JP2539051B2 - Distributed optical fiber sensor - Google Patents
Distributed optical fiber sensorInfo
- Publication number
- JP2539051B2 JP2539051B2 JP1210616A JP21061689A JP2539051B2 JP 2539051 B2 JP2539051 B2 JP 2539051B2 JP 1210616 A JP1210616 A JP 1210616A JP 21061689 A JP21061689 A JP 21061689A JP 2539051 B2 JP2539051 B2 JP 2539051B2
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- JP
- Japan
- Prior art keywords
- optical
- optical fiber
- physical quantity
- pulse
- distribution
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
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- Measuring Temperature Or Quantity Of Heat (AREA)
- Arrangements For Transmission Of Measured Signals (AREA)
- Investigating Or Analysing Materials By Optical Means (AREA)
Description
【発明の詳細な説明】 ［発明の目的］ （産業上の利用分野） この発明は、光ファイバ内を導波する光パルスによる
後方散乱光を検出してファイバ周囲の物理量分布を求め
る分布型光ファイバセンサに関する。DETAILED DESCRIPTION OF THE INVENTION Object of the Invention (Industrial field of application) The present invention detects a backscattered light due to an optical pulse guided in an optical fiber to obtain a physical quantity distribution around the fiber. Regarding a fiber sensor.
（従来の技術） プラントなどにおける反応炉、配管などの長尺構造物
やトンネル、海底などの広域物理量分布、主には温度分
布を測定する場合、従来は点センサを被測定対象の各位
置に配置して測定するようにしている。(Prior art) When measuring a wide range of physical quantity distributions such as reactors, long structures such as pipes, tunnels, seabeds, etc. in plants, mainly temperature distributions, conventionally, point sensors were installed at each position of the measured object. It is arranged and measured.
しかしながら、このような点センサの集合では、デー
タ伝送の面、信号処理時間の問題、および経済性などの
理由から数十から数百のセンサによる荒い分布計測しか
実現できない問題点があった。However, such a set of point sensors has a problem in that only rough distribution measurement by several tens to several hundreds of sensors can be realized due to reasons such as data transmission, signal processing time, and economical reasons.
そこで、広域計測のためには、本質的に分布計測が可
能な装置として、例えば画像計測も利用されるようにな
っているが、分布型光ファイバセンサも本質的に一次元
の分布計測ができる分布型センサである。Therefore, for wide area measurement, for example, image measurement has come to be used as a device that can essentially perform distribution measurement, but a distributed optical fiber sensor can also essentially perform one-dimensional distribution measurement. It is a distributed sensor.
この分布型光ファイバセンサの原理は、第４図に示す
ようにレーザー光源１から単発パルス２を光ファイバ３
に入射し、光ファイバ３内の各部からの後方散乱光4a,4
b,…を検出して、この後方散乱光の長さ方向の分布を時
系列信号５に変換して求める。そうすれば、この後方散
乱光の強度が被測定物理量に依存しているため、散乱光
分布が測定できる。The principle of this distributed optical fiber sensor is that a single pulse 2 is emitted from a laser light source 1 into an optical fiber 3 as shown in FIG.
Backscattered light 4a, 4 from each part in the optical fiber 3
.. are detected, and the distribution of the backscattered light in the lengthwise direction is converted into the time-series signal 5 to be obtained. Then, since the intensity of the backscattered light depends on the physical quantity to be measured, the scattered light distribution can be measured.
ところが、後方散乱光は検出器に至るまでにファイバ
３内を減衰しながら伝播するために、受信される信号強
度は散乱を受けた位置とファイバ３の減衰率との積の形
になり、第４図の時系列信号５のようになる。このた
め、ファイバ３の損失の影響を補償するために、従来
は、あらかじめファイバの減衰特性６を測定しておき、
測定結果５から減衰特性６を引き去ることにより被測定
物理量分布７を求めていた。However, since the backscattered light propagates while being attenuated in the fiber 3 before reaching the detector, the received signal strength is in the form of the product of the scattered position and the attenuation factor of the fiber 3, It becomes like the time-series signal 5 in FIG. Therefore, in order to compensate the influence of the loss of the fiber 3, conventionally, the attenuation characteristic 6 of the fiber is measured in advance,
The measured physical quantity distribution 7 is obtained by subtracting the attenuation characteristic 6 from the measurement result 5.
（発明が解決しようとする課題） しかしながら、このような従来の分布型光ファイバセ
ンサでは、光ファイバの伝送損失が光ファイバケーブル
の敷設状況の影響を受けるために減衰特性が一定ではな
く、敷設現場ごとに減衰特性を求めなければ正しい測定
が実現できない問題点があり、また被測定物理量の影響
を受けない状況で減衰特性を測定する必要があるが、こ
のような条件は実現することが困難であり、結果として
減衰特性の補償精度を向上させることができない問題点
があった。(Problems to be solved by the invention) However, in such a conventional distributed optical fiber sensor, since the transmission loss of the optical fiber is affected by the laying condition of the optical fiber cable, the attenuation characteristic is not constant and the laying site There is a problem that correct measurement cannot be realized unless the attenuation characteristics are obtained for each of them, and it is necessary to measure the attenuation characteristics under the condition that the physical quantity to be measured is not affected, but it is difficult to realize such a condition. As a result, there is a problem that the compensation accuracy of the attenuation characteristic cannot be improved.
この発明は、このような従来の問題点に鑑みてなされ
たもので、光ファイバの伝送損失の影響を考慮すること
無く後方散乱光分布を正確に測定することのできる分布
型光ファイバセンサを提供することを目的とする。The present invention has been made in view of such conventional problems, and provides a distributed optical fiber sensor capable of accurately measuring the backscattered light distribution without considering the influence of the transmission loss of the optical fiber. The purpose is to do.
［発明の構成］ （課題を解決するための手段） この発明の分布型光ファイバセンサは、光パルスを発
生する光源と、この光源からの光パルスを異なった励振
状態で光ファイバに結合させる複数の励振器と、光パル
スを複数の励振器に切り替える光スイッチと、物理量を
測定するために励振器に接続された測定用光ファイバ
と、この測定用光ファイバの後方散乱光を検出器に導く
ための方向性結合器と、後方散乱光を電気信号に変換し
て増幅する検出器と、この検出器の出力に対して前記複
数の励振器からの異なった励振状態の光パルスに対する
あらかじめ決定されている光ファイバの伝送損失比を基
にして補正演算を行い、光ファイバの長さ方向各部の物
理量分布を求める信号処理装置とを備えたものである。[Structure of the Invention] (Means for Solving the Problems) A distributed optical fiber sensor of the present invention comprises a plurality of light sources for generating optical pulses and a plurality of optical pulses from the light sources coupled to optical fibers in different excitation states. Exciter, an optical switch that switches the optical pulse to multiple exciters, a measurement optical fiber connected to the exciter to measure the physical quantity, and the backscattered light of this measurement optical fiber is guided to the detector. A directional coupler for detecting, a detector for converting backscattered light into an electric signal and amplifying the electric signal, and a predetermined for light pulses of different excitation states from the plurality of exciters with respect to the output of the detector. And a signal processing device for obtaining a physical quantity distribution of each part in the length direction of the optical fiber by performing a correction calculation based on the transmission loss ratio of the optical fiber.
（作用） この発明の分布型光ファイバセンサでは、あらかじめ
理想状態で光ファイバケーブルに対して複数の励振状態
の光パルスを入射させてそれぞれの励振状態の光パルス
に対する後方散乱光分布の減衰特性を得て、各位置での
減衰特性比を求めておき、これを伝送損失比として信号
処理装置に補正値として与えておく。(Operation) In the distributed optical fiber sensor of the present invention, the optical characteristics of the backscattered light distribution with respect to the optical pulses in the respective excited states are preliminarily injected into the optical fiber cable in an ideal state. Then, the attenuation characteristic ratio at each position is obtained, and this is given to the signal processing device as a correction value as a transmission loss ratio.
そして、光パルス光源からの光パルスを光スイッチに
より異なる励振状態を作り出す複数の励振器に切り替え
て与え、それぞれの励振器からの光パルスについて検出
器により光ファイバの後方散乱光を検出し、信号処理装
置に与える。Then, the optical pulse from the optical pulse light source is switched to a plurality of exciters that generate different excitation states by an optical switch and given, and the detector detects the backscattered light of the optical fiber for the optical pulse from each exciter, and outputs the signal. Feed to the processor.
信号処理装置では、励振状態の異なる光パルスそれぞ
れについての光ファイバの長さ方向各部の後方散乱光分
布を求め、励振状態の異なる光パルスごとの伝送損失比
を基にして補正演算をなし、光ファイバの長さ方向各部
の最終的な物理量分布を求め、出力する。In the signal processing device, the backscattered light distribution of each part in the longitudinal direction of the optical fiber for each of the optical pulses with different excitation states is obtained, and the correction calculation is performed based on the transmission loss ratio for each optical pulse with different excitation states. The final physical quantity distribution of each part in the length direction of the fiber is calculated and output.
（実施例） 以下、この発明の実施例を図に基づいて説明する。(Example) Hereinafter, an example of the present invention will be described with reference to the drawings.
第１図はこの発明の一実施例の回路構成を示してお
り、光パルスを出力するレーザー光源１と、この光源１
からの光パルスを切り替え出力する光スイッチ２と、光
スイッチ２により切り替えられた光パルスを受けて異な
る励振状態にして出力する低次モード光励振器３と高次
モードまで含む一様モード光励振器４と、これらの光励
振器3,4からの光を光ケーブル側に出力し、光ケーブル
からの後方散乱光を別系統に分離する方向性結合器5,6
と、これらの方向性結合器5,6からの光出力を光ケーブ
ルに伝達する光ファイバ7,8と、これらの光ファイバ7,8
により伝達される光パルスが入射される光ケーブル９と
を備えている。FIG. 1 shows a circuit configuration of an embodiment of the present invention. A laser light source 1 for outputting an optical pulse and this light source 1 are shown.
Optical switch 2 for selectively outputting the optical pulse from the optical switch, a low-order mode optical exciter 3 for receiving the optical pulse switched by the optical switch 2 and outputting it in different excitation states, and a uniform-mode optical excitation including even higher-order modes And the directional couplers 5 and 6 that output the light from the optical exciters 3 and 4 to the optical cable side and separate the backscattered light from the optical cable into another system.
And optical fibers 7 and 8 for transmitting the optical output from these directional couplers 5 and 6 to the optical cable, and these optical fibers 7 and 8
And an optical cable 9 on which the optical pulse transmitted by
また、光ケーブル９から方向性結合器7,8を介して光
ファイバ10,11により取り出される後方散乱光を通過さ
せる方向性結合器12と、後方散乱光を電気信号に変換す
る検出器13と、電気信号の増幅器14と、アナログ信号を
ディジタル信号に変換するA/Dコンバータ15と、ディジ
タル信号処理を行って光ケーブル９の長さ方向の被測定
物理量の分布状態を算出する信号処理装置16と、この信
号処理装置16による信号処理結果を出力するディスプレ
イ17とを備えている。Further, a directional coupler 12 that allows the backscattered light extracted by the optical fibers 10 and 11 from the optical cable 9 via the directional couplers 7 and 8 to pass through, and a detector 13 that converts the backscattered light into an electrical signal. An electric signal amplifier 14, an A / D converter 15 for converting an analog signal into a digital signal, a signal processing device 16 for performing digital signal processing and calculating a distribution state of the physical quantity to be measured in the length direction of the optical cable 9, A display 17 for outputting a signal processing result by the signal processing device 16 is provided.
次に、上記の構成の分布型光ファイバセンサの動作に
ついて説明する。Next, the operation of the distributed optical fiber sensor having the above configuration will be described.
光源１から発せられた光パルスは光ケーブル９に導か
れ、光ケーブル９の内部で発生する後方散乱光は方向性
結合器5,6,12を介して検出器13で電気信号に変換された
後、増幅器14で増幅し、A/Dコンバータ15でディジタル
化され、信号処理記憶装置16で処理され、処理結果はデ
ィスプレイ17により表示される。The light pulse emitted from the light source 1 is guided to the optical cable 9, and the backscattered light generated inside the optical cable 9 is converted into an electric signal by the detector 13 via the directional couplers 5, 6, 12 and then, The signal is amplified by the amplifier 14, digitized by the A / D converter 15, processed by the signal processing memory device 16, and the processing result is displayed on the display 17.
２つの異なった励振状態を実現するために光源１の出
力は励振モードの異なる光励振器3,4の一方に導かれ
る。この切り替えは光スイッチ２により行われ、信号処
理装置16により制御される。In order to realize two different excitation states, the output of the light source 1 is guided to one of the optical exciters 3 and 4 having different excitation modes. This switching is performed by the optical switch 2 and controlled by the signal processing device 16.
一般に光パルスに対する光ケーブル９は、比較的短い
距離では高次モードまで含んだ一様モード光の方が減衰
率が大きく、検出器13で検出される散乱光の時間推移は
第２図に示すようになる。すなわち、一様モード励振状
態の場合には伝送損失が大きく、Ｂに示す特性となり、
低次モード励振状態の場合にはＡに示す特性となる。Generally, in the optical cable 9 for the optical pulse, the uniform mode light including the higher order modes has a larger attenuation rate at a relatively short distance, and the time transition of the scattered light detected by the detector 13 is as shown in FIG. become. That is, in the uniform mode excitation state, the transmission loss is large and the characteristic shown in B is obtained.
In the low-order mode excitation state, the characteristics shown in A are obtained.
そこで、信号処理装置16では、次の考察に基づく演算
を行うことにより後方散乱光の強度分布を算出し、光ケ
ーブル９の周りの被測定物理量の分布をディスプレイ17
に表示する。Therefore, the signal processing device 16 calculates the intensity distribution of the backscattered light by performing the calculation based on the following consideration, and displays the distribution of the measured physical quantity around the optical cable 9 on the display 17.
To be displayed.
つまり、光パルス反射法の場合の検出器13の出力Ｐ
（ｔ）は、次のようになることが知られている。That is, the output P of the detector 13 in the case of the optical pulse reflection method
It is known that (t) becomes as follows.
Ｐ（ｔ）＝Ｋ・Ｓ・αｓ（ｘ）・Po・Ｗ×ｅ
−α・vg・ｔ …（１） ここで、 t :時間 S :散乱光の内の後方散乱光として光ケーブル９内を伝
送する割合 Po：光パルスピークパワー W :光パルス幅 α：光ケーブル９の伝送損失 vg：光ケーブル９内の光の群速度 K :比例定数 であり、αs（ｘ）は位置ｘにおける散乱光となる割合
を示し、その値が被測定物理量に依存している。P (t) = K ・ S ・ αs (x) ・ Po ・ W × e
−α · vg · t (1) where, t: time S: ratio of scattered light that is transmitted in the optical cable 9 as backscattered light Po : optical pulse peak power W: optical pulse width α: optical cable 9 Transmission loss v g : Group velocity K of light in the optical cable 9: Proportional constant, and α s (x) represents a ratio of scattered light at the position x, and the value depends on the measured physical quantity.
そこで、今、後方散乱光の割合Ｓは光ケーブル９内で
一定であり、光パルスピークパワーPo、光パルス幅Ｗは
十分に再現性が良く、一定であると考えることができる
ので、Ｋ・Ｓ・Po・Ｗは改めて Ｋ＝Ｋ・Ｓ・Po・Ｗ と置くことができ、上記の（１）式は、 Ｐ（ｔ）＝Ｋ・αs（ｘ）・ｅ−α・vg・ｔ …（２） となる。Therefore, the ratio S of the backscattered light is now constant in the optical cable 9, and the optical pulse peak power P o and the optical pulse width W are sufficiently reproducible and can be considered to be constant. S · P o · W can be rewritten as K = K · S · P o · W, and the above equation (1) is expressed as P (t) = K · α s (x) · e −α · vg・ T ... (2)
次に、この式（２）に対して、光スイッチ２を光励振
器３に接続した場合の検出信号は、伝送損失をαとすれ
ば、 P1（ｔ）＝Ｋ・αs（ｘ）・ｅ−α・vg・ｔ であり、次に光スイッチ２を光励振器４に接続した場合
の検出信号は、伝送損失をβとすれば、 P2（ｔ）＝Ｋ・αs（ｔ）・ｅ−β・vg・ｔ である。Next, with respect to this equation (2), the detection signal when the optical switch 2 is connected to the optical exciter 3 is P 1 (t) = K · α s (x), where α is the transmission loss.・ E− α ・ vg ・ t , and the detection signal when the optical switch 2 is connected to the optical exciter 4 next is P 2 (t) = K ・ α s (t ) · E −β · vg · t .
ここで、両信号の対数をとれば、 1nP1（ｔ）＝1nK＋1nαs（ｘ）−α・vg・ｔ 1nP2（ｔ）＝1nK＋1nαs（ｘ）−β・vg・ｔ となる。Here, if the logarithm of both signals is taken, it becomes 1nP 1 (t) = 1nK + 1nα s (x) −α · vg · t 1nP 2 (t) = 1nK + 1nα s (x) −β · vg · t.
さらに、上記の両式からvg・ｔの項を消去して1nαs
（ｘ）について整理すれば、 となる。Furthermore, by eliminating the term vg · t from both equations above, 1nα s
As for (x), Becomes
ここで、α／βは２つの励振モードの伝送損失の比を
表わしており、これをｋとすれば、 となり、散乱光の値は伝送損失の比ｋを与えれば求まる
ことが分かる。すなわち、伝送損失そのものの値は周囲
のいろいろな条件により変化するが、２つの励振状態の
違いによる伝送損失の比は１次近似的にほぼ一定に保持
されると考えられる。Here, α / β represents the ratio of the transmission loss in the two excitation modes, and if this is k, then It can be seen that the value of the scattered light can be obtained by giving the transmission loss ratio k. That is, although the value of the transmission loss itself changes depending on various surrounding conditions, it is considered that the ratio of the transmission loss due to the difference between the two excitation states is kept approximately constant in a first-order approximation.
したがって、検出器13により検出される光励振器3,4
それぞれから出る光パルスに対する後方散乱光強度P
1（ｔ），P2（ｔ）を測定することにより伝送損失の変
化に影響されること無く、散乱光分布αs（ｘ）の測定
が可能となり、安定した物理量の測定ができる。Therefore, the optical exciters 3 and 4 detected by the detector 13
Backscattered light intensity P for each light pulse
By measuring 1 (t) and P 2 (t), the scattered light distribution α s (x) can be measured without being affected by the change in transmission loss, and a stable physical quantity can be measured.
なお、この発明は上記の実施例に限定されず、例えば
第３図に示すように方向性結合器5,6と光ケーブル９と
の間に光ファイバ7,8に対して方向性結合器18を備えれ
ば、励振状態を乱さないで１本の光ファイバ19で光ケー
ブル９と光源１側との間の長い距離を接続することがで
き、経済性を向上させることができると共に、散乱係数
αsのばらつきをなくすことができる。The present invention is not limited to the above embodiment, and for example, as shown in FIG. 3, a directional coupler 18 is provided between the optical fibers 7 and 8 between the directional couplers 5 and 6 and the optical cable 9. If provided, it is possible to connect a long distance between the optical cable 9 and the light source 1 side with one optical fiber 19 without disturbing the excitation state, and it is possible to improve the economical efficiency and the scattering coefficient α s. Can be eliminated.
［発明の効果］ 以上のようにこの発明によれば、光パルスの励振状態
を変化させて光ファイバに入射させ、各々の励振状態の
光パルスに対する後方散乱光強度を時系列分布で求め、
減衰特性の補正をあらかじめ求められている励振状態の
異なる２種の光パルスの減衰率の比に基づいて計算し、
被測定物理量の光ファイバの長さ方向の分布を求めるよ
うにしているため、従来のようにあらかじめ決定されて
いる固定的な減衰特性に基づいて後方散乱光強度の時系
列分布を求めるのに比べて光ファイバの外力の影響によ
る測定誤差が出にくく、正確な物理量測定ができる。[Effects of the Invention] As described above, according to the present invention, the excitation state of an optical pulse is changed and made incident on an optical fiber, and the backscattered light intensity for the optical pulse in each excitation state is obtained in a time series distribution,
The correction of the attenuation characteristic is calculated based on the ratio of the attenuation rates of the two types of optical pulses having different excitation states which are obtained in advance,
Since the distribution of the physical quantity to be measured in the length direction of the optical fiber is obtained, compared to the conventional case where the time-series distribution of the backscattered light intensity is obtained based on the fixed attenuation characteristic that is determined in advance. As a result, a measurement error due to the influence of the external force of the optical fiber is less likely to occur, and an accurate physical quantity can be measured.
第１図はこの発明の一実施例の回路ブロック図、第２図
は上記の実施例で用いる２つの異なる励振状態の光パル
スに対する光ファイバの減衰特性を示すグラフ、第３図
はこの発明の他の実施例のブロック図、第４図は一般的
な分布型光ファイバセンサの概略構成を示す説明図であ
る。 １…光パルス光源、２…光スイッチ ３…低次モード光励振器 ４…一様モード光励振器 5,6…方向性結合器、7,8…光ファイバ ９…光ケーブル、10,11…光ファイバ 12…方向性結合器、13…検出器 14…増幅器、15…A/Dコンバータ 16…信号処理装置、17…ディスプレイFIG. 1 is a circuit block diagram of an embodiment of the present invention, FIG. 2 is a graph showing attenuation characteristics of an optical fiber with respect to optical pulses in two different excitation states used in the above embodiment, and FIG. 3 is a graph of the present invention. FIG. 4 is a block diagram of another embodiment, and FIG. 4 is an explanatory diagram showing a schematic configuration of a general distributed optical fiber sensor. 1 ... Optical pulse light source, 2 ... Optical switch 3 ... Low-order mode optical exciter 4 ... Uniform mode optical exciter 5, 6 ... Directional coupler, 7, 8 ... Optical fiber 9 ... Optical cable, 10, 11 ... Optical Fiber 12 ... Directional coupler, 13 ... Detector 14 ... Amplifier, 15 ... A / D converter 16 ... Signal processing device, 17 ... Display
Claims (1)
バに結合させる複数の励振器と、 光パルスを複数の励振器に切り替える光スイッチと、 物理量を測定するために励振器に接続された測定用光フ
ァイバと、 この測定用光ファイバの後方散乱光を検出器に導くため
の方向性結合器と、 後方散乱光を電気信号に変換して増幅する検出器と、 この検出器の出力に対して前記複数の励振器からの異な
った励振状態の光パルスに対するあらかじめ決定されて
いる光ファイバの伝送損失比を基にして補正演算を行
い、光ファイバの長さ方向各部の物理量分布を求める信
号処理装置とを備えて成る分布型光ファイバセンサ。1. A light source for generating an optical pulse, a plurality of exciters for coupling the optical pulse from the light source to an optical fiber in different excitation states, an optical switch for switching the optical pulse to the plurality of exciters, and a physical quantity. Measuring optical fiber connected to the exciter to measure the, the directional coupler for guiding the backscattered light of this measuring optical fiber to the detector, and the backscattered light converted to an electrical signal and amplified. And a correction calculation based on a predetermined transmission loss ratio of the optical fiber with respect to the optical pulses of different excitation states from the plurality of exciters, And a signal processing device for obtaining a physical quantity distribution of each part in the length direction of the distribution type optical fiber sensor.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP1210616A JP2539051B2 (en) | 1989-08-17 | 1989-08-17 | Distributed optical fiber sensor |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP1210616A JP2539051B2 (en) | 1989-08-17 | 1989-08-17 | Distributed optical fiber sensor |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| JPH0375533A JPH0375533A (en) | 1991-03-29 |
| JP2539051B2 true JP2539051B2 (en) | 1996-10-02 |
Family
ID=16592277
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP1210616A Expired - Fee Related JP2539051B2 (en) | 1989-08-17 | 1989-08-17 | Distributed optical fiber sensor |
Country Status (1)
| Country | Link |
|---|---|
| JP (1) | JP2539051B2 (en) |
Families Citing this family (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPH0772141B2 (en) * | 1987-07-29 | 1995-08-02 | マイヤー・ルーイス・コーバル | Gamma and globulin preparations suitable for intravenous administration |
| JP2606638B2 (en) * | 1991-08-02 | 1997-05-07 | 日立電線株式会社 | Detection method of physical quantity distribution along optical fiber |
| CN106644400A (en) * | 2016-12-30 | 2017-05-10 | 江苏骏龙光电科技股份有限公司 | Adaptive-range optical cable measuring device |
-
1989
- 1989-08-17 JP JP1210616A patent/JP2539051B2/en not_active Expired - Fee Related
Also Published As
| Publication number | Publication date |
|---|---|
| JPH0375533A (en) | 1991-03-29 |
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