JP2011024095A

JP2011024095A - Optical path fault searching device

Info

Publication number: JP2011024095A
Application number: JP2009168868A
Authority: JP
Inventors: Takao Tanimoto; 隆生谷本; Kimiaki Iwasaki; 王亮岩崎
Original assignee: Anritsu Corp
Current assignee: Anritsu Corp
Priority date: 2009-07-17
Filing date: 2009-07-17
Publication date: 2011-02-03
Anticipated expiration: 2029-07-17
Also published as: JP5130262B2

Abstract

<P>PROBLEM TO BE SOLVED: To detect a fault in a WDM-PON system connected via a branch with a wavelength fixed in the state of in-service. <P>SOLUTION: A signal light Pc that is conveyed on a common optical fiber path 17 of the WDM-PON system through a path coupler 21 is received, and its spectrum is detected by a signal light spectrum detection part 30. A control part 50 determines that a signal optical wavelength is a test wavelength on the basis of the spectrum detection result so long as it is a wavelength not conveyed on the common optical fiber path 17, and it instructs measurement using the test wavelength to a light reflection measurement part 40. The light reflection measurement part 40 puts the optical pulse Po of the test wavelength into the common optical fiber path 17 and receives a returned light Pr of the optical pulse Po from the WDM-PON system, and attains the transmission loss of an optical path between the common optical fiber path 17 and an individual optical fiber path 18 corresponding to the test wavelength. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

本発明は、ＷＤＭ−ＰＯＮ(Wavelength Division Multiplexing-Passive Optical Network)システムにおける局内のＯＬＴ(Optical Line
Terminal)側から光スプリッタ経由してユーザ宅側の各ＯＮＵ（Optical Network Unit）間の光ファイバ線路の障害検知を行う装置に関する。 The present invention relates to an OLT (Optical Line) in a station in a WDM-PON (Wavelength Division Multiplexing-Passive Optical Network) system.
The present invention relates to an apparatus for detecting a failure in an optical fiber line between each ONU (Optical Network Unit) on the user's home side from the terminal) via an optical splitter.

光アクセス・システムの高速化は著しく、この５年ほどの間に約１００倍程度の高速・広帯域化が実現され、さらなる高速化に向けた研究が行なわれている。 The speed of optical access systems has been remarkably increased, and about 100 times faster and wider bandwidth has been realized in the last five years, and research for further speedup is being conducted.

これを実現する技術としてＰＯＮが知られている。ＰＯＮは、光アクセス回線の途中に受動素子である分岐装置を挿入して、その分岐装置で複数に分岐された各ファイバを複数の加入者宅にそれぞれ引き込み、効率よく光ファイバ通信を行う技術である。 PON is known as a technology for realizing this. PON is a technology that performs optical fiber communication efficiently by inserting a branch device, which is a passive element, in the middle of an optical access line and drawing each fiber branched into a plurality of subscribers into a plurality of subscriber houses. is there.

ＰＯＮシステムは、局内終端装置のＯＬＴと各ユーザ宅のＯＮＵの間を、分岐装置を介して接続するものであり、ＯＬＴと複数のＯＮＵ間の分岐光線路を安価に監視することが要求されている。 The PON system connects the OLT of the in-station terminal device and the ONU of each user's house via a branch device, and is required to monitor the branch optical line between the OLT and a plurality of ONUs at low cost. Yes.

ＰＯＮシステムの１つにＷＤＭ−ＰＯＮがある。このＷＤＭ−ＰＯＮは、各ＯＮＵに異なる光波長を割り当てることによって光ファイバの共有を行うシステムである。この方式は１ユーザに対してそれぞれ１波長を割り当てるため、１０Ｇビット/秒超の高速化が可能と考えられている。 One of the PON systems is WDM-PON. This WDM-PON is a system for sharing an optical fiber by assigning different optical wavelengths to each ONU. Since this method assigns one wavelength to one user, it is considered that a speed exceeding 10 Gbit / sec is possible.

上記のＷＤＭ−ＰＯＮ方式のシステムを試験する技術として、特許文献１には、センタ装置からの共通光ファイバ線路を複数の加入者に割り当てられた個別光ファイバ線路に分岐するスターカップラの光加入者装置（ＯＮＵ）側の各入出力端に、それぞれの信号光の波長を透過し、試験光およびその反射光の波長については通過または遮断を切替可能なフィルタ手段（波長可変フィルタ）をそれぞれ挿入し、各光加入者装置の入出力端に、それぞれの信号光の波長を透過し、試験光については反射する波長選択反射手段（波長選択フィルタ）を設け、通信を行う個別光ファイバ線路のフィルタ手段は試験光遮断状態にし、試験を行う個別光ファイバ線路のフィルタ手段は試験光通過状態にして、センタ装置側の線路に接続された光反射測定装置（ＯＴＤＲ）からパルス状の試験光を入射し、その戻り光に基づいて個別光ファイバ線路毎の障害試験を行う技術が開示されている。 As a technique for testing the above-mentioned WDM-PON system, Patent Document 1 discloses an optical subscriber of a star coupler that branches a common optical fiber line from a center apparatus into individual optical fiber lines assigned to a plurality of subscribers. Filter means (wavelength variable filters) that transmit the wavelength of each signal light and can switch between passing and blocking the wavelength of the test light and its reflected light are inserted into each input / output terminal on the unit (ONU) side. In addition, wavelength selective reflection means (wavelength selective filter) that transmits the wavelength of each signal light and reflects the test light is provided at the input / output ends of each optical subscriber unit, and filter means for individual optical fiber line that performs communication Is the test light blocking state, the filter means of the individual optical fiber line to be tested is in the test light passing state, and the light reflection measuring device connected to the line on the center device side is set. Incident pulsed test light from (OTDR), a technique for fault testing of each individual optical fiber line on the basis of the return light is disclosed.

特許第３２５５２１４号公報Japanese Patent No. 3255214

前記特許文献１では、個別光ファイバ線路毎に波長可変フィルタを設ける必要があり、分岐数が膨大になると、それに応じて波長可変フィルタの数も増加し、コスト高になるという問題がある。 In Patent Document 1, it is necessary to provide a wavelength tunable filter for each individual optical fiber line. When the number of branches becomes enormous, the number of wavelength tunable filters increases accordingly, resulting in a high cost.

一方、ＷＤＭ−ＰＯＮシステムのうち、共通光ファイバ線路を複数の個別光ファイバ線路に分岐するための分岐手段として、複数の固定波長に分波できるＡＷＧ（Arrayed Waveguide Grating）を用いたものが多くあり、これに上記特許文献１のような試験システムを適用することが考えられるが、特許文献１の波長分岐部にＡＷＧを用いた場合、試験光波長を個別光ファイバ線路毎の信号光波長に合わせる必要があり、両者の波長が一致してしまうと、ＯＮＵ側で試験光のみを反射させることができず、信号光と試験光がＯＮＵに入射してしまい、通信の妨げとなり、インサービス状態での試験は困難となる。 On the other hand, many of the WDM-PON systems use AWG (Arrayed Waveguide Grating) capable of demultiplexing into a plurality of fixed wavelengths as a branching means for branching a common optical fiber line into a plurality of individual optical fiber lines. It is conceivable to apply a test system such as that of Patent Document 1 to this, but when AWG is used in the wavelength branching section of Patent Document 1, the test light wavelength is adjusted to the signal light wavelength for each individual optical fiber line. If both wavelengths match, the ONU side cannot reflect only the test light, the signal light and the test light enter the ONU, hindering communication, and in-service state. This test becomes difficult.

また、ＯＴＤＲを用いた光ファイバ線路の障害検知を行う際、ＯＮＵからセンタ装置（ＯＬＴ）側へ出射された信号光（Up stream信号光）が、試験光と混ざり、正しい測定が行えない。 In addition, when performing failure detection of an optical fiber line using OTDR, signal light (Upstream signal light) emitted from the ONU to the center device (OLT) side is mixed with test light, and correct measurement cannot be performed.

本発明は、上記課題を解決し、共通光ファイバ線路と個別光ファイバ線路の間をＡＷＧのような波長固定の分岐器を介して接続したＷＤＭ−ＰＯＮシステムの障害検知を、インサービスの状態で実現できる光線路障害探索装置を提供することを目的とする。 The present invention solves the above-described problem, and detects failure in a WDM-PON system in which a common optical fiber line and individual optical fiber lines are connected via a wavelength-fixed branching device such as an AWG in an in-service state. An object of the present invention is to provide an optical line fault searching device that can be realized.

前記目的を達成するために、本発明の請求項１の光線路障害探索装置は、
異なる複数の波長の信号光を合波して共通光ファイバ線路（１７）の一端に入射し、該共通光ファイバ線路を介して送られてくる光をその波長毎に分離して受信する電話局側光回線終端装置（１０）と、前記共通光ファイバ線路の他端側に接続され、前記電話局側光回線終端装置から送られてくる信号光を受けて、その波長に応じて分離し、波長毎に個別に設けられた個別光ファイバ線路（１８_１〜１８_ｎ）の一端へ入射させ、該各個別光ファイバ線路を介して送られてくる信号光を合波して前記共通光ファイバ線路へ出射する固定波長分波型の分岐器（１５）と、前記個別光ファイバ線路の他端側にそれぞれ接続された加入者側光回線終端装置（１６_１〜１６_ｎ）とを有するＷＤＭ−ＰＯＮシステムの光線路の障害を探索する光線路障害探索装置であって、
前記共通光ファイバ線路に接続された線路カプラ（２１）と、
前記線路カプラを介して前記共通光ファイバ線路を伝送する信号光を受け、そのスペクトラムを検出する信号光スペクトラム検出部（３０）と、
前記信号光スペクトラム検出部の検出結果に基づいて、前記共通光ファイバ線路を伝送していない信号光波長を調べ、該信号光波長を試験波長と決定する制御部（５０）と、
前記制御部によって決定された試験波長の光パルスを生成して、前記線路カプラを介して前記共通光ファイバ線路へ入射し、該光パルスに対する前記ＷＤＭ−ＰＯＮシステムからの戻り光を受光して、前記共通光ファイバ線路から試験波長に対応した個別光ファイバ線路に至る光路の伝送損失特性を求める光反射測定部（４０）とを備えたことを特徴とする。 In order to achieve the above object, an optical line fault searching device according to claim 1 of the present invention includes:
A telephone station that multiplexes signal lights of a plurality of different wavelengths to enter one end of a common optical fiber line (17), and separates and receives the light transmitted through the common optical fiber line for each wavelength. Side optical line terminator (10), connected to the other end of the common optical fiber line, receives signal light transmitted from the telephone station side optical line terminator, and separates it according to its wavelength, The common optical fiber line is made to enter one end of individual optical fiber lines (18 ₁ to 18 _n ) individually provided for each wavelength, and combine the signal lights transmitted through the individual optical fiber lines. WDM-PON having a branching unit (15) of a fixed wavelength demultiplexing type that emits to the optical fiber and a subscriber side optical line terminator (16 _{1 to} 16 _n ) connected to the other end of the individual optical fiber line, respectively. Optical line searching for obstacles in system optical line A harm search apparatus,
A line coupler (21) connected to the common optical fiber line;
A signal light spectrum detector (30) for receiving the signal light transmitted through the common optical fiber line via the line coupler and detecting its spectrum;
Based on the detection result of the signal light spectrum detection unit, a control unit (50) that examines the signal light wavelength not transmitted through the common optical fiber line, and determines the signal light wavelength as a test wavelength;
An optical pulse having a test wavelength determined by the control unit is generated, is incident on the common optical fiber line via the line coupler, receives a return light from the WDM-PON system for the optical pulse, And a light reflection measuring unit (40) for obtaining a transmission loss characteristic of an optical path from the common optical fiber line to an individual optical fiber line corresponding to a test wavelength.

また、本発明の請求項２の光線路障害探索装置は、請求項１記載の光線路障害探索装置において、
前記制御部は装置の動作モードを信号光スペクトラム検出モードと光反射測定モードにいずれかに指定する機能を有しており、
前記信号光スペクトラム検出部および前記光反射測定部が、
前記線路カプラに接続され、前記ＷＤＭ−ＰＯＮシステムが通信に用いる全ての信号光の波長範囲から指定された波長の光を選択的に且つ双方向に通過させる波長可変フィルタ（２２）と、
前記信号光スペクトラム検出モードが指定されているときには、前記波長可変フィルタの通過波長を、前記全ての信号光の波長を含む範囲で掃引させ、前記試験波長が決定されて光反射測定モードが指定されたときには、前記波長可変フィルタの通過波長を前記試験波長に設定する第１の波長コントローラ（２３）と、
前記波長可変フィルタに接続され、前記線路カプラおよび波長可変フィルタを介して入射された光を第１光路で受けて第２光路へ出射し、第３光路から入射された光を前記第１光路の前記波長可変フィルタへ出射するカプラ（２４）と、
前記カプラから前記第２光路へ出射された光を受けてその強度に応じた振幅をもつ電気の信号に変換する受光器（２５）と、
前記信号光スペクトラム検出モードが指定されているときに、前記受光器の出力信号と、前記第１の波長コントローラによって掃引される前記波長可変フィルタの通過波長とを対応付けして信号光スペクトラムとして記憶し、該信号光スペクトラムを前記制御部へ出力する信号光スペクトラム記憶手段（３１）と、
前記光反射測定モードが指定されているときに、前記全ての信号光の波長のいずれかの波長の光を出射する波長可変光源（４１）と、
前記波長可変光源から出射された光を受けて、光パルスを発生させ前記カプラの前記第３光路へ出射する光パルス発生手段（４４）と、
前記光反射測定モードが指定されているときに、前記試験波長に等しい波長の光を前記波長可変光源から出射させて、前記光パルス発生手段、前記カプラ、前記波長可変フィルタおよび前記線路カプラを介して前記ＷＤＭ−ＰＯＮシステムに入射させる第２の波長コントローラ（４２）と、
前記ＷＤＭ−ＰＯＮシステムに入射された光パルスに対する戻り光が、前記線路カプラ、前記波長可変フィルタ、前記カプラを介して前記受光器に入射されている間、前記受光器の出力信号を取得して、前記共通光ファイバ線路から試験波長に対応した個別光ファイバ線路に至る光路の伝送損失特性を求める伝送損失特性算出手段（４３）とにより、構成されていることを特徴とする。 Moreover, the optical line failure searching device according to claim 2 of the present invention is the optical line failure searching device according to claim 1,
The control unit has a function of designating the operation mode of the apparatus to either the signal light spectrum detection mode or the light reflection measurement mode,
The signal light spectrum detection unit and the light reflection measurement unit,
A wavelength tunable filter (22) that is connected to the line coupler and selectively and bidirectionally transmits light having a wavelength specified from a wavelength range of all signal light used for communication by the WDM-PON system;
When the signal light spectrum detection mode is designated, the pass wavelength of the wavelength tunable filter is swept within a range including all the signal light wavelengths, and the test wavelength is determined and the light reflection measurement mode is designated. A first wavelength controller (23) for setting the pass wavelength of the tunable filter to the test wavelength;
Light that is connected to the wavelength tunable filter and received through the line coupler and the wavelength tunable filter is received by the first optical path, emitted to the second optical path, and light incident from the third optical path is transmitted to the first optical path. A coupler (24) that emits light to the tunable filter;
A light receiver (25) that receives light emitted from the coupler to the second optical path and converts the light into an electric signal having an amplitude corresponding to the intensity;
When the signal light spectrum detection mode is designated, the output signal of the light receiver and the passing wavelength of the wavelength tunable filter swept by the first wavelength controller are associated and stored as a signal light spectrum. A signal light spectrum storage means (31) for outputting the signal light spectrum to the control unit;
A variable wavelength light source (41) that emits light of any one of the wavelengths of the signal light when the light reflection measurement mode is designated;
Optical pulse generating means (44) for receiving light emitted from the wavelength tunable light source, generating an optical pulse, and emitting the optical pulse to the third optical path of the coupler;
When the light reflection measurement mode is designated, light having a wavelength equal to the test wavelength is emitted from the wavelength tunable light source, and passes through the optical pulse generating means, the coupler, the wavelength tunable filter, and the line coupler. A second wavelength controller (42) incident on the WDM-PON system,
While the return light corresponding to the optical pulse incident on the WDM-PON system is incident on the optical receiver through the line coupler, the wavelength tunable filter, and the coupler, the output signal of the optical receiver is acquired. The transmission loss characteristic calculating means (43) for obtaining the transmission loss characteristic of the optical path from the common optical fiber line to the individual optical fiber line corresponding to the test wavelength is characterized in that it is constituted.

また、本発明の請求項３の光線路障害探索装置は、請求項１記載の光線路障害探索装置において、
前記信号光スペクトラム検出部と前記光反射測定部は、光スイッチ（２７）を介して前記線路カプラに選択的に接続されるようになっており、
前記光反射測定部は、
前記全ての信号光の波長範囲内で指定された波長の光を出射する波長可変光源（１４１）と、
前記制御部で決定された試験波長に等しい波長の光を前記波長可変光源から出射させる波長コントローラ（１４２）と、
前記波長可変光源から出射された光を２分岐する光分岐器（１４３）と、
前記光分岐器で分岐された一方の光を受け、光パルスを発生させる光パルス発生手段（１５３）と、
前記光パルスを第１光路で受けて第２光路から前記光スイッチおよび前記線路カプラを介して前記共通光ファイバ線路へ出射し、該光パルスに対する戻り光を前記第２光路から受けて第３光路へ出射させるカプラ（１４４）と、
前記光分岐器で分岐された他方の光の光周波数を、前記試験波長の近傍で且つ前記試験波長以外の信号光の光周波数と一致しない範囲で所定量（Δｆ）シフトさせる周波数シフタ（１４６）と、
前記カプラの前記第３光路から出射された戻り光と、前記周波数シフタからの出射光とを合波する合波器（１４７）と、
前記合波器から出射される光を受光する受光器（１４８）と、
前記受光器の出力信号から前記周波数シフタによる周波数のシフト量に等しい周波数のビート成分を抽出するバンドパスフィルタ（１４９）と、
前記バンドパスフィルタによって抽出されたビート成分の振幅を検出する検波器（１５０）と、
前記検波器の出力に基づいて、前記共通光ファイバ線路から試験波長に対応した個別光ファイバ線路に至る光路の伝送損失特性を求める伝送損失特性算出手段（１５２）とを備えていることを特徴とする。 Further, an optical line failure searching device according to claim 3 of the present invention is the optical line failure searching device according to claim 1,
The signal light spectrum detecting unit and the light reflection measuring unit are selectively connected to the line coupler via an optical switch (27),
The light reflection measuring unit is
A wavelength tunable light source (141) that emits light of a specified wavelength within the wavelength range of all the signal lights;
A wavelength controller (142) for emitting light having a wavelength equal to the test wavelength determined by the control unit from the wavelength variable light source;
An optical branching device (143) for branching the light emitted from the wavelength tunable light source into two;
An optical pulse generating means (153) for receiving one of the lights branched by the optical splitter and generating an optical pulse;
The optical pulse is received by the first optical path, is emitted from the second optical path to the common optical fiber line through the optical switch and the line coupler, and the return light for the optical pulse is received from the second optical path to the third optical path. A coupler (144) for emitting light to
A frequency shifter (146) that shifts the optical frequency of the other light branched by the optical splitter by a predetermined amount (Δf) in the vicinity of the test wavelength and in a range that does not coincide with the optical frequency of the signal light other than the test wavelength. When,
A combiner (147) for combining the return light emitted from the third optical path of the coupler and the emitted light from the frequency shifter;
A light receiver (148) that receives light emitted from the multiplexer;
A bandpass filter (149) for extracting a beat component having a frequency equal to the amount of frequency shift by the frequency shifter from the output signal of the light receiver;
A detector (150) for detecting the amplitude of the beat component extracted by the bandpass filter;
Transmission loss characteristic calculating means (152) for obtaining a transmission loss characteristic of an optical path from the common optical fiber line to an individual optical fiber line corresponding to a test wavelength based on the output of the detector; To do.

また、本発明の請求項４の光線路障害探索装置は、請求項１記載の光線路障害探索装置において、
前記信号光スペクトラム検出部と前記光反射測定部は、光スイッチ（２７）を介して前記線路カプラに選択的に接続されるようになっており、
前記光反射測定部は、
前記全ての信号光の波長範囲内で指定された波長の光を出射する波長可変光源（１４１）と、
前記制御部で決定された試験波長に対し、該試験波長の近傍で且つ前記試験波長以外の他の信号光波長と一致しない範囲で所定周波数（Δｆ）の差をもつ波長の光を前記波長可変光源から出射させる波長コントローラ（１４２）と、
前記波長可変光源から出射された光を２分岐する光分岐器（１４３）と、
前記光分岐器で分岐された一方の光を受け、光パルスを発生する光パルスを発生させる光パルス発生手段（１５３）と、
前記光パルスの光周波数を、前記所定周波数シフトさせて前記試験波長にする周波数シフタ（１４６）と、
前記周波数シフタから出射された前記試験波長の光パルスを第１光路で受けて第２光路から前記光スイッチおよび前記線路カプラを介して前記共通光ファイバ線路へ出射し、該光パルスに対する戻り光を前記第２光路から受けて第３光路へ出射させるカプラ（１４４）と、
前記カプラの前記第３光路から出射された戻り光と、前記光分岐器で分岐された他方の光パルスとを合波する合波器（１４７）と、
前記合波器から出射される光を受光する受光器（１４８）と、
前記受光器の出力信号から前記周波数シフタによる周波数のシフト量に等しい周波数のビート成分を抽出するバンドパスフィルタ（１４９）と、
前記バンドパスフィルタによって抽出されたビート成分の振幅を検出する検波器（１５０）と、
前記検波器の出力に基づいて、前記共通光ファイバ線路から試験波長に対応した個別光ファイバ線路に至る光路の伝送損失特性を求める伝送損失特性算出手段（１５２）とを備えていることを特徴とする。 Further, an optical line failure searching device according to claim 4 of the present invention is the optical line failure searching device according to claim 1,
The signal light spectrum detecting unit and the light reflection measuring unit are selectively connected to the line coupler via an optical switch (27),
The light reflection measuring unit is
A wavelength tunable light source (141) that emits light of a specified wavelength within the wavelength range of all the signal lights;
With respect to the test wavelength determined by the controller, light having a wavelength having a difference of a predetermined frequency (Δf) in the vicinity of the test wavelength and in a range that does not coincide with other signal light wavelengths other than the test wavelength is variable in wavelength. A wavelength controller (142) for emitting light from the light source;
An optical branching device (143) for branching the light emitted from the wavelength tunable light source into two;
An optical pulse generating means (153) for receiving one of the lights branched by the optical splitter and generating an optical pulse for generating an optical pulse;
A frequency shifter (146) for shifting the optical frequency of the optical pulse to the test wavelength by shifting the predetermined frequency;
The optical pulse of the test wavelength emitted from the frequency shifter is received by the first optical path, and is emitted from the second optical path to the common optical fiber line through the optical switch and the line coupler, and return light for the optical pulse is returned. A coupler (144) for receiving from the second optical path and emitting to the third optical path;
A multiplexer (147) for multiplexing the return light emitted from the third optical path of the coupler and the other optical pulse branched by the optical splitter;
A light receiver (148) that receives light emitted from the multiplexer;
A bandpass filter (149) for extracting a beat component having a frequency equal to the amount of frequency shift by the frequency shifter from the output signal of the light receiver;
A detector (150) for detecting the amplitude of the beat component extracted by the bandpass filter;
Transmission loss characteristic calculating means (152) for obtaining a transmission loss characteristic of an optical path from the common optical fiber line to an individual optical fiber line corresponding to a test wavelength based on the output of the detector; To do.

また、本発明の請求項５の光線路障害探索装置は、請求項１記載の光線路障害探索装置において、
前記信号光スペクトラム検出部と前記光反射測定部は、光スイッチ（２７）を介して前記線路カプラに選択的に接続されるようになっており、
前記光反射測定部は、
前記全ての信号光の波長範囲内で指定された波長の光を出射する波長可変光源（１４１）と、
前記制御部で決定された試験波長に対し、該試験波長の近傍で且つ前記試験波長以外の他の信号光波長と一致しない範囲で所定周波数（Δｆ）の差をもつ波長の光を前記波長可変光源から出射させる波長コントローラ（１４２）と、
前記波長可変光源から出射された光を２分岐する光分岐器（１４３）と、
前記光分岐器で分岐された一方の光の光周波数を、前記所定周波数シフトさせて前記試験波長にする周波数シフタ（１４６）と、
前記周波数シフタから出射された光を受け、前記試験波長の光パルスを発生させる光パルス発生手段（１５３）と、
前記光パルスを第１光路で受けて第２光路から前記光スイッチおよび前記線路カプラを介して前記共通光ファイバ線路へ出射し、該光パルスに対する戻り光を前記第２光路から受けて第３光路へ出射させるカプラ（１４４）と、
前記カプラの前記第３光路から出射された戻り光と、前記光分岐器で分岐された他方の光とを合波する合波器（１４７）と、
前記合波器から出射される光を受光する受光器（１４８）と、
前記受光器の出力信号から前記周波数シフタによる周波数のシフト量に等しい周波数のビート成分を抽出するバンドパスフィルタ（１４９）と、
前記バンドパスフィルタによって抽出されたビート成分の振幅を検出する検波器（１５０）と、
前記検波器の出力に基づいて、前記共通光ファイバ線路から試験波長に対応した個別光ファイバ線路に至る光路の伝送損失特性を求める伝送損失特性算出手段（１５２）とを備えていることを特徴とする。 Further, an optical line failure searching device according to claim 5 of the present invention is the optical line failure searching device according to claim 1,
The signal light spectrum detecting unit and the light reflection measuring unit are selectively connected to the line coupler via an optical switch (27),
The light reflection measuring unit is
A wavelength tunable light source (141) that emits light of a specified wavelength within the wavelength range of all the signal lights;
With respect to the test wavelength determined by the controller, light having a wavelength having a difference of a predetermined frequency (Δf) in the vicinity of the test wavelength and in a range that does not coincide with other signal light wavelengths other than the test wavelength is variable in wavelength. A wavelength controller (142) for emitting light from the light source;
An optical branching device (143) for branching the light emitted from the wavelength tunable light source into two;
A frequency shifter (146) that shifts the optical frequency of one of the lights branched by the optical splitter to the test wavelength by shifting the predetermined frequency;
Optical pulse generation means (153) for receiving light emitted from the frequency shifter and generating an optical pulse of the test wavelength;
The optical pulse is received by the first optical path, is emitted from the second optical path to the common optical fiber line through the optical switch and the line coupler, and the return light for the optical pulse is received from the second optical path to the third optical path. A coupler (144) for emitting light to
A combiner (147) for combining the return light emitted from the third optical path of the coupler and the other light branched by the optical splitter;
A light receiver (148) that receives light emitted from the multiplexer;
A bandpass filter (149) for extracting a beat component having a frequency equal to the amount of frequency shift by the frequency shifter from the output signal of the light receiver;
A detector (150) for detecting the amplitude of the beat component extracted by the bandpass filter;
Transmission loss characteristic calculating means (152) for obtaining a transmission loss characteristic of an optical path from the common optical fiber line to an individual optical fiber line corresponding to a test wavelength based on the output of the detector; To do.

上記のように、本発明の請求項１の光線路障害探索装置は、線路カプラを介して共通光ファイバ線路を伝送する信号光を受け、そのスペクトラムを検出し、その検出結果に基づいて、共通光ファイバ線路を伝送していない信号光波長があれば、それを試験波長と決定して、その試験波長の光パルスをＷＤＭ−ＰＯＮシステムの共通光ファイバ線路へ入射し、その光パルスに対するＷＤＭ−ＰＯＮシステムからの戻り光を受光して、共通光ファイバ線路から試験波長に対応した個別光ファイバ線路に至る光路の伝送損失特性を求めている。 As described above, the optical line fault searching device according to claim 1 of the present invention receives signal light transmitted through a common optical fiber line via a line coupler, detects its spectrum, and based on the detection result, If there is a signal light wavelength that is not transmitted through the optical fiber line, it is determined as the test wavelength, and an optical pulse of the test wavelength is incident on the common optical fiber line of the WDM-PON system. A return loss characteristic of an optical path from the common optical fiber line to the individual optical fiber line corresponding to the test wavelength is obtained by receiving the return light from the PON system.

このため、たとえ、ＷＤＭ−ＰＯＮシステムの分岐数が膨大になってもコスト高を招くことなく、その障害検知をインサービスの状態で実現できる。 For this reason, even if the number of branches of the WDM-PON system becomes enormous, the failure detection can be realized in an in-service state without incurring high costs.

また、請求項２の構成のものでは、信号光スペクトラム検出部３０と光反射測定部４０を構成する各要素のうち、波長可変フィルタ、第１の波長コントローラ、カプラ、受光器を共用しているので、極めて簡易な構成でさらに低コストに実現できる。 In the configuration of claim 2, among the elements constituting the signal light spectrum detection unit 30 and the light reflection measurement unit 40, the wavelength variable filter, the first wavelength controller, the coupler, and the light receiver are shared. Therefore, it can be realized at a lower cost with a very simple configuration.

また、請求項３〜５のように光反射測定部をヘテロダイン型にしたものでは、光ファイバ線路へ出射した光パルスと、ローカル光との周波数差に等しいビート成分の振幅を検出するので、受光素子の直流バイアスの変動等の影響を受けることなく光ファイバ線路の伝送損失特性を正確に且つ安定に求めることができる。 Further, in the case where the light reflection measuring unit is a heterodyne type as in claims 3 to 5, since the amplitude of the beat component equal to the frequency difference between the light pulse emitted to the optical fiber line and the local light is detected, The transmission loss characteristic of the optical fiber line can be obtained accurately and stably without being affected by fluctuations in the DC bias of the element.

本発明の基本構成を示す図The figure which shows the basic composition of this invention 信号光スペクトラム検出部の動作を説明するためのスペクトラム図Spectrum diagram for explaining the operation of the signal light spectrum detector 光反射測定部の動作を説明するための信号波形図Signal waveform diagram for explaining the operation of the light reflection measurement unit 信号光スペクトラム検出部と光反射測定部のより具体的な構成例を示す図The figure which shows the more concrete structural example of a signal light spectrum detection part and a light reflection measurement part. 光反射測定部の別の構成例を示す図The figure which shows another structural example of a light reflection measurement part. 光反射測定部の別の構成例を示す図The figure which shows another structural example of a light reflection measurement part. 光反射測定部の別の構成例を示す図The figure which shows another structural example of a light reflection measurement part.

以下、図面に基づいて本発明の実施の形態を説明する。
図１は、ＷＤＭ−ＰＯＮシステムと本発明を適用した光線路障害探索装置２０の基本構成を示している。 Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 shows a basic configuration of a WDM-PON system and an optical line fault searching apparatus 20 to which the present invention is applied.

試験対象のＷＤＭ−ＰＯＮシステムは、ＯＬＴ（電話局側光回線終端装置）１０、前記ＡＷＧで代表される固定波長分波型の分岐器１５、複数のＯＮＵ１６_１〜１６_ｎ（加入者側光回線終端装置）、ＯＬＴ１０と分岐器１５の間を接続する単一の共通光ファイバ線路１７、分岐器１５と各ＯＮＵ１６_１〜１６_ｎとの間をそれぞれ個別に接続する個別光ファイバ線路１８_１〜１８_ｎにより構成されている。 The WDM-PON system to be tested includes an OLT (telephone station side optical line terminating device) 10, a fixed wavelength demultiplexing type branching device 15 represented by the AWG, and a plurality of ONUs 16 _{1 to} 16 _n (subscriber side optical lines). Termination device), a single common optical fiber line 17 connecting between the OLT 10 and the branching device 15, and individual optical fiber lines 18 ₁ to 18 connecting individually between the branching device 15 and the ONUs 16 _{1 to} 16 _n. _n .

ここで、ＯＬＴ１０は、それぞれ異なる波長λ_１〜λ_ｎの信号光を送受信する複数の送受信器１１_１〜１１_ｎと、送受信器１１_１〜１１_ｎからの信号光を合波して共通光ファイバ線路１７に出射し、共通光ファイバ線路１７からの光を前記波長毎に分波して、対応波長の送受信器１１_１〜１１_ｎにそれぞれ与えるＡＷＧのような固定波長分波型の分岐器１２により構成されている。 Here, the OLT ₁₀ combines a plurality of transceivers 11 _{1 to} 11 _n that transmit and receive signal lights having different wavelengths λ _{1 to} λ _n and signal lights from the transceivers 11 _{1 to} 11 _n to share a common optical fiber. A fixed wavelength demultiplexing type branching device 12 such as an AWG that emits light to the line 17 and demultiplexes the light from the common optical fiber line 17 for each wavelength and supplies the demultiplexed light to the transceivers 11 _{1 to} 11 _n having the corresponding wavelengths. It is comprised by.

この分岐器１２で波長多重された光は、共通光ファイバ線路１７を経て分岐器１５に入射される。 The light wavelength-multiplexed by the branching device 12 enters the branching device 15 through the common optical fiber line 17.

分岐器１５は分岐器１２と同一構成であり、ＯＬＴ１０側から入射された光を各波長λ_１〜λ_ｎの信号光に分け、その波長に割り当てられた個別光ファイバ線路１８_１〜１８_ｎへ出射し、ＯＮＵ１６_１〜１６_ｎにそれぞれ与える。また、ＯＮＵ１６_１〜１６_ｎから出射された信号光を、個別光ファイバ線路１８_１〜１８_ｎを介して受け、これを合波して共通光ファイバ線路１７へ出射する。 The branching unit 15 has the same configuration as that of the branching unit 12 and divides the light incident from the OLT 10 side into signal lights of the respective wavelengths λ _{1 to} λ _n and to the individual optical fiber lines 18 ₁ to 18 _n assigned to the wavelengths. The light is emitted and given to the ONUs 16 _{1 to} 16 _n , respectively. In addition, the signal light emitted from the ONUs 16 _{1 to} 16 _n is received via the individual optical fiber lines 18 ₁ to 18 _n , combined, and emitted to the common optical fiber line 17.

このＷＤＭ−ＰＯＮシステムの試験を行うための光線路障害探索装置２０は、共通光ファイバ線路１７に接続され、ＯＮＵ側からの信号光を分岐して光線路障害探索装置２０内へ入射させ、反射測定用の試験光をＯＮＵ方向へ入射させる線路カプラ２１、信号光スペクトラム検出部３０、光反射測定部（ＯＴＤＲ：Optical Time Domain Reflectmeter）４０および制御部５０を有している。 The optical line fault searching device 20 for testing this WDM-PON system is connected to the common optical fiber line 17, splits the signal light from the ONU side, enters the optical line fault searching device 20, and reflects it. It has a line coupler 21 that makes test light for measurement incident in the ONU direction, a signal light spectrum detector 30, an optical reflection measurement unit (OTDR: Optical Time Domain Reflectmeter) 40, and a controller 50.

信号光スペクトラム検出部３０は、線路カプラ２１を介して共通光ファイバ線路１７から入射される信号光Ｐｃに対するスペクトラム検出を行うものである。 The signal light spectrum detector 30 performs spectrum detection on the signal light Pc incident from the common optical fiber line 17 via the line coupler 21.

また、光反射測定部４０は波長可変型のＯＴＤＲであり、線路カプラ２１を介して共通光ファイバ線路１７へ試験波長の光パルスＰｏを出射し、その光パルスＰｏに対して共通光ファイバ線路１７および個別光ファイバ線路１８_１〜１８_ｎから戻ってくる戻り光Ｐｒ（レイリー散乱光、フレネル反射光）を受光し、その受光信号の時間経過に伴うレベル変化の波形を求めて、その平均化処理などによって、試験用の光パルスが通過したファイバ線路の伝送損失特性を求める。 The light reflection measuring unit 40 is a wavelength-tunable OTDR, and emits a test wavelength optical pulse Po to the common optical fiber line 17 via the line coupler 21, and the common optical fiber line 17 with respect to the optical pulse Po. Then, the return light Pr (Rayleigh scattered light, Fresnel reflected light) returning from the individual optical fiber lines 18 ₁ to 18 _n is received, and the waveform of the level change with the passage of time of the received light signal is obtained, and the averaging process is performed. Thus, the transmission loss characteristic of the fiber line through which the test optical pulse has passed is obtained.

なお、信号光スペクトラム検出部３０と光反射測定部４０の具体的な構成例については後述するが、両者が光学系を共有している場合があるので、ここでは理解しやすいように、信号光スペクトラム検出部３０と光反射測定部４０の機能を分離して示している。 A specific configuration example of the signal light spectrum detection unit 30 and the light reflection measurement unit 40 will be described later. However, since both may share an optical system, the signal light is easy to understand here. The functions of the spectrum detection unit 30 and the light reflection measurement unit 40 are shown separately.

制御部５０は、信号光スペクトラム検出部３０の検出結果に基づいて、光反射測定部４０による測定を行う。 The control unit 50 performs measurement by the light reflection measurement unit 40 based on the detection result of the signal light spectrum detection unit 30.

例えば、信号光スペクトラム検出部３０によるスペクトル検出結果が、図２の（ａ）のように全ての信号光波長λ_１〜λ_ｎの位置に所定レベル以上のスペクトラムＳ_１〜Ｓ_ｎが定常的に存在している場合には、光反射測定を行わない。 For example, the spectrum detection result by the signal light spectrum detection unit 30 indicates that the spectrums S _{1 to} S _n of a predetermined level or higher are constantly present at all signal light wavelengths λ _{1 to} λ _n as shown in FIG. If present, no light reflection measurement is performed.

しかし、スペクトラム検出結果が、図２の（ｂ）のように、例えば信号光波長λ_２の位置のスペクトラムＳ_２が所定時間以上連続して存在しない場合には、この信号光波長λ_２が割り当てられた個別光ファイバ線路１８_２に異常が発生した可能性があると判定し、光反射測定部４０に対して波長λ_２による光パルスの試験を指示する。 However, if the spectrum detection result shows that, for example, the spectrum S _{2 at} the position of the signal light wavelength λ ₂ does not exist continuously for a predetermined time or more as shown in FIG. 2B, the signal light wavelength λ ₂ is assigned. It is determined that there is a possibility that an abnormality has occurred in the individual optical fiber line 18 ₂ , and the optical reflection measurement unit 40 is instructed to perform an optical pulse test at the wavelength λ ₂ .

この指示に対し、光反射測定部４０は、図３の（ａ）のように、波長λ_２の光パルスＰｏを所定周期Ｔ（波長λ_２の光が、線路カプラ２１からＯＮＵ１６_２に至る光路を往復するのに必要な時間以上）で繰り返し出射する。 In response to this instruction, as shown in FIG. 3A, the light reflection measuring unit 40 applies an optical pulse Po having a wavelength λ ₂ to a predetermined period T (light having a wavelength λ ₂ from the line coupler 21 to the ONU 162 _2. For more than the time necessary to make a round trip.

この光パルスＰｏは、線路カプラ２１を介して共通光ファイバ線路１７に入射され、分岐器１５に入射され、波長λ_２に対応した個別光ファイバ線路１８_２に入射され、その光パルスＰｏの通過によって生じる戻り光Ｐｒ（レイリー散乱光やフレネル反射光等）が、線路カプラ２１を介して光反射測定部４０へ入射されることになり、その伝送損失特性が例えば図３の（ｂ）のように測定される。この測定結果は、ＯＮＵ１６_２そのものが異常状態あるいは非稼働状態でＯＬＴ１０との通信が停止している状態の測定結果であり、回線そのものには異常がなく、測定結果の波形はＯＮＵ１６_２までの距離に対応した所で損失が大きくなってノイズレベルまで低下している。なお、図３の（ｂ）で示されたピークＡは入射端における反射、ピークＢは分岐器１５における反射成分である。 The light pulse Po is incident on a common optical fiber line 17 via a line coupler 21, is incident on the splitter 15, is incident to the individual optical fiber line 18 ₂ corresponding to the wavelength lambda _2, the passage of the light pulse Po Return light Pr (Rayleigh scattered light, Fresnel reflected light, etc.) generated by the above is incident on the light reflection measuring unit 40 via the line coupler 21, and the transmission loss characteristic thereof is, for example, as shown in FIG. Is measured. The measurement results, ONU 16 ₂ itself is the measurement result of the state in which the communication with the OLT10 abnormal state or non-operating state is stopped, no abnormality in the line itself, the distance to the measurement result of the waveform ONU 16 ₂ The loss increases at the place corresponding to, and the noise level is reduced. In addition, the peak A shown in FIG. 3B is the reflection at the incident end, and the peak B is the reflection component in the branching device 15.

また、例えば個別光ファイバ線路１８_２の途中が断線していて、損失が極端に大きくなっていると、光反射測定部４０によって得られる伝送損失特性の波形は、図３の（ｃ）のように、その断線位置でノイズレベルまで落ち込む。 Further, for example, are disconnected in the middle of the individual optical fiber lines 18 _2, the loss becomes extremely large, the waveform of the transmission loss characteristics obtained by the light reflection measurement unit 40, as shown in FIG. 3 (c) In addition, it falls to the noise level at the disconnection position.

制御部５０には、予め各波長についての正常時の伝送損失特性の波形情報が記憶され、その正常時の波形と上記測定波形とを比較し、例えば上記のように線路の遠端より手前の位置でレベルが大きく落ち込んでいることがわかると、断線障害が発生したことを報知する。また、波形の傾きが一部大きくなった場合には、その箇所で線路に異常な圧力等が加わったと判断して、損失増加が発生したことを報知する。なお、この報知は、図示しない通信手段を介して例えばＷＤＭ−ＰＯＮシステムのメンテナンスを行う部署、会社等に行われる。 The control unit 50 stores waveform information of normal transmission loss characteristics for each wavelength in advance, compares the normal waveform with the measured waveform, and, for example, before the far end of the line as described above. When it is found that the level has dropped significantly at the position, it is notified that a disconnection failure has occurred. Further, when the slope of the waveform partially increases, it is determined that abnormal pressure or the like has been applied to the line at that location, and a notification is made that an increase in loss has occurred. This notification is made to a department, a company, or the like that performs maintenance of the WDM-PON system, for example, via a communication means (not shown).

上記したように、実施形態の光線路障害探索装置２０は、固定波長型の分岐器１５を用いたＷＤＭ−ＰＯＮシステムの共通光ファイバ線路１７を伝搬する信号光に対するスペクトラム検出を行い、通信が停止している波長がある場合に、その波長による光反射測定を行って回線の障害を探索している。 As described above, the optical line fault searching apparatus 20 according to the embodiment performs spectrum detection on the signal light propagating through the common optical fiber line 17 of the WDM-PON system using the fixed wavelength type branching device 15 and stops communication. When there is a wavelength that is being used, light reflection measurement is performed using that wavelength to search for a line failure.

このため、ＷＤＭ−ＰＯＮシステムの分岐数が膨大になってもコスト高を招くことなく、その障害検知をインサービスの状態で実現できる。 For this reason, even if the number of branches of the WDM-PON system becomes enormous, the failure detection can be realized in an in-service state without incurring high costs.

（第１の実施形態）
次に、光線路障害探索装置２０の信号光スペクトラム検出部３０と光反射測定部４０の具体的な構成例の一つを、図４を用いて説明する。 (First embodiment)
Next, one specific configuration example of the signal light spectrum detection unit 30 and the light reflection measurement unit 40 of the optical line fault searching device 20 will be described with reference to FIG.

図４において、前記信号光スペクトラム検出部３０の専用の構成要素には３０番代の符号を付し、光反射測定部４０の専用の構成要素には４０番代の符号を付し、共用の構成要素には２０番代の符号を付す。なお、制御部５０は、装置の動作モードを信号光スペクトラム検出モードと光反射測定モードにいずれかに指定する機能を有している。 In FIG. 4, the dedicated component of the signal light spectrum detection unit 30 is assigned a reference number in the thirties, and the dedicated component of the light reflection measurement unit 40 is assigned a reference number of the 40th generation. Components are numbered in the 20th generation. The control unit 50 has a function of designating the operation mode of the apparatus to either the signal light spectrum detection mode or the light reflection measurement mode.

先ず、信号光スペクトラム検出モード（図４で各光を実線の矢印で示す）が指定されている場合について説明する。 First, the case where the signal light spectrum detection mode (each light is indicated by a solid arrow in FIG. 4) is designated will be described.

線路カプラ２１を介して入射される信号光Ｐｃは、波長可変フィルタ２２に入射される。波長可変フィルタ２２は、信号光波長λ_１〜λ_ｎを含む範囲の波長掃引が可能になっており、第１の波長コントローラ２３の制御により、上記信号光波長を含む範囲の波長掃引を繰り返す（この掃引は連続掃引あるいは各信号光波長を含む離散的な掃引のいずれであってもよい）。第１の波長コントローラ２３は、制御部５０の指示（モードおよび試験波長指定）にしたがって波長可変フィルタ２２の通過波長を制御する。 The signal light Pc incident through the line coupler 21 is incident on the wavelength tunable filter 22. The wavelength tunable filter 22 can perform wavelength sweeping in the range including the signal light wavelengths λ _{1 to} λ _n , and repeats wavelength sweeping in the range including the signal light wavelength under the control of the first wavelength controller 23 ( This sweep may be either a continuous sweep or a discrete sweep including each signal light wavelength). The first wavelength controller 23 controls the pass wavelength of the wavelength tunable filter 22 in accordance with an instruction (mode and test wavelength designation) from the control unit 50.

波長可変フィルタ２２を通過した光Ｐｃ′は、光を入出射するための３つの光路をもつカプラ２４の第１光路に入射され、それと異なる第２光路から出射されて受光器２５に入射され、その光の強度に応じた電圧の受光信号Ｖｃが出力される。 The light Pc ′ that has passed through the wavelength tunable filter 22 is incident on the first optical path of the coupler 24 having three optical paths for entering and exiting the light, is emitted from a second optical path different from the first optical path, and is incident on the light receiver 25. A light reception signal Vc having a voltage corresponding to the intensity of the light is output.

この受光信号Ｖｃは、Ａ／Ｄ変換器２６によってデジタルのデータＤｖに変換され、その時系列のデータＤｖｃがスペクトラム波形記憶手段３１により、第１の波形コントローラ２３からの掃引波長情報λにそれぞれ対応付けされて図示しない内部メモリに記憶される。 The light reception signal Vc is converted into digital data Dv by the A / D converter 26, and the time-series data Dvc is associated with the sweep wavelength information λ from the first waveform controller 23 by the spectrum waveform storage unit 31, respectively. And stored in an internal memory (not shown).

これにより、線路カプラ２１から入射される信号光Ｐｃのスペクトラム特性（例えば図２の（ａ）、（ｂ）の特性）が検出されてスペクトラム波形記憶手段３１に記憶されることになる。 As a result, the spectrum characteristics of the signal light Pc incident from the line coupler 21 (for example, the characteristics (a) and (b) of FIG. 2) are detected and stored in the spectrum waveform storage unit 31.

制御部５０はスペクトラム波形記憶部３１に記憶されたスペクトラム特性と、予め記憶している正常時のスペクトラム特性とを比較し、システムが用いる信号光波長のうち、異常のある波長あるいは通信停止状態の波長の有無を調べる。 The control unit 50 compares the spectrum characteristic stored in the spectrum waveform storage unit 31 with the normal spectrum characteristic stored in advance, and out of the signal light wavelengths used by the system, the abnormal wavelength or the communication stopped state Check for wavelength.

そして、異常のある波長あるいは通信停止状態の波長が見つかると、その波長を試験波長とし、反射測定モードに移行する（各光を点線の矢印で示す）。 When an abnormal wavelength or a wavelength in a communication stop state is found, the wavelength is set as a test wavelength, and a transition is made to the reflection measurement mode (each light is indicated by a dotted arrow).

反射測定モードでは、波長可変フィルタ２２の通過波長が試験波長に固定されるように第１の波長コントローラ２３に指示し、波長可変光源４１の出射光Ｐを受けた光パルス発生手段４４が出射する光パルスＰｏの波長が試験波長となるように、第２の波長コントローラ４２に指示を与え、さらにパルス試験用の一定周期Ｔのタイミング信号Ｃを出力する。 In the reflection measurement mode, the first wavelength controller 23 is instructed so that the pass wavelength of the wavelength tunable filter 22 is fixed to the test wavelength, and the optical pulse generation means 44 that receives the emitted light P of the wavelength tunable light source 41 emits. An instruction is given to the second wavelength controller 42 so that the wavelength of the optical pulse Po becomes the test wavelength, and a timing signal C having a constant period T for pulse test is output.

波長可変光源４１および光パルス発生手段４４は、信号光波長λ_１〜λ_ｎの光パルスのいずれかを選択的に出射できるようになっており、タイミング信号Ｃを受ける毎に第２の波長コントローラ４２で指定された試験波長の光パルスＰｏをカプラ２４の第３光路に入射する。ここで、波長可変光源４１および後述の波長可変光源１４１としては例えば半導体レーザと回折格子などを用いた外部共振器型の波長可変光源等を採用でき、光パルス発生手段４４および後述の光パルス発生手段１５３としては、例えばＬＮ型パルス変調器等が採用できるが、その構成については特に限定されない。 The wavelength tunable light source 41 and the optical pulse generator 44 can selectively emit any one of the optical pulses having the signal light wavelengths λ _{1 to} λ _n , and each time the timing signal C is received, the second wavelength controller. An optical pulse Po having a test wavelength designated by 42 is incident on the third optical path of the coupler 24. Here, as the wavelength tunable light source 41 and the wavelength tunable light source 141 described later, for example, an external resonator type wavelength tunable light source using a semiconductor laser and a diffraction grating or the like can be adopted. As the means 153, for example, an LN type pulse modulator or the like can be adopted, but the configuration is not particularly limited.

カプラ２４はこの光パルスＰｏを第１光路から波長可変フィルタ２２へ出射するが、このとき波長可変フィルタ２２の通過波長は試験波長と合っているので、光パルスＰｏは、波長可変フィルタ２２を通過し線路カプラ２１を介して共通光ファイバ線路１７に入射される。そして、共通光ファイバ線路１７から分岐器１５を経て試験波長に対応した個別光ファイバ線路に伝搬され、その間に生じたレイリー散乱光やフレネル反射光が、線路カプラ２１側に戻ってくる。 The coupler 24 emits the optical pulse Po from the first optical path to the wavelength tunable filter 22. At this time, since the passing wavelength of the wavelength tunable filter 22 matches the test wavelength, the optical pulse Po passes through the wavelength tunable filter 22. The light enters the common optical fiber line 17 through the optical line coupler 21. Then, the light is propagated from the common optical fiber line 17 to the individual optical fiber line corresponding to the test wavelength via the branching unit 15, and Rayleigh scattered light and Fresnel reflected light generated in the meantime return to the line coupler 21 side.

その戻り光Ｐｒの波長は試験波長に等しいので、波長可変フィルタ２２を通過し、カプラ２４の第１光路に入射され、第２光路から出射されて受光器２５に入射され、その光強度に対応したデータＤｖｒが伝送損失特性算出手段４３に入力される。なお、試験波長以外の信号光も線路カプラ２１を介して入射されるが、これらの信号光は波長の違いにより波長可変フィルタ２２を通過できないので反射測定への影響は無い。 Since the wavelength of the return light Pr is equal to the test wavelength, it passes through the wavelength tunable filter 22, enters the first optical path of the coupler 24, exits from the second optical path, enters the light receiver 25, and corresponds to the light intensity. The data Dvr is input to the transmission loss characteristic calculation means 43. Signal light other than the test wavelength is also incident through the line coupler 21. However, since the signal light cannot pass through the wavelength tunable filter 22 due to the difference in wavelength, there is no influence on the reflection measurement.

伝送損失特性算出手段４３は、タイミング信号Ｃを受けてから所定時間（光パルスＰｏが試験波長に対応した個別光ファイバ線路の末端までの間を往復するのに必要な時間）が経過するまでの一連のデータＤｖｒを波形データとして取込み、これを複数回繰り返して、平均化処理を行い、ランダム雑音成分を除去して、図３の（ｂ）、（ｃ）に示した伝送損失特性の波形を求める。 The transmission loss characteristic calculating means 43 receives the timing signal C until a predetermined time (the time required for the optical pulse Po to reciprocate to the end of the individual optical fiber line corresponding to the test wavelength) elapses. A series of data Dvr is taken as waveform data, and this is repeated a plurality of times, averaging processing is performed, random noise components are removed, and the waveforms of the transmission loss characteristics shown in FIGS. 3B and 3C are obtained. Ask.

この算出された伝送損失特性は、予めＯＮＵ毎（つまり試験波長毎）に取得されて記憶されている正常時の伝送損失特性と比較され、前記したような障害の有無やその位置が調べられて、その結果が報知される。 This calculated transmission loss characteristic is compared with the normal transmission loss characteristic acquired and stored in advance for each ONU (that is, for each test wavelength), and the presence / absence and position of the above-described failure are examined. The result is notified.

上記実施形態は、信号光スペクトラム検出モードと光反射測定モードとで、波長可変フィルタ２２、第１の波長コントローラ２３、カプラ２４、受光器２５およびＡ／Ｄ変換器２６を共有しているので、構成が簡素化でき、より低コストに実現できる。 In the above embodiment, the signal light spectrum detection mode and the light reflection measurement mode share the wavelength variable filter 22, the first wavelength controller 23, the coupler 24, the light receiver 25, and the A / D converter 26. The configuration can be simplified and realized at a lower cost.

（第２の実施形態）
図５は、信号光スペクトラム検出部３０と光反射測定部４０とが分離した構成例であり、信号光スペクトラム検出部３０の構成は任意（前記実施形態の信号光スペクトラム検出に必要な要素で構成してもよい）とし、光反射測定部４０については、ヘテロダイン型の構成を採用している。 (Second Embodiment)
FIG. 5 is a configuration example in which the signal light spectrum detection unit 30 and the light reflection measurement unit 40 are separated, and the configuration of the signal light spectrum detection unit 30 is arbitrary (it is configured with elements necessary for signal light spectrum detection of the embodiment). The light reflection measurement unit 40 employs a heterodyne type configuration.

ここで、線路カプラ２１、信号光スペクトラム検出部３０および光反射測定部４０の間には制御部５０によって切替制御される光スイッチ２７が挿入されている。制御部５０は、信号光スペクトラム検出部３０による信号光のスペクトラム検出を行う場合には、線路カプラ２１と信号光スペクトラム検出部３０との間を光スイッチ２７を介して接続させ、光反射測定を行う場合には、線路カプラ２１と光反射測定部４０との間を光スイッチ２７を介して接続させる。 Here, an optical switch 27 that is controlled to be switched by the control unit 50 is inserted between the line coupler 21, the signal light spectrum detection unit 30, and the light reflection measurement unit 40. When the signal light spectrum detection unit 30 detects the spectrum of the signal light, the control unit 50 connects the line coupler 21 and the signal light spectrum detection unit 30 via the optical switch 27 to perform light reflection measurement. When performing, the line coupler 21 and the light reflection measuring unit 40 are connected via the optical switch 27.

この構成の場合でも前記同様に、通常は信号光スペクトラムの検出処理を行い、その検出結果で異常や通信停止の波長が制御部５０で検知されたときに、その波長が試験波長と決定されて光反射測定部４０による光反射測定を実行する。 Even in this configuration, the signal light spectrum is normally detected in the same manner as described above, and when the control unit 50 detects a wavelength of abnormality or communication stoppage as a result of the detection, the wavelength is determined as the test wavelength. The light reflection measurement by the light reflection measuring unit 40 is executed.

光反射測定部４０の波長可変光源１４１は、全ての信号光波長λ_１〜λ_ｎの光Ｐのいずれかを選択的に出射できるようになっており、波長コントローラ１４２の制御により、制御部５０で決定された試験波長（光周波数をｆｐとする）の光Ｐを出射する。なお、ここで光Ｐは、少なくとも光パルス試験に必要な測定時間（測定距離に応じた時間）は連続する光である。 The wavelength tunable light source 141 of the light reflection measuring unit 40 can selectively emit any one of the light beams P having the signal light wavelengths λ _{1 to} λ _n . The control unit 50 is controlled by the wavelength controller 142. The light P having the test wavelength (the optical frequency is fp) determined in (1) is emitted. Here, the light P is light that is continuous for at least the measurement time required for the optical pulse test (time corresponding to the measurement distance).

この光Ｐは光分岐器１４３で２分岐され、その一方Ｐ１が光パルス発生手段１５３に入射され、この光パルス発生手段１５３により試験波長の光パルスＰｏが生成され、タイミング信号Ｃに同期してカプラ１４４に出射される。 This light P is branched into two by an optical branching device 143, and one of the light beams P1 is incident on an optical pulse generating means 153. The optical pulse generating means 153 generates an optical pulse Po having a test wavelength, and synchronizes with the timing signal C. The light is emitted to the coupler 144.

カプラ１４４は、光を入出射するための３つの光路を有し、光パルスＰｏを第１光路で受けてそれと異なる第２光路へ出射し、第２光路からの戻り光Ｐｒを第３光路へ出射する。 The coupler 144 has three optical paths for entering and exiting light, receives the optical pulse Po on the first optical path, emits it to a different second optical path, and returns the return light Pr from the second optical path to the third optical path. Exit.

カプラ１４４の第２光路には波長可変フィルタ１４５が接続されている。
波長可変フィルタ１４５は、その通過波長を信号光波長のいずれかに可変できるようになっており、前記波長コントローラ１４２の制御により、制御部５０から指定された試験波長の光を選択的に通過させる。つまり、光パルス生成手段１５３が生成した光パルスＰｏを通過させ、線路カプラ２１を介して共通光ファイバ線路１７へ入射させ、前記したように、その光パルスに対する戻り光Ｐｒを、線路カプラ２１を介して受けてカプラ１４４にの第２光路に入射させ、第３光路から出射させる。なお、信号光波長が少なく、これらの信号光が後述する受光器１４８に入射されても過負荷にならない場合には、この波長可変フィルタ１４５を省略することができる。 A wavelength tunable filter 145 is connected to the second optical path of the coupler 144.
The wavelength tunable filter 145 can change the pass wavelength to any one of the signal light wavelengths, and selectively allows the light of the test wavelength specified by the control unit 50 to pass under the control of the wavelength controller 142. . In other words, the optical pulse Po generated by the optical pulse generation means 153 is allowed to pass through and is incident on the common optical fiber line 17 via the line coupler 21, and the return light Pr corresponding to the optical pulse is passed through the line coupler 21 as described above. And is incident on the second optical path to the coupler 144 and emitted from the third optical path. If the wavelength of the signal light is small and the signal light does not become overloaded even if it enters a light receiver 148 described later, the wavelength variable filter 145 can be omitted.

一方、光分岐器１４３で分岐された他方の光Ｐ２は、周波数シフタ１４６に入射し、その光周波数が所定量Δｆ（例えば１００ＭＨｚ）だけ変化する。 On the other hand, the other light P2 branched by the optical branching device 143 enters the frequency shifter 146, and the optical frequency changes by a predetermined amount Δf (for example, 100 MHz).

ここで、周波数シフトによって変化する光の波長は、試験波長の近傍であって、試験波長以外の信号光波長とは一致しない範囲に設定される。つまり、周波数シフト量は信号光波長の間隔に対して微小である。 Here, the wavelength of the light that changes due to the frequency shift is set in the vicinity of the test wavelength and in a range that does not coincide with the signal light wavelength other than the test wavelength. That is, the frequency shift amount is very small with respect to the interval between the signal light wavelengths.

元の周波数ｆｐに対してΔｆだけ周波数シフトされた光Ｐ２′（ローカル光）は、カプラ１４４の第３光路から出射される戻り光Ｐｒとともに合波器１４７に入射して合波され、その合波光Ｐｓが受光器１４８（例えばバランスド受光器）に入射される。 The light P2 ′ (local light) frequency-shifted by Δf with respect to the original frequency fp enters the combiner 147 together with the return light Pr emitted from the third optical path of the coupler 144, and is combined. The wave light Ps enters a light receiver 148 (for example, a balanced light receiver).

ここで合波光Ｐｓには、周波数ｆｐの戻り光Ｐｒと周波数ｆｐに対して微小な周波数Δｆだけ差のある光Ｐ２′とが含まれているので、受光器１４８の出力信号Ｖｓには、周波数Δｆのビート成分Ｖｂが含まれている。このビート成分Ｖｂの振幅は、光Ｐ２′の強度が一定であれば、戻り光Ｐｒの強度に依存し、しかも、交流信号であるから、直流バイアス等の変動の影響を受けない。 Here, since the multiplexed light Ps includes the return light Pr having the frequency fp and the light P2 ′ having a slight difference Δf from the frequency fp, the output signal Vs of the light receiver 148 includes the frequency A beat component Vb of Δf is included. The amplitude of the beat component Vb depends on the intensity of the return light Pr if the intensity of the light P2 ′ is constant, and is not affected by fluctuations in the DC bias or the like because it is an AC signal.

したがって、受光器１４８の出力信号Ｖｓを通過中心周波数がΔｆに等しいバンドパスフィルタ（ＢＰＦ）１４９に入力して、このビート成分Ｖｂを抽出し、検波器１５０によりその振幅を求め、Ａ／Ｄ変換器１５１によってデジタルのデータＤｖｒに変換して、戻り光の強度を示す値として伝送損失特性算出手段１５２に与え、前記同様に平均化処理等を行うことで、正確な伝送損失特性を安定に求めることができる。 Therefore, the output signal Vs of the light receiver 148 is input to a band pass filter (BPF) 149 whose pass center frequency is equal to Δf, this beat component Vb is extracted, its amplitude is obtained by the detector 150, and A / D conversion is performed. The data 151 is converted to digital data Dvr by the device 151 and given to the transmission loss characteristic calculation means 152 as a value indicating the intensity of the return light, and an averaging process or the like is performed in the same manner as described above, so that accurate transmission loss characteristics can be obtained stably. be able to.

なお、前記したように、波長可変フィルタ１４５を省略した構成では、試験波長以外の信号光が受光器１４８に入射され、それらの信号光によるビート成分も生じるが、それらのビート成分は上記周波数Δｆから大きくかけ離れた周波数成分であるため、バンドパスフィルタ１４９の出力には現れず、測定に影響はない。 As described above, in the configuration in which the wavelength tunable filter 145 is omitted, signal light other than the test wavelength is incident on the light receiver 148, and beat components due to the signal light are also generated, but these beat components have the frequency Δf. Therefore, the frequency component does not appear in the output of the bandpass filter 149 and does not affect the measurement.

なお、前記実施形態では、周波数をシフトしない方の光パルスをＰＯＮシステム側に入射していたが、図６に示すように、周波数シフタ１４６と光パルス発生手段１５３を、光分岐器１４３とカプラ１４４の間に設け、光パルス発生手段１５３によって発生された光パルスＰｏを周波数シフタ１４６により周波数シフトし、その周波数シフトした光パルスＰｏ′をカプラ１４４へ出射し、他方の分岐光Ｐ２を合波器１４７へ出射しても、前記同様にビート成分を得ることができる。 In the above embodiment, the optical pulse whose frequency is not shifted is incident on the PON system side. However, as shown in FIG. 6, the frequency shifter 146 and the optical pulse generating means 153 are combined with the optical branching device 143 and the coupler. 144, the optical pulse Po generated by the optical pulse generating means 153 is frequency-shifted by the frequency shifter 146, and the optical pulse Po ′ that has been frequency-shifted is emitted to the coupler 144, and the other branched light P2 is multiplexed. The beat component can be obtained in the same manner as described above even when the light is emitted to the container 147.

なお、この場合、厳密には波長可変光源１４１から出射される光Ｐの周波数を、試験波長に対応した周波数に対して所定量Δｆだけ差をもたせ、周波数シフタ１４６によって試験波長に対応した周波数に戻すようにする。 In this case, strictly speaking, the frequency of the light P emitted from the wavelength variable light source 141 is different from the frequency corresponding to the test wavelength by a predetermined amount Δf, and the frequency shifter 146 sets the frequency corresponding to the test wavelength. Try to bring it back.

ただし、上記したようにその差Δｆが光の周波数に対して微小で、ＷＤＭ−ＰＯＮシステムの分岐器１５の各波長における通過帯域幅の中にある場合には、波長可変光源１４１から出射される光Ｐの周波数を、試験波長に対応した周波数に設定してもよい。 However, as described above, when the difference Δf is very small with respect to the frequency of light and is within the pass bandwidth at each wavelength of the branching device 15 of the WDM-PON system, it is emitted from the wavelength tunable light source 141. The frequency of the light P may be set to a frequency corresponding to the test wavelength.

また、図７に示すように、光パルス発生手段１５３と周波数シフタ１４６の配置を入れ換えて、光分岐器１４３の出射光Ｐ１を周波数シフトし、その周波数シフトした光Ｐ１′から光パルスＰｏを発生させる構成としてもよい。 Further, as shown in FIG. 7, the arrangement of the optical pulse generating means 153 and the frequency shifter 146 is switched, the outgoing light P1 of the optical branching device 143 is frequency-shifted, and the optical pulse Po is generated from the frequency-shifted light P1 ′. A configuration may be adopted.

１０……ＯＬＴ（電話局側光回線終端装置）、１５……分岐器、１６_１〜１６_ｎ……ＯＮＵ（加入者側光回線終端装置）、１７……共通光ファイバ線路、１８_１〜１８_ｎ……個別光ファイバ線路、２０……光線路障害探索装置、２１……線路カプラ、２２……波長可変フィルタ、２３……第１の波長コントローラ、２４……カプラ、２５……受光器、２６……Ａ／Ｄ変換器、２７……光スイッチ、３０……信号光スペクトラム検出部、３１……信号光スペクトラム記憶手段、４０……光反射測定部、４１……波長可変光源、４２……第２の波長コントローラ、４３……伝送損失特性算出手段、４４……光パルス発生手段、１４１……波長可変光源、１４２……波長コントローラ、１４３……光分岐器、１４４……カプラ、１４５……波長可変フィルタ、１４６……周波数シフタ、１４７……合波器、１４８……受光器、１４９……バンドパスフィルタ、１５０……検波器、１５１……Ａ／Ｄ変換器、１５２……伝送損失特性算出手段、１５３……光パルス発生手段。 DESCRIPTION OF SYMBOLS 10 ... OLT (telephone station side optical line terminator), 15 ... branching device, 16 _{1 to} 16 _n ... ONU (subscriber side optical line terminator), 17 ... common optical fiber line, 18 ₁ to 18 _n: individual optical fiber line, 20: optical line fault searching device, 21: line coupler, 22: wavelength tunable filter, 23: first wavelength controller, 24: coupler, 25: light receiver, 26... A / D converter, 27... Optical switch, 30... Signal light spectrum detector, 31... Signal light spectrum storage means, 40. ... Second wavelength controller 43... Transmission loss characteristic calculating means 44... Optical pulse generating means 141... Wavelength tunable light source 142 ... Wavelength controller 143. ……wave Variable filter, 146... Frequency shifter, 147 ... multiplexer, 148 ... light receiver, 149 ... bandpass filter, 150 ... detector, 151 ... A / D converter, 152 ... transmission loss characteristics Calculation means, 153... Optical pulse generation means.

Claims

A telephone station that multiplexes signal lights of a plurality of different wavelengths to enter one end of a common optical fiber line (17), and separates and receives the light transmitted through the common optical fiber line for each wavelength. Side optical line terminator (10), connected to the other end of the common optical fiber line, receives signal light transmitted from the telephone station side optical line terminator, and separates it according to its wavelength, The common optical fiber line is made to enter one end of individual optical fiber lines (18 ₁ to 18 _n ) individually provided for each wavelength, and combine the signal lights transmitted through the individual optical fiber lines. WDM-PON having a branching unit (15) of a fixed wavelength demultiplexing type that emits to the optical fiber and a subscriber side optical line terminator (16 _{1 to} 16 _n ) connected to the other end of the individual optical fiber line, respectively. Optical line searching for obstacles in system optical line A harm search apparatus,
A line coupler (21) connected to the common optical fiber line;
A signal light spectrum detector (30) for receiving the signal light transmitted through the common optical fiber line via the line coupler and detecting its spectrum;
Based on the detection result of the signal light spectrum detection unit, a control unit (50) that examines the signal light wavelength not transmitted through the common optical fiber line, and determines the signal light wavelength as a test wavelength;
An optical pulse having a test wavelength determined by the control unit is generated, is incident on the common optical fiber line via the line coupler, receives a return light from the WDM-PON system for the optical pulse, An optical line fault searching device comprising: a light reflection measuring unit (40) for obtaining a transmission loss characteristic of an optical path from the common optical fiber line to an individual optical fiber line corresponding to a test wavelength.

The control unit has a function of designating the operation mode of the apparatus as either a signal light spectrum detection mode or a light reflection measurement mode,
The signal light spectrum detection unit and the light reflection measurement unit,
A wavelength tunable filter (22) that is connected to the line coupler and selectively and bidirectionally transmits light having a wavelength specified from a wavelength range of all signal light used for communication by the WDM-PON system;
When the signal light spectrum detection mode is designated, the pass wavelength of the wavelength tunable filter is swept within a range including all the signal light wavelengths, and the test wavelength is determined and the light reflection measurement mode is designated. A first wavelength controller (23) for setting the pass wavelength of the wavelength tunable filter to the test wavelength;
Light that is connected to the wavelength tunable filter and received through the line coupler and the wavelength tunable filter is received by the first optical path, emitted to the second optical path, and light incident from the third optical path is transmitted to the first optical path. A coupler (24) that emits light to the tunable filter;
A light receiver (25) that receives light emitted from the coupler to the second optical path and converts the light into an electric signal having an amplitude corresponding to the intensity;
When the signal light spectrum detection mode is designated, the output signal of the light receiver and the passing wavelength of the wavelength tunable filter swept by the first wavelength controller are associated and stored as a signal light spectrum. A signal light spectrum storage means (31) for outputting the signal light spectrum to the control unit;
A variable wavelength light source (41) that emits light of any one of the wavelengths of the signal light when the light reflection measurement mode is designated;
An optical pulse generator (44) that receives light emitted from the wavelength tunable light source, generates an optical pulse, and outputs the optical pulse to the third optical path of the coupler;
When the light reflection measurement mode is designated, light having a wavelength equal to the test wavelength is emitted from the wavelength tunable light source, and passes through the optical pulse generating means, the coupler, the wavelength tunable filter, and the line coupler. A second wavelength controller (42) incident on the WDM-PON system;
While the return light corresponding to the optical pulse incident on the WDM-PON system is incident on the optical receiver through the line coupler, the wavelength tunable filter, and the coupler, the output signal of the optical receiver is acquired. The transmission loss characteristic calculating means (43) for obtaining the transmission loss characteristic of the optical path from the common optical fiber line to the individual optical fiber line corresponding to the test wavelength is configured by the transmission loss characteristic calculating means (43). Optical line fault search device.

The signal light spectrum detecting unit and the light reflection measuring unit are selectively connected to the line coupler via an optical switch (27),
The light reflection measuring unit is
A wavelength tunable light source (141) that emits light of a specified wavelength within the wavelength range of all the signal lights;
A wavelength controller (142) for emitting light having a wavelength equal to the test wavelength determined by the control unit from the wavelength variable light source;
An optical branching device (143) for branching the light emitted from the wavelength tunable light source into two;
An optical pulse generating means (153) for receiving one of the lights branched by the optical splitter and generating an optical pulse;
The optical pulse is received by the first optical path, is emitted from the second optical path to the common optical fiber line through the optical switch and the line coupler, and the return light for the optical pulse is received from the second optical path to the third optical path. A coupler (144) for emitting light to
A frequency shifter (146) that shifts the optical frequency of the other light branched by the optical splitter by a predetermined amount (Δf) in the vicinity of the test wavelength and in a range that does not coincide with the optical frequency of the signal light other than the test wavelength. When,
A combiner (147) for combining the return light emitted from the third optical path of the coupler and the emitted light from the frequency shifter;
A light receiver (148) that receives light emitted from the multiplexer;
A bandpass filter (149) for extracting a beat component having a frequency equal to the amount of frequency shift by the frequency shifter from the output signal of the light receiver;
A detector (150) for detecting the amplitude of the beat component extracted by the bandpass filter;
Transmission loss characteristic calculating means (152) for obtaining a transmission loss characteristic of an optical path from the common optical fiber line to an individual optical fiber line corresponding to a test wavelength based on the output of the detector; The optical line failure searching device according to claim 1.

The signal light spectrum detecting unit and the light reflection measuring unit are selectively connected to the line coupler via an optical switch (27),
The light reflection measuring unit is
A wavelength tunable light source (141) that emits light of a specified wavelength within the wavelength range of all the signal lights;
With respect to the test wavelength determined by the controller, light having a wavelength having a difference of a predetermined frequency (Δf) in the vicinity of the test wavelength and in a range that does not coincide with other signal light wavelengths other than the test wavelength is variable in wavelength. A wavelength controller (142) for emitting light from the light source;
An optical branching device (143) for branching the light emitted from the wavelength tunable light source into two;
An optical pulse generating means (153) for receiving one of the lights branched by the optical splitter and generating an optical pulse for generating an optical pulse;
A frequency shifter (146) for shifting the optical frequency of the optical pulse to the test wavelength by shifting the predetermined frequency;
The optical pulse of the test wavelength emitted from the frequency shifter is received by the first optical path, and is emitted from the second optical path to the common optical fiber line through the optical switch and the line coupler, and return light for the optical pulse is returned. A coupler (144) for receiving from the second optical path and emitting to the third optical path;
A combiner (147) for combining the return light emitted from the third optical path of the coupler and the other optical pulse branched by the optical splitter;
A light receiver (148) that receives light emitted from the multiplexer;
A bandpass filter (149) for extracting a beat component having a frequency equal to a frequency shift amount by the frequency shifter from the output signal of the light receiver;
A detector (150) for detecting the amplitude of the beat component extracted by the bandpass filter;
Transmission loss characteristic calculating means (152) for obtaining a transmission loss characteristic of an optical path from the common optical fiber line to an individual optical fiber line corresponding to a test wavelength based on the output of the detector; The optical line failure searching device according to claim 1.

The signal light spectrum detecting unit and the light reflection measuring unit are selectively connected to the line coupler via an optical switch (27),
The light reflection measuring unit is
A wavelength tunable light source (141) that emits light of a specified wavelength within the wavelength range of all the signal lights;
With respect to the test wavelength determined by the controller, light having a wavelength having a difference of a predetermined frequency (Δf) in the vicinity of the test wavelength and in a range that does not coincide with other signal light wavelengths other than the test wavelength is variable in wavelength. A wavelength controller (142) for emitting light from the light source;
An optical branching device (143) for branching the light emitted from the wavelength tunable light source into two;
A frequency shifter (146) that shifts the optical frequency of one of the lights branched by the optical splitter to the test wavelength by shifting the predetermined frequency;
Optical pulse generation means (153) for receiving light emitted from the frequency shifter and generating an optical pulse of the test wavelength;
The optical pulse is received by the first optical path, is emitted from the second optical path to the common optical fiber line through the optical switch and the line coupler, and the return light for the optical pulse is received from the second optical path to the third optical path. A coupler (144) for emitting light to
A combiner (147) for combining the return light emitted from the third optical path of the coupler and the other light branched by the optical splitter;
A light receiver (148) that receives light emitted from the multiplexer;
A bandpass filter (149) for extracting a beat component having a frequency equal to the amount of frequency shift by the frequency shifter from the output signal of the light receiver;
A detector (150) for detecting the amplitude of the beat component extracted by the bandpass filter;
Transmission loss characteristic calculating means (152) for obtaining a transmission loss characteristic of an optical path from the common optical fiber line to an individual optical fiber line corresponding to a test wavelength based on the output of the detector; The optical line failure searching device according to claim 1.