JP3440721B2 - Multi-point strain and temperature sensor - Google Patents
Multi-point strain and temperature sensorInfo
- Publication number
- JP3440721B2 JP3440721B2 JP30021896A JP30021896A JP3440721B2 JP 3440721 B2 JP3440721 B2 JP 3440721B2 JP 30021896 A JP30021896 A JP 30021896A JP 30021896 A JP30021896 A JP 30021896A JP 3440721 B2 JP3440721 B2 JP 3440721B2
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- Prior art keywords
- strain
- temperature
- light
- optical fiber
- fbg
- Prior art date
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Description
【０００１】[0001]
【発明の属する技術分野】本発明は、光を利用して歪み
を計測する歪みセンサに係り、特に、多点での計測に適
し、しかも温度と共に正確な歪みを計測できる多点型歪
み及び温度センサに関するものである。BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a strain sensor for measuring strain by using light, and more particularly to a multi-point strain and temperature suitable for multi-point measurement and capable of accurately measuring strain with temperature. It relates to a sensor.
【０００２】[0002]
【従来の技術】従来、歪みセンサには、光を利用したも
のや電気的なものなどがある。光を利用した歪みセンサ
としては、光ファイバ中の後方ブルリアン散乱光を検出
することにより、光ファイバの長手方向の歪み分布を計
測するＢＯＴＤＡ（またはＢＯＴＤＲ；Brillouin Opti
cal Time Domain AnalyzerまたはReflectometer ，参考
文献“ブルリアン分光による光ファイバのひずみ分光測
定”，堀口他，信学論，J73-B-I(1990)pp.144-152 ）、
あるいはファイバブラッググレーティング（Fiber Brag
g Grating;以下ＦＢＧと略す）を複数用いることにより
多点計測を可能にしたもの（参考文献“A 60 elements
fiber Bragg grating sensor system ”M.A.Davis et a
l.,OFS-11(Sapporo,Japan,May 1996)Conference Procee
dings,pp.100-103）があり、今日では、これらの歪みセ
ンサは研究開発段階を経ていわゆる第１世代の製品とし
てようやく市販されつつある。2. Description of the Related Art Conventionally, there are a strain sensor using light and an electric sensor. A strain sensor utilizing light is a BOTDA (or BOTDR; Brillouin Opti) that measures the strain distribution in the longitudinal direction of the optical fiber by detecting backward Brillouin scattered light in the optical fiber.
cal Time Domain Analyzer or Reflectometer, Reference "Strain spectroscopy of optical fiber by Brillouin spectroscopy", Horiguchi et al., Theoretical theory, J73-BI (1990) pp.144-152),
Or Fiber Brag Grating (Fiber Brag
Multi-point measurement is made possible by using a plurality of g Gratings (hereinafter abbreviated as FBGs) (reference “A 60 elements”).
fiber Bragg grating sensor system "MADavis et a
l., OFS-11 (Sapporo, Japan, May 1996) Conference Procee
dings, pp.100-103), and nowadays, these strain sensors are finally being marketed as so-called first-generation products through the research and development stage.
【０００３】電気的な歪みセンサとしては、歪みが加わ
ると抵抗値が変化するという歪みゲージが以前から市販
されている。As an electric strain sensor, a strain gauge, which changes its resistance value when strain is applied, has been commercially available for a long time.
【０００４】[0004]
【発明が解決しようとする課題】ＢＯＴＤＡにしてもＦ
ＢＧによる歪みセンサにしても、歪みに応じて変化する
物理量を光によって測定するものであるが、この歪みを
算出するための物理量が温度によっても変化する。即
ち、ＢＯＴＤＡの場合、ブルリアン周波数のシフト量が
温度によって変化し、ＦＢＧによる歪みセンサの場合、
グレーティングで反射または透過する光のピーク波長が
温度によって変化する。このため、歪み測定の際に周囲
の温度変化があると測定誤差が生じることになる。よっ
て、正確な歪み測定を行うためには、歪みによる物理量
変化と温度による物理量変化とを区別して測定しなけれ
ばならない。[Problems to be Solved by the Invention] F
Even with a strain sensor based on BG, a physical quantity that changes according to strain is measured by light, but the physical quantity for calculating this strain also changes with temperature. That is, in the case of BOTDA, the amount of shift of the Brillouin frequency changes with temperature, and in the case of the strain sensor based on FBG,
The peak wavelength of light reflected or transmitted by the grating changes with temperature. Therefore, if there is a change in ambient temperature during strain measurement, a measurement error will occur. Therefore, in order to perform accurate strain measurement, it is necessary to distinguish between the change in physical quantity due to strain and the change in physical quantity due to temperature.
【０００５】ＢＯＴＤＡにおいては上記の問題は解決さ
れていない。ＦＢＧによる歪みセンサにおいては、第１
に、ＦＢＧによる歪み測定ポイントに別途温度計を取り
付け、この温度計による温度で補正をする方法がある
が、多点計測を行う場合には各々の温度計を読取る手段
が複雑で大掛かりなものとなり、実用的でない。第２
に、１箇所の歪み測定ポイントにタイプの異なるＦＢＧ
を複数用いることにより歪みによる変化と温度による変
化とを区別して測定する方法も研究されているが、この
ためには正確な波長測定（０．０１ｎｍ以下の正確さを
要する）を行わなければならず、波長測定手段が複雑で
高価なものとなる。また、なるべく近接した光ファイバ
上にＦＢＧを製作しなくてはならないが、そこで干渉ノ
イズの生ずる可能性があり、さらに製造技術にも精密さ
を要求される。The above problem has not been solved in BOTDA. In the strain sensor based on FBG, the first
In addition, there is a method in which a thermometer is separately attached to the strain measurement point by the FBG and the temperature is corrected by this thermometer. However, when performing multipoint measurement, the means for reading each thermometer becomes complicated and large-scale. Not practical. Second
In addition, one strain measurement point has different types of FBG
A method of distinguishing between changes due to strain and changes due to temperature by using a plurality of is also studied, but for this purpose, accurate wavelength measurement (accuracy of 0.01 nm or less is required) must be performed. Therefore, the wavelength measuring means becomes complicated and expensive. Further, although it is necessary to manufacture FBGs on optical fibers as close to each other as possible, there is a possibility that interference noise will occur there, and the manufacturing technology also requires precision.
【０００６】電気的な歪みゲージは、多点計測を行う場
合には測定装置が複雑で大掛かりなものとなり、コスト
もかかるため実用的でない。[0006] The electrical strain gauge is not practical because the measuring device is complicated and large-scaled and costly when performing multipoint measurement.
【０００７】そこで、本発明の目的は、上記課題を解決
し、多点での計測に適し、しかも温度と共に正確な歪み
を計測できる多点型歪み及び温度センサを提供すること
にある。SUMMARY OF THE INVENTION An object of the present invention is to solve the above problems and to provide a multi-point strain and temperature sensor suitable for multi-point measurement and capable of measuring accurate strain with temperature.
【０００８】[0008]
【課題を解決するための手段】上記目的を達成するため
に本発明は、歪みに応じて光反射ピーク波長が変化する
ファイバブラッググレーティング（ＦＢＧ）を光ファイ
バに直列に複数挿入し、この光ファイバの一端より各Ｆ
ＢＧからの特定波長の反射光量をＯＴＤＲで測定すると
共に、光ファイバ中からの後方散乱光をＯＴＤＲで測定
することにより上記光ファイバの長手方向に沿った温度
分布を求め、この温度分布に基づき各ＦＢＧの温度依存
による反射光量変化分を補正し、この補正された反射光
量から各ＦＢＧにおける歪みを求めるものである。In order to achieve the above object, the present invention is to insert a plurality of fiber Bragg gratings (FBGs) whose optical reflection peak wavelength changes according to strain into an optical fiber in series. Each F from one end of
The amount of reflected light of a specific wavelength from the BG is measured by OTDR, and the backscattered light from the optical fiber is measured by OTDR to obtain the temperature distribution along the longitudinal direction of the optical fiber, and based on this temperature distribution, The amount of change in reflected light amount due to the temperature dependence of the FBG is corrected, and the distortion in each FBG is obtained from the corrected amount of reflected light.
【０００９】上記ＦＢＧを挿入した光ファイバを予め測
定することにより反射光量を歪みに応じた成分と温度に
応じた成分との和で表した関係式を求めておき、この関
係式に反射光量及び温度を代入して歪みを求めてもよ
い。By measuring the optical fiber in which the FBG is inserted in advance, a relational expression expressing the amount of reflected light as a sum of a component according to strain and a component according to temperature is obtained, and the relational amount of reflected light and The strain may be obtained by substituting the temperature.
【００１０】上記反射光量の測定にはレーリー散乱光を
用い、上記温度分布を求めるための後方散乱光の測定に
はラマン散乱光のストークス光とアンチストークス光と
を用いてもよい。Rayleigh scattered light may be used to measure the reflected light amount, and Stokes light and anti-Stokes light of Raman scattered light may be used to measure the back scattered light for obtaining the temperature distribution.
【００１１】上記ＦＢＧを挿入した光ファイバを複数設
け、これら複数の光ファイバを上記ＯＴＤＲの測定器に
切替え用光スイッチを介して接続してもよい。A plurality of optical fibers having the FBG inserted therein may be provided, and the plurality of optical fibers may be connected to the measuring instrument of the OTDR via an optical switch for switching.
【００１２】[0012]
【発明の実施の形態】以下、本発明の一実施形態を添付
図面に基づいて詳述する。BEST MODE FOR CARRYING OUT THE INVENTION An embodiment of the present invention will be described in detail below with reference to the accompanying drawings.
【００１３】図１に示されるように、本発明の多点型歪
み及び温度センサは、歪みに応じて光反射ピーク波長が
変化するファイバブラッググレーティング（ＦＢＧ）１
を光ファイバ２に直列に複数挿入し、この光ファイバの
一端より各ＦＢＧ１からの特定波長の反射光量をＯＴＤ
Ｒで測定すると共に、光ファイバ２中からの後方散乱光
をＯＴＤＲで測定することにより光ファイバ２の長手方
向に沿った温度分布を求め、この温度分布に基づき各Ｆ
ＢＧ１の温度依存による反射光量変化分を補正し、この
補正された反射光量から各ＦＢＧ１における歪みを求め
るようになっている。As shown in FIG. 1, the multipoint strain and temperature sensor of the present invention is a fiber Bragg grating (FBG) 1 in which the peak wavelength of light reflection changes according to strain.
Are inserted in series in the optical fiber 2 and the amount of reflected light of a specific wavelength from each FBG 1 from one end of this optical fiber is OTD.
The temperature distribution along the longitudinal direction of the optical fiber 2 is obtained by measuring the backscattered light from the optical fiber 2 with the OTDR as well as the R distribution, and measuring each F based on this temperature distribution.
The amount of change in reflected light amount due to the temperature dependence of BG1 is corrected, and the distortion in each FBG 1 is calculated from the corrected amount of reflected light.
【００１４】ＦＢＧ１には、例えば図２（ａ）のような
光反射波長特性を持つものを用いる。即ち、横軸に波
長、縦軸に最大値が１となるよう正規化した反射光量を
とった波長対反射光量のグラフにおいて、ＦＢＧ１に歪
みがないとき（ε＝０）には、ある波長で反射光量がピ
ークとなり、波長がピークから遠ざかるにつれて反射光
量が小さくなるため、山型の特性曲線を呈する。ＦＢＧ
１に歪みが加わると、その歪みε１，ε２，…に応じて
前記特性曲線が波長軸に沿って平行移動し、光反射ピー
ク波長がシフトする。この光反射波長特性について特定
の波長ａに関し、横軸に歪み、縦軸に反射率をとった図
２（ｂ）の歪み対反射率のグラフを見ると、歪みが大き
くなるにつれて反射率が高くなっていることが判る。As the FBG 1, for example, one having a light reflection wavelength characteristic as shown in FIG. 2 (a) is used. That is, in the graph of wavelength vs. reflected light amount in which the horizontal axis represents wavelength and the vertical axis represents reflected light amount normalized so that the maximum value is 1, when FBG1 is not distorted (ε = 0), a certain wavelength The amount of reflected light reaches a peak, and the amount of reflected light decreases as the wavelength moves away from the peak, resulting in a mountain-shaped characteristic curve. FBG
When strain is applied to 1, the characteristic curve moves in parallel along the wavelength axis in accordance with the strains ε1, ε2, ... And the peak wavelength of light reflection shifts. Regarding the light reflection wavelength characteristic, regarding the specific wavelength a, the distortion-reflectance graph of FIG. 2B in which the horizontal axis represents strain and the vertical axis represents reflectance, the reflectance becomes higher as the distortion increases. You can see that it has become.
【００１５】光ファイバ２の一端には図３に示されるよ
うに、ＯＴＤＲ測定器５を接続する。このＯＴＤＲ測定
器５は、例えば後方ラマン散乱光を検出することにより
光ファイバの長手方向に沿った温度分布を求めることが
できる温度分布センサ（参考文献“長距離型光ファイバ
温度分布センサの開発”，K.Ogawa et al.,Proc.of 5th
Meeting on Lightwave sensing Tecnol.,LST5-25(199
0)pp.139-144 ）である。ただし、光源（図示せず）に
は、後方散乱光の一部の波長が図２における特定の波長
ａになるようなものを用いる。これにより、光ファイバ
の長手方向に沿った温度分布を求めると同時に波長ａに
おけるＯＴＤＲ波形からそれぞれのＦＢＧ１での反射光
量を測定し、歪みを求めることができる。ＯＴＤＲ測定
器５には、歪み及び温度を表示する表示部７が接続され
ている。An OTDR measuring instrument 5 is connected to one end of the optical fiber 2 as shown in FIG. The OTDR measuring device 5 is a temperature distribution sensor capable of obtaining a temperature distribution along the longitudinal direction of an optical fiber by detecting, for example, backward Raman scattered light (reference document “Development of long-distance optical fiber temperature distribution sensor”). ， K.Ogawa et al., Proc.of 5th
Meeting on Lightwave sensing Tecnol., LST5-25 (199
0) pp.139-144). However, a light source (not shown) is used such that a part of the wavelength of the backscattered light becomes the specific wavelength a in FIG. Thereby, the temperature distribution along the longitudinal direction of the optical fiber can be obtained, and at the same time, the amount of reflected light at each FBG 1 can be measured from the OTDR waveform at the wavelength a to obtain the strain. A display unit 7 that displays strain and temperature is connected to the OTDR measuring device 5.
【００１６】ＯＴＤＲ測定器５で観測されるＯＴＤＲ波
形の概念図を図４に示す。図示されるように横軸に距
離、縦軸に信号強度の対数をとると、光ファイバのみの
場合は、破線で示すように信号強度が距離に対しほぼ直
線的に減少する。光ファイバにＦＢＧを挿入した場合
は、実線で示すように＃１〜＃９の各ＦＢＧにおいて歪
みに応じた光反射の成分が加わっており、ＦＢＧ間では
光ファイバのみの場合と同じ傾きでほぼ直線的に減少す
る。FIG. 4 shows a conceptual diagram of the OTDR waveform observed by the OTDR measuring device 5. As shown in the figure, when the horizontal axis is the distance and the vertical axis is the logarithm of the signal intensity, in the case of only the optical fiber, the signal intensity decreases almost linearly with the distance as shown by the broken line. When the FBG is inserted into the optical fiber, as shown by the solid line, a light reflection component corresponding to the strain is added in each of the FBGs # 1 to # 9, and the FBGs have almost the same inclination as in the case of only the optical fiber. It decreases linearly.
【００１７】それぞれのＦＢＧからの反射光量は図２
（ｂ）の歪み対反射率のグラフで示したように、基本的
には歪みに比例して増大するので、反射光量から歪みを
求めることができる。しかし、ＦＢＧの光反射波長特性
は温度にも依存して変化するので、この温度による反射
光量の変化を温度分布センサによって得られた温度情報
で補正する。温度によって変化する反射光量は、予め測
定しておき、ＯＴＤＲ測定器５で観測される反射光量を
逐一補正することにより正確な歪みを算出する。The amount of light reflected from each FBG is shown in FIG.
As shown in the graph of strain vs. reflectance in (b), basically, the strain increases in proportion to the strain, and thus the strain can be obtained from the amount of reflected light. However, since the light reflection wavelength characteristic of the FBG also changes depending on the temperature, the change in the reflected light amount due to this temperature is corrected by the temperature information obtained by the temperature distribution sensor. The amount of reflected light that changes with temperature is measured in advance, and the amount of reflected light observed by the OTDR measuring device 5 is corrected step by step to calculate an accurate distortion.
【００１８】なお、ＦＢＧからの波長ａの反射光量を測
定するＯＴＤＲ測定器には、温度分布センサのＯＴＤＲ
測定器を用いてもよいし、別途に設けたＯＴＤＲ測定器
を用いてもよく、光ファイバに測定光を入射する光源は
同一として、出射側に光学フィルタを設置し、温度測定
用の散乱光を温度分布センサのＯＴＤＲ測定器へ導き、
反射光量測定用の散乱光を別途のＯＴＤＲ測定器に導く
構成としてもよい。The OTDR measuring device for measuring the reflected light amount of the wavelength a from the FBG includes the OTDR of the temperature distribution sensor.
A measuring device may be used, or a separately provided OTDR measuring device may be used. The same light source is used to enter the measurement light into the optical fiber, an optical filter is installed on the exit side, and scattered light for temperature measurement is used. To the OTDR measuring instrument of the temperature distribution sensor,
The scattered light for measuring the amount of reflected light may be guided to a separate OTDR measuring device.
【００１９】また、反射光量の測定にはレーリー散乱光
を用い、温度分布を求めるための後方散乱光の測定には
ラマン散乱光のストークス光とアンチストークス光とを
用いるのがよい。It is preferable that Rayleigh scattered light is used for measuring the amount of reflected light, and Stokes light and anti-Stokes light of Raman scattered light are used for measuring the back scattered light for obtaining the temperature distribution.
【００２０】次に、光ファイバ２に挿入するＦＢＧ１の
間隔は、測定対象物にもよるが、温度分布センサの距離
分解能が数十センチとすると（参考文献；“Highresolu
tion analogue detection distributed temperature se
nser using deconvolution ”T.Nakamura et al.,OFS-1
1(Sapporo,Japan,May 1996)Conference Proceedings,p
p.526-529 ）、少なくとも１ｍ間隔とすることができ
る。これより短い間隔での計測が必要なときには、例え
ば図５に示されるように、ＦＢＧ１，１間の光ファイバ
２を適当に巻き回すことによって、光ファイバ２の長手
方向に沿った間隔としては温度分布センサの距離分解能
以上を保ちながら、空間的にはそれよりも近接した位置
にＦＢＧ１，１を配置することができる。また、複数個
のＦＢＧ１をひとつの群として互いに近接させて光ファ
イバ２に挿入してもよく、この場合、温度分布センサの
距離分解能中に含まれる複数個のＦＢＧは同一の温度で
あるとして計測することができる。一般に、温度分布セ
ンサの測定ダイナミックレンジは１０ｄＢ程度であるの
で、ＦＢＧの反射率を波長ピーク値で１０％とすれば、
途中の光ファイバロスを考慮しても十数個のＦＢＧを挿
入しての多点計測が可能である。Next, the distance between the FBGs 1 inserted into the optical fiber 2 depends on the object to be measured, but if the distance resolution of the temperature distribution sensor is several tens of centimeters (reference document: "High resolution").
tion analogue detection distributed temperature se
nser using deconvolution ”T.Nakamura et al., OFS-1
1 (Sapporo, Japan, May 1996) Conference Proceedings, p
p.526-529), and the distance can be at least 1 m. When it is necessary to measure at a shorter interval than this, for example, as shown in FIG. 5, by appropriately winding the optical fiber 2 between the FBGs 1 and 1, it is possible to measure the temperature as an interval along the longitudinal direction of the optical fiber 2. The FBGs 1, 1 can be arranged spatially closer to the distribution sensor while maintaining the distance resolution of the distribution sensor or higher. Further, a plurality of FBGs 1 may be inserted into the optical fiber 2 as one group in close proximity to each other. In this case, the plurality of FBGs included in the distance resolution of the temperature distribution sensor are measured as the same temperature. can do. Generally, the measurement dynamic range of the temperature distribution sensor is about 10 dB, so that if the reflectance of the FBG is 10% in terms of the wavelength peak value,
Even if the optical fiber loss on the way is taken into consideration, it is possible to perform multipoint measurement by inserting ten or more FBGs.
【００２１】さて、光ファイバ２の長手方向に沿った温
度分布の測定を行い、さらに波長ａにおけるＯＴＤＲ波
形で各ＦＢＧ１からの反射光量を測定したならば、それ
ぞれのＦＢＧ１での温度による反射光量変化分を補正す
ることにより、歪みのみに対応する反射光量変化を算出
する。個々のＦＢＧ１の反射光量変化量ΔＲは、歪みに
応じた変化量成分と温度に応じた変化量成分との和で表
すことができる。Now, when the temperature distribution along the longitudinal direction of the optical fiber 2 is measured and the reflected light quantity from each FBG1 is measured by the OTDR waveform at the wavelength a, the reflected light quantity change due to the temperature at each FBG1. By correcting the minute, the change in the reflected light amount corresponding to only the distortion is calculated. The reflected light amount change amount ΔR of each FBG 1 can be represented by the sum of the change amount component corresponding to the strain and the change amount component corresponding to the temperature.
【００２２】
ΔＲ＝Ｃ1 Δε＋Ｃ2 ΔＴ （１）
ただし、Ｃ1 ，Ｃ2 は、それぞれ歪み，温度に対する比
例係数であり、Δεは、歪み変化量であり、ΔＴは、温
度変化量である。ΔＴは、ラマン散乱光などを利用した
前記温度分布センサにより求めることができる。そし
て、比例係数Ｃ1 ，Ｃ2 は、予め測定によって求めてお
いたものである。従って、ΔＲをＯＴＤＲで測定し、上
式に代入することによりΔεを求めることができる。こ
のΔεは、周囲の温度変化に影響されない正確な歪み変
化量である。この歪み変化量よりＦＢＧ１における歪み
を求めることができる。ΔR = C 1 Δε + C 2 ΔT (1) where C 1 and C 2 are proportional coefficients to strain and temperature, Δε is the amount of strain change, and ΔT is the amount of temperature change. ΔT can be obtained by the temperature distribution sensor using Raman scattered light or the like. The proportional coefficients C 1 and C 2 have been previously obtained by measurement. Therefore, Δε can be obtained by measuring ΔR by OTDR and substituting it in the above equation. This Δε is an accurate strain change amount that is not affected by the ambient temperature change. The strain in the FBG 1 can be obtained from this strain change amount.
【００２３】このようにして求めた歪み及び温度は表示
部７に表示される。表示の形態は、例えば、図６に示さ
れるように、横軸に距離、縦軸に歪み及び温度をとり、
温度分布は折れ線グラフで表し、各ＦＢＧにおける歪み
は棒グラフで表してもよいし、各ＦＢＧの位置に対応さ
せ歪み及び温度の数値を表形式で示してもよい。The strain and temperature thus obtained are displayed on the display unit 7. The display form is, for example, as shown in FIG. 6, the horizontal axis represents distance, the vertical axis represents strain and temperature,
The temperature distribution may be represented by a line graph, and the strain in each FBG may be represented by a bar graph, or the numerical values of strain and temperature may be represented in a tabular form in correspondence with the position of each FBG.
【００２４】図７に、さらに多くの点数での歪み及び温
度計測に適した形態を示す。この測定系では、ＦＢＧ１
を挿入した光ファイバ２を複数本敷設し、これら複数の
光ファイバ２を切替え用光スイッチ６に接続し、この切
替え用光スイッチ６からは１本の光ファイバでＯＴＤＲ
測定器５に接続してある。切替え用光スイッチ６を切り
替えることにより、複数本の光ファイバ２について１台
のＯＴＤＲ測定器５で計測を行うことができる。この場
合、切替え用光スイッチ６の能力に応じて光ファイバ２
を増やすことができ、例えば、数百点での計測が可能と
なる。FIG. 7 shows a form suitable for strain and temperature measurement at more points. In this measurement system, FBG1
Laying a plurality of optical fibers 2 each having an optical fiber inserted thereinto, connecting the plurality of optical fibers 2 to a switching optical switch 6, and from the switching optical switch 6 a single optical fiber is used for OTDR.
It is connected to the measuring instrument 5. By switching the switching optical switch 6, a single OTDR measuring device 5 can measure the plurality of optical fibers 2. In this case, depending on the capability of the switching optical switch 6, the optical fiber 2
Can be increased and, for example, measurement at several hundred points becomes possible.
【００２５】本発明の応用としては、例えば、原子力発
電所の設備において、原子炉内に前記ＦＢＧ１を挿入し
た光ファイバ２を布設し、管理者が必要とする原子炉内
壁の歪み及び温度を多点計測して、図６のように表示す
ることができる。As an application of the present invention, for example, in a facility of a nuclear power plant, an optical fiber 2 having the FBG 1 inserted therein is laid in a nuclear reactor to increase the strain and temperature on the inner wall of the nuclear reactor required by a manager. The points can be measured and displayed as shown in FIG.
【００２６】[0026]
【発明の効果】本発明は次の如き優れた効果を発揮す
る。The present invention exhibits the following excellent effects.
【００２７】（１）ＦＢＧを光ファイバに直列に複数挿
入したので、この光ファイバの一端より各ＦＢＧからの
反射光量と光ファイバ中からの後方散乱光とを、いずれ
もＯＴＤＲで測定することができ、構成が簡素で多点で
の計測に適している。(1) Since a plurality of FBGs are inserted in series in the optical fiber, both the amount of reflected light from each FBG and the backscattered light from the optical fiber can be measured by OTDR from one end of this optical fiber. It has a simple structure and is suitable for multipoint measurement.
【００２８】（２）歪みと温度とを計測でき、しかもＦ
ＢＧの温度依存による反射光量変化分を補正して歪みを
求めるようにしたので、正確な計測ができる。(2) Strain and temperature can be measured, and F
Since the amount of change in reflected light amount due to the temperature dependence of BG is corrected to obtain the distortion, accurate measurement can be performed.
【図１】本発明の一実施形態によるＦＢＧ付き光ファイ
バの構成図である。FIG. 1 is a configuration diagram of an optical fiber with an FBG according to an embodiment of the present invention.
【図２】本発明に用いるＦＢＧの（ａ）波長対反射光量
グラフ（ｂ）歪み対反射率グラフによる特性図である。FIG. 2 is a characteristic diagram of an FBG used in the present invention by (a) wavelength vs. reflected light amount graph (b) distortion vs. reflectance graph.
【図３】本発明による多点型歪み及び温度測定系の構成
図である。FIG. 3 is a configuration diagram of a multipoint strain and temperature measurement system according to the present invention.
【図４】本発明により観測されるＯＴＤＲ波形の概念図
である。FIG. 4 is a conceptual diagram of an OTDR waveform observed according to the present invention.
【図５】本発明のＦＢＧ付き光ファイバの布設形態を示
す概念図である。FIG. 5 is a conceptual diagram showing a laid form of an optical fiber with an FBG of the present invention.
【図６】本発明で測定した歪み及び温度の表示形態を示
す図である。FIG. 6 is a diagram showing a display form of strain and temperature measured by the present invention.
【図７】本発明による多点型歪み及び温度測定系の構成
図である。FIG. 7 is a configuration diagram of a multipoint strain and temperature measurement system according to the present invention.
１ ファイバブラッググレーティング（ＦＢＧ） ２ 光ファイバ 1 Fiber Bragg Grating (FBG) 2 optical fiber
───────────────────────────────────────────────────── フロントページの続き (56)参考文献 特開 平３−120437（ＪＰ，Ａ) 特開 平８−240451（ＪＰ，Ａ) 特開 平10−48067（ＪＰ，Ａ) 特開 平７−218353（ＪＰ，Ａ) 特開 平８−159882（ＪＰ，Ａ) 特開 平２−201130（ＪＰ，Ａ) 特開 平５−322696（ＪＰ，Ａ) 特表 平８−506185（ＪＰ，Ａ) 国際公開95／24614（ＷＯ，Ａ１) (58)調査した分野(Int.Cl.7，ＤＢ名) G01B 11/00 - 11/30 G01K 11/12 ─────────────────────────────────────────────────── ─── Continuation of the front page (56) Reference JP-A-3-120437 (JP, A) JP-A-8-240451 (JP, A) JP-A-10-48067 (JP, A) JP-A-7- 218353 (JP, A) JP 8-159882 (JP, A) JP 2-201130 (JP, A) JP 5-322696 (JP, A) JP 8-506185 (JP, A) International Publication 95/24614 (WO, A1) (58) Fields investigated (Int.Cl. 7 , DB name) G01B 11/00-11/30 G01K 11/12
Claims (4)
るファイバブラッググレーティング（ＦＢＧ）を光ファ
イバに直列に複数挿入し、この光ファイバの一端より各
ＦＢＧからの特定波長の反射光量をＯＴＤＲで測定する
と共に、光ファイバ中からの後方散乱光をＯＴＤＲで測
定することにより上記光ファイバの長手方向に沿った温
度分布を求め、この温度分布に基づき各ＦＢＧの温度依
存による反射光量変化分を補正し、この補正された反射
光量から各ＦＢＧにおける歪みを求めることを特徴とす
る多点型歪み及び温度センサ。1. A plurality of fiber Bragg gratings (FBGs) whose light reflection peak wavelength changes according to strain are inserted in series in an optical fiber, and the amount of reflected light of a specific wavelength from each FBG is OTDR from one end of this optical fiber. The temperature distribution along the longitudinal direction of the optical fiber is obtained by measuring the backscattered light from the optical fiber with the OTDR as well as the measurement, and the variation of the reflected light amount due to the temperature dependence of each FBG is corrected based on this temperature distribution. Then, the multipoint strain and temperature sensor is characterized in that the strain in each FBG is obtained from the corrected amount of reflected light.
測定することにより反射光量を歪みに応じた成分と温度
に応じた成分との和で表した関係式を求めておき、この
関係式に反射光量及び温度を代入して歪みを求めること
を特徴とする請求項１記載の多点型歪み及び温度セン
サ。2. An optical fiber having the FBG inserted therein is measured in advance to obtain a relational expression expressing the amount of reflected light as a sum of a component according to strain and a component according to temperature. The multipoint strain and temperature sensor according to claim 1, wherein the strain is obtained by substituting the light amount and the temperature.
を用い、上記温度分布を求めるための後方散乱光の測定
にはラマン散乱光のストークス光とアンチストークス光
とを用いることを特徴とする請求項１又は２記載の多点
型歪み及び温度センサ。3. The Rayleigh scattered light is used for measuring the reflected light amount, and the Stokes light and anti-Stokes light of Raman scattered light are used for measuring the back scattered light for obtaining the temperature distribution. The multipoint strain and temperature sensor according to claim 1.
設け、これら複数の光ファイバを上記ＯＴＤＲの測定器
に切替え用光スイッチを介して接続することを特徴とす
る請求項１〜３いずれか記載の多点型歪み及び温度セン
サ。4. A plurality of optical fibers having the FBG inserted therein are provided, and the plurality of optical fibers are connected to the measuring instrument of the OTDR via an optical switch for switching. Multi-point strain and temperature sensor.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP30021896A JP3440721B2 (en) | 1996-11-12 | 1996-11-12 | Multi-point strain and temperature sensor |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP30021896A JP3440721B2 (en) | 1996-11-12 | 1996-11-12 | Multi-point strain and temperature sensor |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| JPH10141922A JPH10141922A (en) | 1998-05-29 |
| JP3440721B2 true JP3440721B2 (en) | 2003-08-25 |
Family
ID=17882151
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP30021896A Expired - Fee Related JP3440721B2 (en) | 1996-11-12 | 1996-11-12 | Multi-point strain and temperature sensor |
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| Country | Link |
|---|---|
| JP (1) | JP3440721B2 (en) |
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| JPH10141922A (en) | 1998-05-29 |
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