JPWO2004088893A1 - Optical branching device - Google Patents

Optical branching device Download PDF

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JPWO2004088893A1
JPWO2004088893A1 JP2004570146A JP2004570146A JPWO2004088893A1 JP WO2004088893 A1 JPWO2004088893 A1 JP WO2004088893A1 JP 2004570146 A JP2004570146 A JP 2004570146A JP 2004570146 A JP2004570146 A JP 2004570146A JP WO2004088893 A1 JPWO2004088893 A1 JP WO2004088893A1
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signal light
optical
branching device
input signal
optical branching
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泉 横田
泉 横田
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Fujitsu Ltd
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    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04B—TRANSMISSION
    • H04B10/00—Transmission systems employing electromagnetic waves other than radio-waves, e.g. infrared, visible or ultraviolet light, or employing corpuscular radiation, e.g. quantum communication
    • H04B10/07—Arrangements for monitoring or testing transmission systems; Arrangements for fault measurement of transmission systems
    • H04B10/075—Arrangements for monitoring or testing transmission systems; Arrangements for fault measurement of transmission systems using an in-service signal
    • H04B10/077—Arrangements for monitoring or testing transmission systems; Arrangements for fault measurement of transmission systems using an in-service signal using a supervisory or additional signal
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04B—TRANSMISSION
    • H04B10/00—Transmission systems employing electromagnetic waves other than radio-waves, e.g. infrared, visible or ultraviolet light, or employing corpuscular radiation, e.g. quantum communication
    • H04B10/07—Arrangements for monitoring or testing transmission systems; Arrangements for fault measurement of transmission systems
    • H04B10/075—Arrangements for monitoring or testing transmission systems; Arrangements for fault measurement of transmission systems using an in-service signal
    • H04B10/079—Arrangements for monitoring or testing transmission systems; Arrangements for fault measurement of transmission systems using an in-service signal using measurements of the data signal
    • H04B10/0795—Performance monitoring; Measurement of transmission parameters
    • H04B10/07955—Monitoring or measuring power
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04J—MULTIPLEX COMMUNICATION
    • H04J14/00—Optical multiplex systems
    • H04J14/02—Wavelength-division multiplex systems
    • H04J14/0227—Operation, administration, maintenance or provisioning [OAMP] of WDM networks, e.g. media access, routing or wavelength allocation
    • H04J14/0241—Wavelength allocation for communications one-to-one, e.g. unicasting wavelengths
    • H04J14/0242—Wavelength allocation for communications one-to-one, e.g. unicasting wavelengths in WDM-PON
    • H04J14/0245—Wavelength allocation for communications one-to-one, e.g. unicasting wavelengths in WDM-PON for downstream transmission, e.g. optical line terminal [OLT] to ONU
    • H04J14/0246—Wavelength allocation for communications one-to-one, e.g. unicasting wavelengths in WDM-PON for downstream transmission, e.g. optical line terminal [OLT] to ONU using one wavelength per ONU
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04J—MULTIPLEX COMMUNICATION
    • H04J14/00—Optical multiplex systems
    • H04J14/02—Wavelength-division multiplex systems
    • H04J14/0201—Add-and-drop multiplexing
    • H04J14/0202—Arrangements therefor
    • H04J14/0204—Broadcast and select arrangements, e.g. with an optical splitter at the input before adding or dropping
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04J—MULTIPLEX COMMUNICATION
    • H04J14/00—Optical multiplex systems
    • H04J14/02—Wavelength-division multiplex systems
    • H04J14/0201—Add-and-drop multiplexing
    • H04J14/0202—Arrangements therefor
    • H04J14/0205—Select and combine arrangements, e.g. with an optical combiner at the output after adding or dropping
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04J—MULTIPLEX COMMUNICATION
    • H04J14/00—Optical multiplex systems
    • H04J14/02—Wavelength-division multiplex systems
    • H04J14/0201—Add-and-drop multiplexing
    • H04J14/0202—Arrangements therefor
    • H04J14/0206—Express channels arrangements
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04J—MULTIPLEX COMMUNICATION
    • H04J14/00—Optical multiplex systems
    • H04J14/02—Wavelength-division multiplex systems
    • H04J14/0227—Operation, administration, maintenance or provisioning [OAMP] of WDM networks, e.g. media access, routing or wavelength allocation
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04J—MULTIPLEX COMMUNICATION
    • H04J14/00—Optical multiplex systems
    • H04J14/02—Wavelength-division multiplex systems
    • H04J14/0278—WDM optical network architectures
    • H04J14/028—WDM bus architectures
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04J—MULTIPLEX COMMUNICATION
    • H04J14/00—Optical multiplex systems
    • H04J14/02—Wavelength-division multiplex systems
    • H04J14/0287—Protection in WDM systems
    • H04J14/0289—Optical multiplex section protection
    • H04J14/0291—Shared protection at the optical multiplex section (1:1, n:m)

Abstract

本発明は、波長多重信号光通信システムのトランク回線を波長多重信号光単位でブランチ回線に分岐する光分岐装置において、トランク回線からの入力信号光とブランチ回線からの入力信号光を合わせた信号光のパワーをモニタするモニタ手段と、モニタ手段で得た信号光パワーが閾値を上回ったときトランク回線からの入力信号光を減衰してブランチ回線からの入力信号光を出力し、モニタ手段で得た信号光パワーが閾値を下回ったときトランク回線からの入力信号光の減衰を解除して出力する切り替え手段を有するよう構成することにより、ガードバンドが不要で波長多重数を減少することなく、かつ、任意のブランチ回線の障害時に障害のない他のブランチ回線で通信を行うことができる。The present invention relates to an optical branching device that branches a trunk line of a wavelength division multiplexing optical signal communication system into a branch line in units of wavelength division multiplexed signal light, and combines the signal light from the trunk line and the input signal light from the branch line. A monitoring means for monitoring the power of the signal, and when the signal light power obtained by the monitoring means exceeds a threshold value, the input signal light from the trunk line is attenuated and the input signal light from the branch line is output and obtained by the monitoring means By configuring so as to have a switching means for releasing the attenuation of the input signal light from the trunk line and outputting it when the signal light power falls below the threshold, a guard band is unnecessary and the number of wavelength multiplexing is not reduced, and Communication can be performed on another branch line that does not have a failure when an arbitrary branch line fails.

Description

本発明は、光分岐装置に関し、特に、波長多重信号光通信システムで使用される光分岐装置に関する。  The present invention relates to an optical branching device, and more particularly to an optical branching device used in a wavelength division multiplexing optical communication system.

インターネットの普及などにより、ネットワークを介して伝送される情報の量が急激に増加してきており、伝送システムのさらなる大容量化が求められており、伝送システムの大容量化を実現する技術の１つとして、波長多重（ＷＤＭ：Ｗａｖｅｌｅｎｇｔｈ Ｄｉｖｉｓｉｏｎ Ｍｕｌｔｉｐｌｅｘ）光通信システムが実用化されている。波長多重信号光通信システムでは、光伝送路と光分岐装置と光中継器により複数の端局を結んでいる。
端局が少なくとも３つ以上ある波長多重信号光通信システムにおいて適用される光分岐装置の働きは、大きく２つに分けられる。一つは、中継器（光アンプ）への給電経路を切り替える働きであり、もう一つは信号光が伝送する経路を分ける働きである。後者の信号光の伝送経路を分ける構成として、二つが考えられる。一つは、信号光の伝送路である光ファイバ毎に経路を分ける構成（以降、「ファイバ分岐」と呼ぶ）であり、もう一つは、信号光波長毎にブランチ回線に伝送するかトランク回線に伝送するかを選択する波長選択分岐の構成（以降、「アッド／ドロップ分岐」と呼ぶ）である。
図１は、ファイバ分岐構成の一例の構成図を示す。同図中、端局１０はトランク回線の光ファイバペア１１，１２で光分岐装置１３に接続されている。光分岐装置１３では光ファイバペア１１で伝送される全ての信号光波長をトランク回線の光ファイバペア１４で光分岐装置１５に伝送し、光ファイバペア１２で伝送される全ての信号光波長をブランチ回線の光ファイバペア１６で端局１７に伝送する。また、端局１７からブランチ回線の光ファイバペア１８で伝送される全ての信号光波長は、光分岐装置１３を通してトランク回線の光ファイバペア２０から光分岐装置１５に伝送される。
光分岐装置１５ではトランク回線の光ファイバペア１４で伝送される全ての信号光波長をトランク回線の光ファイバペア２１で端局２２に伝送し、トランク回線の光ファイバペア２０で伝送される全ての信号光波長をブランチ回線の光ファイバペア２３で端局２４に伝送する。また、端局２４からブランチ回線の光ファイバペア２５で伝送される全ての信号光波長は、光分岐装置１５を通してトランク回線の光ファイバペア２６から端局２２に伝送される。上記の各トランク回線及びブランチ回線それぞれには中継器（光アンプ）が挿入接続されている。
図２は、アッド／ドロップ分岐構成の一例の構成図を示す。同図中、端局３０はトランク回線の光ファイバペア３１，３２で光分岐装置３３に接続されている。光分岐装置３３はファイバグレーティング（ＦＢＧ）及び光サーキュレータを有しており、光ファイバペア３２で伝送されている信号光波長のうち特定波長Ｂを分岐してブランチ回線の光ファイバペア３４で端局３５に伝送し、また、端局３５からブランチ回線の光ファイバペア３６で伝送される特定波長Ｂを上記特定波長以外の波長と合波してトランク回線３７で光分岐装置３８に伝送する。
また、光分岐装置３８も同様にファイバグレーティング及び光サーキュレータを有しており、トランク回線３７で伝送されている信号光波長のうち特定波長Ａを分岐してブランチ回線の光ファイバペア３９で端局４０に伝送し、また、端局４０からブランチ回線の光ファイバペア４１で伝送される特定波長Ａを上記特定波長以外の波長と合波してトランク回線の光ファイバペア４２，４３で端局４４に伝送する。上記の各トランク回線及びブランチ回線それぞれには中継器（光アンプ）が挿入接続されている。
なお、障害発生時に分岐すべき信号光の漏洩を防止する従来の光分岐挿入ノード装置として、特許文献１に記載のものがある。
特開２０００−３５４００６号公報 With the spread of the Internet and the like, the amount of information transmitted over a network has increased rapidly, and there is a demand for further increase in the capacity of the transmission system, which is one of the technologies for realizing an increase in capacity of the transmission system. A wavelength division multiplexing (WDM) optical communication system has been put into practical use. In a wavelength division multiplexing optical communication system, a plurality of terminal stations are connected by an optical transmission line, an optical branching device, and an optical repeater.
The function of the optical branching device applied in the wavelength division multiplexing optical communication system having at least three terminal stations is roughly divided into two. One is a function of switching a power feeding path to a repeater (optical amplifier), and the other is a function of dividing a path through which signal light is transmitted. There are two possible configurations for dividing the latter signal light transmission path. One is a configuration (hereinafter referred to as “fiber branching”) that divides the path for each optical fiber that is a transmission path for signal light, and the other is a trunk line that transmits to a branch line for each signal light wavelength. This is a configuration of wavelength selective branching (hereinafter referred to as “add / drop branching”) for selecting whether or not to transmit data.
FIG. 1 shows a configuration diagram of an example of a fiber branching configuration. In the figure, a terminal station 10 is connected to an optical branching device 13 through trunk line optical fiber pairs 11 and 12. The optical branching device 13 transmits all the signal light wavelengths transmitted by the optical fiber pair 11 to the optical branching device 15 by the optical fiber pair 14 of the trunk line, and branches all the signal light wavelengths transmitted by the optical fiber pair 12. The data is transmitted to the terminal station 17 through the optical fiber pair 16 of the line. All signal light wavelengths transmitted from the terminal station 17 through the branch line optical fiber pair 18 are transmitted from the trunk line optical fiber pair 20 to the optical branch device 15 through the optical branch device 13.
In the optical branching device 15, all signal light wavelengths transmitted through the trunk line optical fiber pair 14 are transmitted to the terminal station 22 through the trunk line optical fiber pair 21, and all signals transmitted through the trunk line optical fiber pair 20 are transmitted. The signal light wavelength is transmitted to the terminal station 24 via the branch line optical fiber pair 23. All signal light wavelengths transmitted from the terminal station 24 through the branch line optical fiber pair 25 are transmitted from the trunk line optical fiber pair 26 to the terminal station 22 through the optical branching device 15. A repeater (optical amplifier) is inserted and connected to each of the trunk lines and branch lines.
FIG. 2 shows a configuration diagram of an example of an add / drop branch configuration. In the figure, the terminal station 30 is connected to an optical branching device 33 by optical fiber pairs 31 and 32 of trunk lines. The optical branching device 33 has a fiber grating (FBG) and an optical circulator, branches a specific wavelength B out of the signal light wavelengths transmitted by the optical fiber pair 32, and is terminated by an optical fiber pair 34 of a branch line. The specific wavelength B transmitted from the terminal station 35 via the branch line optical fiber pair 36 is combined with a wavelength other than the specific wavelength and transmitted to the optical branching device 38 via the trunk line 37.
Similarly, the optical branching device 38 also has a fiber grating and an optical circulator, branches a specific wavelength A out of the signal light wavelength transmitted through the trunk line 37, and terminates at the branch line optical fiber pair 39. The specific wavelength A transmitted from the terminal station 40 through the branch line optical fiber pair 41 is combined with a wavelength other than the specific wavelength, and the trunk line optical fiber pairs 42 and 43 are used as the terminal station 44. Transmit to. A repeater (optical amplifier) is inserted and connected to each of the trunk lines and branch lines.
As a conventional optical add / drop node device for preventing leakage of signal light to be branched when a failure occurs, there is one described in Patent Document 1.
JP 2000-354006 A

図１に示すファイバ分岐構成において、２つのトランク回線の端局１０，２２と２つ以上のブランチ回線の端局１７，２４が存在する場合、通常は、少なくとも一つの光ファイバペア１１，２１はブランチ回線の端局１７，２４を介すことなく、二つのトランク回線の端局１０，２２を結ぶ構成をとる。それ以外の光ファイバペア１２は光分岐装置１３，１５毎にブランチ回線に分岐されてブランチ回線の端局１７，２４を結ぶ構成となる。また、ブランチ回線の端局１７，２４で、光ファイバペア内の一部の信号光波長Ａ，Ｂは通信せず、そのまま光分岐装置１３，１５に折り返す構成を考える。
この場合、ブランチ回線の光ファイバペア内の信号光波長Ａは、端局１０と端局１７、及び端局１７と端局２２を結び、信号光波長Ｂは端局１０と端局２４、及び端局２４と端局２２を結ぶ。
ここで、端局１７につながるブランチ回線の光ファイバペア１６，１８において障害が生じた場合、ブランチ回線１６，１８の光ファイバペアで伝送している全ての信号光がストップしてしまう。ブランチ回線の光ファイバペア１６，１８で伝送されている信号光波長Ａは端局１７との通信に関係しないのにもかかわらず、信号光波長Ａによる端局１０と端局２４間の伝送ができなくなるという問題があった。
図２に示すアッド／ドロップ分岐構成では、光分岐装置３３，３８内で端局３５，４０に必要な波長のみを選択して、ブランチ回線の光ファイバペア３４，３９に伝送する。このような構成により前述のファイバ分岐構成における問題は解決される。端局３５につながるブランチ回線の光ファイバペア３４，３６で障害が生じたときでも信号光波長Ａは端局３５につながるブランチ回線の光ファイバペア３４，３６を通らないため、上記障害に影響されずに端局３０と端局３５の通信は確保される。
近年、波長多重信号光通信システムでは、波長多重数を増やすために信号光波長間隔が狭めることが行われている。光分岐装置３３，３８内の波長選択を行っている図３に示すファイバグレーティング（ＦＢＧ）５０は、かなり急峻な光透過特性を有しており、例えば信号光波長間隔が１．０ｎｍ程度あれば十分に波長選択を行なえる。しかし、信号光波長間隔が０．４ｎｍ以下に狭まると、ファイバグレーティング５０で隣り合う信号光波長を充分に選択できなくなる。そのため、隣り合う信号光波長間にガードバンドＧＢを設ける必要が生じる。図２の例では、信号光波長ＡとＢ間にガードバンドＧＢが必要であり、決められた信号帯域内で波長多重数が少なくなるという問題が生じる。In the fiber branching configuration shown in FIG. 1, when there are two trunk line end stations 10 and 22 and two or more branch line end stations 17 and 24, normally, at least one optical fiber pair 11 and 21 is A configuration is adopted in which the terminal stations 10 and 22 of the two trunk lines are connected without passing through the terminal stations 17 and 24 of the branch line. The other optical fiber pairs 12 are branched into branch lines for each of the optical branching devices 13 and 15 to connect the branch stations 17 and 24. In addition, a configuration is considered in which branch signal terminals 17 and 24 do not communicate part of the signal light wavelengths A and B in the optical fiber pair and return them to the optical branching devices 13 and 15 as they are.
In this case, the signal light wavelength A in the branch line optical fiber pair connects the terminal station 10 and the terminal station 17, and the terminal station 17 and the terminal station 22, and the signal light wavelength B is in the terminal station 10 and the terminal station 24. The terminal station 24 and the terminal station 22 are connected.
Here, when a failure occurs in the branch line optical fiber pair 16, 18 connected to the terminal station 17, all signal light transmitted through the branch line 16, 18 optical fiber pair stops. Although the signal light wavelength A transmitted through the branch line optical fiber pairs 16 and 18 is not related to the communication with the terminal station 17, the signal light wavelength A can be transmitted between the terminal station 10 and the terminal station 24. There was a problem that it was impossible.
In the add / drop branching configuration shown in FIG. 2, only wavelengths necessary for the terminal stations 35 and 40 are selected in the optical branching devices 33 and 38 and transmitted to the optical fiber pairs 34 and 39 of the branch line. Such a configuration solves the above-described problems in the fiber branch configuration. Even when a failure occurs in the branch line optical fiber pair 34, 36 connected to the terminal station 35, the signal light wavelength A does not pass through the branch line optical fiber pair 34, 36 connected to the terminal station 35. Therefore, communication between the terminal station 30 and the terminal station 35 is ensured.
In recent years, in a wavelength division multiplexing optical signal communication system, in order to increase the number of wavelength multiplexing, the signal light wavelength interval is reduced. The fiber grating (FBG) 50 shown in FIG. 3 that performs wavelength selection in the optical branching devices 33 and 38 has a rather steep light transmission characteristic. For example, if the signal light wavelength interval is about 1.0 nm. The wavelength can be selected sufficiently. However, if the signal light wavelength interval is narrowed to 0.4 nm or less, the adjacent signal light wavelengths cannot be sufficiently selected by the fiber grating 50. Therefore, it is necessary to provide a guard band GB between adjacent signal light wavelengths. In the example of FIG. 2, a guard band GB is required between the signal light wavelengths A and B, which causes a problem that the number of wavelength multiplexing is reduced within a determined signal band.

本発明は、波長多重数を減少することなく、かつ、任意のブランチ回線の障害時に障害のない他のブランチ回線で通信を行うことができる光分岐装置を提供することを総括的な目的とする。
この目的を達成するため、本発明は、波長多重信号光通信システムのトランク回線を波長多重信号光単位でブランチ回線に分岐する光分岐装置において、前記トランク回線からの入力信号光と前記ブランチ回線からの入力信号光を合わせた信号光のパワーをモニタするモニタ手段と、前記モニタ手段で得た信号光パワーが閾値を上回ったとき前記トランク回線からの入力信号光を減衰して前記ブランチ回線からの入力信号光を出力し、前記モニタ手段で得た信号光パワーが閾値を下回ったとき前記トランク回線からの入力信号光の減衰を解除して出力する切り替え手段を有するよう構成される。
このような光分岐装置によれば、ガードバンドが不要で波長多重数を減少することなく、かつ、任意のブランチ回線の障害時に障害のない他のブランチ回線で通信を行うことができる。SUMMARY OF THE INVENTION It is a general object of the present invention to provide an optical branching device that can perform communication on another branch line that does not have a failure at the time of failure of an arbitrary branch line without reducing the number of wavelength multiplexing. .
In order to achieve this object, the present invention provides an optical branching device for branching a trunk line of a wavelength division multiplexing optical signal communication system into a branch line in units of wavelength division multiplexed signal light, from the input signal light from the trunk line and the branch line. Monitoring means for monitoring the power of the signal light combined with the input signal light, and when the signal light power obtained by the monitoring means exceeds a threshold value, the input signal light from the trunk line is attenuated to There is provided switching means for outputting the input signal light and releasing the attenuation of the input signal light from the trunk line when the signal light power obtained by the monitoring means falls below a threshold value.
According to such an optical branching device, a guard band is not required, and the number of wavelength multiplexing can be reduced, and communication can be performed on another branch line that does not have a failure when an arbitrary branch line fails.

図１は、ファイバ分岐構成の一例の構成図である。
図２は、アッド／ドロップ分岐構成の一例の構成図である。
図３は、アッド／ドロップ分岐構成の問題点を説明するための図である。
図４は、本発明の光分岐装置の第１実施例のブロック構成図である。
図５は、本発明の光分岐装置の変形例のブロック構成図である。
図６は、立上げ時の動作のフローチャートである。
図７は、立上げ時の動作を説明するためのヒステリシスコンパレータの特性図である。
図８は、ブランチ回線障害時の動作のフローチャートである。
図９は、ブランチ回線障害復旧時の動作のフローチャートである。
図１０は、ブランチ回線障害とブランチ回線障害復旧時の動作を説明するためのヒステリシスコンパレータの特性図である。
図１１は、本発明の光分岐装置での信号光波長数が４０波から１波に減設した時の出力波形図である。
図１２は、本発明の光分岐装置の他の変形例のブロック構成図である。
図１３は、コンパレータの特性図である。FIG. 1 is a configuration diagram of an example of a fiber branch configuration.
FIG. 2 is a configuration diagram of an example of an add / drop branch configuration.
FIG. 3 is a diagram for explaining a problem of the add / drop branch configuration.
FIG. 4 is a block diagram of the first embodiment of the optical branching device of the present invention.
FIG. 5 is a block diagram of a modification of the optical branching device of the present invention.
FIG. 6 is a flowchart of the operation at startup.
FIG. 7 is a characteristic diagram of a hysteresis comparator for explaining the operation at startup.
FIG. 8 is a flowchart of the operation when a branch line failure occurs.
FIG. 9 is a flowchart of the operation at the time of branch line failure recovery.
FIG. 10 is a characteristic diagram of a hysteresis comparator for explaining operations at the time of branch line failure and branch line failure recovery.
FIG. 11 is an output waveform diagram when the number of signal light wavelengths in the optical branching device of the present invention is reduced from 40 waves to one wave.
FIG. 12 is a block diagram of another modification of the optical branching device of the present invention.
FIG. 13 is a characteristic diagram of the comparator.

以下、本発明の実施例を図面に基づいて説明する。
図４は、本発明の光分岐装置の第１実施例のブロック構成図を示す。この光分岐装置６０は、光経路切換えを波長多重信号光単位で行うファイバ分岐構成である。
同図中、光分岐装置６０内にはトランク回線６１からの入力信号光（波長多重信号光）を２つに分岐する光分岐器６２が設けられている。その光分岐器６２の一方の出力は光パワー制御器６３に供給され、他方の出力はブランチ回線６４に伝送される。また、ブランチ回線６５からの入力信号光と先の光パワー制御器６３の出力は光分岐器６６に供給され、光分岐器６６の一方の出力はトランク回線６７に出力され、他方の出力はモニタ用の光−電気変換器６８に供給される。
光−電気変換器６８で光電変換された信号は増幅器６９で増幅されてヒステリシスコンパレータ７０に供給される。ヒステリシスコンパレータ７０には端子７１，７２から閾値ａ，ｂが供給されており、ヒステリシスコンパレータ７０は光電変換信号を上記閾値ａ，ｂと比較して制御信号を生成し、この制御信号で前述の光パワー制御器６３を制御する。
図５は、本発明の光分岐装置の変形例のブロック構成図を示す。図５に示す光分岐装置７４で、図４と異なる部分は、光分岐器６２，６６として光カプラ７５，７６を用い、光パワー制御器６３として光スイッチ７７を用い、光−電気変換器６８としてモニタＰＤ（フォトダイオード）７８を用い、光カプラ７６とフォトダイオード７８との間に光透過器７９を設けた点である。光透過器７９は、光分岐装置７４にブランチ回線６４，６５で接続される端局８０で折り返される信号光波長λａ帯域のみを透過する。これにより、モニタＰＤ７８に供給される信号光は端局８０で折り返す信号のみになる。
図５の光分岐装置７４における立上げ時の動作を図６のフローチャートを用いて説明する。また、図７に増幅器６９からヒステリシスコンパレータ７０に供給される信号レベルを示し、フローチャートのステップ番号を丸付き数字で示す。
給電立上げ時には、光スイッチ７７はオンとなっており（ステップＳ１）、トランク回線６１から入力された信号光は、光スイッチ７７を通りモニタＰＤ７８に供給され、また、ブランチ回線６５からの信号光もモニタＰＤ７８に供給される（ステップＳ２，Ｓ３）。これにより、増幅器６９からヒステリシスコンパレータ７０に供給される信号レベルは図７に示すように増大する。
増幅器６９からヒステリシスコンパレータ７０に供給される信号レベルが閾値ａを超えると、光スイッチ７７はオフに制御され（ステップＳ５）、モニタＰＤ７８にはブランチ回線６５からの信号光のみが供給されることになる。この状態が定常状態となる（ステップＳ６）。
次に、図５の光分岐装置７４におけるブランチ回線障害時とブランチ回線障害復旧時の動作を図８，図９のフローチャートを用いて説明する。また、図１０に増幅器６９からヒステリシスコンパレータ７０に供給される信号レベルを示し、フローチャートのステップ番号を丸付き数字で示す。
ブランチ回線６４，６５で障害が生じると、ブランチ回線６５からの信号光がなくなり（ステップＳ１１）、増幅器６９からヒステリシスコンパレータ７０に供給される信号レベルがヒステリシスコンパレータ７０の閾値ｂを超えて下がると（ステップＳ１２）、光スイッチ７７をＯＮに制御する（ステップＳ１３）。するとトランク回線６１から光スイッチ７７を通り、モニタＰＤ７８に信号光が入力され、定常状態になる（ステップＳ１４）。ブランチ回線６４に分岐されていた信号光がブランチ回線の障害により、ブランチ回線６４，６５の端局８０を経由せず、光分岐装置をスルーでトランク回線６７に伝送されるため、他の局へ影響を与えることはない。
ブランチ回線６４，６５における障害が復旧すると、ブランチ回線６５からの信号光が増加し（ステップＳ１５）、増幅器６９からヒステリシスコンパレータ７０に供給される信号レベルがヒステリシスコンパレータ７０の閾値ａを超えて上がると（ステップＳ１６）、光スイッチ７７をＯＦＦに制御する（ステップＳ１７）。するとブランチ回線６５から光スイッチ７７を通り、モニタＰＤ７８に信号光が入力され、定常状態になる（ステップＳ１８）。
このように、本発明の光分岐装置の基本的な構成は、光経路切換えを波長多重信号光単位で行うファイバ分岐構成であるため、アッド／ドロップ構成で問題となっていたガードバンドを設けるために波長多重数が減少することを解決できる。また、ブランチ回線６４，６５の障害時に他の回線への影響をなくすために、分岐装置６０内で信号光パワーをモニタすることでブランチ回線６４，６５の障害の有無を判別する。そして、ブランチ回線６４，６５の障害があれば信号光をブランチ回線からトランク回線に切り替えて出力し、ブランチ回線の障害がなければその逆の光経路切換えを自動的に行なう。波長多重信号光通信システムに、上記のような光分岐装置を適用することにより、波長多重数を減らすことなく、またブランチ回線の障害時に他の回線への影響をなくすことができる。
なお、図５の光分岐装置７４では光パワー制御器６３として光スイッチ７７を使用しているが、光減衰器を使用しても良い。また、モニタＰＤ７８の直前の光透過器７９は、ファイバグレーティング（ＦＢＧ）または光学膜でも良い。
図１１は、本発明の光分岐装置の他の変形例のブロック構成図を示す。図１１に示す光分岐装置８２で、図５と異なる部分は、トランク回線６１から供給される波長多重信号光のうち端局８０で折り返される信号光波長λａだけに周波数ｆａ（数ｋＨｚ〜数中ｋＨｚ）の微小信号を重畳（例えば振幅変調）しておき、モニタＰＤ７８の出力信号を周波数ｆａのみ通過させる帯域フィルタ（ＢＰＦ）８３を通して増幅器６９に供給する点である。この場合、光透過器７９は不要である。
図１２は、本発明の光分岐装置の第２実施例のブロック構成図を示す。この光分岐装置８５は、光経路切換えを波長多重信号光単位で行うファイバ分岐構成である。
同図中、図５と同一部分には同一符号を付す。図１２中、光分岐装置８５内ではトランク回線６１からの入力信号光（波長多重信号光）が光カプラ７５で２分岐され、一方の出力は光スイッチ７７に供給され、他方の出力はブランチ回線６４に伝送される。
また、ブランチ回線６５からの入力信号光は光カプラ８６で２分岐され、一方の出力は光スイッチ８７に供給され、他方の出力は光透過器７９に供給される。光透過器７９は、光分岐装置７４にブランチ回線６４，６５で接続される端局８０で折り返される信号光波長λａ帯域のみを透過し、モニタＰＤ７８では端局８０で折り返された信号のみを光電変換し増幅器６９を通してコンパレータ８８に供給する。
コンパレータ８８には端子８９から閾値ｃが供給されている。コンパレータ８８は図１３に示すように、光電変換信号を上記閾値ｃと比較して２値の制御信号を生成し、この制御信号で前述の光スイッチ７７，８７を制御する。光スイッチ７７は制御信号がローレベルでオン、ハイレベルでオフとなり、光スイッチ８７は制御信号がローレベルでオフ、ハイレベルでオンとなる。光スイッチ７７，８７それぞれの出力する信号光は光合成器９０で合成されてトランク回線６７に出力される。
この実施例では、ブランチ回線６４，６５の障害時に、光スイッチ８７がオフとなることで、ブランチ回線６５に中継器として設けられている光アンプ９１の発生ノイズがトランク回線６７に送出されることを防止できる。
なお、この実施例においても、トランク回線６１から供給される波長多重信号光のうち端局８０で折り返される信号光波長λａだけに周波数ｆａ（数ｋＨｚ〜数中ｋＨｚ）の微小信号を重畳（例えば振幅変調）しておき、モニタＰＤ７８の出力信号を周波数ｆａのみ通過させる帯域フィルタ８３を通して増幅器６９に供給し、光透過器７９を除去した構成とすることもできる。
このようにして、本発明の光分岐装置を波長多重信号光通信システムに適用することにより、波長多重数を減らすことなく、かつ、任意のブランチ回線の障害時に他の回線への影響をなくすことができる。
なお、光−電気変換器６８が請求項記載のモニタ手段に対応し、光パワー制御器６３，ヒステリシスコンパレータ７０が切り替え手段及び第１切り替え手段に対応し、光透過器７９がフィルタ手段に対応し、帯域フィルタ８３が周波数抽出手段に対応し、コンパレータ８８，光スイッチ７７が第１切り替え手段及び第１切り替え手段に対応し、コンパレータ８８，光スイッチ８７が第２切り替え手段に対応し、光スイッチ７７が第１光スイッチに対応し、光スイッチ８７が第２光スイッチに対応する。Embodiments of the present invention will be described below with reference to the drawings.
FIG. 4 is a block diagram of the first embodiment of the optical branching device of the present invention. This optical branching device 60 has a fiber branching configuration in which optical path switching is performed in units of wavelength multiplexed signal light.
In the figure, an optical branching device 62 for branching the input signal light (wavelength multiplexed signal light) from the trunk line 61 into two is provided in the optical branching device 60. One output of the optical branching device 62 is supplied to the optical power controller 63, and the other output is transmitted to the branch line 64. Also, the input signal light from the branch line 65 and the output of the optical power controller 63 are supplied to the optical branching unit 66, one output of the optical branching unit 66 is output to the trunk line 67, and the other output is monitored. Is supplied to an optical / electrical converter 68.
The signal photoelectrically converted by the photoelectric converter 68 is amplified by the amplifier 69 and supplied to the hysteresis comparator 70. The hysteresis comparator 70 is supplied with threshold values a and b from terminals 71 and 72, and the hysteresis comparator 70 compares the photoelectric conversion signal with the threshold values a and b to generate a control signal. The power controller 63 is controlled.
FIG. 5 shows a block diagram of a modification of the optical branching device of the present invention. The optical branching device 74 shown in FIG. 5 differs from FIG. 4 in that optical couplers 75 and 76 are used as the optical branching devices 62 and 66, an optical switch 77 is used as the optical power controller 63, and an optical-electrical converter 68. The monitor PD (photodiode) 78 is used, and a light transmitter 79 is provided between the optical coupler 76 and the photodiode 78. The optical transmitter 79 transmits only the signal light wavelength λa band that is turned back at the terminal station 80 connected to the optical branching device 74 through the branch lines 64 and 65. As a result, the signal light supplied to the monitor PD 78 is only the signal that returns at the terminal station 80.
The operation at startup in the optical branching device 74 of FIG. 5 will be described with reference to the flowchart of FIG. FIG. 7 shows the signal level supplied from the amplifier 69 to the hysteresis comparator 70, and step numbers in the flowchart are indicated by circled numbers.
At the start of power supply, the optical switch 77 is turned on (step S1), and the signal light input from the trunk line 61 is supplied to the monitor PD 78 through the optical switch 77, and the signal light from the branch line 65 is supplied. Is also supplied to the monitor PD 78 (steps S2 and S3). As a result, the signal level supplied from the amplifier 69 to the hysteresis comparator 70 increases as shown in FIG.
When the signal level supplied from the amplifier 69 to the hysteresis comparator 70 exceeds the threshold value a, the optical switch 77 is controlled to be turned off (step S5), and only the signal light from the branch line 65 is supplied to the monitor PD 78. Become. This state becomes a steady state (step S6).
Next, operations at the time of branch line failure and branch line failure recovery in the optical branching device 74 of FIG. 5 will be described with reference to the flowcharts of FIGS. FIG. 10 shows a signal level supplied from the amplifier 69 to the hysteresis comparator 70, and step numbers in the flowchart are indicated by circled numbers.
When a failure occurs in the branch lines 64 and 65, the signal light from the branch line 65 disappears (step S11), and the signal level supplied from the amplifier 69 to the hysteresis comparator 70 falls below the threshold value b of the hysteresis comparator 70 ( In step S12), the optical switch 77 is controlled to be ON (step S13). Then, the signal light is input from the trunk line 61 through the optical switch 77 to the monitor PD 78, and a steady state is obtained (step S14). Since the signal light branched to the branch line 64 is transmitted through the optical branching device through the trunk line 67 without passing through the terminal station 80 of the branch lines 64 and 65 due to the failure of the branch line, it is transmitted to other stations. There is no impact.
When the failure in the branch lines 64 and 65 is recovered, the signal light from the branch line 65 increases (step S15), and when the signal level supplied from the amplifier 69 to the hysteresis comparator 70 exceeds the threshold value a of the hysteresis comparator 70. (Step S16), the optical switch 77 is controlled to be OFF (Step S17). Then, signal light is input from the branch line 65 through the optical switch 77 to the monitor PD 78, and a steady state is reached (step S18).
As described above, since the basic configuration of the optical branching device of the present invention is a fiber branching configuration in which optical path switching is performed in units of wavelength multiplexed signal light, a guard band that has been a problem in the add / drop configuration is provided. It is possible to solve the problem that the wavelength multiplexing number decreases. Further, in order to eliminate the influence on the other lines when the branch lines 64 and 65 fail, the presence or absence of the failure of the branch lines 64 and 65 is determined by monitoring the signal light power in the branch device 60. If there is a failure in the branch lines 64 and 65, the signal light is switched from the branch line to the trunk line and output. If there is no failure in the branch line, the reverse optical path switching is automatically performed. By applying the optical branching device as described above to the wavelength division multiplexing optical communication system, it is possible to reduce the number of wavelength multiplexing and to eliminate the influence on other lines when a branch line fails.
5 uses the optical switch 77 as the optical power controller 63, but an optical attenuator may be used. Further, the light transmitter 79 immediately before the monitor PD 78 may be a fiber grating (FBG) or an optical film.
FIG. 11 shows a block diagram of another modification of the optical branching device of the present invention. The optical branching device 82 shown in FIG. 11 is different from FIG. 5 in that the frequency fa (several kHz to several) is included only in the signal light wavelength λa returned from the terminal station 80 among the wavelength multiplexed signal light supplied from the trunk line 61. (kHz) is superposed (for example, amplitude modulated) and supplied to the amplifier 69 through a band-pass filter (BPF) 83 that allows the output signal of the monitor PD 78 to pass only the frequency fa. In this case, the light transmitter 79 is unnecessary.
FIG. 12 shows a block diagram of a second embodiment of the optical branching apparatus of the present invention. This optical branching device 85 has a fiber branching configuration in which optical path switching is performed in units of wavelength multiplexed signal light.
In the figure, the same parts as those in FIG. In FIG. 12, in the optical branching device 85, the input signal light (wavelength multiplexed signal light) from the trunk line 61 is branched into two by the optical coupler 75, one output is supplied to the optical switch 77, and the other output is the branch line. 64.
Further, the input signal light from the branch line 65 is branched into two by the optical coupler 86, one output is supplied to the optical switch 87, and the other output is supplied to the light transmitter 79. The optical transmitter 79 transmits only the signal light wavelength λa band returned by the terminal station 80 connected to the optical branching device 74 through the branch lines 64 and 65, and the monitor PD 78 photoelectrically transmits only the signal returned by the terminal station 80. The signal is converted and supplied to the comparator 88 through the amplifier 69.
The threshold value c is supplied from the terminal 89 to the comparator 88. As shown in FIG. 13, the comparator 88 compares the photoelectric conversion signal with the threshold value c to generate a binary control signal, and controls the optical switches 77 and 87 with this control signal. The optical switch 77 is turned on when the control signal is at a low level and turned off when the control signal is at a high level. The optical switch 87 is turned off when the control signal is at a low level and turned on when the control signal is at a high level. The signal lights output from the optical switches 77 and 87 are combined by the optical combiner 90 and output to the trunk line 67.
In this embodiment, when the branch lines 64 and 65 fail, the optical switch 87 is turned off, so that the noise generated by the optical amplifier 91 provided as a repeater in the branch line 65 is sent to the trunk line 67. Can be prevented.
In this embodiment as well, a minute signal having a frequency fa (several kHz to several kHz) is superimposed only on the signal light wavelength λa returned from the terminal station 80 among the wavelength multiplexed signal light supplied from the trunk line 61 (for example, (Amplitude modulation), and the output signal of the monitor PD 78 is supplied to the amplifier 69 through the band-pass filter 83 that passes only the frequency fa, and the light transmitter 79 is removed.
In this way, by applying the optical branching apparatus of the present invention to a wavelength division multiplexing optical communication system, the number of wavelength multiplexing is not reduced, and the influence on other lines is eliminated when an arbitrary branch line fails. Can do.
The photoelectric converter 68 corresponds to the monitoring means described in the claims, the optical power controller 63 and the hysteresis comparator 70 correspond to the switching means and the first switching means, and the light transmitter 79 corresponds to the filter means. The band filter 83 corresponds to the frequency extraction means, the comparator 88 and the optical switch 77 correspond to the first switching means and the first switching means, the comparator 88 and the optical switch 87 correspond to the second switching means, and the optical switch 77. Corresponds to the first optical switch, and the optical switch 87 corresponds to the second optical switch.

Claims (9)

波長多重信号光通信システムのトランク回線を波長多重信号光単位でブランチ回線に分岐する光分岐装置において、
前記トランク回線からの入力信号光と前記ブランチ回線からの入力信号光を合わせた信号光のパワーをモニタするモニタ手段と、
前記モニタ手段で得た信号光パワーが閾値を上回ったとき前記トランク回線からの入力信号光を減衰して前記ブランチ回線からの入力信号光を出力し、前記モニタ手段で得た信号光パワーが閾値を下回ったとき前記トランク回線からの入力信号光の減衰を解除して出力する切り替え手段を有する光分岐装置。In an optical branching device that branches a trunk line of a wavelength division multiplexing optical communication system into branch lines in units of wavelength division multiplexing optical signals,
Monitoring means for monitoring the power of the signal light combining the input signal light from the trunk line and the input signal light from the branch line;
When the signal light power obtained by the monitoring means exceeds a threshold value, the input signal light from the trunk line is attenuated to output the input signal light from the branch line, and the signal light power obtained by the monitoring means is a threshold value An optical branching device having switching means for canceling the attenuation of the input signal light from the trunk line and outputting the signal when it falls below 請求項１記載の光分岐装置において、
前記トランク回線からの入力信号光と前記ブランチ回線からの入力信号光を合わせた信号光から、前記ブランチ回線に接続された端局で折り返す信号光波長を通過して前記モニタ手段に供給するフィルタ手段を有する光分岐装置。The optical branching device according to claim 1,
Filter means for supplying to the monitoring means a signal light wavelength that is turned back at a terminal connected to the branch line from a signal light obtained by combining the input signal light from the trunk line and the input signal light from the branch line An optical branching device. 請求項１または２記載の光分岐装置において、
前記切り替え手段は、前記モニタ手段で得た信号光パワーを第１閾値及び前記第１閾値より小さい第２閾値それぞれと比較して制御信号を生成するヒステリシス特性を持ったコンパレータと、
前記トランク回線からの入力信号光を供給されており、前記制御信号に従って導通／遮断し、前記導通時に前記トランク回線からの入力信号光を出力する光スイッチを有する光分岐装置。The optical branching device according to claim 1 or 2,
The switching means comprises a comparator having a hysteresis characteristic for generating a control signal by comparing the signal light power obtained by the monitoring means with a first threshold and a second threshold smaller than the first threshold;
An optical branching device having an optical switch which is supplied with input signal light from the trunk line, is turned on / off in accordance with the control signal, and outputs the input signal light from the trunk line when turned on. 請求項３記載の光分岐装置において、
前記光スイッチの代りに、前記制御信号に従って前記トランク回線からの入力信号光に対する減衰／減衰解除を行って出力する光減衰器を有する光分岐装置。The optical branching device according to claim 3, wherein
An optical branching device having an optical attenuator for outputting after performing attenuation / attenuation cancellation on input signal light from the trunk line in accordance with the control signal, instead of the optical switch. 請求項１記載の光分岐装置において、
前記トランク回線からの入力信号光のうち前記ブランチ回線に接続された端局で折り返す信号光波長にのみ所定周波数の信号が重畳されており、
前記モニタ手段の出力信号から前記所定周波数の成分を抽出して前記切り替え手段に供給する周波数抽出手段を有する光分岐装置。The optical branching device according to claim 1,
A signal having a predetermined frequency is superimposed only on the signal light wavelength that is turned back at the terminal station connected to the branch line among the input signal light from the trunk line,
An optical branching device comprising frequency extracting means for extracting the component of the predetermined frequency from the output signal of the monitoring means and supplying the extracted component to the switching means. 波長多重信号光通信システムのトランク回線を波長多重信号光単位でブランチ回線に分岐する光分岐装置において、
前記ブランチ回線からの入力信号光のパワーをモニタするモニタ手段と、
前記モニタ手段で得た信号光パワーが閾値を上回ったとき前記トランク回線からの入力信号光を減衰し、前記モニタ手段で得た信号光パワーが閾値を下回ったとき前記トランク回線からの入力信号光の減衰を解除する第１切り替え手段と、
前記モニタ手段で得た信号光パワーが閾値を上回ったとき前記ブランチ回線からの入力信号光の減衰を解除し、前記モニタ手段で得た信号光パワーが閾値を下回ったとき前記ブランチ回線からの入力信号光を減衰する第２切り替え手段と、
前記第１切り替え手段の出力する信号光と第２切り替え手段の出力する信号光を合波して出力する合波手段を有する光分岐装置。In an optical branching device that branches a trunk line of a wavelength division multiplexing optical communication system into branch lines in units of wavelength division multiplexing optical signals,
Monitoring means for monitoring the power of the input signal light from the branch line;
When the signal light power obtained by the monitoring means exceeds a threshold value, the input signal light from the trunk line is attenuated, and when the signal light power obtained by the monitoring means falls below a threshold value, the input signal light from the trunk line First switching means for canceling the attenuation of
When the signal light power obtained by the monitoring means exceeds a threshold, the attenuation of the input signal light from the branch line is canceled, and when the signal light power obtained by the monitoring means falls below the threshold, the input from the branch line A second switching means for attenuating the signal light;
An optical branching device having a multiplexing unit that combines the signal light output from the first switching unit and the signal light output from the second switching unit and outputs the combined signal light. 請求項６記載の光分岐装置において、
前記ブランチ回線からの入力信号光から、前記ブランチ回線に接続された端局で折り返す信号光波長を通過して前記モニタ手段に供給するフィルタ手段を有する光分岐装置。The optical branching device according to claim 6, wherein
An optical branching device having filter means for supplying to the monitoring means through signal light wavelength that is turned back at a terminal connected to the branch line from input signal light from the branch line. 請求項６または７記載の光分岐装置において、
前記第１，第２切り替え手段は、前記モニタ手段で得た信号光パワーを閾値と比較して制御信号を生成するコンパレータと、
前記トランク回線からの入力信号光を供給されており、前記制御信号に従って導通／遮断し、前記導通時に前記トランク回線からの入力信号光を前記合波手段に供給する第１光スイッチと、
前記トランク回線からの入力信号光を供給されており、前記制御信号に従って前記第１光スイッチの遮断時に導通して前記トランク回線からの入力信号光を前記合波手段に供給する出力する第２光スイッチを有する光分岐装置。The optical branching device according to claim 6 or 7,
The first and second switching means compare the signal light power obtained by the monitoring means with a threshold value to generate a control signal;
A first optical switch that is supplied with the input signal light from the trunk line, conducts / cuts off according to the control signal, and supplies the input signal light from the trunk line to the multiplexing means at the conduction time;
Second light that is supplied with the input signal light from the trunk line and that conducts when the first optical switch is shut off according to the control signal and supplies the input signal light from the trunk line to the multiplexing means An optical branching device having a switch. 請求項６記載の光分岐装置において、
前記トランク回線からの入力信号光のうち前記ブランチ回線に接続された端局で折り返す信号光波長にのみ所定周波数の信号が重畳されており、
前記モニタ手段の出力信号から前記所定周波数の成分を抽出して前記第１，第２切り替え手段に供給する周波数抽出手段を有する光分岐装置。The optical branching device according to claim 6, wherein
A signal having a predetermined frequency is superimposed only on the signal light wavelength that is turned back at the terminal station connected to the branch line among the input signal light from the trunk line,
An optical branching device comprising frequency extracting means for extracting the component of the predetermined frequency from the output signal of the monitoring means and supplying the extracted component to the first and second switching means.
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