JPH09113415A - Method for measuring wavelength distribution of optical fiber - Google Patents
Method for measuring wavelength distribution of optical fiberInfo
- Publication number
- JPH09113415A JPH09113415A JP27451395A JP27451395A JPH09113415A JP H09113415 A JPH09113415 A JP H09113415A JP 27451395 A JP27451395 A JP 27451395A JP 27451395 A JP27451395 A JP 27451395A JP H09113415 A JPH09113415 A JP H09113415A
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- Prior art keywords
- optical fiber
- chromatic dispersion
- light
- wavelength
- bent portion
- Prior art date
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Abstract
Description
【０００１】[0001]
【発明の属する技術分野】本発明は、光ファイバの波長
分散を非破壊で測定する光ファイバの波長分散測定方法
に関するものである。BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical fiber chromatic dispersion measuring method for nondestructively measuring chromatic dispersion of an optical fiber.
【０００２】[0002]
【従来の技術】光ファイバを伝搬する信号は、その伝搬
時間が波長依存性をもつことから、波長分散により遅延
歪みが発生し、信号波形に歪みを生じる。従って、光フ
ァイバの波長分散特性は、伝送路の伝送速度を決定する
重要な特性である。2. Description of the Related Art A signal propagating through an optical fiber has a wavelength-dependent propagation time, so that chromatic dispersion causes delay distortion, which causes distortion in a signal waveform. Therefore, the wavelength dispersion characteristic of the optical fiber is an important characteristic that determines the transmission speed of the transmission line.
【０００３】この光ファイバの波長分散は、光ファイバ
を伝搬する光の伝搬時間の波長依存性を測定し、その伝
搬時間を波長によって微分することにより求められる。
このような光ファイバの波長分散の測定方法としては、
パルス法や位相法があることが知られている。ここで
は、従来の位相法による波長分散測定方法を、図５を用
いて説明する。The chromatic dispersion of this optical fiber is obtained by measuring the wavelength dependence of the propagation time of light propagating through the optical fiber and differentiating the propagation time by the wavelength.
As a method of measuring the chromatic dispersion of such an optical fiber,
It is known that there are a pulse method and a phase method. Here, a conventional chromatic dispersion measuring method by the phase method will be described with reference to FIG.
【０００４】図５に示すように、光源２０から出射され
た光を強度変調したものを、カプラー２２によって２つ
に分岐し、その一方の光を被測定光ファイバ２４の一端
に入射する。被測定光ファイバ２４中を伝搬し、他端か
ら出射した光は、光受信器２６によって受信され、電気
信号に変換される。また、カプラー２２によって分岐さ
れた他方の光は、参照光として、直接に光受信器２８に
よって受信され、電気信号に変換される。これら光受信
器２６、２８によって変換された２つの電気信号の位相
差を位相計３０によって測定する。そしてこの位相差か
ら被測定光ファイバ２４による伝搬時間を求める。更
に、こうした操作を、光の波長を変えて繰り返し、被測
定光ファイバを伝搬する光の伝搬時間の波長依存性を求
め、その伝搬時間を波長によって微分することにより波
長分散値を求める。As shown in FIG. 5, the intensity-modulated light emitted from the light source 20 is branched into two by a coupler 22, and one of the lights is incident on one end of an optical fiber 24 to be measured. The light propagating through the measured optical fiber 24 and emitted from the other end is received by the optical receiver 26 and converted into an electric signal. The other light branched by the coupler 22 is directly received by the optical receiver 28 as reference light and converted into an electric signal. The phase difference between the two electric signals converted by the optical receivers 26 and 28 is measured by the phase meter 30. Then, the propagation time through the measured optical fiber 24 is obtained from this phase difference. Further, such an operation is repeated by changing the wavelength of the light, the wavelength dependence of the propagation time of the light propagating through the optical fiber under measurement is obtained, and the chromatic dispersion value is obtained by differentiating the propagation time by the wavelength.
【０００５】[0005]
【発明が解決しようとする課題】しかしながら、上記従
来の光ファイバの波長分散測定方法においては、光ファ
イバ全長における波長分散値を求めることができるが、
光ファイバの特定の区間における波長分散値を求めるこ
とは困難であった。即ち、長尺の光ファイバにおける波
長分散値が長手方向に変化している場合において、ある
特定の区間における波長分散値を求めようとしても、ま
た長手方向における波長分散値の分布を求めようとして
も、直接に測定することができず、光ファイバを切断し
て測定しなければならないという問題があった。However, in the above conventional chromatic dispersion measuring method for an optical fiber, the chromatic dispersion value over the entire length of the optical fiber can be obtained.
It was difficult to obtain the chromatic dispersion value in a specific section of the optical fiber. That is, in the case where the chromatic dispersion value in a long optical fiber is changing in the longitudinal direction, even when trying to find the chromatic dispersion value in a certain section, or trying to find the distribution of the chromatic dispersion value in the longitudinal direction. However, there is a problem that the optical fiber cannot be directly measured and the optical fiber must be cut and measured.
【０００６】そこで本発明は、上記の状況を鑑みてなさ
れたものであり、光ファイバの特定の区間における波長
分散値及び光ファイバの長手方向における波長分散値の
分布を非破壊で精度よく測定することができる光ファイ
バの波長分散測定方法を提供することを目的とする。Therefore, the present invention has been made in view of the above circumstances, and accurately and nondestructively measures the chromatic dispersion value in a specific section of an optical fiber and the distribution of the chromatic dispersion value in the longitudinal direction of the optical fiber. An object of the present invention is to provide a method for measuring chromatic dispersion of an optical fiber that can be used.
【０００７】[0007]
【課題を解決するための手段】請求項１の光ファイバの
波長分散測定方法は、（ａ）第１の端から第１の光路距
離だけ離れた部分を屈曲させ屈曲部とした光ファイバの
第１の端から複数の波長の光を入射する第１のステップ
と、（ｂ）屈曲部から光ファイバの外へ漏洩した各波長
の光の検出する第２のステップと、（ｃ）第１の端から
の光の入射時刻と屈曲部からの漏洩光の検出時刻との差
である第１の伝搬時間を各波長について求める第３のス
テップと、（ｄ）各波長に関する第１の伝搬時間と第１
の端から屈曲部までの光路距離と基づいて、第１の端か
ら屈曲部までの部分に関する第１の波長分散を求める第
４のステップとを備えることを特徴とする。According to a first aspect of the present invention, there is provided a method for measuring wavelength dispersion of an optical fiber, comprising: (a) bending a portion apart from the first end by a first optical path distance to form a bent portion; A first step of injecting light of a plurality of wavelengths from one end, (b) a second step of detecting light of each wavelength leaked from the bent portion to the outside of the optical fiber, and (c) a first step. A third step of obtaining a first propagation time which is a difference between an incident time of light from the end and a detection time of leaked light from the bent portion for each wavelength, and (d) a first propagation time for each wavelength. First
And a fourth step of obtaining a first chromatic dispersion for the portion from the first end to the bent portion based on the optical path distance from the end to the bent portion.
【０００８】請求項１の光ファイバの波長分散測定方法
では、光ファイバの任意の箇所で光ファイバを屈曲さ
せ、その屈曲部から漏洩させた光を検出して、光ファイ
バへの光の入射時刻と屈曲部からの漏洩光の検出時刻と
の差から伝搬時間を測定するため、光ファイバの入射端
（第１の端）から任意の箇所までの波長分散値を非破壊
で求めることができる。According to the wavelength dispersion measuring method of the optical fiber of the first aspect, the optical fiber is bent at an arbitrary position of the optical fiber, the light leaked from the bent portion is detected, and the time of incidence of the light on the optical fiber is detected. Since the propagation time is measured from the difference between the detection time of the leaked light from the bent portion and the detection time, the chromatic dispersion value from the incident end (first end) of the optical fiber to an arbitrary position can be obtained nondestructively.
【０００９】請求項２の光ファイバの波長分散測定方法
は、請求項１の光ファイバの波長分散測定方法の第４の
ステップに引き続き、（ｅ）光ファイバの第２の端から
複数の波長の光を入射する第５のステップと、（ｆ）屈
曲部から光ファイバの外へ漏洩した各波長の光と第１の
端から出射した各波長の光の夫々検出する第６のステッ
プと、（ｇ）屈曲部からの漏洩光の検出時刻と第１の端
からの出射光の検出時刻との差である第２の伝搬時間を
各波長について求める第７のステップと、（ｈ）各波長
に関する第２の伝搬時間と屈曲部から第１の端までの光
路距離とに基づいて、屈曲部から第１の端までの部分に
関する第２の波長分散を求める第８のステップと、
（ｉ）第１の波長分散と第２の波長分散との平均値であ
る第３の波長分散を求める第９のステップとを備えるこ
とを特徴とする。A method of measuring chromatic dispersion of an optical fiber according to a second aspect of the present invention is the same as the fourth step of the method of measuring the chromatic dispersion of an optical fiber according to the first aspect, further comprising (e) a plurality of wavelengths from the second end of the optical fiber. A fifth step of injecting light, and (f) a sixth step of detecting light of each wavelength leaked from the bent portion to the outside of the optical fiber and light of each wavelength emitted from the first end, respectively ( g) Seventh step of obtaining the second propagation time which is the difference between the detection time of the leaked light from the bent portion and the detection time of the emitted light from the first end for each wavelength, and (h) each wavelength An eighth step of obtaining a second chromatic dispersion for the portion from the bent portion to the first end based on the second propagation time and the optical path distance from the bent portion to the first end,
(I) A ninth step of obtaining a third chromatic dispersion which is an average value of the first chromatic dispersion and the second chromatic dispersion.
【００１０】請求項２の光ファイバの波長分散測定方法
では、請求項１の光ファイバの波長分散測定方法による
波長分散の測定に加えて、光ファイバの第２の端から光
を入射して屈曲部からの漏洩光と第１の端からの出射光
とを検出する。そして、２つの検出時刻との差から伝搬
時間を測定し、請求項１の光ファイバの波長分散測定方
法による波長分散の測定対象部の波長分散を別途測定
し、２つの測定値を平均しては測定対象部の波長分散を
求めるので、精度良く測定対象部の波長分散を求めるこ
とができる。According to the wavelength dispersion measuring method of the optical fiber of claim 2, in addition to the measurement of the wavelength dispersion by the wavelength dispersion measuring method of the optical fiber of claim 1, light is incident from the second end of the optical fiber and bent. The leaked light from the unit and the light emitted from the first end are detected. Then, the propagation time is measured from the difference between the two detection times, the chromatic dispersion of the measurement target part of the chromatic dispersion according to the chromatic dispersion measuring method of the optical fiber according to claim 1 is separately measured, and the two measured values are averaged. Since the wavelength dispersion of the measurement target portion is obtained, the wavelength dispersion of the measurement target portion can be obtained with high accuracy.
【００１１】請求項３の光ファイバの波長分散測定方法
は、（ａ）第１の端から第１の光路距離だけ離れた部分
を屈曲させた第１の屈曲部と第１の端から第２の光路距
離だけ離れた部分を屈曲させた第２の屈曲部とを有する
光ファイバの第１の端から複数の波長の光を入射する第
１のステップと、（ｂ）第１の屈曲部および第２の屈曲
部の夫々から前記光ファイバの外へ漏洩した各波長の光
の夫々検出する第２のステップと、（ｃ）第１の端から
の光の入射時刻と第１の屈曲部からの漏洩光の検出時刻
との差である第１の伝搬時間と第１の端からの光の入射
時刻と第２の屈曲部からの漏洩光の検出時刻との差であ
る第２の伝搬時間とを各波長について求める第３のステ
ップと、（ｄ）各波長に関する第１の伝搬時間と第１の
端から第１の屈曲部までの光路距離と基づいて、第１の
端から第１の屈曲部までの部分に関する第１の波長分散
を求めるとともに、各波長に関する第２の伝搬時間と第
１の端から第２の屈曲部までの光路距離と基づいて、第
１の端から第２の屈曲部までの部分に関する第２の波長
分散を求める第４ステップと、（ｅ）第１の波長分散と
第２の波長分散と第１の屈曲部から第２の屈曲部までの
光路距離とに基づいて、第１の屈曲部から第２の屈曲部
までの部分に関する第３の波長分散を求める第５のステ
ップとを備えることを特徴とする。According to a third aspect of the present invention, there is provided a method of measuring chromatic dispersion of an optical fiber, which comprises: A first step of injecting light of a plurality of wavelengths from a first end of an optical fiber having a second bent portion formed by bending a portion separated by an optical path distance of, and (b) a first bent portion and A second step of detecting the light of each wavelength leaked out of the optical fiber from each of the second bent portions, and (c) the time of incidence of the light from the first end and the first bent portion. Propagation time which is the difference between the detection time of the leaked light and the second propagation time which is the difference between the incident time of the light from the first end and the detection time of the leaked light from the second bent portion And (d) a first propagation time for each wavelength and a first bend from the first end. A first chromatic dispersion for the portion from the first end to the first bent portion based on the optical path distance to the second end portion, and a second propagation time for each wavelength and the second bent portion from the first end. And (e) the first chromatic dispersion, the second chromatic dispersion, and the fourth step of obtaining the second chromatic dispersion for the portion from the first end to the second bent portion based on the optical path distance to A fifth step of obtaining a third chromatic dispersion regarding a portion from the first bent portion to the second bent portion based on the optical path distance from the first bent portion to the second bent portion. Characterize.
【００１２】請求項３の光ファイバの波長分散測定方法
では、光ファイバの任意の２箇所で光ファイバを屈曲さ
せ、その屈曲部から漏洩させた光を検出して、光ファイ
バへの光の入射時刻と２つの屈曲部からの漏洩光の検出
時刻との差から光の入射端からの伝搬時間を測定し、光
ファイバの光入射端（第１の端）から任意の２箇所まで
の波長分散を夫々求めた後、２つの屈曲部の間の部分の
波長分散を求めるので、任意の２箇所の間の部分の波長
分散を非破壊で求めることができる。According to the wavelength dispersion measuring method of the optical fiber of the third aspect, the optical fiber is bent at any two points of the optical fiber, the light leaked from the bent portion is detected, and the light is incident on the optical fiber. The propagation time from the light incident end is measured from the difference between the time and the detection time of the leaked light from the two bent portions, and the chromatic dispersion from the light incident end (first end) of the optical fiber to two arbitrary locations is measured. Since the chromatic dispersion of the portion between the two bent portions is calculated after each of the above, the chromatic dispersion of the portion between any two positions can be calculated nondestructively.
【００１３】請求項４の光ファイバの波長分散測定方法
は、請求項３の光ファイバの波長分散測定方法の第５の
ステップに引き続き、（ｆ）光ファイバの第２の端から
複数の波長の光を入射する第６のステップと、（ｇ）第
１の屈曲部および第２の屈曲部の夫々から光ファイバの
外へ漏洩した各波長の光の夫々検出する第７のステップ
と、（ｈ）第２の端からの光の入射時刻と第１の屈曲部
からの漏洩光の検出時刻との差である第３の伝搬時間と
第２の端からの光の入射時刻と前記第２の屈曲部からの
漏洩光の検出時刻との差である第４の伝搬時間とを各波
長について求める第８のステップと、（ｉ）各波長に関
する第３の伝搬時間と第１の端から第１の屈曲部までの
光路距離と基づいて、第２の端から第１の屈曲部までの
部分に関する第４の波長分散を求めるとともに、各波長
に関する第４の伝搬時間と第２の端から第２の屈曲部ま
での光路距離と基づいて、第２の端から前記第２の屈曲
部までの部分に関する第５の波長分散を求める第９ステ
ップと、（ｊ）第４の波長分散と第５の波長分散と第１
の屈曲部から第２の屈曲部までの光路距離とに基づい
て、第１の屈曲部から第２の屈曲部までの部分に関する
第６の波長分散を求める第１０のステップと、（ｋ）第
３の波長分散と第６の波長分散との平均値である第７の
波長分散を求める第１１のステップとを備えることを特
徴とする。A method of measuring chromatic dispersion of an optical fiber according to a fourth aspect of the present invention is the same as the fifth step of the method of measuring the chromatic dispersion of an optical fiber according to the third aspect, further comprising (f) a plurality of wavelengths from the second end of the optical fiber. A sixth step of injecting light, (g) a seventh step of detecting light of each wavelength leaked out of the optical fiber from each of the first bent portion and the second bent portion, and (h) ) A third propagation time, which is the difference between the time of incidence of light from the second end and the time of detection of leaked light from the first bent portion, the time of incidence of light from the second end, and the second time An eighth step of obtaining a fourth propagation time, which is a difference from the detection time of the leaked light from the bent portion, for each wavelength, and (i) a third propagation time for each wavelength and a first from the first end. A fourth portion related to a portion from the second end to the first bent portion based on the optical path distance to the bent portion of The chromatic dispersion is obtained, and the fifth portion related to the portion from the second end to the second bent portion is calculated based on the fourth propagation time for each wavelength and the optical path distance from the second end to the second bent portion. Step (j) fourth chromatic dispersion, fifth chromatic dispersion and first
A tenth step of obtaining a sixth chromatic dispersion relating to a portion from the first bent portion to the second bent portion, based on the optical path distance from the bent portion to the second bent portion. An eleventh step of obtaining a seventh chromatic dispersion, which is an average value of the third chromatic dispersion and the sixth chromatic dispersion.
【００１４】請求項４の光ファイバの波長分散測定方法
では、請求項３の光ファイバの波長分散測定方法による
波長分散の測定に加えて、光ファイバの第２の端から光
を入射して第１および第２の屈曲部からの漏洩光を検出
する。そして、第１の端からの光入射時刻と２つの検出
時刻との差から夫々伝搬時間を測定し、光ファイバの光
入射端（第２の端）から第１および第２の屈曲部までの
波長分散を夫々求めた後、第１の屈曲部と第２の屈曲部
との間の部分の波長分散を測定することにより、請求項
３の光ファイバの波長分散測定方法による波長分散の測
定対象部の波長分散を別途測定し、２つの測定値を平均
しては測定対象部の波長分散を求めるので、精度良く測
定対象部の波長分散を求めることができる。According to the chromatic dispersion measuring method of the optical fiber of claim 4, in addition to the measurement of the chromatic dispersion by the chromatic dispersion measuring method of the optical fiber according to claim 3, light is incident from the second end of the optical fiber to measure the chromatic dispersion. The leaked light from the first and second bent portions is detected. Then, the propagation time is measured from the difference between the light incident time from the first end and the two detection times, and from the light incident end (second end) of the optical fiber to the first and second bent portions. An object of measurement of chromatic dispersion by the chromatic dispersion measuring method of an optical fiber according to claim 3, by measuring chromatic dispersion in a portion between the first bent portion and the second bent portion after obtaining the chromatic dispersion respectively. Since the chromatic dispersion of the part is separately measured and the two measured values are averaged to obtain the chromatic dispersion of the part to be measured, the chromatic dispersion of the part to be measured can be accurately obtained.
【００１５】請求項５の光ファイバの波長分散測定方法
は、（ａ）複数の区間に区分され、夫々の区間の境界部
を夫々屈曲した屈曲部を有する光ファイバの第１の端か
ら複数の波長の光を入射する第１のステップと、（ｂ）
夫々の屈曲部から光ファイバの外へ漏洩した各波長の光
および前記光ファイバの第２の端からの出射光を夫々検
出する第２のステップと、（ｃ）第１の端からの光の入
射時刻と夫々の屈曲部からの漏洩光の検出時刻または第
２の端からの出射光の検出時刻との差である第１の伝搬
時間を各波長について各屈曲部または第２の端に関して
求める第３のステップと、（ｄ）各波長に関する夫々の
第１の伝搬時間と第１の端から夫々の屈曲部または第２
の端までの光路距離と基づいて、第１の端から夫々の屈
曲部または第２の端までの部分に関する第１の波長分散
を求める第４ステップと、（ｅ）各区間の両端に関する
夫々の第１の波長分散と各区間の光路距離とに基づい
て、各区間の第２の波長分散を求める第５のステップと
を備えることを特徴とする。According to a fifth aspect of the present invention, there is provided a method for measuring chromatic dispersion of an optical fiber, comprising: (a) dividing a plurality of sections, each of which has a bent portion in which a boundary portion is bent, from a first end of the optical fiber; A first step of injecting light of a wavelength, (b)
A second step of detecting the light of each wavelength leaked from the respective bent portions to the outside of the optical fiber and the light emitted from the second end of the optical fiber, and (c) the light from the first end. The first propagation time, which is the difference between the time of incidence and the time of detection of light leaked from each bent portion or the time of detection of light emitted from the second end, is obtained for each bent portion or second end for each wavelength. A third step, (d) a respective first propagation time for each wavelength and a respective bend or second from the first end.
Based on the optical path distance to the end of the first end, the fourth step of obtaining the first chromatic dispersion for the portion from the first end to each bent portion or the second end, and (e) for each end of each section. And a fifth step of obtaining the second chromatic dispersion of each section based on the first chromatic dispersion and the optical path distance of each section.
【００１６】請求項５の光ファイバの波長分散測定方法
では、光ファイバの各区間の両端に対応する屈曲部また
は第２の端からの漏洩光または出射光を検出して、光フ
ァイバへの光の入射時刻と各屈曲部または第２の端での
光の検出時刻との差から光の入射端からの伝搬時間を測
定し、光ファイバの光入射端（第１の端）から各屈曲部
または第２の端までの波長分散を夫々求めた後、各区間
の波長分散を求めるので、光ファイバの全域にわたっ
て、任意に区分した区間の波長分散を非破壊で求めるこ
とができる。従って、できるだけ長尺のままでの使用が
望まれる実際の敷設用光ファイバ等において、非常に有
効である。In the method of measuring wavelength dispersion of an optical fiber according to a fifth aspect of the present invention, leak light or outgoing light from the bent portion or the second end corresponding to both ends of each section of the optical fiber is detected, and the light to the optical fiber is detected. From the light incident end (first end) of each of the optical fibers by measuring the propagation time from the light incident end from the difference between the incident time of light and the detection time of light at each bent portion or the second end. Alternatively, since the chromatic dispersion of each section is calculated after the chromatic dispersion up to the second end is calculated, the chromatic dispersion of the arbitrarily divided section can be calculated nondestructively over the entire area of the optical fiber. Therefore, it is very effective in an actual laying optical fiber or the like, which is desired to be used as long as possible.
【００１７】請求項６の光ファイバの波長分散測定方法
は、請求項５の光ファイバの波長分散測定方法の第５の
ステップに引き続き、（ｆ）光ファイバの第２の端から
複数の波長の光を入射する第６のステップと、（ｇ）夫
々の屈曲部から光ファイバの外へ漏洩した各波長の光お
よび光ファイバの第１の端からの出射光を夫々検出する
第７のステップと、（ｈ）第２の端からの光の入射時刻
と夫々の屈曲部からの漏洩光の検出時刻または第１の端
からの出射光の検出時刻との差である第２の伝搬時間を
各波長について各屈曲部または第２の端に関して求める
第８のステップと、（ｉ）各波長に関する夫々の第２の
伝搬時間と第２の端から夫々の屈曲部または第１の端ま
での光路距離と基づいて、第２の端から夫々の屈曲部ま
たは第１の端までの部分に関する第３の波長分散を求め
る第９ステップと、（ｊ）各区間の両端に関する夫々の
第３の波長分散と各区間の光路距離とに基づいて、各区
間の第４の波長分散を求める第１０のステップと、
（ｋ）第２の波長分散と第４の波長分散との平均値であ
る第５の波長分散を求める第１１のステップとを備える
ことを特徴とする。An optical fiber chromatic dispersion measuring method according to a sixth aspect of the present invention is the same as the fifth step of the optical fiber chromatic dispersion measuring method according to the fifth aspect, and further comprises (f) a plurality of wavelengths from the second end of the optical fiber. A sixth step of injecting light, and (g) a seventh step of detecting the light of each wavelength leaked from the respective bent portions to the outside of the optical fiber and the light emitted from the first end of the optical fiber, respectively. , (H) The second propagation time, which is the difference between the time of incidence of light from the second end and the time of detection of leaked light from each bent portion or the time of detection of light emitted from the first end, Eighth step for each bend or second end for wavelength, (i) Each second propagation time for each wavelength and optical path distance from second end to each bend or first end. From the second end to the respective bend or the first end A ninth step of obtaining a third chromatic dispersion of the section, and (j) a fourth chromatic dispersion of each section based on the third chromatic dispersion of both ends of each section and the optical path distance of each section. The tenth step,
(K) An eleventh step of obtaining a fifth chromatic dispersion which is an average value of the second chromatic dispersion and the fourth chromatic dispersion.
【００１８】請求項６の光ファイバの波長分散測定方法
では、請求項５の光ファイバの波長分散測定方法による
波長分散の測定に加えて、光ファイバの第２の端から光
を入射して各区間の両端に対応する屈曲部または第１の
端からの漏洩光または出射光を検出する。そして、光フ
ァイバへの光の入射時刻と各屈曲部または第１の端での
光の検出時刻との差から光の入射端からの伝搬時間を測
定し、光ファイバの光入射端（第２の端）から各屈曲部
または第１の端までの波長分散を夫々求めた後、各区間
の波長分散を測定することにより、請求項５の光ファイ
バの波長分散測定方法による波長分散の測定対象部の波
長分散を別途測定し、２つの測定値を平均しては測定対
象部の波長分散を求めるので、精度良く測定対象部の波
長分散を求めることができる。According to the wavelength dispersion measuring method of the optical fiber of claim 6, in addition to the measurement of the wavelength dispersion by the method of measuring the wavelength dispersion of the optical fiber of claim 5, light is made incident from the second end of the optical fiber. Leakage light or emission light from the bent portion or the first end corresponding to both ends of the section is detected. Then, the propagation time from the light incident end is measured from the difference between the light incident time on the optical fiber and the light detection time at each bent portion or the first end, and the light incident end of the optical fiber (second (From the end) to each bent portion or the first end, and then the chromatic dispersion in each section is measured to measure the chromatic dispersion by the chromatic dispersion measuring method of the optical fiber according to claim 5. Since the chromatic dispersion of the part is separately measured and the two measured values are averaged to obtain the chromatic dispersion of the part to be measured, the chromatic dispersion of the part to be measured can be accurately obtained.
【００１９】[0019]
【発明の実施の形態】本発明の実施形態に係る光ファイ
バの波長分散測定方法を、図１を用いて説明する。ここ
で、図１は本発明の一実施の形態に係る光ファイバの波
長分散測定方法を実施するための波長分散測定装置を示
す概略図である。BEST MODE FOR CARRYING OUT THE INVENTION A chromatic dispersion measuring method for an optical fiber according to an embodiment of the present invention will be described with reference to FIG. Here, FIG. 1 is a schematic diagram showing a chromatic dispersion measuring apparatus for carrying out the chromatic dispersion measuring method for an optical fiber according to an embodiment of the present invention.
【００２０】図１に示すように、この波長分散測定装置
においては、所定の波長の光を出射する光源１０が、全
長Ｌの被測定光ファイバ１２の一端と光学的に結合され
ている。この被測定光ファイバ１２は、その一端から距
離Ｌi にある特定の地点で曲げられている。そしてこの
被測定光ファイバ１２の屈曲部の近傍には、被測定光フ
ァイバ１２からの漏洩光を検出して電気信号に変換する
光受信器１４が設置されている。また、被測定光ファイ
バ１２を伝搬する光の伝搬時間を測定し、その測定デー
タに基づいて波長分散値を演算する伝搬時間測定器１６
が、光源１０及び光受信器１４に接続して設置されてい
る。As shown in FIG. 1, in this wavelength dispersion measuring apparatus, a light source 10 for emitting light of a predetermined wavelength is optically coupled to one end of an optical fiber 12 to be measured having a total length L. The optical fiber 12 to be measured is bent at a specific point at a distance L i from one end thereof. An optical receiver 14 that detects leaked light from the measured optical fiber 12 and converts it into an electric signal is installed near the bent portion of the measured optical fiber 12. In addition, a propagation time measuring device 16 that measures a propagation time of light propagating through the optical fiber 12 to be measured and calculates a chromatic dispersion value based on the measurement data.
Is installed by being connected to the light source 10 and the optical receiver 14.
【００２１】次に、この波長分散測定装置を用いた光フ
ァイバの波長分散測定方法を説明する。Next, a method for measuring chromatic dispersion of an optical fiber using this chromatic dispersion measuring device will be described.
【００２２】光源１０から出射した所定の波長の光を被
測定光ファイバ１２の一端に入射し、被測定光ファイバ
１２中を伝搬させる。この被測定光ファイバ１２中を伝
搬する光は、被測定光ファイバ１２の入射端から距離Ｌ
i にある屈曲部において光ファイバ１２から漏洩する。
そしてこの漏洩光を屈曲部近傍に設置した光受信器１４
によって検出し、電気信号に変換する。この電気信号を
伝搬時間測定器１６に送り、被測定光ファイバ１２の入
射端から距離Ｌi を伝搬した光の伝搬時間を測定する。
更に、こうした操作を、光源１０から出射する光の波長
を変えて繰り返し、被測定光ファイバ１２の入射端から
距離Ｌi を伝搬する光の伝搬時間の波長（λ）依存性Ｔ
i （λ）を求める。そして、その伝搬時間を波長によっ
て微分することにより、被測定光ファイバ１２の入射端
から距離Ｌi までの波長分散値Ｄi を Ｄi ＝［ｄＴi （λ）／ｄλ］／Ｌi …（１） で求める。Light having a predetermined wavelength emitted from the light source 10 enters one end of the optical fiber 12 to be measured and propagates in the optical fiber 12 to be measured. The light propagating through the optical fiber 12 to be measured has a distance L from the incident end of the optical fiber 12 to be measured.
It leaks from the optical fiber 12 at the bent portion at i .
An optical receiver 14 in which this leaked light is installed near the bent portion
Detected by and converted into an electric signal. This electric signal is sent to the propagation time measuring device 16 and the propagation time of the light propagated the distance L i from the incident end of the measured optical fiber 12 is measured.
Further, such an operation is repeated by changing the wavelength of the light emitted from the light source 10, and the wavelength (λ) dependence T of the propagation time of the light propagating the distance L i from the incident end of the optical fiber 12 to be measured.
Find i (λ). Then, by differentiating the propagation time by wavelength, the wavelength dispersion value D i D i = [dT i (λ) / dλ] from the incident end of the optical fiber under test 12 to the distance L i / L i ... ( 1) Find in.
【００２３】このように本発明の実施の形態に係る光フ
ァイバの波長分散測定方法によれば、被測定光ファイバ
１２の一端から所定の距離Ｌi にある特定の箇所で被測
定光ファイバ１２を曲げ、その屈曲部からの漏洩光を光
受信器１４により検出し、伝搬時間測定器１６において
被測定光ファイバ１２の入射端から距離Ｌi を伝搬した
光の伝搬時間を測定するため、被測定光ファイバ１２の
入射端から距離Ｌi にある特定の地点までの波長分散値
Ｄi を非破壊で求めることができる。As described above, according to the chromatic dispersion measuring method for an optical fiber according to the embodiment of the present invention, the optical fiber 12 to be measured is measured at a specific position at a predetermined distance L i from one end of the optical fiber 12 to be measured. Since the light receiver 14 bends and detects leaked light from the bent portion, and the propagation time measuring device 16 measures the propagation time of the light propagated the distance L i from the incident end of the measured optical fiber 12, The chromatic dispersion value D i from the incident end of the optical fiber 12 to a specific point at a distance L i can be obtained nondestructively.
【００２４】上記に加えて、被測定光ファイバ１２の入
射端から距離Ｌi+1 に屈曲部を設け、同様にして、被測
定光ファイバ１２の入射端から距離Ｌi+1 までの波長分
散値Ｄi+1 を Ｄi+1 ＝［ｄＴi+1 （λ）／ｄλ］／Ｌi+1 …（２） で求め、更に、 Ｄi+1,i ＝（Ｄi+1 ・Ｌi+1 −Ｄi ・Ｌi ）／（Ｌi+1 −Ｌi ）…（３） を演算することにより、屈曲部間の波長分散Ｄi+1,i を
求めることができる。In addition to the above, the bent portion is provided from the incident end of the optical fiber under test 12 to the distance L i + 1, in the same way, the wavelength dispersion from the incident end of the optical fiber under test 12 to the distance L i + 1 The value D i + 1 is calculated by D i + 1 = [dT i + 1 (λ) / dλ] / L i + 1 (2), and further, D i + 1, i = (D i + 1 · L The wavelength dispersion D i + 1, i between the bent portions can be obtained by calculating i + 1− D i · L i ) / (L i + 1 −L i ) ... (3).
【００２５】以上を、被測定用光ファイバ１２を複数の
区間に区分し、各区間について適用すれば、被測定光フ
ァイバ１２の全域にわたって、任意区間の波長分散を測
定することができる。ここで、被測定光ファイバ１２の
光出射端を含む領域の波長分散の測定にあたっては、光
出射端からの出射光の検出が必要となる。If the above-described optical fiber 12 for measurement is divided into a plurality of sections and applied to each section, the chromatic dispersion of an arbitrary section can be measured over the entire area of the optical fiber 12 for measurement. Here, in measuring the chromatic dispersion in the region including the light emitting end of the optical fiber 12 to be measured, it is necessary to detect the light emitted from the light emitting end.
【００２６】なお、被測定光ファイバ１２の一方の端か
ら光を入射して波長分散を測定後、他方の端から光を入
射して波長分散を測定し、同一領域の波長分散の測定値
の平均を求めることにより測定精度を向上することがで
きる。It should be noted that after the light is incident from one end of the optical fiber 12 to be measured to measure the chromatic dispersion, the light is incident from the other end to measure the chromatic dispersion, and the measured value of the chromatic dispersion in the same region is The measurement accuracy can be improved by obtaining the average.
【００２７】[0027]
【実施例】上記図１を用いて説明した実施の形態に係る
光ファイバの波長分散測定方法により、実際の光ファイ
バについてその波長分散を測定した結果を、以下の実施
例として述べる。EXAMPLES The results of measuring the chromatic dispersion of an actual optical fiber by the chromatic dispersion measuring method of the optical fiber according to the embodiment described with reference to FIG. 1 will be described as the following examples.
【００２８】（実施例１）被測定光ファイバとして、長
さ１０ｋｍ、波長分散値−０．５ｐｓ／ｎｍ／ｋｍの第
１の光ファイバと、長さ１０ｋｍ、波長分散値０．０ｐ
ｓ／ｎｍ／ｋｍの第２の光ファイバと、長さ１０ｋｍ、
波長分散値０．５ｐｓ／ｎｍ／ｋｍの第３の光ファイバ
とを順に溶融接続した全長３０ｋｍの光ファイバを使用
した。以下、被測定光ファイバの第１の光ファイバの部
分を区間Ａ、第２の光ファイバの部分を区間Ｂ、第３の
光ファイバの部分を区間Ｃと呼ぶ。Example 1 As an optical fiber to be measured, a first optical fiber having a length of 10 km and a wavelength dispersion value of −0.5 ps / nm / km, a length of 10 km and a wavelength dispersion value of 0.0 p are used.
a second optical fiber of s / nm / km and a length of 10 km,
An optical fiber having a total length of 30 km was used in which a third optical fiber having a chromatic dispersion value of 0.5 ps / nm / km was sequentially spliced and connected. Hereinafter, the first optical fiber portion of the measured optical fiber will be referred to as section A, the second optical fiber portion will be referred to as section B, and the third optical fiber portion will be referred to as section C.
【００２９】この被測定光ファイバについて、上記図１
を用いて説明した測定方法により、区間Ａにおける波長
分散を測定した。The optical fiber to be measured is shown in FIG.
The chromatic dispersion in the section A was measured by the measuring method described using.
【００３０】光源から所定の波長の光を被測定光ファイ
バの第１の光ファイバ側の一端に入射して、被測定光フ
ァイバ中を伝搬させ、入射端から１０ｋｍの地点、即ち
区間Ａと区間Ｂとの境界で被測定光ファイバを曲げて、
その屈曲部から光を漏洩させた。そしてこの漏洩光を光
受信器により検出し、伝搬時間測定器により被測定光フ
ァイバの入射端から１０ｋｍの距離を伝搬した光の伝搬
時間を測定した。更に、こうした操作を、光の波長を変
えて繰り返して、被測定光ファイバの区間Ａを伝搬する
光の伝搬時間の波長依存性を求め、その伝搬時間を波長
によって微分して、被測定光ファイバの区間Ａにおける
波長分散値ＤA を求めた。Light having a predetermined wavelength is incident on one end of the measured optical fiber on the side of the first optical fiber from the light source, propagated through the measured optical fiber, and a point 10 km from the incident end, that is, a section A and a section. Bend the optical fiber to be measured at the boundary with B,
Light was leaked from the bent portion. Then, the leaked light was detected by an optical receiver, and the propagation time of the light propagated a distance of 10 km from the incident end of the optical fiber to be measured was measured by the propagation time measuring device. Further, such an operation is repeated by changing the wavelength of light to obtain the wavelength dependence of the propagation time of the light propagating in the section A of the optical fiber under measurement, and the propagation time is differentiated by the wavelength to measure the optical fiber under measurement. were determined wavelength dispersion value D a of the section a.
【００３１】この実施例１による被測定光ファイバの区
間Ａにおける波長分散の測定結果を図２のグラフに示
す。図２のグラフ中、実線は、実際に測定した被測定光
ファイバの区間Ａにおける波長分散値を示し、破線は、
被測定光ファイバを構成する第１乃至第３の光ファイバ
のそれぞれの波長分散値を示す。The measurement result of the chromatic dispersion in the section A of the optical fiber to be measured according to this Example 1 is shown in the graph of FIG. In the graph of FIG. 2, the solid line indicates the chromatic dispersion value in the section A of the actually measured optical fiber, and the broken line indicates
The respective chromatic dispersion values of the first to third optical fibers forming the optical fiber to be measured are shown.
【００３２】この図２のグラフから明らかなように、実
線で示す被測定光ファイバの区間Ａにおける波長分散値
ＤA は−０．５ｐｓ／ｎｍ／ｋｍとなり、破線で示す第
１の光ファイバの波長分散値と一致した。これにより、
上記図１を用いて説明した光ファイバの波長分散測定方
法の有効性を確認することができた。As is apparent from the graph of FIG. 2, the chromatic dispersion value D A in the section A of the optical fiber to be measured shown by the solid line is −0.5 ps / nm / km, which is the value of the first optical fiber shown by the broken line. It agrees with the chromatic dispersion value. This allows
The effectiveness of the chromatic dispersion measuring method of the optical fiber described with reference to FIG. 1 was confirmed.
【００３３】なお、上記実施例１においては、被測定光
ファイバの第１の光ファイバ側の一端から光を入射して
いるが、被測定光ファイバの第３の光ファイバ側の他端
から光を入射して、被測定光ファイバの区間Ａにおける
波長分散値ＤA を求めてもよい。In the first embodiment, the light is incident from one end of the measured optical fiber on the first optical fiber side, but the light is incident from the other end of the measured optical fiber on the third optical fiber side. May be incident to obtain the chromatic dispersion value D A in the section A of the optical fiber to be measured.
【００３４】また、被測定光ファイバの第１の光ファイ
バ側の一端及び第３の光ファイバ側の他端の両方からそ
れぞれ光を入射して、被測定光ファイバの区間Ａにおけ
る波長分散値ＤA を求めてもよい。この場合、第１の光
ファイバ側の一端から光を入射して求めた区間Ａにおけ
る波長分散値と被測定光ファイバの第３の光ファイバ側
の他端から光を入射して求めた区間Ａにおける波長分散
値とを平均化して、区間Ａにおける波長分散値ＤA を決
定することとなる。従って、被測定光ファイバのいずれ
か一方の端部のみから光を入射して波長分散値を求めた
場合より、測定精度を２倍に向上させることができる。The wavelength dispersion value D in the section A of the optical fiber to be measured is obtained by injecting light from both the one end on the first optical fiber side and the other end on the third optical fiber side of the optical fiber to be measured. You may ask for A. In this case, the chromatic dispersion value in the section A obtained by entering the light from one end on the first optical fiber side and the section A obtained by entering the light from the other end of the measured optical fiber on the third optical fiber side The chromatic dispersion value in the section A is averaged to determine the chromatic dispersion value D A in the section A. Therefore, the measurement accuracy can be doubled as compared with the case where the chromatic dispersion value is obtained by injecting light from only one end of the measured optical fiber.
【００３５】（実施例２）被測定光ファイバとして、上
記実施例１と同一の光ファイバを使用し、この被測定光
ファイバについて、上記図１を用いて説明した方法によ
り、区間Ｂにおける波長分散を測定した。(Example 2) The same optical fiber as in Example 1 was used as the optical fiber to be measured, and this optical fiber to be measured was subjected to chromatic dispersion in section B by the method described with reference to FIG. Was measured.
【００３６】光源から所定の波長の光を被測定光ファイ
バの第１の光ファイバ側の一端に入射して、被測定光フ
ァイバ中を伝搬させ、入射端から１０ｋｍの地点及び２
０ｋｍの地点、即ち区間Ａと区間Ｂとの境界及び区間Ｂ
と区間Ｃとの境界で被測定光ファイバをそれぞれ曲げ
て、それら２か所の屈曲部から光を漏洩させた。そして
これらの漏洩光を光受信器によりそれぞれ検出し、伝搬
時間測定器により被測定光ファイバの入射端から１０ｋ
ｍの距離及び２０ｋｍの距離を伝搬した光の伝搬時間を
測定した。更に、こうした操作を、光の波長を変えて繰
り返して、被測定光ファイバの区間Ａ及び区間ＡＢを伝
搬する光の伝搬時間の波長依存性を求め、その伝搬時間
を波長によって微分して、被測定光ファイバの区間Ａ及
び区間ＡＢにおける波長分散値ＤA 及び波長分散値ＤAB
を求めた。そして区間Ｂにおける波長分散値ＤB を、 ＤB ＝（２０ＤAB−１０ＤA ）／（２０−１０）…（４） により求めた。Light of a predetermined wavelength is incident from the light source on one end of the measured optical fiber on the side of the first optical fiber and propagated through the measured optical fiber, and a point 10 km from the incident end and 2
A point of 0 km, that is, the boundary between section A and section B and section B
The measured optical fiber was bent at the boundary between the section C and the section C, and light was leaked from the two bent portions. Then, each of these leaked lights is detected by an optical receiver, and a propagation time measuring device measures 10 k from the incident end of the measured optical fiber.
The propagation time of light propagating at a distance of m and a distance of 20 km was measured. Further, such an operation is repeated by changing the wavelength of the light to obtain the wavelength dependence of the propagation time of the light propagating in the section A and the section AB of the optical fiber to be measured, and the propagation time is differentiated by the wavelength, Chromatic dispersion value D A and chromatic dispersion value D AB in section A and section AB of the measurement optical fiber
I asked. The wavelength dispersion value D B in Section B, the determined by D B = (20D AB -10D A ) / (20-10) ... (4).
【００３７】この実施例２による被測定光ファイバの区
間Ｂにおける波長分散の測定結果を図３のグラフに示
す。図３のグラフ中、実線は、実際に測定した被測定光
ファイバの区間Ｂにおける波長分散値を示し、破線は、
被測定光ファイバを構成する第１乃至第３の光ファイバ
のそれぞれの波長分散値を示す。The measurement result of the chromatic dispersion in the section B of the measured optical fiber according to the second embodiment is shown in the graph of FIG. In the graph of FIG. 3, the solid line indicates the chromatic dispersion value in the section B of the actually measured optical fiber, and the broken line indicates
The respective chromatic dispersion values of the first to third optical fibers forming the optical fiber to be measured are shown.
【００３８】この図３のグラフから明らかなように、実
線で示す被測定光ファイバの区間Ｂにおける波長分散値
ＤB は０．０ｐｓ／ｎｍ／ｋｍとなり、破線で示す第２
の光ファイバの波長分散値と一致した。これにより、上
記図１を用いて説明した光ファイバの波長分散測定方法
の有効性を確認することができた。As is clear from the graph of FIG. 3, the chromatic dispersion value D B in the section B of the optical fiber to be measured shown by the solid line is 0.0 ps / nm / km, and the second line shown by the broken line is shown.
It was in agreement with the chromatic dispersion value of the optical fiber. From this, it was possible to confirm the effectiveness of the chromatic dispersion measuring method for the optical fiber described with reference to FIG.
【００３９】なお、上記実施例２においては、被測定光
ファイバの第１の光ファイバ側の一端から光を入射して
いるが、被測定光ファイバの第３の光ファイバ側の他端
から光を入射して、被測定光ファイバの区間Ｂにおける
波長分散値ＤB を求めてもよい。この場合、被測定光フ
ァイバの区間Ｃ及び区間ＢＣにおける波長分散値ＤC及
び波長分散値ＤBCを求めた後、 ＤB ＝（２０ＤBC−１０ＤB ）／（２０−１０）…（５） により、区間Ｂにおける波長分散値ＤB を求めることと
なる。In the second embodiment, the light is incident from one end of the measured optical fiber on the first optical fiber side, but the light is incident from the other end of the measured optical fiber on the third optical fiber side. May be incident to obtain the chromatic dispersion value D B in the section B of the optical fiber to be measured. In this case, after obtaining the wavelength dispersion value D C and a wavelength dispersion value D BC in the section C and the section BC of the measured optical fiber, D B = (20D BC -10D B) / (20-10) ... (5) makes possible to obtain a wavelength dispersion value D B in the section B.
【００４０】また、被測定光ファイバの第１の光ファイ
バ側の一端及び第３の光ファイバ側の他端の両方からそ
れぞれ光を入射して、被測定光ファイバの区間Ｂにおけ
る波長分散値ＤB を求めてもよい。この場合、第１の光
ファイバ側の一端から光を入射して求めた区間Ｂにおけ
る波長分散値と被測定光ファイバの第３の光ファイバ側
の他端から光を入射して求めた区間Ｂにおける波長分散
値とを平均化して、区間Ｂにおける波長分散値ＤB を決
定することとなる。従って、被測定光ファイバのいずれ
か一方の端部のみから光を入射して波長分散値を求めた
場合より、測定精度を２倍に向上させることができる。The wavelength dispersion value D in the section B of the optical fiber to be measured is made by injecting light from both the one end on the first optical fiber side and the other end on the third optical fiber side of the optical fiber to be measured. You may ask for B. In this case, the chromatic dispersion value in the section B obtained by injecting light from one end on the first optical fiber side and the section B obtained by injecting light from the other end on the third optical fiber side of the measured optical fiber The chromatic dispersion value in the section B is averaged to determine the chromatic dispersion value D B in the section B. Therefore, the measurement accuracy can be doubled as compared with the case where the chromatic dispersion value is obtained by injecting light from only one end of the measured optical fiber.
【００４１】（実施例３）被測定光ファイバとして、上
記実施例１と同一の光ファイバを使用し、この被測定光
ファイバについて、上記図１を用いて説明した方法によ
り、区間Ａ、区間Ｂ、及び区間Ｃにおける波長分散をそ
れぞれ測定し、被測定光ファイバ長手方向における波長
分散値の分布を求めた。(Embodiment 3) As the optical fiber to be measured, the same optical fiber as in Embodiment 1 is used, and the optical fiber to be measured is divided into sections A and B by the method described with reference to FIG. , And the chromatic dispersion in the section C were measured, and the distribution of chromatic dispersion values in the longitudinal direction of the optical fiber to be measured was obtained.
【００４２】上記実施例２の場合と同様にして、光源か
ら所定の波長の光を被測定光ファイバの第１の光ファイ
バ側の一端に入射して、被測定光ファイバ中を伝搬さ
せ、入射端から１０ｋｍの地点及び２０ｋｍの地点で被
測定光ファイバをそれぞれ曲げて、それら２か所の屈曲
部から光を漏洩させた。そしてこれらの漏洩光を光受信
器によりそれぞれ検出し、伝搬時間測定器により被測定
光ファイバの入射端から１０ｋｍの距離及び２０ｋｍの
距離を伝搬した光の伝搬時間を測定した。また、光源か
ら所定の波長の光を被測定光ファイバの第１の光ファイ
バ側の一端に入射し、測定光ファイバ中を伝搬した後、
被測定光ファイバの第３の光ファイバ側の他端から出射
した光を光受信器により検出し、伝搬時間測定器により
被測定光ファイバの全長３０ｋｍの距離を伝搬した光の
伝搬時間を測定した。更に、こうした操作を、光の波長
を変えて繰り返して、被測定光ファイバの区間Ａ、区間
ＡＢ、及び区間ＡＢＣを伝搬する光の伝搬時間の波長依
存性を求め、その伝搬時間を波長によって微分して、被
測定光ファイバの区間Ａ、区間ＡＢ、及び区間ＡＢＣに
おける波長分散値ＤA 、波長分散値ＤAB、及び波長分散
値ＤABC を求めた。そして区間Ｂにおける波長分散値Ｄ
B を、（４）式により求め、区間Ｃにおける波長分散値
ＤC を、 ＤC ＝（２０ＤABC −１０ＤAB）／（３０−２０）…（６） により求めた。こうして、被測定光ファイバの長手方向
における波長分散値の分布を求めた。In the same manner as in the case of the above-mentioned second embodiment, light of a predetermined wavelength is made incident on one end of the measured optical fiber on the side of the first optical fiber, propagated through the measured optical fiber, and made incident. The optical fibers to be measured were respectively bent at a point 10 km and a point 20 km from the end, and light was leaked from the two bent portions. Then, each of these leaked lights was detected by an optical receiver, and the propagation time of the light propagating a distance of 10 km and a distance of 20 km from the incident end of the optical fiber to be measured was measured by a propagation time measuring device. In addition, after the light of a predetermined wavelength is incident on one end of the measured optical fiber on the first optical fiber side from the light source and propagated in the measured optical fiber,
The light emitted from the other end of the measured optical fiber on the side of the third optical fiber was detected by the optical receiver, and the propagation time of the light propagated over the distance of 30 km of the measured optical fiber was measured by the propagation time measuring device. . Further, such an operation is repeated by changing the wavelength of the light to obtain the wavelength dependence of the propagation time of the light propagating in the section A, the section AB, and the section ABC of the optical fiber under measurement, and the propagation time is differentiated by the wavelength. Then, the chromatic dispersion value D A , the chromatic dispersion value D AB , and the chromatic dispersion value D ABC in the section A, the section AB, and the section ABC of the optical fiber to be measured were obtained. Then, the chromatic dispersion value D in the section B
B was determined by (4) determined by the equation, the wavelength dispersion value D C in the section C, D C = (20D ABC -10D AB) / (30-20) ... (6). In this way, the distribution of the chromatic dispersion value in the longitudinal direction of the measured optical fiber was obtained.
【００４３】この実施例３による被測定光ファイバの区
間Ａ、区間Ｂ、及び区間Ｃにおける波長分散の測定結果
を図４のグラフに示す。図４のグラフ中、実線は、実際
に測定した被測定光ファイバの区間Ａ、区間Ｂ、及び区
間Ｃにおける波長分散値を示し、破線は、被測定光ファ
イバを構成する第１乃至第３の光ファイバのそれぞれの
波長分散値を示す。The graph of FIG. 4 shows the measurement results of the chromatic dispersion in the section A, section B, and section C of the optical fiber to be measured according to the third embodiment. In the graph of FIG. 4, the solid line indicates the chromatic dispersion value in the section A, the section B, and the section C of the actually measured optical fiber, and the broken lines indicate the first to third parts constituting the measured optical fiber. The chromatic dispersion value of each optical fiber is shown.
【００４４】この図４のグラフから明らかなように、実
線で示す被測定光ファイバの区間Ａ、区間Ｂ、及び区間
Ｃにおける波長分散値ＤA 、波長分散値ＤB 、及び波長
分散値ＤC はそれぞれ−０．５ｐｓ／ｎｍ／ｋｍ、０．
０ｐｓ／ｎｍ／ｋｍ、及び０．５ｐｓ／ｎｍ／ｋｍとな
り、破線で示す第１乃至第３の光ファイバの波長分散値
と一致した。これにより、上記図１を用いて説明した光
ファイバの波長分散測定方法の有効性を確認することが
できた。As is apparent from the graph of FIG. 4, the chromatic dispersion value D A , the chromatic dispersion value D B , and the chromatic dispersion value D C in the sections A, B, and C of the optical fiber to be measured shown by solid lines. Are -0.5 ps / nm / km, 0.
The values are 0 ps / nm / km and 0.5 ps / nm / km, which are in agreement with the chromatic dispersion values of the first to third optical fibers indicated by the broken line. From this, it was possible to confirm the effectiveness of the chromatic dispersion measuring method for the optical fiber described with reference to FIG.
【００４５】なお、上記実施例３においても、被測定光
ファイバの第１の光ファイバ側の一端から光を入射する
代わりに、被測定光ファイバの第３の光ファイバ側の他
端から光を入射して、被測定光ファイバの被測定光ファ
イバの区間Ａ、区間Ｂ、及び区間Ｃにおける波長分散値
ＤA 、波長分散値ＤB 、及び波長分散値ＤC を求めても
よい。この場合、被測定光ファイバの区間Ｃ、区間Ｂ
Ｃ、及び区間ＡＢＣにおける波長分散値ＤC 、波長分散
値ＤBC、及び波長分散値ＤABC を求めた後、（５）式及
び ＤA ＝（２０ＤABC −１０ＤBC）／（３０−２０）…（７） により、区間Ｂ及び区間Ａにおける波長分散値ＤB 及び
波長分散値ＤA を求めることとなる。Also in the third embodiment, instead of entering the light from one end of the measured optical fiber on the first optical fiber side, the light is input from the other end of the measured optical fiber on the third optical fiber side. The wavelength dispersion value D A , the wavelength dispersion value D B , and the wavelength dispersion value D C in the section A, the section B, and the section C of the measured optical fiber of the measured optical fiber may be obtained by incidence. In this case, section C and section B of the optical fiber to be measured
C, and after obtaining the wavelength dispersion value D C, the wavelength dispersion value D BC, and a wavelength dispersion value D ABC in the section ABC, (5) and Formula D A = (20D ABC -10D BC ) / (30-20) (7) The chromatic dispersion value D B and the chromatic dispersion value D A in the section B and the section A are obtained.
【００４６】また、被測定光ファイバの第１の光ファイ
バ側の一端及び第３の光ファイバ側の他端の両方からそ
れぞれ光を入射して、被測定光ファイバの区間Ａ、区間
Ｂ、及び区間Ｃにおける波長分散値ＤA 、波長分散値Ｄ
B 、及び波長分散値ＤC を求めてもよい。この場合、第
１の光ファイバ側の一端から光を入射して求めた区間
Ａ、区間Ｂ、及び区間Ｃにおける波長分散値と被測定光
ファイバの第３の光ファイバ側の他端から光を入射して
求めた区間Ａ、区間Ｂ、及び区間Ｃにおける波長分散値
とをそれぞれ平均化して、区間Ａ、区間Ｂ、及び区間Ｃ
における波長分散値ＤA 、波長分散値ＤB 、及び波長分
散値ＤC を決定することとなる。従って、被測定光ファ
イバのいずれか一方の端部のみから光を入射して波長分
散値を求めた場合より、測定精度を２倍に向上させるこ
とができる。Light is incident from both one end of the measured optical fiber on the side of the first optical fiber and the other end of the measured optical fiber on the side of the third optical fiber to measure sections A, B, and Chromatic dispersion value D A , chromatic dispersion value D in section C
B and the chromatic dispersion value D C may be obtained. In this case, the chromatic dispersion values in the sections A, B, and C obtained by entering the light from one end on the first optical fiber side and the light from the other end on the third optical fiber side of the measured optical fiber are measured. The wavelength dispersion values in the sections A, B, and C obtained by incidence are averaged to obtain sections A, B, and C.
The chromatic dispersion value D A , the chromatic dispersion value D B , and the chromatic dispersion value D C are determined. Therefore, the measurement accuracy can be doubled as compared with the case where the chromatic dispersion value is obtained by injecting light from only one end of the measured optical fiber.
【００４７】[0047]
【発明の効果】以上、詳細に説明した通り、本発明に係
る光ファイバの波長分散測定方法によれば、光ファイバ
の任意の箇所で光ファイバを曲げ、その屈曲部から漏洩
させた光を受信して伝搬時間を測定することにより、光
ファイバの入射端から任意の箇所までの波長分散値を非
破壊で求めることができる。As described above in detail, according to the wavelength dispersion measuring method for an optical fiber according to the present invention, the optical fiber is bent at an arbitrary portion of the optical fiber and the light leaked from the bent portion is received. Then, by measuring the propagation time, the chromatic dispersion value from the incident end of the optical fiber to an arbitrary position can be obtained nondestructively.
【００４８】また、光ファイバの任意の２箇所で光ファ
イバを曲げ、それらの屈曲部から漏洩させた光を受信し
て伝搬時間を測定することにより、光ファイバの任意の
区間における波長分散値を非破壊で求めることができ
る。Further, the chromatic dispersion value in an arbitrary section of the optical fiber is measured by bending the optical fiber at any two points of the optical fiber and receiving the light leaked from the bent portions to measure the propagation time. It can be obtained nondestructively.
【００４９】また、光ファイバの全長にわたって任意に
分割した各区間における波長分散値を非破壊で求めるこ
とができるため、光ファイバの長手方向における波長分
散値の分布を非破壊で求めることがができる。従って、
できるだけ長尺のままでの使用が望まれる実際の敷設用
光ファイバ等において、非常に有効である。Since the chromatic dispersion value in each section arbitrarily divided over the entire length of the optical fiber can be obtained nondestructively, the distribution of the chromatic dispersion value in the longitudinal direction of the optical fiber can be obtained nondestructively. . Therefore,
This is very effective for actual laying optical fibers and the like, which are desired to be used as long as possible.
【００５０】また、光ファイバの両端からそれぞれ光を
入射し、それぞれに求めた光ファイバの任意の区間にお
ける波長分散値の平均をとって、その区間における波長
分散値とすることにより、波長分散測定の精度を高める
ことがができる。Further, the chromatic dispersion is measured by irradiating light from both ends of the optical fiber and averaging the chromatic dispersion values in the respective sections of the optical fiber obtained respectively to obtain the chromatic dispersion value in the section. The accuracy of can be improved.
【図１】本発明の実施の形態に係る光ファイバの波長分
散測定方法を実施するための波長分散測定装置を示す概
略図である。FIG. 1 is a schematic diagram showing a chromatic dispersion measuring apparatus for carrying out a chromatic dispersion measuring method for an optical fiber according to an embodiment of the present invention.
【図２】実施例１による被測定光ファイバの区間Ａにお
ける波長分散の測定結果を示すグラフである。FIG. 2 is a graph showing a measurement result of chromatic dispersion in a section A of the optical fiber to be measured according to Example 1.
【図３】実施例２による被測定光ファイバの区間Ｂにお
ける波長分散の測定結果を示すグラフである。FIG. 3 is a graph showing measurement results of chromatic dispersion in section B of the optical fiber under measurement according to the second embodiment.
【図４】実施例３による被測定光ファイバの区間Ａ、区
間Ｂ、及び区間Ｃにおける波長分散の測定結果を示すグ
ラフである。FIG. 4 is a graph showing measurement results of chromatic dispersion in section A, section B, and section C of the measured optical fiber according to the third embodiment.
【図５】従来の光ファイバの波長分散測定方法を説明す
るための図である。FIG. 5 is a diagram for explaining a conventional chromatic dispersion measuring method for an optical fiber.
１０…光源、１２…被測定光ファイバ、１４…光受信
器、１６…伝搬時間測定器、２０…光源、２２…カプラ
ー、２４…被測定光ファイバ、２６、２８…光受信器、
３０…位相計。10 ... Light source, 12 ... Optical fiber to be measured, 14 ... Optical receiver, 16 ... Propagation time measuring device, 20 ... Light source, 22 ... Coupler, 24 ... Optical fiber to be measured, 26, 28 ... Optical receiver,
30 ... Phase meter.
Claims (6)
部分を屈曲させ屈曲部とした光ファイバの前記第１の端
から複数の波長の光を入射する第１のステップと、 前記屈曲部から前記光ファイバの外へ漏洩した各波長の
光の検出する第２のステップと、 前記第１の端からの光の入射時刻と前記屈曲部からの漏
洩光の検出時刻との差である第１の伝搬時間を各波長に
ついて求める第３のステップと、 前記第１の伝搬時間と前記第１の端から前記屈曲部まで
の光路距離と基づいて、前記第１の端から前記屈曲部ま
での部分に関する第１の波長分散を求める第４のステッ
プと、 を備えることを特徴とする光ファイバの波長分散測定方
法。1. A first step of injecting light of a plurality of wavelengths from the first end of an optical fiber in which a portion apart from the first end by a first optical path distance is bent to form a bent portion, The second step of detecting the light of each wavelength leaked from the bent portion to the outside of the optical fiber, and the difference between the incident time of the light from the first end and the detected time of the leaked light from the bent portion. A third step of obtaining a certain first propagation time for each wavelength, and based on the first propagation time and the optical path distance from the first end to the bent portion, from the first end to the bent portion And a fourth step of obtaining a first chromatic dispersion for the above parts, and a chromatic dispersion measuring method for an optical fiber, comprising:
る第５のステップと、 前記屈曲部から前記光ファイバの外へ漏洩した各波長の
光と前記第１の端から出射した各波長の光の夫々検出す
る第６のステップと、 前記屈曲部からの漏洩光の検出時刻と前記第１の端から
の出射光の検出時刻との差である第２の伝搬時間を各波
長について求める第７のステップと、 各波長に関する前記第２の伝搬時間と前記屈曲部から前
記第１の端までの光路距離とに基づいて、前記屈曲部か
ら前記第１の端までの部分に関する第２の波長分散を求
める第８のステップと、 前記第１の波長分散と前記第２の波長分散との平均値で
ある第３の波長分散を求める第９のステップと、 を備えることを特徴とする請求項１記載の光ファイバの
波長分散測定方法。2. Following the fourth step, a fifth step of injecting light of a plurality of wavelengths from the second end of the optical fiber, and each wavelength leaked from the bent portion to the outside of the optical fiber. Of the light of each wavelength emitted from the first end, and the detection time of the leaked light from the bent portion and the detection time of the emitted light from the first end. A seventh step of obtaining a second propagation time which is a difference for each wavelength, and the bending portion based on the second propagation time for each wavelength and an optical path distance from the bending portion to the first end. An eighth step of obtaining a second chromatic dispersion for the portion from the first to the first end, and a third chromatic dispersion that is an average value of the first chromatic dispersion and the second chromatic dispersion. 9. The steps of 9 and 10 are included. 1. The method for measuring wavelength dispersion of an optical fiber according to 1.
部分を屈曲させた第１の屈曲部と前記第１の端から第２
の光路距離だけ離れた部分を屈曲させた第２の屈曲部と
を有する光ファイバの前記第１の端から複数の波長の光
を入射する第１のステップと、 前記第１の屈曲部および前記第２の屈曲部の夫々から前
記光ファイバの外へ漏洩した各波長の光の夫々検出する
第２のステップと、 前記第１の端からの光の入射時刻と前記第１の屈曲部か
らの漏洩光の検出時刻との差である第１の伝搬時間と前
記第１の端からの光の入射時刻と前記第２の屈曲部から
の漏洩光の検出時刻との差である第２の伝搬時間とを各
波長について求める第３のステップと、 各波長に関する前記第１の伝搬時間と前記第１の端から
前記第１の屈曲部までの光路距離と基づいて、前記第１
の端から前記第１の屈曲部までの部分に関する第１の波
長分散を求めるとともに、各波長に関する前記第２の伝
搬時間と前記第１の端から前記第２の屈曲部までの光路
距離と基づいて、前記第１の端から前記第２の屈曲部ま
での部分に関する第２の波長分散を求める第４ステップ
と、 前記第１の波長分散と前記第２の波長分散と前記第１の
屈曲部から前記第２の屈曲部までの光路距離とに基づい
て、前記第１の屈曲部から前記第２の屈曲部までの部分
に関する第３の波長分散を求める第５のステップと、 を備えることを特徴とする光ファイバの波長分散測定方
法。3. A first bent portion obtained by bending a portion apart from the first end by a first optical path distance and a second portion from the first end.
A first step of injecting light of a plurality of wavelengths from the first end of an optical fiber having a second bent portion formed by bending a portion separated by an optical path distance of, and the first bent portion and the A second step of detecting light of each wavelength leaked from each of the second bent portions to the outside of the optical fiber, an incident time of light from the first end, and a light from the first bent portion. The first propagation time, which is the difference between the leaked light detection time, the second propagation time, which is the difference between the light incident time from the first end and the leaked light detection time from the second bent portion. A third step of obtaining time for each wavelength; the first propagation time for each wavelength; and the optical path distance from the first end to the first bend,
The first chromatic dispersion for the portion from the end to the first bend, and based on the second propagation time for each wavelength and the optical path distance from the first end to the second bend. And a fourth step of obtaining a second chromatic dispersion for the portion from the first end to the second bent portion, the first chromatic dispersion, the second chromatic dispersion, and the first bent portion. To a second optical path distance from the second optical path to the second optical path, the fifth step of obtaining a third chromatic dispersion regarding the portion from the first optical path to the second optical path. Characteristic optical fiber chromatic dispersion measuring method.
る第６のステップと、 前記第１の屈曲部および前記第２の屈曲部の夫々から前
記光ファイバの外へ漏洩した各波長の光の夫々検出する
第７のステップと、 前記第２の端からの光の入射時刻と前記第１の屈曲部か
らの漏洩光の検出時刻との差である第３の伝搬時間と前
記第２の端からの光の入射時刻と前記第２の屈曲部から
の漏洩光の検出時刻との差である第４の伝搬時間とを各
波長について求める第８のステップと、 各波長に関する前記第３の伝搬時間と前記第１の端から
前記第１の屈曲部までの光路距離と基づいて、前記第２
の端から前記第１の屈曲部までの部分に関する第４の波
長分散を求めるとともに、各波長に関する前記第４の伝
搬時間と前記第２の端から前記第２の屈曲部までの光路
距離と基づいて、前記第２の端から前記第２の屈曲部ま
での部分に関する第５の波長分散を求める第９ステップ
と、 前記第４の波長分散と前記第５の波長分散と前記第１の
屈曲部から前記第２の屈曲部までの光路距離とに基づい
て、前記第１の屈曲部から前記第２の屈曲部までの部分
に関する第６の波長分散を求める第１０のステップと、 前記第３の波長分散と前記第６の波長分散との平均値で
ある第７の波長分散を求める第１１のステップと、 を備えることを特徴とする請求項３記載の光ファイバの
波長分散測定方法。4. Following the fifth step, a sixth step of injecting light of a plurality of wavelengths from the second end of the optical fiber, and a first bent portion and a second bent portion. A seventh step of detecting light of each wavelength leaked out of the optical fiber, an incident time of light from the second end, and a detected time of leak light from the first bent portion. For each wavelength, a third propagation time which is the difference between the first and second times, and a fourth propagation time which is the difference between the time of incidence of light from the second end and the time of detection of leaked light from the second bent portion. Based on the eighth step of obtaining, the third propagation time for each wavelength, and the optical path distance from the first end to the first bent portion, the second
A fourth chromatic dispersion for the portion from the end to the first bent portion, and based on the fourth propagation time for each wavelength and the optical path distance from the second end to the second bent portion. And a fifth step of obtaining a fifth chromatic dispersion for the portion from the second end to the second bent portion, the fourth chromatic dispersion, the fifth chromatic dispersion, and the first bent portion. From the first bending portion to the second bending portion based on the optical path distance from the second bending portion to the second bending portion, and a tenth step of obtaining a sixth chromatic dispersion relating to a portion from the first bending portion to the second bending portion; The chromatic dispersion measuring method for an optical fiber according to claim 3, further comprising: an eleventh step of obtaining a seventh chromatic dispersion which is an average value of the chromatic dispersion and the sixth chromatic dispersion.
の境界部を夫々屈曲した屈曲部を有する光ファイバの第
１の端から複数の波長の光を入射する第１のステップ
と、 夫々の前記屈曲部から前記光ファイバの外へ漏洩した各
波長の光および前記光ファイバの第２の端からの出射光
を夫々検出する第２のステップと、 前記第１の端からの光の入射時刻と夫々の前記屈曲部か
らの漏洩光の検出時刻または前記第２の端からの出射光
の検出時刻との差である第１の伝搬時間を各波長につい
て各屈曲部または前記第２の端に関して求める第３のス
テップと、 各波長に関する夫々の前記第１の伝搬時間と前記第１の
端から夫々の前記屈曲部または前記第２の端までの光路
距離と基づいて、前記第１の端から夫々の前記屈曲部ま
たは前記第２の端までの部分に関する第１の波長分散を
求める第４ステップと、 各前記区間の両端に関する夫々の第１の波長分散と各前
記区間の光路距離とに基づいて、各前記区間の第２の波
長分散を求める第５のステップと、 を備えることを特徴とする光ファイバの波長分散測定方
法。5. A first step of injecting light of a plurality of wavelengths from a first end of an optical fiber which is divided into a plurality of sections and has a bent portion in which a boundary portion of each of the sections is bent, respectively. Second step of detecting light of each wavelength leaked from the bent portion to the outside of the optical fiber and emitted light from the second end of the optical fiber, and incidence of light from the first end. The first propagation time, which is the difference between the time and the detection time of the leaked light from each of the bent portions or the detection time of the emitted light from the second end, is set to each bent portion or the second end for each wavelength. And a first optical path distance from each of the first propagation times and each of the first ends to each of the bends or the second ends for each wavelength. From each said bend or said second end A fourth step of obtaining a first chromatic dispersion for each section, and a second chromatic dispersion of each section based on the respective first chromatic dispersion at both ends of each section and the optical path distance of each section. A fifth step, and a method of measuring chromatic dispersion of an optical fiber, comprising:
射する第６のステップと、 夫々の前記屈曲部から前記光ファイバの外へ漏洩した各
波長の光および前記光ファイバの第１の端からの出射光
を夫々検出する第７のステップと、 前記第２の端からの光の入射時刻と夫々の前記屈曲部か
らの漏洩光の検出時刻または前記第１の端からの出射光
の検出時刻との差である第２の伝搬時間を各波長につい
て各屈曲部または前記第２の端に関して求める第８のス
テップと、 各波長に関する夫々の前記第２の伝搬時間と前記第２の
端から夫々の前記屈曲部または前記第１の端までの光路
距離と基づいて、前記第２の端から夫々の前記屈曲部ま
たは前記第１の端までの部分に関する第３の波長分散を
求める第９ステップと、 各前記区間の両端に関する夫々の第３の波長分散と各前
記区間の光路距離とに基づいて、各前記区間の第４の波
長分散を求める第１０のステップと、 前記第２の波長分散と前記第４の波長分散との平均値で
ある第５の波長分散を求める第１１のステップと、 を備えることを特徴とする請求項５記載の光ファイバの
波長分散測定方法。6. Following the fifth step, a sixth step of injecting light of a plurality of wavelengths from the second end of the optical fiber, and leakage from the respective bent portions to the outside of the optical fiber. The seventh step of detecting the respective wavelengths of light and the light emitted from the first end of the optical fiber, the time of incidence of the light from the second end, and the leakage of light from the respective bent portions. Eighth step of determining a detection time or a second propagation time, which is a difference from the detection time of the light emitted from the first end, for each bent portion or the second end for each wavelength, and for each wavelength, On the basis of the second propagation time and the optical path distance from the second end to each of the bent portions or the first end, the respective bent portion or the first end from the second end. Find the third chromatic dispersion for the parts up to A ninth step; a tenth step of obtaining a fourth chromatic dispersion of each section based on a third chromatic dispersion of each end of each section and an optical path distance of each section; 11. An optical fiber chromatic dispersion measuring method according to claim 5, further comprising: an eleventh step of obtaining a fifth chromatic dispersion, which is an average value of the chromatic dispersion and the fourth chromatic dispersion.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP27451395A JPH09113415A (en) | 1995-10-23 | 1995-10-23 | Method for measuring wavelength distribution of optical fiber |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP27451395A JPH09113415A (en) | 1995-10-23 | 1995-10-23 | Method for measuring wavelength distribution of optical fiber |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| JPH09113415A true JPH09113415A (en) | 1997-05-02 |
Family
ID=17542752
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP27451395A Pending JPH09113415A (en) | 1995-10-23 | 1995-10-23 | Method for measuring wavelength distribution of optical fiber |
Country Status (1)
| Country | Link |
|---|---|
| JP (1) | JPH09113415A (en) |
Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP2002365165A (en) * | 2001-06-08 | 2002-12-18 | Sumitomo Electric Ind Ltd | Wavelength dispersion measuring device and method |
| US7495832B2 (en) | 2002-12-17 | 2009-02-24 | Nec Corporation | Light dispersion filter and optical module |
| JP2009169429A (en) * | 2009-04-17 | 2009-07-30 | Nec Corp | Optical module |
-
1995
- 1995-10-23 JP JP27451395A patent/JPH09113415A/en active Pending
Cited By (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP2002365165A (en) * | 2001-06-08 | 2002-12-18 | Sumitomo Electric Ind Ltd | Wavelength dispersion measuring device and method |
| US7495832B2 (en) | 2002-12-17 | 2009-02-24 | Nec Corporation | Light dispersion filter and optical module |
| WO2009075006A1 (en) * | 2002-12-17 | 2009-06-18 | Kenji Sato | Light dispersion filter and optical module |
| US7944613B2 (en) | 2002-12-17 | 2011-05-17 | Nec Corporation | Optical module having three or more optically transparent layers |
| US8456741B2 (en) | 2002-12-17 | 2013-06-04 | Nec Corporation | Optical module having three or more optically transparent layers |
| JP2009169429A (en) * | 2009-04-17 | 2009-07-30 | Nec Corp | Optical module |
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