0055]
The drive signal of the variable optical attenuator 10 is detected by the drive value monitor 111 and converted into a digital signal by the A / D converter 112. The digital signal is converted into an analog signal by the D / A converter 115 again after the attenuation value calculation circuit 113 processes the drive value and the converted numerical value from the correction data memory 114 of the actual optical attenuation amount of the variable optical attenuator 10. The actual monitor value and the attenuation amount of the variable optical attenuator 10 are added by the adder 122 to obtain the optical signal input. For example, in the variable attenuator 10 based on the magneto-optical technique, the attenuation amount is not linear with respect to the drive current, but the relationship between the attenuation amount and the current is obtained in advance and the data is stored in the correction data memory 114 as a converted numerical value. At this time, since the magneto-optical effect type has temperature dependence, temperature monitoring and correction may be used. Here, the method of obtaining the attenuation amount of the variable optical attenuator 10 once by digital conversion is shown, but the point is to branch the monitor of the input of the optical signal input 1 by the process of adding the attenuation amount of the variable optical attenuator 10. It can be obtained without increasing the number.
[0056]
Next, optical input fluctuation detection and optical input signal break detection for optical surge countermeasures using an optical input monitor will be described. First, the detection operation route 3-3 without relative light input with respect to steady light input will be described. The monitor value of the optical signal input is transmitted to the optical input averaging circuit 123. The optical input averaging circuit 123 averages the optical signal input over a time of 100 ms or longer, for example, 1 second. The analog method can be configured by inserting a low-speed RC filter circuit and detecting a signal after low-speed optical / electrical conversion. The digital method can be configured by accumulating a sampling signal of a specific time, for example, 1 ms, and performing an averaging process by replacing old data with new data as time passes. At this time, sampling of 1 ms uses an optical signal input averaged within 1 ms.
[0057]
A function for performing control for countermeasure against optical surge when the optical input is reduced by a specific level with respect to the steady optical input will be described. In order to prevent optical surges from occurring during rapid optical input recovery, the optical surge countermeasure control suppresses optical excitation when the optical input drops so that the potential gain of the amplification optical fiber is not high. is necessary. In order to use an abnormal decrease in optical input as an input determination value, the input determination relative threshold is subtracted from the steady input by, for example, 6 dB to provide a determination reference value for no optical signal input. An actual stationary optical signal corresponds to a random signal form, and the optical level may fluctuate by about 3 dB even on the order of 10 μs. If the optical surge countermeasure control is operated during steady signal transmission, it greatly affects transmission traffic, so a margin of 6 dB or 9 dB is set. If the fluctuation is about 9 dB, an optical surge that causes fatal destruction does not occur. The relative input determination circuit 126 compares the actual optical signal input. When the optical signal input is low, the excitation suppression signal 132 is transmitted. This determination is made within 10 μs. By using the optical input monitor described above, an abnormal drop in relative optical input can be detected. An optical fiber amplifier is not necessarily used for a transmission line having a constant section loss. If no optical signal input is detected only by absolute value, steady optical input is high when the section loss is small, and excitation follows the level difference fluctuation even when the optical connector is attached or detached, etc., from low optical input to high optical input There is a risk of generating an optical surge during recovery. Further, when a plurality of optical fiber amplifiers are connected like a repeater, the optical surge light output propagates. Depending on the control method of the optical fiber amplifier, the optical surge light output may grow, and there is a risk of destroying the optical components at the relay destination. On the other hand, if this detection method is taken, an abnormal light fall is detected according to a use condition and excitation is suppressed, so that generation of an optical surge can be suppressed.
[0058]
Although the detection of the relative decrease in the optical input abnormality for the purpose of suppressing the optical surge has been described, the averaging process of the optical signal input employed in the present embodiment is an abnormal process with respect to the level change gently about the averaging time. Decline cannot be detected. For this reason, there is a concern that the optical input abnormality decrease cannot be detected in some cases against a decrease in the optical signal level which is impossible as a transmission path.
[0059]
Therefore, a decrease in the absolute level of the optical signal input is detected by the circuit of route 3-4. The absolute input value determination circuit 128 determines whether the monitor value of the optical signal input is higher or lower than the absolute input determination value 127. This generates a signal if the absolute value is too low to be possible. Since both the signal from the route 3-3 and the signal from the route 3-4 are dangerous for the occurrence of an optical surge, they are input to the drive circuit 131 of the excitation LD 130 by the OR logic 129 as the excitation suppression signal 132.
[0060]
In the above configuration, the method of processing the optical input monitor value based on the attenuation information from the variable optical attenuator has been described. However, in the configuration in which an optical branch is provided immediately after the optical input unit and the signal is used as the optical input monitor. Applicable.
[0061]
Next, optical output control and optical input attenuation adjustment control during wavelength multiplexing will be described.
[0062]
The light output control will be described with reference to FIG. FIG. 3 is a diagram showing the control of the post-amplifying unit 4 in particular of the two-stage amplification as an embodiment of a control method that combines the constant gain control and the constant optical output control based on the transmitted wavelength number information. .
[0063]
An optical signal from the amplification optical fiber 41 at the subsequent stage passes through the pumping light / signal optical multiplexing coupler 31, and a part of the light of the optical branching coupler 23 having a branching ratio of, for example, 99: 1 goes to the branching monitor PD170. An optical signal is emitted as an optical signal output 2.
[0064]
First, loop 4-1 which is constant gain control will be described. The optical output 2 converts the branched light into an electrical signal by the monitor PD 170 and transmits it to the gain calculation circuit 174. The gain calculation circuit 174 performs a division operation on the electrical signal value 121 of the optical signal input 1 and the electrical signal value of the optical signal output of the pre-stage optical amplifying unit 3. Thereby, the gain in the entire optical fiber amplifier 5 is obtained. The constant gain control unit 173 obtains a difference from the reference signal value of the gain and inputs it as a feedback signal to the drive circuit 181 of the excitation LD 180. Thus, the control loop 4-1 is configured so that a predetermined gain can be obtained. At this time, since there is no element for limiting the signal pass band of the amplification optical fiber 41 in the constant gain control, there is no problem even if the normal feedback control on the order of μs is performed. In addition, the drive circuit 181 performs a shut-off operation by the suppression signal 132 at the front stage or the rear stage.
[0065]
The optical output constant control 4-2 according to the wavelength number information of the latter-stage optical amplifying unit 4 will be described. The monitor signal of the optical signal output converted into an electric signal by the monitor PD 170 is transmitted to a circuit 171 for obtaining a constant output difference. The wavelength number information 210 separately input is compared 211 with the previous wavelength number information and the wavelength number information stored in the memory 212. The numerical value of the set value 213 of the optical output corresponding to the above is read out from another memory 214. This is set as the optical output 175 corresponding to the number of wavelengths defined by the D / A conversion 215. The set value 175 is compared with the constant output difference, and the gain is controlled by the control feedback 4-2 so that the difference disappears. In the control feedback 4-2, the low-frequency electric filter 172 is inserted so that the constant optical output control does not limit the band of the amplification optical fiber 41, so that the control is about 1 kHz or less. By combining the control of the loop 4-1 and the loop 4-2, the constant gain control works for a sudden change in the number of channels of 1 ms or less, and the decrease in the minimum light level per channel is suppressed.
[0066]
The optical output level corresponding to the number of wavelengths will be described. For example, when the number of wavelengths is increased from 1 to 16, in order to keep the optical output per wavelength channel constant, the output of the optical fiber amplifier including all 16 wavelengths must typically increase the optical output by 12 dB. Thus, the necessary light output corresponding to the number of wavelengths is stored in the memory, and the optimum light output is adjusted. As a simple example, when the number of wavelengths increases to 16, the total light output is increased by 12 dB.
[0067]
As for the optical input, the total optical input increases as the number of wavelengths input increases, so that the adjustment value of the optical level by the variable optical attenuator is increased according to the wavelength number information. As a simple example, when the number of wavelengths increases to 16, the optical level setting value at one wavelength is increased by 12 dB. As a result, the overall gain of the front and rear stages is always constant, and the wavelength flatness of the gain is maintained.
[0068]
A monitoring system is used to obtain the wavelength number information. When a repeater optical fiber amplifier is used, the operation state of the optical fiber amplifier is communicated with the main signal light by another optical signal. The information on the number of wavelengths to be transmitted is put on this monitoring signal, and the above-mentioned light output control is performed based on the information.
[0069]
The monitoring system will be briefly described with reference to FIG. FIG. 10 is a block diagram of a wavelength division multiplexing optical transmission system using the wavelength division multiplexing optical amplifier of the present invention. Sixteen optical signal transmitters 701 to 716 having different wavelengths are multiplexed into one optical fiber by a wavelength multiplexer WDM (Wavelength Division Multiplexer) 719. Thereafter, in order to obtain the required optical power, the light enters the optical power amplifier for transmission 720 and is amplified in a batch. The loss of the transmission line is compensated by the optical fiber amplifiers 724 and 726 for the relay through the transmission line 723. On the receiving side, the signals are amplified together by a receiving optical amplifier 729, separated by a WDDM (Wavelength Division Multiplexer) 731 and incident on a receiver 751-766 corresponding to each wavelength, and a signal of each wavelength is detected. In each of the wavelength multiplexing optical amplifiers 724, 726, and 729, dispersion dispersion fibers 725, 727, and 730 are inserted when the dispersion of the transmission line is large. These correspond to the optical component 50 of FIG. Regarding the transfer of the wavelength number information, for example, in the system configuration diagram of FIG. 10, information on the number of wavelengths is placed on the transmission light of the monitoring optical signal transmitter 721, and the wavelength multiplexing for the monitoring signal is placed behind the transmission optical power amplifier 720. A monitor optical signal is placed on the transmission line through the device WDM 722. Each of the repeater optical amplifiers 724 and 726 and the reception optical amplifier 729 receives the wavelength number information from the monitoring optical signal. Alternatively, the wavelength information is sent via another operation system network 771-774.
[0070]
If the wavelength number information and the actual wavelength number change timing do not match, there is a possibility that the optical output per channel cannot be secured when the wavelength number changes. Returning to FIG. 3 again, in this embodiment, the control speed of the constant output control loop 4-2 is set to a gradual change of 1 ms or more with respect to the constant gain control loop 4-1, thereby preventing an instantaneous output decrease. . Further, the control of the optical output loop 4-2 and the adjustment value of the variable optical attenuator 10 for optical input control are interlocked to control the overall gain of the entire optical amplifier to be constant.
[0071]
As another method of transmitting the number of wavelengths information, a modulation signal that does not affect the transmission signal of the main signal light is superimposed on the main signal light that is transmitted and modulated by the excitation laser, and the modulation signal is detected by the next optical amplifier Means are also conceivable.
[0072]
[Example 2]
A configuration in which an optical component is inserted in the middle of the two-stage optical fiber amplifier of Example 2 of the optical fiber amplifier according to the first embodiment of the present invention will be described with reference to FIG.
[0073]
FIG. 4 shows the configuration from the output monitoring branch 21 on the front stage of the two-stage configuration optical fiber amplifier 5 to the pump light / signal optical multiplexing coupler 22 on the rear stage. The light output level from the pre-stage optical amplifying unit 3 is determined by the level determination circuit 421 as to whether the light output is within a specified range after the monitor light is received by the monitor PD 420 and converted into an electric signal. The determination information is sent to the optical component removal determination circuit 422. Further, the optical input to the subsequent optical amplifying unit is separated into a part of light by the monitoring optical branching coupler 22 and enters the monitor PD 423. The level determination circuit 424 receives this monitor value, and determines whether or not the light level has reached the light input value that should be. For example, when the optical output level at the front stage is 0 dBm and the loss of the optical component is 10 dB, the optical input at the rear stage optical amplification unit is −10 dBm. At this time, if -15 dBm is set as the optical input determination value of the optical amplification unit at the subsequent stage, a signal is passed to the optical component removal determination 422 with the level determination at the subsequent stage as input when the optical input is -10 dBm. However, when the optical level from the optical component 50 is less than −15 dBm due to a poor optical connector connection, a signal indicating no optical input is sent to the optical component removal determination 422. In the optical output determination 421 in the previous stage, for example, when the optical output is -5 dBm or less, a signal higher than the optical output is passed to the optical component removal determination circuit 422. In the optical component extraction circuit 422, when the output of the optical amplification unit at the preceding stage is less than or equal to (−5 dBm), it is natural that there is no optical input at the subsequent stage, so that no extraction signal is transmitted. . It is determined that the optical component has been removed only when the light output of the previous stage is determined to be steady at a specified value (−5 dBm) or more and the light input of the subsequent stage is determined to be equal to or less than the specified value (−15 dBm), The optical component removal information 246 is given.
[0074]
Furthermore, when the optical signal input monitor at the rear stage determines that there is no optical input at a predetermined level or less, a signal 425 for suppressing the excitation at the rear stage is output in order to avoid the risk of optical surge. In the subsequent stage pumping control, this signal and the pumping suppression signal 132 from the optical input determination in the previous stage are taken by the OR logic 427 and input to the pumping drive circuit 181 of the subsequent stage amplifier. The pumping output of the pumping LD 180 is suppressed to a level that does not generate an optical surge. Further, the optical component removal information 246 masks the optical output signal decrease with respect to the optical output decrease signal at the subsequent stage if the AHD logic circuit 247 has the extraction information, and the output abnormality decrease signal 248 that is an inherent failure of the optical amplifier. To do. The present embodiment is a relay or reception-side pre-fiber amplifier that incorporates a dispersion compensating fiber having a loss of up to about 10 dB as the optical component 50.
[0075]
Examples of the optical component 50 used here include optical components that cause optical loss, such as dispersion compensating fibers, fiber gratings, and filters.
[0076]
[Example 3]
A configuration in which one pump is used for the two-stage amplifying unit of the optical fiber amplifier according to the third embodiment of the first embodiment of the present invention will be described with reference to FIG. In FIG. 5, the excitation light source is only in the control unit 100 in the previous stage. After exciting the amplification optical fiber 40 in the previous stage, the pumping light / signal light separator 33 separates the residual pumping light 35 from the signal light. The signal light goes to the signal light branch 21, but the residual pump light goes to the subsequent pump light / signal light coupler 34. It is combined with the signal light again and enters the subsequent amplification optical fiber 41. With this configuration, even if the intermediate optical component 50 is inserted with one excitation light source, the loss can be compensated efficiently. This basic configuration is shown in “Dispersion-Compensator-Incorporated Er-Doped Fiber Amplifier” described in the conventional example. In this configuration, a method for suppressing an optical surge when the optical component 50 is inserted and removed will be described. When the optical component 50 is not coupled, there is no light from the monitor branch 22 at the rear stage, and the light input interruption at the rear stage is detected. For example, when the loss of the optical component 50 is 5 dB, the loss of the fixed optical attenuator is 5 dB, and the optical output of the previous stage is 0 dBm, the light input cutoff level is set to −25 dBm. When the level is below this level, a pump laser suppression signal is sent from the post-stage control system 150 to the pre-stage control system. At this time, the control system 100 at the front stage controls the pump laser to pump the residual pump light 35 so as to suppress the optical surge from the amplification optical fiber at the rear stage so that no optical surge is generated when the optical component 50 is coupled. The input monitor branch 22 is controlled so as to emit light that can determine the coupling. The control is performed so that the level of the output light monitor branch 21 in the preceding stage becomes constant. For example, the optical output of the previous stage is controlled to be −10 dBm, which is 1/10 of the normal output. When the optical component 50 is appropriately coupled, the light level is -20 dBm in the example, so that the optical input break detection at the subsequent stage is -25 dBm or more, and the coupling is determined. At this time, the excitation control is switched so that the optical output of the optical output monitor branch 22 at the subsequent stage becomes constant.
[0077]
Examples of the optical component 50 used here include optical components that cause optical loss, such as dispersion compensating fibers, fiber gratings, and filters.
[0078]
[Example 4]
Example 4 of the optical fiber amplifier according to the first embodiment of the present invention will be described with reference to FIG. FIG. 8 shows an optical module mounting configuration. An example in which an optical component is mounted on a case 500 having a size of 120 mm × 165 mm is shown. This embodiment is an implementation example of the two-stage amplifier configuration of FIG. As optical components, optical level adjustment input unit variable optical attenuator 10, optical branching coupler + monitor PD + excitation light / signal optical multiplexing + optical isolator composite component 2030, erbium-doped optical fiber for the previous stage optical amplification unit 40, 41, (optical isolator + optical branching coupler + gain flattening filter + optical branching coupler) composite part 2132, (optical branching coupler + monitor PD + optical isolator) composite part 1122, erbium addition Fiber type optical components such as an optical fiber 41 for amplification and a composite component 2331 of (pumping light / signal optical multiplexer + optical isolator + optical branching coupler + gain flattening filter + monitor PD) are accommodated. At this time, by projecting each optical component from about 20 ° to about 45 ° with respect to the side of the case 500, the projection on the side of the optical composite component having a length of 70 mm is shortened. In this embodiment, one optical component having a length of 70 mm and a width of 25 mm, four optical components having a length of 70 mm and a width of 16 mm, and a bobbin wound with an amplification optical fiber having an outer diameter of 70 mm are placed in the box. Fit. If the interval between parts is 2 mm and the end space is 5 mm as the fiber route, the length direction is {5 + 70 (EDF bobbin) + (8 + 2 + 16 + 2 + 8) / sin (45 °) +35 (half part length) * sin (45 (°)) ) + (1−sin (45 °) * 30 (fiber bending space) +5} = 164 mm, the width direction is {5+ (1-cos (30 °)) * 30 (fiber bending space) + sin (30 °) * 70 (Optical component length) +10 (Space for fiber) + sin (45 °) * 70 (Optical component length) + (1-sin (45 °)) * 30 (Fiber bending space) +5} = 117 mm.
[0079]
Now, the case where parts are put in parallel for comparison is shown. The length direction is {5 + 70 (EDF bobbin) + 2 + 16 + 2 + 16 + 2 + 16 + 2 + 16 + 2 + 25 + 5} = 179 mm, and the width direction is {5 + 30 (fiber bending space) +70 (component bending space) +30 (fiber bending space) +5} = 140 mm. A space that is 15 mm wide and 23 mm wide is required.
[0080]
[Example 5]
[0081]
[Table 1]

Example 5 of the optical fiber amplifier according to the first embodiment of the present invention will be described with reference to Table 1 and FIG. Table 1 shows the pin arrangement of a commercially available 14-pin excitation laser module. There are four main types: A, B, C, and D types. The pump laser pins are TEC (Peltier element) positive and negative poles (TEC +, TEC-), laser diode drive anode and cathode (LD_A, LD_C), monitor photodiode anode and cathode (PA, PC) And thermistors for temperature monitoring (TR, TR). FIG. 9 is a diagram showing the relationship between the excitation laser module part of the wiring pattern of the substrate 640 and the pin arrangement of A of the excitation laser 600. In the substrate pattern, the TEC + control terminal 611, the TEC− control terminal 612, the PD cathode control terminal 615, the laser diode anode control terminal 616, the thermistor control terminal 617, the ground terminal 618, the PD cathode control terminal 619, the PD anode terminal 620, TEC−. The circuit end 621, laser diode control end 622, thermistor control end 623, thermistor connection end 625, ground 627, laser diode cathode control end 628, and PD anode end 629 are arranged as shown in FIG. By using a 0 ohm chip resistor, four types of pump laser pin connections can be handled. The notation shown inside is the pin arrangement of A of the excitation laser 600. Thermistor circuit input (TR) 613 and laser module No. 2 pin 602, monitor PD anode circuit input (PD_A) 614 and laser module No. 3 pin 603, laser diode anode control circuit input (LD_A) 626 and laser module Connection corresponding to the A type laser module by inserting a total of four 0 ohm chip resistors between the 10th pin 609, the laser diode cathode control circuit input (LD_C) 624 and the 11th pin 608 pad of the laser module Can be done. In this embodiment, it is assumed that one of the LD_A, PD_C, and thermistor (TR (G)) is always connected to the ground. It can cope with other types of laser modules by connecting 5 or less 0 ohm chip resistors.
[0082]
In this embodiment, an example in which a 0 ohm chip resistor is used has been described. This may be replaced by a jumper line with a pin instead of a bad.
[0083]
Further, the chip resistor pad may be a hole pad on which the pin of the laser module stands, and the insertion of the pin may be selected as a hole having a function corresponding to the pin arrangement.
[0084]
[Example 6]
Example 6 of the optical transmission system according to the second embodiment of the present invention will be described with reference to FIG.
[0085]
FIG. 10 shows a configuration of an optical transmission system using an optical repeater fiber amplifier capable of multiplexing up to 16 wavelengths.
[0086]
A case will be described in which multiplexing is performed with wavelengths up to n on the transmission side and the 16th wavelength channel. When the transmitters (Tx) 701 to 716 are set, the transmitter setting information 717 is displayed in the monitoring system (SV) 718. For example, when the n-th transmitter 70n is set, information on the total number of n wavelengths of the transmission channels up to n-1 and the 16th channel 716 is changed to n + 1. This information is immediately transmitted to an optical monitoring signal system (L-SV) 721. The signal light is subjected to signal wavelength multiplexing by a wavelength multiplexing signal optical multiplexing coupler 719 in the optical fiber transmission line 723 and is collectively amplified by a transmission optical amplifier 720.
[0087]
The monitoring signal is superimposed by the monitoring light / signal optical coupler 722 as monitoring signal light of another wavelength. The superimposed wavelength number information is detected by each of the repeater fiber amplifiers (LA) 724 and 726 and the reception optical fiber amplifier (RA) 729. The multiplexed main signal light is amplified while compensating for the dispersion amount by the optical fiber amplifiers 724, 726, and 729. After the signal is separated into each wavelength by the wavelength separator 731 in the receiving unit, the signal of each wavelength is optical. It is converted into an electrical signal by a signal receiver 751-766. After the information on the number of wavelengths is transmitted by the monitoring signal, each optical fiber amplifier gradually changes the optical output corresponding to the change in the number of channels and the internal setting in a specific time of several ms to several hundred ms. Thereby, the change of the state of each channel signal accompanying the change of the wavelength multiplexing number of the optical transmission system is suppressed, and the transmission quality of the entire system is maintained.
[0088]
Further, regarding the wavelength number information, not only the optical monitoring signal system but also another monitoring signal transmission system 771-774 can be used.
[0089]
By controlling the gain of the fast response of the optical fiber amplifier, even if the number of wavelengths fluctuates suddenly, the output fluctuation for each channel is small and there is no fluctuation with ripples. Can be configured.
[0090]
An optical fiber amplifier having a function of suppressing an abnormal peak output of light generated when recovering from an abnormal drop in optical input or when a dispersion compensator 725, 727, 730 such as a dispersion compensating optical fiber (DCF) is inserted or removed. Since the optical surge is suppressed by being used in the optical transmission system, the downstream optical repeater, the optical components 751-766 of the receiving apparatus, and the like accompanying the transmission of the optical surge generated upstream of the signal are prevented.
[0091]
Furthermore, by suppressing the frequency band of the optical attenuator inserted in the optical fiber amplifier for wavelength flattening to 1 kHz or less, even in the case of a signal at a transmission speed of 600 Mbit / s, there is no occurrence of low-frequency waveform distortion, and an optical transmission system. Can keep the quality. In particular, when the repeater is configured with an optical fiber amplifier, since the optical fiber amplifier is a 1R (Reshape) relay, the frequency characteristics are accumulated. Here, the wide frequency range means that the number of relays increases. However, an optical transmission system with low waveform deterioration can be configured.
[0092]
Further, each of the optical fiber amplifiers 720, 724, 726, and 729 may be any optical fiber amplifier described in another embodiment.
[0093]
【The invention's effect】
According to the present invention, it is possible to perform a general-purpose wavelength-multiplexed optical fiber amplifier that has less gain wavelength dependency and does not depend on transmission section loss or the number of wavelengths. It is possible to increase or decrease the number of wavelengths when operating an optical transmission system, thereby bringing flexibility to the system. Suppresses optical surges and improves the reliability of optical transmission systems that use optical fiber amplifiers. Informs the user of the presence or absence of the insertion of optical components and improves usability. Miniaturization can be achieved by high-density mounting of optical components. Various types of lasers can be used properly with a single substrate pattern, thereby reducing costs.
[Brief description of the drawings]
FIG. 1 is a diagram illustrating a configuration of a two-stage two-pumped optical fiber amplifier of an optical fiber amplifier according to a first embodiment of the present invention.
FIG. 2 is a diagram showing a control configuration around a variable amplifier at the front stage of the optical fiber amplifier according to the first embodiment of the present invention.
FIG. 3 is a diagram illustrating a configuration of an optical output control of a rear stage amplification unit of the optical fiber amplifier according to the first embodiment of the present invention.
FIG. 4 is a diagram illustrating a control configuration of an intermediate light insertion section of an optical fiber amplifier according to a second embodiment of the present invention.
FIG. 5 is a diagram showing a configuration of a post-stage use type optical fiber amplifier of residual pre-stage pumping light of an optical fiber amplifier according to a third embodiment of the present invention.
FIG. 6 is a diagram showing an optical level diagram when the transmission section loss of the optical fiber amplifier according to the first embodiment of the present invention is different.
FIG. 7 is a diagram for explaining the wavelength dependence of the optical output during the total output constant control.
FIG. 8 is a diagram illustrating a storage example of fiber type optical components of the optical fiber amplifier according to the fourth embodiment of the present invention.
FIG. 9 is a diagram illustrating an example of connecting a commercially available pump laser A type of the optical fiber amplifier according to the fifth embodiment of the present invention.
FIG. 10 is a diagram illustrating a configuration example of a wavelength division multiplexing optical transmission system according to a sixth embodiment of the present invention.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Optical signal input, 2 ... Optical signal output, 3 ... Pre-stage optical amplification part, 4 ... Rear stage optical amplification part, 5 ... Two-stage optical fiber amplifier, 10 ... Pre-stage input part variable optical attenuator, 11 ... Rear stage input part light Attenuator, 20: optical branch coupler for upstream input monitor, 21: optical branch coupler for upstream optical output monitor, 22: optical branch coupler for downstream optical input monitor, 23: optical branch coupler for downstream optical output monitor, 30: forward of front stage Pumping light / signal optical coupler for pumping 31... Backward pumping light / signal optical coupler for backward pumping, 33... 0.98 μm pumping light / signal optical separator, 34... 0.98 μm pumping light / signal optical multiplexing coupler 35... 0.98 μm residual pumping light at the front stage, 40... Optical fiber for the front stage amplification, 41... Optical fiber for the rear stage amplification, 50. Control circuit, 200... Supervisory control circuit, 20 ... Monitoring information including wavelength number information, 202 ... Monitoring information of two-stage optical fiber amplifier, 110 ... Variable attenuator driving circuit, 111 ... Variable attenuator driving value monitor, 112 ... A / D converter, 113 ... Attenuation calculation 114, attenuation correction data, 115, D / A converter, 116, low speed filter, 120, input monitor PD, 121, calculation derived light input monitor value, 122, adder, 123, averaging circuit, 124,. Relative determination reference value, 125 ... subtractor, 126 ... relative value input determination, 127 ... absolute value input determination value, 128 ... absolute value input determination, 129 ... OR logic circuit, 130 ... pre-excitation excitation LD, 131 ... excitation LD Drive circuit, 132 ... Excitation suppression signal, 133 ... Control signal from front stage light output control circuit, 170 ... Rear stage light output monitor, 171 ... Reference value / monitor value difference, 172 ... Low frequency filter 173 ... Gain constant control, 174 ... Gain calculation circuit, 175 ... Output reference value, 176 ... Output abnormality detection threshold, 177 ... Output abnormality determination, 178 ... Output abnormality signal, 180 ... Subsequent excitation LD, 181 ... Excitation LD drive circuit , 210 ... wavelength number information, 211 ... wavelength number information comparison, 212 ... previous wavelength number information, 213 ... wavelength number corresponding output, 214 ... wavelength number corresponding output data, 215 ... D / A converter, 216 ... wavelength number corresponding input Data, 217 ... Optical input reference value corresponding to the number of wavelengths of the latter stage optical amplification unit, 218 ... Optical input reference value corresponding to the number of wavelengths, 300 ... Optical fiber amplifier of the previous stage, 301 ... Optical fiber transmission of 120 km, 302 ... Optical fiber transmission path of 82 km , 303... 47 km optical fiber transmission line, 420... Pre-stage optical amplifier optical output monitor PD, 421... Level determination, 422. Optical amplification unit optical input monitor PD, 424... Level determination, 425... Excitation suppression signal, 426... Optical component removal information, 427... AND logic, 428. 2030... (Optical branching + pumping light / signal optical multiplexing combination + optical isolator + monitor PD) composite optical module, 2132... (Optical branch + gain flattening filter + optical isolator + monitor PD) composite optical module, 1122. + Optical isolator + monitor PD) composite optical module, 2331... (Pumping light / signal optical coupling + optical isolator + optical branching + monitor PD) composite optical module, 600 ... excitation laser module, 601 ... laser Peltier positive electrode pin, 602 ... thermistor Pin 603... PD anode pin 604. PD cathode pin 605. Thermistor pin 6 06 ... Laser Peltier negative pin, 607 ... Ground pin, 608 ... LD cathode pin, 609 ... Laser anode pin, 611 ... Laser Peltier drive positive output, 612 ... Laser Peltier drive negative output, 613 ... Thermistor connection, 614 ... PD anode control end, 615... PD cathode control end, 616... LD anode control end, 617... Thermistor ground side connection end, 618... PD cathode control end, 620 ... PD anode control end, 621. 622 ... LD anode control end, 623 ... Thermistor ground side connection end, 624 ... Laser cathode control end, 625 ... Thermistor connection end, 626 ... Laser anode control end, 627 ... Thermistor ground side connection end, 628 ... Laser cathode control end, PD anode control end, 701... Optical signal transmitter 1 ( Length 1), 702 ... Optical signal transmitter 2 (wavelength 2), 70n ... Optical signal transmitter n (wavelength n), 716 ... Optical signal transmitter 16 (wavelength 16), 717 ... Transmitter operation information, 718 ... Monitoring Signal system, 719... Wavelength multi-polymerization wave coupler, 720... Optical fiber amplifier for collective amplification transmission, 721... Monitoring signal transmitter, 722 ... Monitoring signal light / multiple signal optical multiplexing coupler, 723 ... Optical fiber transmission line, 724 ... optical repeater amplifier, 725 ... dispersion compensator, 726 ... optical repeater amplifier, 727 ... dispersion compensator, 729 ... optical fiber amplifier for collective amplification reception, 730 ... dispersion compensator, 731 ... multiple wavelength signal separator, 751 ... light Signal receiver 1 (wavelength 1), 752 ... Optical signal receiver 2 (wavelength 2), 75n ... Optical wavelength receiver n (wavelength n), 766 ... Optical signal receiver 16 (wavelength 16), 771-774 ... Management Signal system, A ... 1 0km optical fiber transmission line 301 the optical input level after transmission, B ... 82km optical fiber transmission line 302 the optical input level after transmission, C ... 47km optical fiber transmission line 303 the optical input level after transmission. 3-1 ... Variable optical attenuator control path, 3-2 ... Optical attenuation amount information path, 3-3 ... Relative light level decrease determination path, 3-4 ... Absolute light level decrease determination path, 4-1 ... Constant gain Control path, 4-2... Light output constant control path.

Claims (5)

A first rare earth-doped optical amplification fiber;
A second rare earth-doped optical amplification fiber connected downstream of the first rare earth-doped optical amplification fiber;
An excitation light source for exciting each of the first and second rare earth-doped optical amplification fibers;
An optical functional component that is freely inserted and removed between the first and second rare earth-doped optical amplification fibers;
An optical output monitor for monitoring the optical output power of the first rare earth-doped optical amplification fiber;
An optical input monitor unit for monitoring optical input power to the second rare earth-doped optical amplification fiber;
The optical power detected by the optical output monitor unit exceeds a predetermined first level value, and the optical power detected by the optical input monitor unit is converted into an optical signal by the optical functional component. In the case where it is equal to or lower than a second level value that is predetermined to be lower than the first level value based on the loss to be given, the intensity of the pumping light to the first and second rare earth-doped optical amplification fibers And a controller that suppresses optical surge from the second rare earth-doped optical amplification fiber when the optical functional component is inserted,
While the control unit suppresses the excitation light intensity, the optical input monitor unit causes the first rare earth-doped optical amplification fiber to suppress the excitation light intensity when the optical function component is inserted. When light intensity equal to or higher than a third level value preset to a value lower than the second level value based on the amount of decrease in optical output power from the rare earth-doped optical amplification fiber is detected, An optical fiber amplifier characterized by stopping suppression of the intensity of pumping light output to the first and second rare earth-doped optical amplification fibers. The optical fiber amplifier according to claim 1, wherein
An optical fiber amplifier, wherein the optical functional component is a dispersion compensation functional component. The optical fiber amplifier according to claim 2, wherein
An optical fiber amplifier, wherein the dispersion compensation functional component is a dispersion compensation fiber. The optical fiber amplifier according to claim 2, wherein
An optical fiber amplifier, wherein the dispersion compensation functional component has a dispersion compensation configuration including fiber grating. A first rare earth-doped optical amplification fiber;
A second rare earth-doped optical amplification fiber connected downstream of the first rare earth-doped optical amplification fiber;
An excitation light source for exciting each of the first and second rare earth-doped optical amplification fibers;
An optical functional component that is freely inserted and removed between the first and second rare earth-doped optical amplification fibers;
An optical output monitor for monitoring the optical output power of the first rare earth-doped optical amplification fiber;
An optical input monitor unit for monitoring optical input power to the second rare earth-doped optical amplification fiber;
The optical power detected by the optical output monitor unit exceeds a predetermined first level value, and the optical power detected by the optical input monitor unit is converted into an optical signal by the optical functional component. In the case where it is equal to or lower than a second level value that is predetermined to be lower than the first level value based on the loss to be given, the intensity of the pumping light to the first and second rare earth-doped optical amplification fibers Is suppressed to such an extent that no optical surge is generated from the second rare earth-doped optical amplification fiber when the optical functional component is inserted, and during the insertion, the optical input monitor unit causes the first rare earth element to be inserted when the optical functional component is inserted. Based on the amount of decrease in the optical output power from the first rare earth-doped optical amplification fiber accompanying the suppression of the excitation light intensity to the doped optical amplification fiber, the value is lower than the second level value. When detecting a third level or more values of the light intensity of which is determined, the optical fiber amplifier and a controller for stopping the suppression of the intensity of the pump light output to the first and second rare earth doped optical amplifying fiber When,
A signal light transmitter connected to the optical fiber amplifier by an optical transmission line;
An optical transmission system comprising a signal light receiver connected to the optical fiber amplifier by an optical transmission line.

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