JP4068102B2 - FBG strain sensor system - Google Patents

FBG strain sensor system Download PDF

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JP4068102B2
JP4068102B2 JP2005120031A JP2005120031A JP4068102B2 JP 4068102 B2 JP4068102 B2 JP 4068102B2 JP 2005120031 A JP2005120031 A JP 2005120031A JP 2005120031 A JP2005120031 A JP 2005120031A JP 4068102 B2 JP4068102 B2 JP 4068102B2
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崇記 斉藤
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本発明は、ＦＢＧ（ファイバブラッググレーティング）に波長可変光源と受光器を組み合わせて遠隔地にある測定対象の歪測定や温度測定等を行うＦＢＧ歪センサシステムに関し、特に波長可変光源を往復掃引させ、その掃引方向の違いによって生じる波長ずれの差を検出することによって、例えＦＢＧまでのファイバ長（光路長）が不明な場合であっても測定対象の歪み測定を高速かつ正確に行えるとともに、ＦＢＧまでの光路長の測定をも可能にしたＦＢＧ歪センサシステムに関する。   The present invention relates to an FBG strain sensor system for performing strain measurement, temperature measurement, etc. of a measurement object in a remote place by combining a wavelength variable light source and a light receiver with an FBG (fiber Bragg grating), and in particular, reciprocating a wavelength variable light source, By detecting the difference in wavelength shift caused by the difference in the sweep direction, even if the fiber length (optical path length) to the FBG is unknown, the distortion of the measurement object can be measured at high speed and accurately. The present invention relates to an FBG strain sensor system that can also measure the optical path length of the FBG.

ＦＢＧは、ファイバの所定長さ範囲のコア部の屈折率を一定間隔で周期的に変化させたもので、このＦＢＧの一端側に光を入射すると、その入射光のうち特定波長（ブラッグ波長という）の光だけが反射されて、他の波長の光は透過する。このブラッグ波長は、屈折率が一定間隔で周期的に変化している部分が受ける軸方向の歪み（圧縮、伸長）に応じて変化する。したがって、このＦＢＧの一端側に光を入射して反射してくる光の波長（反射波長）あるいは透過してくる光の波長を測定することで、ＦＢＧに加わった歪みを測定することができる。   The FBG is obtained by periodically changing the refractive index of the core portion within a predetermined length range of the fiber at regular intervals. When light is incident on one end side of the FBG, a specific wavelength (referred to as a Bragg wavelength) is included in the incident light. ) Is reflected, and light of other wavelengths is transmitted. This Bragg wavelength changes according to axial distortion (compression, expansion) received by a portion whose refractive index periodically changes at regular intervals. Therefore, the strain applied to the FBG can be measured by measuring the wavelength of light that is incident upon and reflected from one end of the FBG (reflection wavelength) or the wavelength of light that is transmitted.

従来、このようなＦＢＧの性質を利用して測定対象の歪測定や温度測定等を行うＦＢＧ歪センサシステムとして、ＦＢＧの反射波長の測定を、波長可変光源と受光器を組み合わせて行うものがあった。（例えば、特許文献1参照）すなわち、波長可変光源はＦＢＧへ入射する光（測定光）の波長を変えて出射し、受光器はそのＦＢＧへ出射された光に対するＦＢＧからの反射光の光強度を検出する。この場合、表示器を想定し、横軸に測定光の波長（波長可変光源の発振波長）、縦軸に受光器で検出した反射光の光強度をプロットしてＦＢＧからの反射光のスペクトルを描いている。したがって、ＦＢＧの反射波長は、受光器がＦＢＧからの反射光のスペクトル（反射スペクトル）のピーク値を検出した時の、波長可変光源からＦＢＧへ出射している測定光の波長と同一であるとして測定される。   Conventionally, as an FBG strain sensor system for measuring strain or temperature of an object to be measured using such properties of FBG, there is one that measures the reflected wavelength of FBG by combining a wavelength variable light source and a light receiver. It was. (For example, refer to Patent Document 1) That is, the wavelength variable light source emits light having a different wavelength (measurement light) incident on the FBG, and the light receiver reflects the light intensity of the reflected light from the FBG with respect to the light emitted to the FBG. Is detected. In this case, assuming a display, the wavelength of the measurement light (oscillation wavelength of the variable wavelength light source) is plotted on the horizontal axis, and the light intensity of the reflected light detected by the light receiver is plotted on the vertical axis, and the spectrum of the reflected light from the FBG is plotted. I'm drawing. Accordingly, the reflection wavelength of the FBG is assumed to be the same as the wavelength of the measurement light emitted from the wavelength tunable light source to the FBG when the light detector detects the peak value of the spectrum (reflection spectrum) of the reflected light from the FBG. Measured.

特開２００５−６２１３８号公報JP 2005-62138 A 「Extended-Cavity Semiconductor Wavelength-Swept Laser for Biomedical Imaging」S.H.Yun, C.Boudoux, M.C.Pierce, J.F.de Boer, G.J.Tearney, and B.E.Bouma, IEEE Photonic Technology Letters VOL.16, NO.1, JANUARY 2004`` Extended-Cavity Semiconductor Wavelength-Swept Laser for Biomedical Imaging '' S.H.Yun, C.Boudoux, M.C.Pierce, J.F.de Boer, G.J.Tearney, and B.E.Bouma, IEEE Photonic Technology Letters VOL.16, NO.1, JANUARY 2004

このような従来のＦＢＧ歪センサシステムにおけるＦＢＧの反射波長の測定は、波長可変光源−ＦＢＧ間のファイバ長Ｌによる測定光と反射光の遅れ時間τ、すなわち波長可変光源から出射された測定光がＦＢＧで反射されて反射光として受光器に入射されるまでの時間τが、波長可変光源の波長可変時間（掃引速度）に対して十分小さく無視できることを前提としている。なお、遅れ時間τは、ｎをファイバの屈折率、Ｃを光速とすると、（１）式で表される。
τ＝２ｎＬ／Ｃ （１） The measurement of the reflection wavelength of the FBG in such a conventional FBG strain sensor system is performed by measuring the delay time τ between the measurement light and the reflected light due to the fiber length L between the wavelength variable light source and the FBG, that is, the measurement light emitted from the wavelength variable light source. It is premised that the time τ from being reflected by the FBG and being incident on the light receiver as reflected light is sufficiently small and negligible with respect to the wavelength variable time (sweep speed) of the wavelength variable light source. The delay time τ is expressed by the equation (1) where n is the refractive index of the fiber and C is the speed of light.
τ = 2nL / C (1)

ここで、遅れ時間τと波長可変光源の掃引速度との関係を具体的に説明する。波長可変光源の掃引がほぼ線形な場合において、発振波長λは、Ｋを掃引速度に比例した定数、ｔを時間とすると、（２）式で表される。
λ＝λ0＋Ｋ・ｔ （２）
（２）式において、ｔ＝０のときに、ＦＢＧの反射波長に対応する波長λFが波長可変光源で発振されてＦＢＧに出射され、τ＝２ｎＬ／Ｃ時間後に、その反射光がＦＢＧから受光器に入射されたとすると、ＦＢＧの反射波長は見かけ上、仮の反射波長λTとして（３）式のように表される。
λT＝λF＋Ｋ・２ｎＬ／Ｃ （３）
したがって、（３）式から分かるように、Ｋが非常に小さい（掃引速度が非常に遅い）とき、またファイバ長Ｌが非常に短いときは、（４）式のように見なすことができる。
λT＝λF （４） Here, the relationship between the delay time τ and the sweep speed of the wavelength tunable light source will be specifically described. In the case where the sweep of the wavelength tunable light source is almost linear, the oscillation wavelength λ is expressed by the following equation (2), where K is a constant proportional to the sweep speed and t is time.
λ = λ 0 + K · t (2)
In the equation (2), when t = 0, a wavelength λ F corresponding to the reflected wavelength of the FBG is oscillated by the wavelength variable light source and emitted to the FBG, and after τ = 2 nL / C time, the reflected light is emitted from the FBG. Assuming that the light is incident on the light receiver, the reflected wavelength of the FBG is apparently expressed as the provisional reflected wavelength λ T as shown in the equation (3).
λ T = λ F + K · 2 nL / C (3)
Therefore, as can be seen from the equation (3), when K is very small (the sweep speed is very slow) and the fiber length L is very short, it can be regarded as the equation (4).
λ T = λ F (4)

波長可変光源として、回折格子、ミラー等をモータ駆動して半導体レーザの発振波長を可変（掃引）するような外部共振型の波長可変光源を用いる場合には、掃引速度が遅いために、上記のような方法でＦＢＧの反射波長を測定しても問題はなかった。しかしながら、歪み測定を高速化するために、波長可変光源の掃引速度を出来るだけ速くするような場合には、上記（３）式で示したように、遅れ時間τ＝２ｎＬ／Ｃの影響を受けて反射スペクトルがずれる。この結果、ＦＢＧの本来の反射波長λFが見かけ上、仮の反射波長λTとして測定され、次のような問題を生じる。 When using an external resonance type wavelength tunable light source that variably (sweeps) the oscillation wavelength of a semiconductor laser by driving a diffraction grating, mirror, or the like as a wavelength tunable light source, the sweep speed is low. There was no problem even if the reflection wavelength of FBG was measured by such a method. However, when the sweep speed of the wavelength tunable light source is made as fast as possible in order to speed up the distortion measurement, it is affected by the delay time τ = 2 nL / C as shown in the above equation (3). And the reflection spectrum shifts. As a result, the original reflection wavelength λ F of the FBG is apparently measured as the provisional reflection wavelength λ T , resulting in the following problems.

すなわち、ＦＢＧ歪センサシステムにおいて、反射波長の異なる複数のＦＢＧを直列に接続した場合、スペクトル中にはＦＢＧの数だけＦＢＧからの反射スペクトルが観測される。歪み測定では、どの反射スペクトルがどのＦＢＧからの反射光なのかを識別する必要があるが、ＦＢＧまでのファイバ長Ｌが不明の場合には、その識別が困難となる。例えば、ＦＢＧの反射波長が１５００ｎｍから１５７０ｎｍまで５ｎｍ間隔に１５本のＦＢＧが接続されているとする。その場合、１５５０ｎｍに反射スペクトルが観測されたとしても、その反射スペクトルは、近くにある反射波長１５５０ｎｍのＦＢＧのものなのか、遠方にある反射波長１５４５ｎｍのＦＢＧの反射スペクトルがずれて（シフトして）観測されているものなのかを判別することができない。したがって、それぞれのＦＢＧの反射波長（反射スペクトル）を正確に測定するためには、それぞれのＦＢＧまでのファイバ長ＬをＯＴＤＲ等で予め測定してそれによる遅れ時間τを補正し、かつ、ＦＢＧの反射波長の短いものが近くに、長いものが遠方になるように順番に並べることが必要となる。その結果、ＦＢＧ歪センサシステムの構成が複雑になり、歪み測定の操作性が悪くなるという問題を生じる。   That is, in the FBG strain sensor system, when a plurality of FBGs having different reflection wavelengths are connected in series, a reflection spectrum from the FBG is observed in the spectrum by the number of FBGs. In the distortion measurement, it is necessary to identify which reflection spectrum is the reflected light from which FBG. However, when the fiber length L up to the FBG is unknown, the identification becomes difficult. For example, it is assumed that 15 FBGs are connected at an interval of 5 nm from an FBG reflection wavelength of 1500 nm to 1570 nm. In that case, even if a reflection spectrum is observed at 1550 nm, the reflection spectrum of the FBG with a reflection wavelength of 1550 nm in the vicinity or the reflection spectrum of an FBG with a reflection wavelength of 1545 nm in the distance is shifted (shifted). ) Cannot determine if it is being observed. Therefore, in order to accurately measure the reflection wavelength (reflection spectrum) of each FBG, the fiber length L up to each FBG is measured in advance with OTDR or the like to correct the delay time τ, and the FBG It is necessary to arrange in order so that the short reflection wavelength is near and the long reflection wavelength is far away. As a result, the configuration of the FBG strain sensor system is complicated, and the operability of strain measurement is deteriorated.

本発明は、波長可変光源を往復掃引させ、その掃引方向の違いによって生じる波長ずれの差を検出することによって、これらの課題を解決し、例えＦＢＧまでの光路長が不明な場合であっても測定対象の歪み測定を高速かつ正確に行えるとともに、ＦＢＧまでの光路長の測定をも可能にしたＦＢＧ歪センサシステムを提供することを目的としている。   The present invention solves these problems by reciprocally sweeping a wavelength tunable light source and detecting the difference in wavelength shift caused by the difference in the sweep direction, even if the optical path length to the FBG is unknown. An object of the present invention is to provide an FBG strain sensor system capable of measuring a strain to be measured at high speed and accurately and also capable of measuring an optical path length up to the FBG.

上記課題を解決するために、本発明の請求項１のＦＢＧ歪センサシステムでは、歪みの測定対象に設けられたＦＢＧ（１３ａ〜１３ｃ）と、所定の波長範囲の光を発振し、該光を測定光として前記ＦＢＧに入射させる波長可変光源（１０）と、前記ＦＢＧに入射された前記測定光であって、該ＦＢＧによって反射された光又は該ＦＢＧを透過した光を受けて第１の電気信号に変換する第１の受光器（１４）と、該第１の受光器から出力される前記第１の電気信号と前記波長可変光源の発振波長から前記ＦＢＧの反射波長を測定して当該ＦＢＧに加わった歪み量を求める処理手段（２０）とを備えたＦＢＧ歪センサシステムにおいて、前記波長可変光源は、前記所定の波長範囲を含んで短波から長波へかつ長波から短波へ所定の掃引周期で光を発振し、該光を前記測定光として前記ＦＢＧに入射させ、前記処理手段は、前記波長可変光源が前記所定の波長範囲を含んで短波から長波へ掃引している期間に前記第１の受光器から出力される前記第１の電気信号と当該波長可変光源の発振波長から前記ＦＢＧの反射波長を第１の仮の反射波長λTUとして測定し、かつ、前記波長可変光源が前記所定の波長範囲を含んで長波から短波へ掃引している期間に前記第１の受光器から出力される前記第１の電気信号と当該波長可変光源の発振波長から前記ＦＢＧの反射波長を第２の仮の反射波長λTDとして測定し、さらに、測定した前記第１の仮の反射波長λTU及び前記第２の仮の反射波長λTDに基づいて、前記波長可変光源から前記ＦＢＧまで及び該ＦＢＧから前記第１の受光器までの光路長に起因して発生する、前記ＦＢＧの反射波長の測定時の波長ずれを含まない当該ＦＢＧの反射波長λFを求めるようにした。 In order to solve the above problems, in the FBG strain sensor system according to claim 1 of the present invention, the FBG (13a to 13c) provided in a strain measurement target and light in a predetermined wavelength range are oscillated, and the light is transmitted. A wavelength tunable light source (10) that is incident on the FBG as measurement light, and a first electric light that receives the light reflected by the FBG or transmitted through the FBG, which is the measurement light incident on the FBG. A reflected wavelength of the FBG is measured from a first light receiver (14) for converting the signal, the first electric signal output from the first light receiver and the oscillation wavelength of the wavelength tunable light source, and the FBG is measured. And a processing unit (20) for determining the amount of distortion applied to the wavelength tunable light source, wherein the wavelength tunable light source includes the predetermined wavelength range from a short wave to a long wave and from a long wave to a short wave at a predetermined sweep period. the light And the processing unit is configured to cause the wavelength tunable light source to sweep from a short wave to a long wave including the predetermined wavelength range. The reflected wavelength of the FBG is measured as the first temporary reflected wavelength λ TU from the first electrical signal output from the oscillation wavelength of the wavelength tunable light source, and the wavelength tunable light source is in the predetermined wavelength range. The reflected wavelength of the FBG is second provisionally reflected from the first electrical signal output from the first light receiver and the oscillation wavelength of the wavelength tunable light source during a period of sweeping from a long wave to a short wave. measured as the wavelength lambda TD, further measured on the basis of the first temporary reflection wavelength lambda TU and reflection wavelength lambda TD of the second temporary, said from the FBG to and the FBG from the variable wavelength light source first Due to the optical path length up to 1 receiver Thus, the reflection wavelength λ F of the FBG that does not include a wavelength shift at the time of measurement of the reflection wavelength of the FBG is calculated.

また、本発明の請求項２のＦＢＧ歪センサシステムでは、上述した請求項１のＦＢＧ歪センサシステムにおいて、前記処理手段が、さらに、前記ＦＢＧの前記第１の仮の反射波長λTU及び前記第２の仮の反射波長λTDに基づいて、前記波長可変光源から前記ＦＢＧまで及び該ＦＢＧから前記第１の受光器までの前記光路長を求めるようにした。 In the FBG strain sensor system according to claim 2 of the present invention, in the FBG strain sensor system according to claim 1 described above, the processing means further includes the first temporary reflection wavelength λ TU of the FBG and the first The optical path length from the wavelength tunable light source to the FBG and from the FBG to the first light receiver is obtained based on the provisional reflection wavelength λ TD of 2.

また、本発明の請求項３のＦＢＧ歪センサシステムでは、上述した請求項１のＦＢＧ歪センサシステムにおいて、前記処理手段は、前記波長可変光源が前記所定の波長範囲を含んで短波から長波へ掃引している期間に前記第１の受光器から出力される前記第１の電気信号の中から前記ＦＢＧの反射波長に対応するピーク値を検出するとともに、検出した該ピーク値に対応した光が前記第１の受光器に入射された時の当該波長可変光源の発振波長を求め、求めた該発振波長を前記ＦＢＧの第１の仮の反射波長λTUとし、かつ、前記波長可変光源が前記所定の波長範囲を含んで長波から短波へ掃引している期間に前記第１の受光器から出力される前記第１の電気信号の中から前記ＦＢＧの反射波長に対応するピーク値を検出するとともに、検出した該ピーク値に対応した光が前記第１の受光器に入射された時の当該波長可変光源の発振波長を求め、求めた該発振波長を前記ＦＢＧの第２の仮の反射波長λTDとし、さらに、前記ＦＢＧの前記第１の仮の反射波長λTU及び前記第２の仮の反射波長λTD並びに前記波長可変光源の発振波長の掃引特性に基づいて当該ＦＢＧの反射波長λFを求めるようにした。 Further, in the FBG strain sensor system according to claim 3 of the present invention, in the FBG strain sensor system according to claim 1, the processing means sweeps the wavelength tunable light source from a short wave to a long wave including the predetermined wavelength range. The peak value corresponding to the reflected wavelength of the FBG is detected from the first electric signal output from the first light receiver during the period when the light is detected, and the light corresponding to the detected peak value is The oscillation wavelength of the wavelength tunable light source when incident on the first light receiver is obtained, the obtained oscillation wavelength is set as the first provisional reflection wavelength λ TU of the FBG, and the wavelength tunable light source is the predetermined light source. And detecting a peak value corresponding to the reflected wavelength of the FBG from the first electric signal output from the first light receiver during a period of sweeping from a long wave to a short wave including the wavelength range of Detect Obtains the oscillation wavelength of the wavelength tunable light source when the light corresponding to the peak value is incident on the first light receiver, the oscillation wavelength determined by the reflection wavelength lambda TD of the second temporary the FBG, Further, the reflection wavelength λ F of the FBG is obtained based on the sweep characteristics of the first temporary reflection wavelength λ TU and the second temporary reflection wavelength λ TD of the FBG and the oscillation wavelength of the wavelength variable light source. I made it.

また、本発明の請求項４のＦＢＧ歪センサシステムでは、上述した請求項３のＦＢＧ歪センサシステムにおいて、前記処理手段が、さらに、前記ＦＢＧの前記第１の仮の反射波長λTU及び前記第２の仮の反射波長λTD並びに前記波長可変光源の発振波長の掃引特性に基づいて、前記波長可変光源から前記ＦＢＧまで及び該ＦＢＧから前記第１の受光器までの光路長を求めるようにした。 Further, in the FBG strain sensor system according to claim 4 of the present invention, in the FBG strain sensor system according to claim 3 described above, the processing means further includes the first provisional reflection wavelength λ TU of the FBG and the first The optical path length from the tunable light source to the FBG and from the FBG to the first light receiver is obtained based on the provisional reflection wavelength λ TD of 2 and the oscillation characteristics of the oscillation wavelength of the tunable light source. .

また、本発明の請求項５のＦＢＧ歪センサシステムでは、上述した請求項１〜４のいずれかのＦＢＧ歪センサシステムにおいて、前記波長可変光源は、一方のレーザ光出射端面がＡＲコートされている半導体レーザ（１）と、該半導体レーザのＡＲコートされている端面から出射された光をコリメートするコリメートレンズ（２）と、該コリメートレンズから出射されたコリメート光を受けて波長に応じた角度で回折させる回折格子（３）と、反射体（３５）と反射体駆動手段（５０）とを含んで構成され、前記回折格子から入射される前記コリメート光に対する回折光が、前記反射体の反射面で該回折格子へ反射されて、再び該回折格子で回折され、それによって得られた回折光が前記コリメートレンズを介して前記半導体レーザに入射されるとき、該半導体レーザに入射される回折光が所望の波長の光となるようにするとともに、該所望の波長が前記所定の波長範囲を含んで往復掃引されるように前記反射体の反射面の角度を前記反射体駆動手段により前記所定の周期で繰り返し変化させるＭＥＭＳスキャナ（６０）とを備えた。   Further, in the FBG strain sensor system according to claim 5 of the present invention, in the FBG strain sensor system according to any one of claims 1 to 4 described above, one of the laser light emission end faces of the wavelength variable light source is AR-coated. A semiconductor laser (1), a collimating lens (2) for collimating light emitted from the end surface of the semiconductor laser that is AR-coated, and an angle corresponding to the wavelength received by the collimated light emitted from the collimating lens A diffraction grating (3) to be diffracted, a reflector (35), and a reflector driving means (50) are configured, and diffracted light with respect to the collimated light incident from the diffraction grating is reflected on the reflecting surface of the reflector. Is reflected by the diffraction grating and diffracted by the diffraction grating again, and the diffracted light obtained thereby is incident on the semiconductor laser through the collimator lens. The reflecting surface of the reflector so that the diffracted light incident on the semiconductor laser becomes light having a desired wavelength and the desired wavelength is swept back and forth including the predetermined wavelength range. And a MEMS scanner (60) that repeatedly changes the angle at the predetermined period by the reflector driving means.

また、本発明の請求項６のＦＢＧ歪センサシステムでは、上述した請求項５のＦＢＧ歪センサシステムにおいて、前記ＭＥＭＳスキャナの反射体は、固定基板（３６、３７）と、該固定基板の縁部から所定幅で所定長さ延設され、その長さ方向に沿って捩じれ変形可能な軸部（３８、３９）と、該軸部の先端に自身の縁部で連結されて形成され、一面側に前記回折格子からの回折光を反射させるための前記反射面が設けられた反射板（４０）とを有しており、かつ、前記ＭＥＭＳスキャナの反射体駆動手段は、前記反射体の軸部と反射板とからなる部分の固有振動数に対応した周波数の駆動信号によって前記反射板に力を与えて、該反射板を前記固有振動数又はそれに近い振動数の前記所定の周期で往復回転させるように構成した。   Further, in the FBG strain sensor system according to claim 6 of the present invention, in the FBG strain sensor system according to claim 5 described above, the reflector of the MEMS scanner includes a fixed substrate (36, 37) and an edge portion of the fixed substrate. A shaft portion (38, 39) that is extended by a predetermined width with a predetermined width and that can be twisted and deformed along the length direction, and is connected to the tip of the shaft portion at its own edge, And a reflector (40) provided with the reflecting surface for reflecting the diffracted light from the diffraction grating, and the reflector driving means of the MEMS scanner is a shaft portion of the reflector. A force is applied to the reflecting plate by a driving signal having a frequency corresponding to the natural frequency of the portion consisting of the reflecting plate and the reflecting plate, and the reflecting plate is reciprocated at the predetermined period of the natural frequency or a frequency close thereto. It was configured as follows.

また、本発明の請求項７のＦＢＧ歪センサシステムでは、上述した請求項５又は６のＦＢＧ歪センサシステムにおいて、前記波長可変光源は、さらに、前記回折格子の０次光が出射される光路上に設けられて所定の波長の光を透過させる光共振器（４）と、該光共振器から出射される透過光を受けて第２の電気信号に変換する第２の受光器（５）とを備え、該第２の受光器から出力される前記第２の電気信号から当該波長可変光源の発振波長を求めることを可能にした。   In the FBG strain sensor system according to claim 7 of the present invention, in the FBG strain sensor system according to claim 5 or 6, the wavelength tunable light source further includes an optical path on which the zero-order light of the diffraction grating is emitted. An optical resonator (4) that transmits light of a predetermined wavelength, and a second light receiver (5) that receives the transmitted light emitted from the optical resonator and converts it into a second electrical signal; The oscillation wavelength of the wavelength tunable light source can be obtained from the second electric signal output from the second light receiver.

また、本発明の請求項８のＦＢＧ歪センサシステムでは、上述した請求項５又は６のＦＢＧ歪センサシステムにおいて、前記波長可変光源は、前記回折格子の０次光を出力光とした。   In the FBG strain sensor system according to claim 8 of the present invention, in the FBG strain sensor system according to claim 5 or 6 described above, the wavelength variable light source uses the 0th-order light of the diffraction grating as output light.

また、本発明の請求項９のＦＢＧ歪センサシステムでは、上述した請求項８のＦＢＧ歪センサシステムにおいて、前記波長可変光源は、さらに、前記回折格子の０次光が出射される光路上に設けられ、該０次光を２つに分岐して一方の０次光を前記出力光として出射する光分岐手段（６）と、該光分岐手段から出射される他方の０次光を受けて所定の波長の光を透過させる光共振器（４）と、該光共振器から出射される透過光を受けて第２の電気信号に変換する第２の受光器（５）とを備え、該第２の受光器から出力される前記第２の電気信号から当該波長可変光源の発振波長を求めることを可能にした。   Further, in the FBG strain sensor system according to claim 9 of the present invention, in the FBG strain sensor system according to claim 8, the wavelength tunable light source is further provided on an optical path from which the 0th-order light of the diffraction grating is emitted. A light branching means (6) for branching the zero-order light into two and emitting one of the zero-order lights as the output light, and receiving the other zero-order light emitted from the light branching means and receiving a predetermined An optical resonator (4) that transmits light having a wavelength of 2 and a second light receiver (5) that receives the transmitted light emitted from the optical resonator and converts it into a second electrical signal, The oscillation wavelength of the wavelength tunable light source can be obtained from the second electric signal output from the second light receiver.

また、本発明の請求項１０のＦＢＧ歪センサシステムでは、上述した請求項７又は９のＦＢＧ歪センサシステムにおいて、前記処理手段は、前記第１の受光器からの前記第１の電気信号及び前記第２の受光器からの前記第２の電気信号を受けてそれぞれディジタル値に変換するＡ／Ｄ変換器（１５）と、該Ａ／Ｄ変換器から出力される前記第１の電気信号のディジタル値を順次所定のアドレスに記憶する第１のメモリ（１６ａ）と、前記Ａ／Ｄ変換器から出力される前記第２の電気信号のディジタル値を順次所定のアドレスに記憶する第２のメモリ（１６ｂ）と、前記第１のメモリの前記所定のアドレスに記憶されているディジタル値を読み出して、前記波長可変光源が前記所定の波長範囲を含んで短波から長波へ掃引している期間における前記ＦＢＧの反射波長に対応する第１のピーク値を検出し、かつ、前記波長可変光源が前記所定の波長範囲を含んで長波から短波へ掃引している期間における前記ＦＢＧの反射波長に対応する第２のピーク値を検出するピーク値検出手段（１７）と、前記第２のメモリの前記所定のアドレスに記憶されている前記波長可変光源の発振波長を求めるためのディジタル値を読み出して、前記光共振器の前記所定の波長が記憶されているアドレスを検出し、検出した該アドレスと前記ピーク値検出手段から出力される、前記第１のピーク値及び前記第２のピーク値がそれぞれ記憶されているアドレスとに基づいて、当該第１のピーク値及び第２のピーク値にそれぞれ対応した光が前記第１の受光器に入射された時の当該波長可変光源の発振波長を求め、求めたそれぞれの該発振波長を前記ＦＢＧの第１の仮の反射波長λTU及び第２の仮の反射波長λTDとするピーク値波長算出手段（１８）と、該ピーク値波長算出手段から出力される前記第１の仮の反射波長λTU及び前記第２の仮の反射波長λTDと前記波長可変光源の発振波長の掃引特性とに基づいて、前記ＦＢＧの反射波長λFを求めるとともに、前記波長可変光源から前記ＦＢＧまで及び該ＦＢＧから前記第１の受光器までの光路長を求める反射波長／光路長算出手段（１９）とを備えた。 In the FBG strain sensor system according to claim 10 of the present invention, in the FBG strain sensor system according to claim 7 or 9, the processing means includes the first electric signal from the first light receiver and the first electrical signal. An A / D converter (15) that receives the second electric signal from the second light receiver and converts it into a digital value, and a digital of the first electric signal output from the A / D converter A first memory (16a) for sequentially storing values at predetermined addresses, and a second memory (for sequentially storing digital values of the second electric signals output from the A / D converter at predetermined addresses). 16b) and a digital value stored at the predetermined address of the first memory, and the wavelength variable light source sweeps from a short wave to a long wave including the predetermined wavelength range. The first peak value corresponding to the reflected wavelength of the FBG is detected, and the wavelength tunable light source corresponds to the reflected wavelength of the FBG during a period in which the wavelength tunable light source is swept from the long wave to the short wave including the predetermined wavelength range. A peak value detecting means (17) for detecting a second peak value, and reading out a digital value for obtaining an oscillation wavelength of the wavelength variable light source stored at the predetermined address of the second memory; The address where the predetermined wavelength of the optical resonator is stored is detected, and the detected first address and the second peak value output from the peak value detecting means are stored. The oscillation wavelength of the wavelength tunable light source when the light corresponding to the first peak value and the second peak value is incident on the first light receiver is obtained based on the received address. , And each of the oscillating first temporary reflection wavelength lambda TU and second temporary peak wavelength calculator that the reflection wavelength lambda TD of the wavelength the FBG obtained (18), from the peak value wavelength calculation means Based on the first provisional reflection wavelength λ TU and the second provisional reflection wavelength λ TD output and the sweep characteristic of the oscillation wavelength of the wavelength variable light source, the reflection wavelength λ F of the FBG is obtained. And a reflection wavelength / optical path length calculating means (19) for obtaining an optical path length from the wavelength variable light source to the FBG and from the FBG to the first light receiver.

本発明の請求項1〜４及び１０のＦＢＧ歪センサシステムでは、波長可変光源が所定の波長範囲を含んで短波から長波へ掃引している期間に第１の受光器から出力される第１の電気信号と波長可変光源の発振波長からＦＢＧの反射波長を第１の仮の反射波長λTUとして測定し、かつ、波長可変光源が所定の波長範囲を含んで長波から短波へ掃引している期間に第１の受光器から出力される第１の電気信号と波長可変光源の発振波長からＦＢＧの反射波長を第２の仮の反射波長λTDとして測定し、さらに、これら２つの第１の仮の反射波長λTU及び第２の仮の反射波長λTDに基づいてＦＢＧの反射波長λFを求めるようにしたので、例えＦＢＧまでの光路長が不明な場合であってもＦＢＧの反射波長を正確に測定でき、その結果、測定対象の歪み測定を正確に行える。また、上記２つの第１の仮の反射波長λTU及び第２の仮の反射波長λTDに基づいてＦＢＧまでの光路長を測定することができる。 In the FBG strain sensor system according to claims 1 to 4 and 10 of the present invention, the first light output from the first light receiver during a period in which the wavelength tunable light source sweeps from a short wave to a long wave including a predetermined wavelength range. The period during which the reflected wavelength of the FBG is measured as the first provisional reflected wavelength λ TU from the oscillation wavelength of the electrical signal and the wavelength tunable light source, and the wavelength tunable light source is swept from a long wave to a short wave including a predetermined wavelength range The reflected wavelength of the FBG is measured as the second temporary reflected wavelength λ TD from the first electrical signal output from the first light receiver and the oscillation wavelength of the wavelength tunable light source, and the two first temporary signals are further measured. The reflection wavelength λ F of the FBG is obtained based on the reflection wavelength λ TU and the second provisional reflection wavelength λ TD , so even if the optical path length to the FBG is unknown, the reflection wavelength of the FBG is Accurate measurement, resulting in distortion measurement Can be performed accurately. Further, it is possible to measure the optical path length to the FBG based on the reflected wavelength lambda TD of the two first temporary reflection wavelength lambda TU and the second tentative.

本発明の請求項５及び６のＦＢＧ歪センサシステムでは、波長可変光源の往復掃引をＭＥＭＳスキャナで行うようにしたので、掃引速度を速くでき、歪み測定の高速化が可能となる。   In the FBG strain sensor system according to claims 5 and 6 of the present invention, since the reciprocal sweep of the wavelength variable light source is performed by the MEMS scanner, the sweep speed can be increased and the strain measurement can be performed at a higher speed.

本発明の請求項７及び９のＦＢＧ歪センサシステムでは、波長可変光源における回折格子の０次光の所定の波長の光を第２の電気信号に変換するようにしたので、この第２の電気信号から波長可変光源の発振波長を求めることができる。   In the FBG strain sensor system according to the seventh and ninth aspects of the present invention, the light of a predetermined wavelength of the zero-order light of the diffraction grating in the wavelength tunable light source is converted into the second electric signal. The oscillation wavelength of the wavelength tunable light source can be obtained from the signal.

本発明の請求項８のＦＢＧ歪センサシステムでは、波長可変光源における回折格子の０次光を出力光としたので、半導体レーザの内部共振モードの影響によって生じる出力光の強度変動を小さくできる。具体的には、半導体レーザのＡＲコートされていない端面から出射された光を出力光とする場合の強度変動（約１ｄＢ）の約１／１０にできる。   In the FBG strain sensor system according to the eighth aspect of the present invention, since the 0th-order light of the diffraction grating in the wavelength tunable light source is used as the output light, the intensity fluctuation of the output light caused by the influence of the internal resonance mode of the semiconductor laser can be reduced. Specifically, it can be about 1/10 of the intensity fluctuation (about 1 dB) when the light emitted from the end surface of the semiconductor laser not coated with AR is used as the output light.

本発明の実施形態のＦＢＧ歪センサシステムの構成を図１及び図２に示す。まず、波長可変光源１０は、図２に示すように、半導体レーザ（ＬＤ）１のＡＲコートされている端面から出射された光をコリメートレンズ２によってコリメート光に変換して回折格子３へ入射し、その入射光に対して回折格子３が出射する回折光をＭＥＭＳスキャナ６０に入射する。ＭＥＭＳスキャナ６０は、反射体３５と反射体駆動手段５０で構成され、回折格子３から入射されるコリメート光に対する回折光が、反射体３５の反射面で回折格子３へ反射されて、再び回折格子３で回折され、それによって得られた回折光がコリメートレンズ２を介してＬＤ１に入射されるとき、ＬＤ１に入射される回折光が所望の波長の光となるようにするとともに、この所望の波長が所定の波長範囲を含んで往復掃引されるように反射体３５の反射面の角度を反射体駆動手段５０により所定の周期で繰り返し変化（往復回転）させている。このような構成によって、波長掃引された光が発振されて、ＬＤ１のＡＲコートされていない端面から出力されて出力光（測定光ａ）となる。   The configuration of the FBG strain sensor system according to the embodiment of the present invention is shown in FIGS. First, as shown in FIG. 2, the wavelength tunable light source 10 converts the light emitted from the AR-coated end face of the semiconductor laser (LD) 1 into collimated light by the collimator lens 2 and enters the diffraction grating 3. The diffracted light emitted from the diffraction grating 3 is incident on the MEMS scanner 60 with respect to the incident light. The MEMS scanner 60 includes a reflector 35 and reflector drive means 50, and the diffracted light with respect to the collimated light incident from the diffraction grating 3 is reflected by the reflection surface of the reflector 35 to the diffraction grating 3, and again the diffraction grating. When the diffracted light diffracted by the light beam 3 is incident on the LD 1 via the collimator lens 2, the diffracted light incident on the LD 1 becomes light having a desired wavelength, and the desired wavelength. Is reciprocally changed (reciprocatingly rotated) at a predetermined period by the reflector driving means 50 so that the reciprocating sweep is performed including a predetermined wavelength range. With such a configuration, the wavelength-swept light is oscillated and output from the end surface of the LD 1 which is not AR-coated, and becomes output light (measurement light a).

なお、図２においては、ＬＤ１のＡＲコートされている端面から出射された光をコリメートレンズ２によってコリメート光に変換して回折格子３へ入射するようにしたが、ＬＤ１とコリメートレンズ２との間に集光レンズとファイバを設け、ＬＤ１のＡＲコートされている端面から出射された光を集光レンズで集光してファイバに入射し、ファイバを通った光をコリメートレンズ２によってコリメート光に変換して回折格子３へ入射するようにしてもよい。   In FIG. 2, the light emitted from the end surface of the LD 1 that is AR-coated is converted into collimated light by the collimating lens 2 so as to be incident on the diffraction grating 3, but between the LD 1 and the collimating lens 2. A condensing lens and a fiber are provided in the lens, and the light emitted from the end surface of the LD 1 that is AR-coated is condensed by the condensing lens and incident on the fiber. The light passing through the fiber is converted into collimated light by the collimating lens 2. Then, the light may enter the diffraction grating 3.

ＭＥＭＳスキャナ６０を構成する反射体３５及び反射体駆動手段５０については後で詳述する。なお、ＭＥＭＳ（Micro Electro Mechanical Systems）スキャナとは、マイクロ電気機械式構造体（電気信号の制御を受けて機械的に動作する構造体）によって形成されたスキャナを意味している。   The reflector 35 and the reflector driving means 50 constituting the MEMS scanner 60 will be described in detail later. Note that a MEMS (Micro Electro Mechanical Systems) scanner means a scanner formed by a micro electro mechanical structure (a structure that operates mechanically under the control of an electrical signal).

ここで、ＭＥＭＳスキャナ６０による波長掃引について説明する。図５に示す駆動信号Ｄａ、Ｄｂ（詳細は後述する）を印加してＭＥＭＳスキャナ６０を所定の掃引周期で往復掃引する（上述の反射体３５を往復回転させる）と、図６（ａ）に示すように、ＭＥＭＳスキャナ６０の往復回転角度はほぼ正弦波的に変化し、その結果、掃引される波長も正弦波状に変化する。したがって、測定光ａの所定の波長範囲（測定波長範囲）が、図６（ｂ）に示すように、その正弦波状に変化する波形の直線に近い部分に来るように、ＭＥＭＳスキャナ６０の往復掃引の波長範囲（往復回転角度の範囲）が設定される。つまり、駆動信号Ｄａ、Ｄｂの振幅の調整により設定される。具体例としては、例えば、測定波長範囲を１５２０〜１５７０ｎｍとした場合、ＭＥＭＳスキャナ６０の往復掃引の波長範囲（掃引波長範囲）は、この測定波長範囲に対して十分に広い約１４７０〜１６２０ｎｍに設定される。なお、上述の駆動信号Ｄａ、Ｄｂのいずれか一方はトリガ信号Ｔｒとして処理手段２０へ出力される。   Here, wavelength sweeping by the MEMS scanner 60 will be described. When the drive signals Da and Db (details will be described later) shown in FIG. 5 are applied to sweep the MEMS scanner 60 back and forth at a predetermined sweep period (the above-described reflector 35 is rotated back and forth), FIG. As shown, the reciprocating rotation angle of the MEMS scanner 60 changes substantially sinusoidally, and as a result, the swept wavelength also changes sinusoidally. Accordingly, as shown in FIG. 6B, the reciprocal sweep of the MEMS scanner 60 is performed so that the predetermined wavelength range (measurement wavelength range) of the measurement light a is close to the straight line of the waveform that changes in a sine wave shape. Is set (range of reciprocating rotation angle). That is, it is set by adjusting the amplitude of the drive signals Da and Db. As a specific example, for example, when the measurement wavelength range is 1520 to 1570 nm, the reciprocal sweep wavelength range (sweep wavelength range) of the MEMS scanner 60 is set to about 1470 to 1620 nm that is sufficiently wide with respect to this measurement wavelength range. Is done. One of the drive signals Da and Db is output to the processing means 20 as a trigger signal Tr.

また、図２において、回折格子３の０次光は、エタロン等の光共振器４に入射されて所定の波長の光のみが透過される。そして、その透過光は受光器（ＰＤ）５で第２の電気信号ｃに変換されて図１に示す処理手段２０へ出力される。すなわち、出力光（測定光ａ）の波長掃引に対応して所定の波長間隔、例えば周波数で１５ＧＨｚ間隔の透過光を発生し、受光器５で第２の電気信号ｃに変換される。この透過光の波長（周波数）は既知である。したがって、その透過光を光電変換して得られた第２の電気信号ｃを用いて、波長可変光源１０の発振波長（波長掃引された測定光ａの波長）を求めることができる。   In FIG. 2, the zero-order light of the diffraction grating 3 is incident on an optical resonator 4 such as an etalon, and only light of a predetermined wavelength is transmitted. Then, the transmitted light is converted into a second electrical signal c by the light receiver (PD) 5 and output to the processing means 20 shown in FIG. That is, transmitted light having a predetermined wavelength interval, for example, a frequency of 15 GHz corresponding to the wavelength sweep of the output light (measurement light a) is generated and converted into the second electric signal c by the light receiver 5. The wavelength (frequency) of this transmitted light is known. Therefore, the oscillation wavelength of the wavelength tunable light source 10 (the wavelength of the measurement light a swept) can be obtained using the second electric signal c obtained by photoelectrically converting the transmitted light.

なお、波長可変光源１０は、図２に示したような、ＬＤ１のＡＲコートされていない端面から出射された光を出力光とするものに限定されるわけではなく、回折格子３の０次光を出力光とするものであってもよい。その場合には、図３に示すように、回折格子３からの０次光を光カプラ等の光分岐手段６で分岐して、一方を出力光とし、他方を光共振器４に入射する。このように０次光を出力光とすると、ＬＤ１の内部共振モードの影響によって生じる出力光の強度変動を、ＬＤ１のＡＲコートされていない端面から出射された光を出力光とする場合に比べて小さくできる。具体的には、ＬＤ１を出力光とする場合の強度変動（約１ｄＢの）を約１／１０に小さくできる。また、ＬＤ１のＡＲコートされていない端面にＨＲコート（HR：High-Reflection）を施すことによって、０次光を出力光とする場合の出力光の光強度を増加させることができる。   The tunable light source 10 is not limited to the light output from the end surface of the LD 1 that is not AR-coated as shown in FIG. May be output light. In that case, as shown in FIG. 3, the 0th-order light from the diffraction grating 3 is branched by an optical branching means 6 such as an optical coupler, and one is output and the other is incident on the optical resonator 4. When the 0th-order light is output light in this way, the intensity fluctuation of the output light caused by the influence of the internal resonance mode of the LD1 is compared with the case where the light emitted from the end surface of the LD1 that is not AR-coated is output light. Can be small. Specifically, the intensity fluctuation (about 1 dB) when LD1 is used as output light can be reduced to about 1/10. Further, by applying HR coating (HR: High-Reflection) to the end surface of the LD 1 which is not AR-coated, the light intensity of the output light when the 0th-order light is output light can be increased.

また、往復掃引可能な波長可変光源としては、上記図２及び図３に示したＭＥＭＳスキャナを用いて往復掃引させるものに限定されるわけではなく、例えば、ＭＥＭＳスキャナの代わりにガルバノメーターとこのガルバノメーターに固定されたミラーとを用いて往復掃引させるようなものであってもよい。（例えば、非特許文献1参照）   Further, the wavelength variable light source capable of reciprocating sweep is not limited to the one that reciprocates and sweeps using the MEMS scanner shown in FIGS. 2 and 3, for example, instead of the MEMS scanner, a galvanometer and the galvanometer A reciprocating sweep may be performed using a mirror fixed to the meter. (For example, see Non-Patent Document 1)

次に、図１において、光サーキュレータ１１は、波長可変光源１０からの測定光ａを、ファイバ１２ａ〜１２ｃを介して直列に接続された反射波長の異なる複数のＦＢＧ１３ａ〜１３ｃに入射するとともに、各ＦＢＧ１３ａ〜１３ｃからそれぞれの反射波長で反射されて戻ってきたその測定光ａの反射光を受けて受光器（ＰＤ）１４に出射する。受光器１４は、その反射光を第１の電気信号ｂに変換して処理手段２０に出力する。   Next, in FIG. 1, the optical circulator 11 makes the measurement light a from the wavelength tunable light source 10 incident on a plurality of FBGs 13a to 13c having different reflection wavelengths connected in series via the fibers 12a to 12c, and The reflected light of the measurement light “a” reflected and returned from each of the FBGs 13 a to 13 c is received and emitted to the light receiver (PD) 14. The light receiver 14 converts the reflected light into a first electric signal b and outputs it to the processing means 20.

処理手段２０は、受光器１４からの第１の電気信号ｂ及び波長可変光源１０からの第２の電気信号ｃに基づいて、上述した光路長（主にファイバ１２ａ〜１２ｃの長さで決まる）に起因して発生する波長ずれのない状態での各ＦＢＧ１３ａ〜１３ｃの反射波長の算出（測定対象の歪み測定）及びその光路長の算出を行うもので、Ａ／Ｄ変換器１５、メモリ１６ａ、１６ｂ、ピーク値検出手段１７、ピーク値波長算出手段１８及び反射波長／光路長算出手段１９によって構成されている。   The processing means 20 is based on the first electrical signal b from the light receiver 14 and the second electrical signal c from the wavelength tunable light source 10, and the optical path length described above (mainly determined by the length of the fibers 12a to 12c). The reflection wavelength of each of the FBGs 13a to 13c is calculated (measurement of the measurement target distortion) and the optical path length thereof is calculated in a state where there is no wavelength shift caused by the A / D converter 15, the memory 16a, 16 b, a peak value detection unit 17, a peak value wavelength calculation unit 18, and a reflection wavelength / optical path length calculation unit 19.

すなわち、Ａ／Ｄ変換器１５は、例えば２ｃｈのＡ／Ｄ変換器であり、波長可変光源１０から入力される上述のトリガ信号Ｔｒを起点にして、周波数確度の高い内部クロック（例えば１０ＭＨｚ）によって第１の電気信号ｂ及び第２の電気信号ｃを同じタイミングで順次ディジタル値に変換する。   That is, the A / D converter 15 is, for example, a 2ch A / D converter, and starts from the above-described trigger signal Tr input from the wavelength tunable light source 10, and uses an internal clock (for example, 10 MHz) with high frequency accuracy. The first electric signal b and the second electric signal c are sequentially converted into digital values at the same timing.

メモリ１６ａ、１６ｂは、それぞれ、制御部（図示しない）からの指示に基づいて、Ａ／Ｄ変換器１５からそれぞれ順次出力される第１の電気信号ｂのディジタル値及び第２の電気信号ｃのディジタル値の内から少なくとも、上述の測定波長範囲と光路長に起因して発生する波長ずれ（以下単に波長ずれという）分、すなわち図６（ｂ）に示す、短波から長波へ掃引している（以下アップ掃引という）ときの測定波長範囲と波長ずれ分及び長波から短波へ掃引している（以下ダウン掃引という）ときの測定波長範囲と波長ずれ分、に含まれるディジタル値を順次所定のアドレスに記憶する。具体例を示すと、例えば、第１の電気信号ｂのディジタル値及び第２の電気信号ｃのディジタル値は、アップ掃引のときは、共にそれぞれのメモリ１６ａ、１６ｂのアドレス０〜４０００に記憶され、またダウン掃引のときは、共にそれぞれのメモリ１６ａ、１６ｂのアドレス５０００〜９０００に記憶される。   The memories 16a and 16b respectively receive the digital value of the first electric signal b and the second electric signal c that are sequentially output from the A / D converter 15 based on an instruction from a control unit (not shown). Among the digital values, at least a wavelength shift (hereinafter simply referred to as a wavelength shift) generated due to the above-described measurement wavelength range and optical path length, that is, sweeping from a short wave to a long wave as shown in FIG. The measurement wavelength range and the wavelength shift when it is swept up (hereinafter referred to as “up sweep”), and the digital values contained in the measurement wavelength range and the wavelength shift when swept from the long wave to the short wave (hereinafter referred to as “down sweep”) are sequentially assigned to predetermined addresses. Remember. As a specific example, for example, the digital value of the first electric signal b and the digital value of the second electric signal c are both stored in the addresses 0 to 4000 of the memories 16a and 16b during the up sweep. In the case of the down sweep, both are stored in addresses 5000 to 9000 of the memories 16a and 16b.

なお、上記では、メモリ１６ａ、１６ｂへの記憶を制御部（図示しない）からの指示で行うようにしたが、トリガ信号Ｔｒの位相が上記測定波長範囲及び波長ずれとの関係において適切であれば、Ａ／Ｄ変換器１５からそれぞれ出力される第１の電気信号ｂのディジタル値及び第２の電気信号ｃのディジタル値をそのまま記憶するようにしてもよい。   In the above, storage in the memories 16a and 16b is performed by an instruction from the control unit (not shown). However, if the phase of the trigger signal Tr is appropriate in relation to the measurement wavelength range and the wavelength shift, The digital value of the first electric signal b and the digital value of the second electric signal c respectively output from the A / D converter 15 may be stored as they are.

ピーク値検出手段１７は、第１の読み出信号Ｍ１によって第１のメモリ１６ａの所定のアドレス（例えば上述のアップ掃引の０〜４０００、ダウン掃引の５０００〜９０００）に記憶されているディジタル値を読み出して、各ＦＢＧ１３ａ〜１３ｃの反射波長に対応する３つの、アップ掃引の場合における第１のピーク値、及びダウン掃引の場合における第２のピーク値を検出する。そして、検出した３つの第１のピーク値が記憶されているそれぞれのアドレス、及び３つの第２のピーク値が記憶されているそれぞれのアドレスの情報をピーク値波長算出手段１８に出力する。   The peak value detection means 17 uses the first read signal M1 to obtain a digital value stored in a predetermined address of the first memory 16a (for example, 0 to 4000 for the above-mentioned up sweep and 5000 to 9000 for the down sweep). Reading is performed to detect three first peak values in the case of up sweep and second peak value in the case of down sweep corresponding to the reflection wavelengths of the FBGs 13a to 13c. Then, the information on the respective addresses where the three detected first peak values and the addresses where the three second peak values are stored is outputted to the peak value wavelength calculating means 18.

ピーク値波長算出手段１８は、第２の読み出信号Ｍ２によって第２のメモリ１６ｂの所定のアドレス（例えば上述のアップ掃引の０〜４０００、ダウン掃引の５０００〜９０００）に記憶されている波長可変光源１０の発振波長（測定光ａの波長）を求めるためのディジタル値を読み出して、光共振器４（図２参照）の所定の波長（既知波長）が記憶されているアドレスを検出する。例えば、上述の１５ＧＨｚ間隔で発生された既知波長（周波数）の透過光のピーク値が記憶されているそれぞれのアドレスを検出する。   The peak value wavelength calculating means 18 uses the second read signal M2 to change the wavelength stored in a predetermined address of the second memory 16b (for example, 0 to 4000 for the above-mentioned up sweep and 5000 to 9000 for the down sweep). A digital value for obtaining the oscillation wavelength of the light source 10 (the wavelength of the measurement light a) is read, and an address at which a predetermined wavelength (known wavelength) of the optical resonator 4 (see FIG. 2) is stored is detected. For example, each address where the peak value of the transmitted light of the known wavelength (frequency) generated at the 15 GHz interval is stored is detected.

そして、ピーク値検出手段１７から出力される、各ＦＢＧ１３ａ〜１３ｃの反射波長に対応する３つの第１のピーク値がそれぞれ記憶されているアドレスと、上記の既知波長が記憶されているそれぞれのアドレスとを対比して、３つの第１のピーク値のそれぞれに対応した光が第１の受光器１４に入射された時の波長可変光源１０の発振波長を求め、求めた３つの発振波長のそれぞれについて、それらを第１の仮の反射波長λTUとする。また同様に、ピーク値検出手段１７から出力される、各ＦＢＧ１３ａ〜１３ｃの反射波長に対応する３つの第２のピーク値がそれぞれ記憶されているアドレスと、上記の既知波長が記憶されているそれぞれのアドレスとを対比して、３つの第２のピーク値のそれぞれに対応した光が第１の受光器１４に入射された時の波長可変光源１０の発振波長を求め、求めた３つの発振波長のそれぞれについて、それらを第２の仮の反射波長λTDとする。 Then, the addresses at which the three first peak values corresponding to the reflection wavelengths of the FBGs 13a to 13c, which are output from the peak value detection means 17, are stored, and the addresses at which the above known wavelengths are stored. , The oscillation wavelength of the wavelength tunable light source 10 when light corresponding to each of the three first peak values is incident on the first light receiver 14 is obtained, and each of the obtained three oscillation wavelengths is obtained. For the first provisional reflection wavelength λ TU . Similarly, the addresses at which the three second peak values corresponding to the reflection wavelengths of the FBGs 13a to 13c, which are output from the peak value detection means 17, are stored, respectively, and the above known wavelengths are stored. The oscillation wavelength of the wavelength tunable light source 10 when light corresponding to each of the three second peak values is incident on the first light receiver 14 is obtained, and the obtained three oscillation wavelengths are compared. For each of the second provisional reflection wavelength λ TD .

反射波長／光路長算出手段１９は、ピーク値波長算出手段１８から出力される第１の仮の反射波長λTU及び第２の仮の反射波長λTDと波長可変光源１０の発振波長の掃引特性とに基づいて、各ＦＢＧ１３ａ〜１３ｃの反射波長λFを求めるとともに、波長可変光源１０から各ＦＢＧ１３ａ〜１３ｃまで及び各ＦＢＧ１３ａ〜１３ｃから第１の受光器１４までの光路長を求める。 The reflection wavelength / optical path length calculation unit 19 sweeps the first temporary reflection wavelength λ TU and the second temporary reflection wavelength λ TD output from the peak value wavelength calculation unit 18 and the oscillation wavelength of the wavelength variable light source 10. Based on the above, the reflection wavelength λ F of each of the FBGs 13a to 13c is obtained, and the optical path length from the wavelength variable light source 10 to each of the FBGs 13a to 13c and from each of the FBGs 13a to 13c to the first light receiver 14 is obtained.

まず、光路長に起因して発生する波長ずれのない状態での各ＦＢＧ１３ａ〜１３ｃの反射波長をどのように求めるかの基本概念を説明する。各ＦＢＧ１３ａ〜１３ｃの反射波長λFが、それぞれ図７（ａ）に示す反射スペクトルのような波長であるとする。各ＦＢＧ１３ａ〜１３ｃの反射波長λFを測定するときには、光路長による遅れ時間τの影響を受けて、アップ掃引のときはそれらの反射波長λFが見かけ上、図７（ｂ）に示すように波長の長い方へずれて第１の仮の反射波長λTUとなり、またダウン掃引のときは逆に図７（ｃ）に示すように波長の短い方へずれて第２の仮の反射波長λTDとなる。したがって、第１の仮の反射波長λTUと第２の仮の反射波長λTDが分かれば、それらの真ん中にある反射波長λFを求めることができる。なお、図７（ｂ）、（ｃ）において、アップ掃引とダウン掃引の発振波長の掃引特性（掃引時間に対する発振波長）の絶対値は同じであり、また各ＦＢＧ１３ａ〜１３ｃまでの光路長はＦＢＧ１３ａまでを基準にしてＦＢＧ１３ｂまではその２倍、ＦＢＧ１３ｃまではその３倍であるとしている。 First, the basic concept of how to obtain the reflection wavelength of each of the FBGs 13a to 13c in a state where there is no wavelength shift caused by the optical path length will be described. It is assumed that the reflection wavelength λ F of each of the FBGs 13a to 13c is a wavelength like the reflection spectrum shown in FIG. When measuring the reflection wavelength λ F of each of the FBGs 13a to 13c, it is affected by the delay time τ due to the optical path length, and the reflection wavelength λ F is apparently shown in FIG. The first temporary reflection wavelength λ TU is shifted to the longer wavelength, and the second temporary reflection wavelength λ is shifted to the shorter wavelength as shown in FIG. It becomes TD . Therefore, if the first temporary reflection wavelength λ TU and the second temporary reflection wavelength λ TD are known, the reflection wavelength λ F in the middle of them can be obtained. 7B and 7C, the absolute values of the sweep characteristics (oscillation wavelengths with respect to the sweep time) of the oscillation wavelengths of the up sweep and the down sweep are the same, and the optical path lengths from the FBGs 13a to 13c are the FBG 13a. Up to FBG 13b is doubled, and up to FBG 13c is tripled.

次に、上記の基本概念に基づいて、第１の仮の反射波長λTU及び第２の仮の反射波長λTDと波長可変光源１０の発振波長の掃引特性から各ＦＢＧ１３ａ〜１３ｃの反射波長λFを求める方法を説明する。図８に示す測定波長範囲付近の掃引特性が、一般式λ＝Ａ0＋Ａ1・ｘで表される一次関数で近似できるとすると、アップ掃引のときの発振波長λは、Ｋを掃引速度に比例した定数、ｔを時間とすると、（５）式（上述の（２）式と同一）で表され、またダウン掃引のときの発振波長λは、Ｊを掃引速度に比例した定数、ｔを時間、αを掃引周期に関するパラメータとすると、（６）式で表される。
λ＝λ0＋Ｋ・ｔ （５）
λ＝λ0−Ｊ・（ｔ−α） （６） Next, based on the basic concept described above, the reflection wavelength λ of each of the FBGs 13a to 13c is determined from the sweep characteristics of the first temporary reflection wavelength λ TU, the second temporary reflection wavelength λ TD, and the oscillation wavelength of the wavelength tunable light source 10. A method for obtaining F will be described. Assuming that the sweep characteristic in the vicinity of the measurement wavelength range shown in FIG. 8 can be approximated by a linear function represented by the general formula λ = A 0 + A 1 · x, the oscillation wavelength λ at the time of the up sweep is obtained by using K as the sweep speed. When the proportional constant, t is time, it is expressed by the equation (5) (same as the above equation (2)), and the oscillation wavelength λ at the time of the down sweep is expressed as follows: J is a constant proportional to the sweep speed, and t is When time and α are parameters related to the sweep period, the following expression (6) is given.
λ = λ 0 + K · t (5)
λ = λ 0 −J · (t−α) (6)

アップ掃引のときの各ＦＢＧ１３ａ〜１３ｃの反射波長λFと第１の仮の反射波長λTUとの関係は上記（５）式により（７）式のように表され、またダウン掃引のときの各ＦＢＧ１３ａ〜１３ｃの反射波長λFと第２の仮の反射波長λTDとの関係は上記（６）式により（８）式のように表される。なお、（７）、（８）式においては、波長可変光源１０から各ＦＢＧ１３ａ〜１３ｃまで及び各ＦＢＧ１３ａ〜１３ｃから第１の受光器１４までの光路長によるそれぞれの遅れ時間τは、主にファイバ１２ａ〜１２ｃの長さによる遅れ時間であるため、上述の（１）式と同一としている。
λTU＝λF＋Ｋ・２ｎＬ／Ｃ （７）
λTD＝λF−Ｊ・２ｎＬ／Ｃ （８） The relationship between the reflection wavelength λ F of each of the FBGs 13a to 13c during the up sweep and the first provisional reflection wavelength λ TU is expressed by the above equation (5) as shown in equation (7). The relationship between the reflection wavelength λ F of each of the FBGs 13a to 13c and the second provisional reflection wavelength λ TD is expressed by the above equation (6) as in equation (8). In the equations (7) and (8), each delay time τ depending on the optical path length from the wavelength variable light source 10 to each of the FBGs 13a to 13c and from each of the FBGs 13a to 13c to the first light receiver 14 is mainly a fiber. Since it is a delay time due to the length of 12a to 12c, it is the same as the above-mentioned formula (1).
λ TU = λ F + K · 2nL / C (7)
λ TD = λ F −J · 2nL / C (8)

そして、各ＦＢＧ１３ａ〜１３ｃの反射波長λFと、波長可変光源１０から各ＦＢＧ１３ａ〜１３ｃまで及び各ＦＢＧ１３ａ〜１３ｃから第１の受光器１４までの光路長（２ｎＬ）は、上記（７）、（８）式から（９）、（１０）式に示すように求めることができる。
λF＝（Ｊ・λTU＋Ｋ・λTD）／（Ｋ＋Ｊ） （９）
２ｎＬ＝（λTU−λTD）・Ｃ／（Ｋ＋Ｊ） （１０）
この結果、上記（９）、（１０）式から分かるように、各ＦＢＧ１３ａ〜１３ｃまでの光路長が不明で、しかも各ＦＢＧ１３ａ〜１３ｃの本来の反射波長が不明な場合であっても、各ＦＢＧ１３ａ〜１３ｃの反射波長λFを求めることができる。また、光路長も求めることができる。さらに、屈折率ｎが既知であればファイバ長Ｌも求めることができる。 The reflection wavelength λ F of each of the FBGs 13a to 13c and the optical path length (2nL) from the variable wavelength light source 10 to each of the FBGs 13a to 13c and from each of the FBGs 13a to 13c to the first light receiver 14 are (7), ( It can be obtained from equations (8) to (9) and (10).
λ F = (J · λ TU + K · λ TD ) / (K + J) (9)
2nL = (λ TU −λ TD ) · C / (K + J) (10)
As a result, as can be seen from the above formulas (9) and (10), even when the optical path length to each of the FBGs 13a to 13c is unknown and the original reflection wavelength of each of the FBGs 13a to 13c is unknown, each FBG 13a The reflection wavelength λ F of ˜13c can be obtained. Also, the optical path length can be obtained. Furthermore, if the refractive index n is known, the fiber length L can also be obtained.

ここで、上述の方法でファイバ長Ｌを測定する場合の測定可能な最長ファイバ長Ｌmaxについて説明する。すなわち、図７（ｂ）、（ｃ）及び図８から分かる通り、波長ずれが大きくなれば、λTUはアップ掃引の期間には観測できなくなり、ダウン掃引の期間で観測されてしまい測定不能となる。測定波長範囲の長波側の限界であるλmaxが、アップ掃引の期間から外れずに観測されるには、ファイバ長Ｌによる遅れ時間τは（１１）式を満足しなければならない。したがって、最長ファイバ長Ｌmaxは（１２）式で表される。なお、（１１）、（１２）式において、ｎはファイバの屈折率、Ｃは光速、Ｋは掃引速度に比例した定数、αは掃引周期に関するパラメータである。
τ ＜ α／２−（λmax−λ0）／Ｋ （１１）
２ｎＬmax／Ｃ ＜ α／２−（λmax−λ0）／Ｋ （１２）
具体例を示すと、例えば、ｎ＝１．５、Ｃ＝３×１０5ｋｍ／ｓ、α＝１ｍｓ、λmax＝１５７０ｎｍ、λ0＝１５４５ｎｍ、Ｋ＝１０5ｎｍ／ｓの場合には、Ｌmax＜２５ｋｍとなる。 Here, the maximum measurable fiber length L max when the fiber length L is measured by the above-described method will be described. That is, as can be seen from FIGS. 7B, 7C, and 8, if the wavelength shift increases, the λ TU cannot be observed during the up sweep period, and is not observed during the down sweep period. Become. In order to observe λ max , which is the limit on the long wave side of the measurement wavelength range, without departing from the period of the up sweep, the delay time τ due to the fiber length L must satisfy the equation (11). Therefore, the longest fiber length L max is expressed by equation (12). In equations (11) and (12), n is the refractive index of the fiber, C is the speed of light, K is a constant proportional to the sweep speed, and α is a parameter related to the sweep period.
τ <α / 2− (λ max −λ 0 ) / K (11)
2 nL max / C <α / 2− (λ max −λ 0 ) / K (12)
Specifically, for example, when n = 1.5, C = 3 × 10 5 km / s, α = 1 ms, λ max = 1570 nm, λ 0 = 1545 nm, and K = 10 5 nm / s, L max <25 km.

なお、上記反射波長／光路長算出手段１９では、波長可変光源１０の測定波長付近の掃引特性が、一般式λ＝Ａ0＋Ａ1・ｘで表される一次関数で近似できる場合について説明したが、一般式λ＝Ａ0＋Ａ1・ｘ＋Ａ2・ｘ2＋・・・で表される多次関数で近似する場合も同様に上述の方法を適用して、反射波長λF及び光路長（２ｎＬ）を求めることができることは言うまでもない。また、図１では、各ＦＢＧ１３ａ〜１３ｃからの反射光を受光器１４に入射するようにしたが、各ＦＢＧ１３ａ〜１３ｃからの透過光を受光器１４に入射するようにしてもよい。 In the reflection wavelength / optical path length calculation means 19, the sweep characteristic near the measurement wavelength of the wavelength tunable light source 10 has been described as being approximated by a linear function represented by the general formula λ = A 0 + A 1 · x. In the case of approximation by a multi-order function represented by the general formula λ = A 0 + A 1 · x + A 2 · x 2 +..., The reflection wavelength λ F and the optical path length (2 nL) are similarly applied. ) Needless to say, In FIG. 1, the reflected light from each of the FBGs 13 a to 13 c is incident on the light receiver 14, but the transmitted light from each of the FBGs 13 a to 13 c may be incident on the light receiver 14.

次に、図２に示した波長可変光源１０の一部を構成するＭＥＭＳスキャナ６０の反射体３５及び反射体駆動手段５０について詳述する。反射体３５は、図４に示すように、横長矩形で互いに平行に配置された一対の固定基板３６、３７と、この一対の固定基板３６、３７の長辺側縁部の中央からこの固定基板３６、３７と直交する方向に所定幅、所定長さで延設され、その長さ方向に沿って捩じれ変形可能な一対の軸部３８、３９と、横長矩形で一方の長辺側縁部の中央部で軸部３８の先端に連結され、他方の長辺側縁部の中央部で軸部３９の先端に連結された反射板４０とを有している。この反射板４０は、捩じれ変形可能な軸部３８、３９に中心部が支持されているので、この軸部３８、３９を結ぶ線を中心軸として固定基板３６、３７に対して回転することができる。また、軸部３８、３９と反射板４０とからなる部分の固有振動数ｆ0は、反射板４０自体の形状や質量及び軸部３８、３９のバネ定数によって決まる。 Next, the reflector 35 and the reflector driving means 50 of the MEMS scanner 60 constituting a part of the wavelength tunable light source 10 shown in FIG. 2 will be described in detail. As shown in FIG. 4, the reflector 35 includes a pair of fixed substrates 36 and 37 arranged in parallel with each other in a horizontally long rectangle, and the fixed substrate from the center of the long side edge of the pair of fixed substrates 36 and 37. A pair of shaft portions 38 and 39 that extend in a direction perpendicular to 36 and 37 with a predetermined width and length and can be twisted and deformed along the length direction, and one of the long side edges of the horizontally long rectangle. The reflector 40 is connected to the tip of the shaft portion 38 at the center and connected to the tip of the shaft 39 at the center of the other long side edge. Since the central portion of the reflector 40 is supported by the shaft portions 38 and 39 that can be torsionally deformed, the reflector 40 can rotate with respect to the fixed substrates 36 and 37 with the line connecting the shaft portions 38 and 39 as the central axis. it can. Further, the natural frequency f 0 of the portion composed of the shaft portions 38 and 39 and the reflecting plate 40 is determined by the shape and mass of the reflecting plate 40 itself and the spring constant of the shaft portions 38 and 39.

また、反射板４０の一面側には、光を反射するための反射面４１が形成されている。この反射面４１は、反射板４０自体を鏡面仕上げして形成したり、反射率の高い膜（図示しない）を蒸着あるいは接着して形成したりしたものであってもよい。なお、この反射体３５は、薄い半導体基板からエッチング処理等により一体的に切り出されたもので、金属膜の蒸着加工により高導電性を有している。   A reflective surface 41 for reflecting light is formed on one surface side of the reflective plate 40. The reflecting surface 41 may be formed by mirror-finishing the reflecting plate 40 itself, or may be formed by depositing or bonding a highly reflective film (not shown). The reflector 35 is integrally cut out from a thin semiconductor substrate by etching or the like, and has high conductivity by metal film vapor deposition.

支持基板４５は絶縁性を有する材料からなり、その一面側の上部と下部には、前方へ突出する支持台４５ａ、４５ｂが形成されており、反射体３５の固定基板３６、３７は、この上下の支持台４５ａ、４５ｂに接した状態で固定されている。また、支持基板４５の一面側中央部の両端には、反射体３５の反射板４０の両端にそれぞれ対向する電極板４６、４７がパターン形成されている。この電極板４６、４７は、後述する駆動信号発生器５５とともに反射体駆動手段５０（図２参照）を構成するものであり、反射板４０の両端部に静電力を交互にかつ周期的に印加して、反射板４０を、軸部３８、３９を結ぶ線を中心に往復回転運動させる。なお、反射板４０の回転軸は回折格子１の回折溝と平行となるように設定されている。このように構成された反射体３５は、回折格子３からの回折光を反射板４０の反射面４１で受けて、その反射光を回折格子３へ入射させて、再度回折させる。   The support substrate 45 is made of an insulating material, and support bases 45a and 45b projecting forward are formed on the upper and lower portions on one side, and the fixed substrates 36 and 37 of the reflector 35 are formed on the upper and lower sides. Are fixed in contact with the support bases 45a and 45b. In addition, electrode plates 46 and 47 that are opposed to both ends of the reflection plate 40 of the reflector 35 are formed in patterns at both ends of the central portion on the one surface side of the support substrate 45. The electrode plates 46 and 47 constitute a reflector driving means 50 (see FIG. 2) together with a drive signal generator 55 which will be described later, and an electrostatic force is alternately and periodically applied to both ends of the reflector plate 40. Then, the reflecting plate 40 is reciprocally rotated around the line connecting the shaft portions 38 and 39. The rotation axis of the reflecting plate 40 is set to be parallel to the diffraction groove of the diffraction grating 1. The reflector 35 configured as described above receives the diffracted light from the diffraction grating 3 by the reflection surface 41 of the reflection plate 40, makes the reflected light incident on the diffraction grating 3, and diffracts it again.

一方、反射体駆動手段５０（図２参照）の一部を構成する駆動信号発生器５５は、例えば図５（ａ）、（ｂ）に示すように、反射体３５の電位を基準として電極板４６、４７に対して、固有振動数ｆ0に対応した周波数（あるいは固有振動数ｆ0の近傍の振動数に対応した周波数）を有し、位相が１８０°ずれた駆動信号Ｄａ、Ｄｂを印加して、電極板４６と反射板４０の一端側との間及び電極板４７と反射板４０の他端側との間に、交互にかつ周期的に静電力(引力）を与え、反射板４０を固有振動数ｆ0あるいはその近傍の振動数で所定角度範囲を往復回転させる。また、この駆動信号発生器５５は、２つの駆動信号Ｄａ、Ｄｂのいずれか一方を受光素子１４からの第１の電気信号ｂ及び波長可変光源１０からの第２の電気信号ｃをＡ／Ｄ変換するためのトリガ信号ＴｒとしてＡ／Ｄ変換器１５（図１参照）に出力する。なお、図５では、２つの駆動信号Ｄａ、Ｄｂがデューティ比５０％の矩形波の場合を示しているが、両信号のデューティ比は５０％以下であってもよく、また、波形も矩形波に限らず、正弦波、三角波等であってもよい。 On the other hand, the drive signal generator 55 constituting a part of the reflector driving means 50 (see FIG. 2) is an electrode plate based on the potential of the reflector 35 as shown in FIGS. 5 (a) and 5 (b), for example. applied to 46 and 47, has a frequency corresponding to the natural frequency f 0 (or a frequency corresponding to the frequency in the vicinity of the natural frequency f 0), the drive signal Da whose phases are shifted from each other by 180 °, the Db Then, an electrostatic force (attraction) is alternately and periodically applied between the electrode plate 46 and one end side of the reflection plate 40 and between the electrode plate 47 and the other end side of the reflection plate 40. Is rotated back and forth within a predetermined angular range at the natural frequency f 0 or a frequency in the vicinity thereof. The drive signal generator 55 converts one of the two drive signals Da and Db into the first electric signal b from the light receiving element 14 and the second electric signal c from the wavelength variable light source 10 as A / D. A trigger signal Tr for conversion is output to the A / D converter 15 (see FIG. 1). FIG. 5 shows the case where the two drive signals Da and Db are rectangular waves with a duty ratio of 50%, but the duty ratio of both signals may be 50% or less, and the waveform is also a rectangular wave. It is not limited to sine waves, triangular waves, and the like.

このような反射体３５及び反射体駆動手段５０によって構成されたＭＥＭＳスキャナ６０では、反射体３５を、一対の固定基板３６、３７と、その縁部から所定幅で所定長さ延設され、その長さ方向に沿って捩じれ変形可能な軸部３８、３９と、軸部３８、３９の先端に自身の縁部で連結され、軸部３８、３９に対して対称な形状に形成され、一面側に反射面４１が形成された反射板４０とによって構成するとともに、反射体３５の軸部３８、３９と反射板４０とからなる部分の固有振動数ｆ0に対応した周波数の駆動信号によって反射板４０に力を与えて、反射板４０を固有振動数ｆ0又はその近傍の振動数で往復回転させている。 In the MEMS scanner 60 configured by the reflector 35 and the reflector driving means 50, the reflector 35 is extended from the pair of fixed substrates 36 and 37 and the edge thereof with a predetermined width and a predetermined length. The shaft portions 38, 39 that can be twisted and deformed along the length direction, and are connected to the ends of the shaft portions 38, 39 at their edges, are formed in a symmetrical shape with respect to the shaft portions 38, 39, and are on one side. And a reflecting plate 40 having a frequency corresponding to the natural frequency f 0 of the portion composed of the shaft portions 38 and 39 of the reflector 35 and the reflecting plate 40. A force is applied to 40 to rotate the reflector 40 back and forth at the natural frequency f 0 or a frequency in the vicinity thereof.

このため、僅かな電気エネルギーで反射板４０を高速に往復回転させることができ、しかも、その回転中心が反射板４０の内部（この場合、中央部）にあるので、反射板４０の反射面４１への入射光の反射角の変化量を大きくすることができる。なお、軸部３８、３９のバネ定数は、軸部３８、３９の長さ、幅、厚み、材質によって決まり、このバネ定数と、反射板４０の形状、厚み、材質等で固有振動数ｆ0が決定され、これらのパラメータを選ぶことにより、固有振動数ｆ0を数１００Ｈｚ〜数１０ｋＨｚの範囲内で設定することができる。 For this reason, the reflector 40 can be reciprocally rotated at a high speed with a small amount of electrical energy, and the center of rotation is inside the reflector 40 (in this case, the central portion). The amount of change in the reflection angle of the incident light on can be increased. The spring constants of the shaft portions 38 and 39 are determined by the length, width, thickness, and material of the shaft portions 38 and 39, and the natural frequency f 0 depends on the spring constant and the shape, thickness, material, and the like of the reflector 40. By selecting these parameters, the natural frequency f 0 can be set within a range of several hundreds of Hz to several tens of kHz.

したがって、本発明のＦＢＧ歪センサシステムの波長可変光源１０（図２参照）は、上記のような反射体３５及び反射体駆動手段５０を用いてＭＥＭＳスキャナ６０を構成するようにしたので、掃引速度の高速化（最大数１０ｋＨｚ）ができる。   Therefore, since the wavelength tunable light source 10 (see FIG. 2) of the FBG strain sensor system of the present invention is configured with the MEMS scanner 60 using the reflector 35 and the reflector driving means 50 as described above, the sweep speed is set. (Up to several 10 kHz).

なお、上述の図４の説明では、反射体３５を導電性の高い材料で構成していたが、反射体３５を導電性の低い材料で構成する場合には、反射板４０の反射面４１と反対面の両側（全面でもよい）に電極板４６、４７と対向する電極板をそれぞれ設け、更に固定基板３６、３７の背面側にも電極板を設け、それらの電極板の間をパターン等によって接続する。そして、支持基板４５の支持台４５ａ、４５ｂの表面に、固定基板３６、３７の背面側の電極板と接触する電極板をパターン形成して、その少なくとも一方を基準電位ラインとして上述した駆動信号発生器５５に接続すればよい。   In the description of FIG. 4 described above, the reflector 35 is made of a material with high conductivity. However, when the reflector 35 is made of a material with low conductivity, the reflecting surface 41 of the reflector 40 Electrode plates facing the electrode plates 46 and 47 are provided on both sides (or the entire surface) of the opposite surface, and electrode plates are also provided on the back side of the fixed substrates 36 and 37, and the electrode plates are connected by a pattern or the like. . Then, the electrode plate that contacts the electrode plates on the back side of the fixed substrates 36 and 37 is formed on the surface of the support bases 45a and 45b of the support substrate 45, and at least one of them is used as a reference potential line to generate the drive signal described above. What is necessary is just to connect to the device 55.

また、固定基板３６、３７の一端側同士の間あるいは両端の間を連結して、固定基板をコの字枠あるいは矩形枠状に形成してもよい。また、反射板４０の形状も任意であり、上述の横長矩形の他に、円形、楕円形、長円形、菱形、正方形、多角形等であってもよい。また、高速往復回転時の空気抵抗を減らすために、反射板４０の内側に大きな穴あるいは多数の小さな穴を設けてもよい。   Further, the fixed substrates may be formed in a U-shaped frame or a rectangular frame shape by connecting one end side or both ends of the fixed substrates 36 and 37. Moreover, the shape of the reflecting plate 40 is also arbitrary, and may be a circle, an ellipse, an oval, a rhombus, a square, a polygon, or the like in addition to the above-described horizontally long rectangle. Further, in order to reduce air resistance during high-speed reciprocating rotation, a large hole or a large number of small holes may be provided inside the reflector plate 40.

また、上述の図４の説明では、反射体３５の反射板４０の両端にそれぞれ対向する２つの電極板４６、４７を設けていたが、一方側の電極板（例えば電極板４６）だけによって静電力を印加してもよい。また、駆動方式についても、上述の静電力の他に、電磁力によって反射板４０を往復回転させてもよい。この場合、例えば、上述の電極板４６、４７の代わりにコイルを用い、反射板４０の両端部に磁性体あるいはコイルを設け、コイル間あるいはコイルと磁性体との間に発生する磁界による吸引力及び反発力によって、反射板４０を往復回転させる。   In the description of FIG. 4 described above, the two electrode plates 46 and 47 facing each other at both ends of the reflection plate 40 of the reflector 35 are provided. However, only one electrode plate (for example, the electrode plate 46) is used for static electricity. Electric power may be applied. Moreover, also about a drive system, you may rotate the reflecting plate 40 reciprocatingly with an electromagnetic force other than the above-mentioned electrostatic force. In this case, for example, a coil is used in place of the electrode plates 46 and 47 described above, a magnetic material or a coil is provided at both ends of the reflection plate 40, and an attractive force due to a magnetic field generated between the coils or between the coil and the magnetic material. And the reflecting plate 40 is reciprocated by the repulsive force.

また、上述の静電力や電磁力を反射板４０に直接与える方法の他に、超音波振動子等によって上述の固有振動数ｆ0又はその近傍の振動を反射体３５全体に加えて、その振動を反射板４０に伝達させて往復回転させることも可能である。この場合、振動子を支持基板４５の背面側や支持台４５ａ、４５ｂの部分に設けることで、その振動を反射板４０に効率的に伝達することができる。 In addition to the above-described method of directly applying the electrostatic force or electromagnetic force to the reflector 40, the above-described natural frequency f 0 or a vibration in the vicinity thereof is applied to the entire reflector 35 by an ultrasonic vibrator or the like, and the vibration It is also possible to transmit the light to the reflecting plate 40 for reciprocal rotation. In this case, the vibration can be efficiently transmitted to the reflection plate 40 by providing the vibrator on the back side of the support substrate 45 and the support bases 45a and 45b.

本発明の実施形態の構成を示す図The figure which shows the structure of embodiment of this invention 波長可変光源の構成を示す図Diagram showing the configuration of a wavelength tunable light source 波長可変光源の別の構成を示す図The figure which shows another structure of a wavelength variable light source ＭＥＭＳスキャナを説明するための分解斜視図Exploded perspective view for explaining a MEMS scanner 駆動信号を説明するための図Diagram for explaining drive signals ＭＥＭＳスキャナによる波長掃引について説明するための図The figure for demonstrating the wavelength sweep by a MEMS scanner 反射波長の求め方の基本概念を説明するための図Diagram for explaining the basic concept of how to obtain the reflection wavelength 波長可変光源の発振波長の掃引特性を説明するための図Diagram for explaining the oscillation wavelength sweep characteristics of a tunable light source

符号の説明Explanation of symbols

１・・・半導体レーザ（ＬＤ）、２・・・コリメートレンズ、３・・・回折格子、４・・・光共振器、５，１４・・・受光器（ＰＤ）、６・・・光分岐手段、１０・・・波長可変光源、１１・・・光サーキュレータ、１２ａ〜１２ｃ・・・ファイバ、１３ａ〜１３ｃ・・・ファイバブラッググレーティング（ＦＢＧ）、１５・・・Ａ／Ｄ変換器、１６ａ，１６ｂ・・・メモリ、１７・・・ピーク値検出手段、１８・・・ピーク値波長算出手段、１９・・・反射波長／光路長算出手段、２０・・・処理手段、３５・・・反射体、３６，３７・・・固定基板、３８，３９・・・軸部、４０・・・反射板、４１・・・反射面、４５・・・支持基板、４５ａ，４５ｂ・・・支持台、４６，４７・・・電極板、５０・・・反射体駆動手段、５５・・・駆動信号発生器、６０・・・ＭＥＭＳスキャナ。
DESCRIPTION OF SYMBOLS 1 ... Semiconductor laser (LD), 2 ... Collimating lens, 3 ... Diffraction grating, 4 ... Optical resonator, 5, 14 ... Light receiver (PD), 6 ... Optical branching Means: 10 ... wavelength variable light source, 11 ... optical circulator, 12a-12c ... fiber, 13a-13c ... fiber Bragg grating (FBG), 15 ... A / D converter, 16a, 16b ... Memory, 17 ... Peak value detection means, 18 ... Peak value wavelength calculation means, 19 ... Reflection wavelength / optical path length calculation means, 20 ... Processing means, 35 ... Reflector , 36, 37 ... fixed substrate, 38, 39 ... shaft portion, 40 ... reflector, 41 ... reflector, 45 ... support substrate, 45a, 45b ... support base, 46 47 ... Electrode plate, 50 ... Reflector driving means, 55 ... Drive Signal generator, 60 · · · MEMS scanner.

Claims (10)

歪みの測定対象に設けられたＦＢＧ（１３ａ〜１３ｃ）と、
所定の波長範囲の光を発振し、該光を測定光として前記ＦＢＧに入射させる波長可変光源（１０）と、
前記ＦＢＧに入射された前記測定光であって、該ＦＢＧによって反射された光又は該ＦＢＧを透過した光を受けて第１の電気信号に変換する第１の受光器（１４）と、
該第１の受光器から出力される前記第１の電気信号と前記波長可変光源の発振波長から前記ＦＢＧの反射波長を測定して当該ＦＢＧに加わった歪み量を求める処理手段（２０）とを備えたＦＢＧ歪センサシステムにおいて、
前記波長可変光源は、
前記所定の波長範囲を含んで短波から長波へかつ長波から短波へ所定の掃引周期で光を発振し、該光を前記測定光として前記ＦＢＧに入射させ、
前記処理手段は、
前記波長可変光源が前記所定の波長範囲を含んで短波から長波へ掃引している期間に前記第１の受光器から出力される前記第１の電気信号と当該波長可変光源の発振波長から前記ＦＢＧの反射波長を第１の仮の反射波長λTUとして測定し、かつ、前記波長可変光源が前記所定の波長範囲を含んで長波から短波へ掃引している期間に前記第１の受光器から出力される前記第１の電気信号と当該波長可変光源の発振波長から前記ＦＢＧの反射波長を第２の仮の反射波長λTDとして測定し、さらに、測定した前記第１の仮の反射波長λTU及び前記第２の仮の反射波長λTDに基づいて、前記波長可変光源から前記ＦＢＧまで及び該ＦＢＧから前記第１の受光器までの光路長に起因して発生する、前記ＦＢＧの反射波長の測定時の波長ずれを含まない当該ＦＢＧの反射波長λFを求めることを特徴とするＦＢＧ歪センサシステム。 FBGs (13a to 13c) provided for distortion measurement targets;
A wavelength tunable light source (10) that oscillates light in a predetermined wavelength range and makes the light incident on the FBG as measurement light;
A first light receiver (14) that receives the measurement light incident on the FBG and receives the light reflected by the FBG or the light transmitted through the FBG and converts the light into a first electrical signal;
Processing means (20) for measuring the reflection wavelength of the FBG from the first electric signal output from the first light receiver and the oscillation wavelength of the wavelength tunable light source and determining the amount of distortion applied to the FBG; In the provided FBG strain sensor system,
The wavelength tunable light source is
The light is oscillated from a short wave to a long wave and from a long wave to a short wave in a predetermined sweep period including the predetermined wavelength range, and the light is incident on the FBG as the measurement light,
The processing means includes
From the first electrical signal output from the first light receiver and the oscillation wavelength of the wavelength tunable light source during the period in which the wavelength tunable light source sweeps from a short wave to a long wave including the predetermined wavelength range, the FBG Is output as the first provisional reflection wavelength λ TU and output from the first light receiver during a period in which the wavelength tunable light source sweeps from the long wave to the short wave including the predetermined wavelength range. The reflected wavelength of the FBG is measured as the second temporary reflected wavelength λ TD from the first electrical signal and the oscillation wavelength of the wavelength tunable light source, and the measured first temporary reflected wavelength λ TU And the reflection wavelength of the FBG generated due to the optical path length from the wavelength tunable light source to the FBG and from the FBG to the first light receiver based on the second temporary reflection wavelength λ TD . This does not include wavelength shift during measurement BG FBG strain sensor system and obtains the reflection wavelength lambda F of. 前記処理手段が、さらに、
前記ＦＢＧの前記第１の仮の反射波長λTU及び前記第２の仮の反射波長λTDに基づいて、前記波長可変光源から前記ＦＢＧまで及び該ＦＢＧから前記第１の受光器までの前記光路長を求めることを特徴とする請求項１に記載のＦＢＧ歪センサシステム。 The processing means further comprises:
Based on the first temporary reflection wavelength λ TU and the second temporary reflection wavelength λ TD of the FBG, the optical path from the wavelength variable light source to the FBG and from the FBG to the first light receiver The FBG strain sensor system according to claim 1, wherein a length is obtained. 前記処理手段は、
前記波長可変光源が前記所定の波長範囲を含んで短波から長波へ掃引している期間に前記第１の受光器から出力される前記第１の電気信号の中から前記ＦＢＧの反射波長に対応するピーク値を検出するとともに、検出した該ピーク値に対応した光が前記第１の受光器に入射された時の当該波長可変光源の発振波長を求め、求めた該発振波長を前記ＦＢＧの第１の仮の反射波長λTUとし、かつ、前記波長可変光源が前記所定の波長範囲を含んで長波から短波へ掃引している期間に前記第１の受光器から出力される前記第１の電気信号の中から前記ＦＢＧの反射波長に対応するピーク値を検出するとともに、検出した該ピーク値に対応した光が前記第１の受光器に入射された時の当該波長可変光源の発振波長を求め、求めた該発振波長を前記ＦＢＧの第２の仮の反射波長λTDとし、さらに、前記ＦＢＧの前記第１の仮の反射波長λTU及び前記第２の仮の反射波長λTD並びに前記波長可変光源の発振波長の掃引特性に基づいて当該ＦＢＧの反射波長λFを求めることを特徴とする請求項１に記載のＦＢＧ歪センサシステム。 The processing means includes
Corresponding to the reflected wavelength of the FBG from the first electric signal output from the first light receiver during a period in which the wavelength tunable light source sweeps from a short wave to a long wave including the predetermined wavelength range. The peak value is detected, the oscillation wavelength of the wavelength tunable light source when the light corresponding to the detected peak value is incident on the first light receiver is obtained, and the obtained oscillation wavelength is calculated as the first wavelength of the FBG. a provisional reflection wavelength lambda TU, and the first electrical signal the wavelength tunable light source is output from the first photodetector in a period that is swept to short the long wave including the predetermined wavelength range A peak value corresponding to the reflected wavelength of the FBG is detected, and an oscillation wavelength of the wavelength tunable light source when light corresponding to the detected peak value is incident on the first light receiver, The determined oscillation wavelength is the FB Second and reflection wavelength lambda TD tentative, further sweep characteristic of the oscillation wavelength of the first temporary reflection wavelength lambda TU and the second temporary reflection wavelength lambda TD and the wavelength tunable light source of the FBG 2. The FBG strain sensor system according to claim 1, wherein a reflection wavelength λ F of the FBG is obtained based on the FBG strain sensor system. 前記処理手段が、さらに、
前記ＦＢＧの前記第１の仮の反射波長λTU及び前記第２の仮の反射波長λTD並びに前記波長可変光源の発振波長の掃引特性に基づいて、前記波長可変光源から前記ＦＢＧまで及び該ＦＢＧから前記第１の受光器までの光路長を求めることを特徴とする請求項３に記載のＦＢＧ歪センサシステム。 The processing means further comprises:
Based on the first provisional reflection wavelength λ TU and the second provisional reflection wavelength λ TD of the FBG and the sweep characteristics of the oscillation wavelength of the wavelength tunable light source, from the wavelength tunable light source to the FBG and the FBG The FBG strain sensor system according to claim 3, wherein an optical path length from the first to the first light receiver is obtained. 前記波長可変光源は、
一方のレーザ光出射端面がＡＲコートされている半導体レーザ（１）と、
該半導体レーザのＡＲコートされている端面から出射された光をコリメートするコリメートレンズ（２）と、
該コリメートレンズから出射されたコリメート光を受けて波長に応じた角度で回折させる回折格子（３）と、
反射体（３５）と反射体駆動手段（５０）とを含んで構成され、前記回折格子から入射される前記コリメート光に対する回折光が、前記反射体の反射面で該回折格子へ反射されて、再び該回折格子で回折され、それによって得られた回折光が前記コリメートレンズを介して前記半導体レーザに入射されるとき、該半導体レーザに入射される回折光が所望の波長の光となるようにするとともに、該所望の波長が前記所定の波長範囲を含んで往復掃引されるように前記反射体の反射面の角度を前記反射体駆動手段により前記所定の周期で繰り返し変化させるＭＥＭＳスキャナ（６０）とを備えたことを特徴とする請求項１〜４のいずれかに記載のＦＢＧ歪センサシステム。 The wavelength tunable light source is
A semiconductor laser (1) in which one laser light emitting end face is AR coated;
A collimating lens (2) for collimating light emitted from the AR-coated end face of the semiconductor laser;
A diffraction grating (3) that receives collimated light emitted from the collimating lens and diffracts the collimated light at an angle corresponding to the wavelength;
A diffracted light for the collimated light incident from the diffraction grating is reflected to the diffraction grating by the reflection surface of the reflector, and includes a reflector (35) and a reflector driving means (50). When diffracted light is again diffracted by the diffraction grating and incident on the semiconductor laser through the collimating lens, the diffracted light incident on the semiconductor laser becomes light of a desired wavelength. And a MEMS scanner (60) for repeatedly changing the angle of the reflecting surface of the reflector at the predetermined period by the reflector driving means so that the desired wavelength is swept back and forth including the predetermined wavelength range. The FBG strain sensor system according to any one of claims 1 to 4, further comprising: 前記ＭＥＭＳスキャナの反射体は、
固定基板（３６、３７）と、
該固定基板の縁部から所定幅で所定長さ延設され、その長さ方向に沿って捩じれ変形可能な軸部（３８、３９）と、
該軸部の先端に自身の縁部で連結されて形成され、一面側に前記回折格子からの回折光を反射させるための前記反射面が設けられた反射板（４０）とを有しており、かつ、
前記ＭＥＭＳスキャナの反射体駆動手段は、
前記反射体の軸部と反射板とからなる部分の固有振動数に対応した周波数の駆動信号によって前記反射板に力を与えて、該反射板を前記固有振動数又はそれに近い振動数の前記所定の周期で往復回転させるように構成されていることを特徴とする請求項５に記載のＦＢＧ歪センサシステム。 The reflector of the MEMS scanner is:
A fixed substrate (36, 37);
Shaft portions (38, 39) that extend from the edge of the fixed substrate with a predetermined width and have a predetermined length and can be twisted and deformed along the length direction;
A reflection plate (40) formed by being connected to the tip of the shaft portion at its edge and provided with the reflection surface for reflecting the diffracted light from the diffraction grating on one surface side; ,And,
The reflector driving means of the MEMS scanner includes:
A force is applied to the reflecting plate by a driving signal having a frequency corresponding to the natural frequency of the portion composed of the shaft portion and the reflecting plate of the reflector, and the reflecting plate is given the predetermined frequency at or near the natural frequency. The FBG strain sensor system according to claim 5, wherein the FBG strain sensor system is configured to be reciprocally rotated at a period of 前記波長可変光源は、さらに、
前記回折格子の０次光が出射される光路上に設けられて所定の波長の光を透過させる光共振器（４）と、
該光共振器から出射される透過光を受けて第２の電気信号に変換する第２の受光器（５）とを備え、該第２の受光器から出力される前記第２の電気信号から当該波長可変光源の発振波長を求めることを可能にしたことを特徴とする請求項５又は６に記載のＦＢＧ歪センサシステム。 The wavelength tunable light source further includes:
An optical resonator (4) provided on an optical path from which the zero-order light of the diffraction grating is emitted and transmitting light of a predetermined wavelength;
A second light receiver (5) that receives the transmitted light emitted from the optical resonator and converts it into a second electric signal, and from the second electric signal output from the second light receiver. 7. The FBG strain sensor system according to claim 5, wherein an oscillation wavelength of the wavelength tunable light source can be obtained. 前記波長可変光源は、
前記回折格子の０次光を出力光とすることを特徴とする請求項５又は６に記載のＦＢＧ歪センサシステム。 The wavelength tunable light source is
The FBG strain sensor system according to claim 5 or 6, wherein the 0th-order light of the diffraction grating is output light. 前記波長可変光源は、さらに、
前記回折格子の０次光が出射される光路上に設けられ、該０次光を２つに分岐して一方の０次光を前記出力光として出射する光分岐手段（６）と、
該光分岐手段から出射される他方の０次光を受けて所定の波長の光を透過させる光共振器（４）と、
該光共振器から出射される透過光を受けて第２の電気信号に変換する第２の受光器（５）とを備え、該第２の受光器から出力される前記第２の電気信号から当該波長可変光源の発振波長を求めることを可能にしたことを特徴とする請求項８に記載のＦＢＧ歪センサシステム。 The wavelength tunable light source further includes:
A light branching means (6) provided on an optical path from which the zero-order light of the diffraction grating is emitted, branching the zero-order light into two and emitting one zero-order light as the output light;
An optical resonator (4) for receiving the other zero-order light emitted from the light branching means and transmitting light of a predetermined wavelength;
A second light receiver (5) that receives the transmitted light emitted from the optical resonator and converts it into a second electric signal, and from the second electric signal output from the second light receiver. 9. The FBG strain sensor system according to claim 8, wherein an oscillation wavelength of the wavelength tunable light source can be obtained. 前記処理手段は、
前記第１の受光器からの前記第１の電気信号及び前記第２の受光器からの前記第２の電気信号を受けてそれぞれディジタル値に変換するＡ／Ｄ変換器（１５）と、
該Ａ／Ｄ変換器から出力される前記第１の電気信号のディジタル値を順次所定のアドレスに記憶する第１のメモリ（１６ａ）と、
前記Ａ／Ｄ変換器から出力される前記第２の電気信号のディジタル値を順次所定のアドレスに記憶する第２のメモリ（１６ｂ）と、
前記第１のメモリの前記所定のアドレスに記憶されているディジタル値を読み出して、前記波長可変光源が前記所定の波長範囲を含んで短波から長波へ掃引している期間における前記ＦＢＧの反射波長に対応する第１のピーク値を検出し、かつ、前記波長可変光源が前記所定の波長範囲を含んで長波から短波へ掃引している期間における前記ＦＢＧの反射波長に対応する第２のピーク値を検出するピーク値検出手段（１７）と、
前記第２のメモリの前記所定のアドレスに記憶されている前記波長可変光源の発振波長を求めるためのディジタル値を読み出して、前記光共振器の前記所定の波長が記憶されているアドレスを検出し、検出した該アドレスと前記ピーク値検出手段から出力される、前記第１のピーク値及び前記第２のピーク値がそれぞれ記憶されているアドレスとに基づいて、当該第１のピーク値及び第２のピーク値にそれぞれ対応した光が前記第１の受光器に入射された時の当該波長可変光源の発振波長を求め、求めたそれぞれの該発振波長を前記ＦＢＧの第１の仮の反射波長λTU及び第２の仮の反射波長λTDとするピーク値波長算出手段（１８）と、
該ピーク値波長算出手段から出力される前記第１の仮の反射波長λTU及び前記第２の仮の反射波長λTDと前記波長可変光源の発振波長の掃引特性とに基づいて、前記ＦＢＧの反射波長λFを求めるとともに、前記波長可変光源から前記ＦＢＧまで及び該ＦＢＧから前記第１の受光器までの光路長を求める反射波長／光路長算出手段（１９）とを備えたことを特徴とする請求項７又は９に記載のＦＢＧ歪センサシステム。
The processing means includes
An A / D converter (15) that receives the first electric signal from the first light receiver and the second electric signal from the second light receiver and converts them into digital values, respectively;
A first memory (16a) for sequentially storing a digital value of the first electric signal output from the A / D converter at a predetermined address;
A second memory (16b) for sequentially storing the digital value of the second electric signal output from the A / D converter at a predetermined address;
The digital value stored at the predetermined address of the first memory is read, and the reflected wavelength of the FBG during the period in which the wavelength variable light source sweeps from the short wave to the long wave including the predetermined wavelength range is obtained. A corresponding first peak value is detected, and a second peak value corresponding to the reflected wavelength of the FBG in a period in which the wavelength tunable light source sweeps from a long wave to a short wave including the predetermined wavelength range is obtained. A peak value detecting means (17) for detecting;
A digital value for obtaining the oscillation wavelength of the wavelength tunable light source stored at the predetermined address of the second memory is read, and an address where the predetermined wavelength of the optical resonator is stored is detected. , Based on the detected address and the address output from the peak value detecting means and storing the first peak value and the second peak value, respectively. The oscillation wavelength of the wavelength tunable light source when light corresponding to each of the peak values is incident on the first light receiver is obtained, and each of the obtained oscillation wavelengths is determined as the first provisional reflection wavelength λ of the FBG. A peak value wavelength calculating means (18) for setting the TU and the second provisional reflection wavelength λ TD ;
Based on the first provisional reflection wavelength λ TU and the second provisional reflection wavelength λ TD output from the peak value wavelength calculation means and the sweep characteristic of the oscillation wavelength of the wavelength tunable light source, the FBG A reflection wavelength / optical path length calculating means (19) for obtaining a reflection wavelength λ F and obtaining an optical path length from the wavelength tunable light source to the FBG and from the FBG to the first light receiver; The FBG strain sensor system according to claim 7 or 9.
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