WO2014091754A1 - Optical fiber sensor and sensing method of same - Google Patents

Optical fiber sensor and sensing method of same Download PDF

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WO2014091754A1
WO2014091754A1 PCT/JP2013/007283 JP2013007283W WO2014091754A1 WO 2014091754 A1 WO2014091754 A1 WO 2014091754A1 JP 2013007283 W JP2013007283 W JP 2013007283W WO 2014091754 A1 WO2014091754 A1 WO 2014091754A1
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light
optical fiber
frequency
fiber sensor
modulated
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鈴木　尚文
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日本電気株式会社
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    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01D—MEASURING NOT SPECIALLY ADAPTED FOR A SPECIFIC VARIABLE; ARRANGEMENTS FOR MEASURING TWO OR MORE VARIABLES NOT COVERED IN A SINGLE OTHER SUBCLASS; TARIFF METERING APPARATUS; MEASURING OR TESTING NOT OTHERWISE PROVIDED FOR
    • G01D5/00—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable
    • G01D5/26—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable characterised by optical transfer means, i.e. using infrared, visible, or ultraviolet light
    • G01D5/32—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable characterised by optical transfer means, i.e. using infrared, visible, or ultraviolet light with attenuation or whole or partial obturation of beams of light
    • G01D5/34—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable characterised by optical transfer means, i.e. using infrared, visible, or ultraviolet light with attenuation or whole or partial obturation of beams of light the beams of light being detected by photocells
    • G01D5/353—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable characterised by optical transfer means, i.e. using infrared, visible, or ultraviolet light with attenuation or whole or partial obturation of beams of light the beams of light being detected by photocells influencing the transmission properties of an optical fibre
    • G01D5/35338—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable characterised by optical transfer means, i.e. using infrared, visible, or ultraviolet light with attenuation or whole or partial obturation of beams of light the beams of light being detected by photocells influencing the transmission properties of an optical fibre using other arrangements than interferometer arrangements
    • G01D5/35354—Sensor working in reflection
    • G01D5/35358—Sensor working in reflection using backscattering to detect the measured quantity
    • G01D5/35364—Sensor working in reflection using backscattering to detect the measured quantity using inelastic backscattering to detect the measured quantity, e.g. using Brillouin or Raman backscattering
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01K—MEASURING TEMPERATURE; MEASURING QUANTITY OF HEAT; THERMALLY-SENSITIVE ELEMENTS NOT OTHERWISE PROVIDED FOR
    • G01K11/00—Measuring temperature based upon physical or chemical changes not covered by groups G01K3/00, G01K5/00, G01K7/00 or G01K9/00
    • G01K11/32—Measuring temperature based upon physical or chemical changes not covered by groups G01K3/00, G01K5/00, G01K7/00 or G01K9/00 using changes in transmittance, scattering or luminescence in optical fibres
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01K—MEASURING TEMPERATURE; MEASURING QUANTITY OF HEAT; THERMALLY-SENSITIVE ELEMENTS NOT OTHERWISE PROVIDED FOR
    • G01K11/00—Measuring temperature based upon physical or chemical changes not covered by groups G01K3/00, G01K5/00, G01K7/00 or G01K9/00
    • G01K11/32—Measuring temperature based upon physical or chemical changes not covered by groups G01K3/00, G01K5/00, G01K7/00 or G01K9/00 using changes in transmittance, scattering or luminescence in optical fibres
    • G01K11/322—Measuring temperature based upon physical or chemical changes not covered by groups G01K3/00, G01K5/00, G01K7/00 or G01K9/00 using changes in transmittance, scattering or luminescence in optical fibres using Brillouin scattering
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01M—TESTING STATIC OR DYNAMIC BALANCE OF MACHINES OR STRUCTURES; TESTING OF STRUCTURES OR APPARATUS, NOT OTHERWISE PROVIDED FOR
    • G01M11/00—Testing of optical apparatus; Testing structures by optical methods not otherwise provided for
    • G01M11/30—Testing of optical devices, constituted by fibre optics or optical waveguides
    • G01M11/31—Testing of optical devices, constituted by fibre optics or optical waveguides with a light emitter and a light receiver being disposed at the same side of a fibre or waveguide end-face, e.g. reflectometers
    • G01M11/319—Reflectometers using stimulated back-scatter, e.g. Raman or fibre amplifiers
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01B—MEASURING LENGTH, THICKNESS OR SIMILAR LINEAR DIMENSIONS; MEASURING ANGLES; MEASURING AREAS; MEASURING IRREGULARITIES OF SURFACES OR CONTOURS
    • G01B11/00—Measuring arrangements characterised by the use of optical techniques
    • G01B11/16—Measuring arrangements characterised by the use of optical techniques for measuring the deformation in a solid, e.g. optical strain gauge
    • G01B11/18—Measuring arrangements characterised by the use of optical techniques for measuring the deformation in a solid, e.g. optical strain gauge using photoelastic elements

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  • Physics & Mathematics (AREA)
  • General Physics & Mathematics (AREA)
  • Optics & Photonics (AREA)
  • Chemical & Material Sciences (AREA)
  • Analytical Chemistry (AREA)
  • Optical Transform (AREA)
  • Length Measuring Devices By Optical Means (AREA)
  • Measuring Temperature Or Quantity Of Heat (AREA)
  • Testing Of Optical Devices Or Fibers (AREA)

Abstract

This optical fiber sensor is characterized by comprising: a first generating means that generates first light that propagates within an optical fiber; a second generating means that generates a second light having a lower frequency than the first light and that propagates in the opposite direction to the first light; a third generating means that generates third light that propagates in the same direction as the second light; and a measuring means that measures scattered light from the third light. As a result of this configuration, it is possible to provide an optical fiber sensor that satisfies high positional resolution, high measurement accuracy, short measurement time and low cost.

Description

光ファイバセンサおよびそのセンス方法Optical fiber sensor and sensing method thereof
　本発明は、光ファイバの長手方向における温度分布や歪分布などを測定する光ファイバセンサおよびそのセンス方法に関する。 The present invention relates to an optical fiber sensor for measuring temperature distribution, strain distribution, and the like in the longitudinal direction of an optical fiber and a sensing method thereof.
　光ファイバセンサは、連続光またはパルス光を光ファイバに入射させ、光ファイバ内において生ずる散乱光または反射光を受光することにより、光ファイバの長手方向における温度や歪の分布などの特性を測定するものである。 An optical fiber sensor measures characteristics such as temperature and strain distribution in the longitudinal direction of an optical fiber by making continuous light or pulsed light incident on the optical fiber and receiving scattered light or reflected light generated in the optical fiber. Is.
　ＢＯＴＤＡ（Ｂｒｉｌｌｏｕｉｎ　Ｏｐｔｉｃａｌ　Ｔｉｍｅ　Ｄｏｍａｉｎ　Ａｎａｌｙｓｉｓ）はそのようなファイバセンシング方式の１種である。これは、光ファイバの一方の端から光パルス、他方の端から連続光を入射し、この２つの光により誘導ブリルアン散乱を生じさせ、それによって生じる散乱光を測定するものである。この方式では位置分解能を向上させるためには、パルス幅を狭くする必要がある。 BOTDA (Brillouin Optical Time Domain Analysis) is one type of such fiber sensing system. In this method, a light pulse is incident from one end of an optical fiber, and continuous light is incident from the other end. Stimulated Brillouin scattering is caused by the two lights, and the scattered light generated thereby is measured. In this method, it is necessary to narrow the pulse width in order to improve the position resolution.
　一方、パルス幅を狭くするとパルスの周波数スペクトルが広くなり、測定されるブリルアンゲインスペクトルもそれに伴って広くなる。このためピーク位置の検出精度が低下し、結果として温度や歪の測定精度が低下する。すなわち、本方式では、位置分解能と、温度や歪の測定精度との間にトレードオフの関係がある。 On the other hand, if the pulse width is narrowed, the frequency spectrum of the pulse becomes wider, and the measured Brillouin gain spectrum becomes wider accordingly. For this reason, the detection accuracy of the peak position is lowered, and as a result, the measurement accuracy of temperature and strain is lowered. That is, in this method, there is a trade-off relationship between position resolution and temperature and strain measurement accuracy.
　特許文献１には、光強度と幅が異なる２種類のパルスを組み合わせることによって、上記のトレードオフを解消する方法が開示されている。 Patent Document 1 discloses a method for eliminating the above trade-off by combining two types of pulses having different light intensity and width.
　また、非特許文献１では、次のような測定方法が示されている。すなわち、この方法では偏光保持ファイバの一方の端から連続光１を入射し、他方の端から連続光１よりもブリルアンシフト分だけ周波数の低い連続光２を入射して、この両者間で誘導ブリルアン散乱を生じさせる。さらに連続光１と同じ方向からパルス光を入射し、その反射光を測定するものである。パルス光は、連続光１と２の誘導ブリルアン散乱によって生じた音響フォノンによって散乱される。ここで、連続光１と２は同じ偏光方向の直線偏光であり、パルス光はそれと直交する直線偏光としている。直交する偏光間では、誘導ブリルアン散乱が生じないため、パルス光と連続光間では誘導ブリルアン散乱が生じない。このためパルス幅を狭くし、パルス光のスペクトル幅が広くなった場合でも、測定されるブリルアンスペクトルには影響せず、ピーク位置の検出精度は低下しない。したがって、高い位置分解能と、温度や歪の高い測定精度とを両立させることが可能である。 Further, Non-Patent Document 1 discloses the following measurement method. That is, in this method, continuous light 1 is incident from one end of the polarization-maintaining fiber, and continuous light 2 having a frequency lower than the continuous light 1 by the Brillouin shift is incident from the other end. Causes scattering. Further, pulsed light is incident from the same direction as the continuous light 1, and the reflected light is measured. The pulsed light is scattered by acoustic phonons generated by stimulated Brillouin scattering of continuous light 1 and 2. Here, the continuous lights 1 and 2 are linearly polarized light having the same polarization direction, and the pulsed light is linearly polarized light orthogonal thereto. Stimulated Brillouin scattering does not occur between orthogonally polarized light, so that stimulated Brillouin scattering does not occur between pulsed light and continuous light. For this reason, even when the pulse width is narrowed and the spectrum width of the pulsed light is widened, the measured Brillouin spectrum is not affected, and the peak position detection accuracy is not lowered. Therefore, it is possible to achieve both high position resolution and high temperature and distortion measurement accuracy.
　光ファイバセンシングの他の方式として、ＢＯＦＤＡ（Ｂｒｉｌｌｏｕｉｎ　Ｏｐｔｉｃａｌ　Ｆｒｅｑｕｅｎｃｙ　Ｄｏｍａｉｎ　Ａｎａｌｙｓｉｓ）がある。これは光ファイバの一方の端から連続光、他方の端から正弦波により強度変調された変調光を入射し、誘導ブリルアン散乱で生じる変調光の散乱光を測定するものである。本方式では位置分解能を高くするには、変調波の変調周波数を高くする必要があるが、その場合にはブリルアンゲインスペクトルの形状に影響が生じる。この結果、ピーク位置の検出精度が低下し、温度や歪の測定精度が低下する。　 There is BOFDA (Brillouin Optical Frequency Domain Analysis) as another method of optical fiber sensing. In this method, modulated light intensity-modulated by continuous light from one end of the optical fiber and sine wave from the other end is incident, and the scattered light of modulated light generated by stimulated Brillouin scattering is measured. In this method, in order to increase the position resolution, it is necessary to increase the modulation frequency of the modulated wave. In this case, the shape of the Brillouin gain spectrum is affected. As a result, the peak position detection accuracy decreases, and the temperature and strain measurement accuracy decreases. *
　この問題の解決方法として、非特許文献２には、測定されたブリルアンゲインスペクトルと理論計算によって得られるスペクトルを比較、フィッティングすることによりピーク位置を高精度で検出する方法が提案されている。 As a solution to this problem, Non-Patent Document 2 proposes a method of detecting the peak position with high accuracy by comparing and fitting the measured Brillouin gain spectrum and the spectrum obtained by theoretical calculation.
特許第３９３００２３号公報Japanese Patent No. 3930023
　特許文献１に記載の方法は、測定対象である光ファイバが短い場合には有効であるが、比較的長い光ファイバに対しては光スイッチからの漏れ光の影響が顕著となり、測定の精度が低下する。 The method described in Patent Document 1 is effective when the optical fiber to be measured is short, but the influence of leakage light from the optical switch becomes significant for a relatively long optical fiber, and the measurement accuracy is improved. descend.
　非特許文献１に記載の方法は、偏光保持ファイバを用いているが、偏光保持ファイバは通常の光ファイバと比べて価格が高い。また、無歪、一定温度の条件下でのブリルアンシフト量の長手方向の均一性が通常の光ファイバと比べて低い。これらのことから、長い距離のセンシングには不向きである。また、同方法では先述のように連続光とパルス光の偏光方向を直交させる必要があるが、偏光保持ファイバには複屈折性があり、２つの直交する直線偏光に対する屈折率が異なる。連続光１の偏光をＸ、パルス光のＹとし、それぞれの屈折率をｎｘ，ｎｙ、周波数をｆｘ，ｆｙとすれば、ｎｘ・ｆｘ＝ｎｙ・ｆｙを満たすように、周波数を調整する必要がある。ｎｘとｎｙの比は個々の偏光保持ファイバによって異なり、また歪や温度によっても異なるため、測定時にパルス光の周波数ｆｙを掃引する必要が生じる。これにより測定器が複雑化しコストが増加するとともに、測定時間が増加する。 The method described in Non-Patent Document 1 uses a polarization maintaining fiber, but the polarization maintaining fiber is more expensive than a normal optical fiber. In addition, the uniformity in the longitudinal direction of the Brillouin shift amount under the conditions of no distortion and a constant temperature is lower than that of a normal optical fiber. For these reasons, it is not suitable for long-distance sensing. In the same method, the polarization directions of the continuous light and the pulsed light need to be orthogonal as described above. However, the polarization maintaining fiber has birefringence, and the refractive indexes for two orthogonal linearly polarized light are different. Continuous light 1 the polarization X, and Y of the pulsed light, the respective refractive indices n x, n y, if the frequency f x, and f y, to meet the n x · f x = n y · f y In addition, it is necessary to adjust the frequency. The ratio of n x and n y are different depending on the particular polarization maintaining fiber, and because different depending strain or temperature, it is necessary to sweep the frequency f y of the pulsed light at the time of measurement. This complicates the measuring instrument and increases the cost, and increases the measurement time.
　偏光保持ファイバの代わりに通常の光ファイバを用いれば、上記の点は解消される。すなわち、長距離のセンシングも問題なく、またパルス光の波長は連続光１と同じで良いため、測定器の構造の簡略化、低コスト化が可能となる。ただしこの場合、各光の偏光状態が維持されないため、パルス光と連続光２の偏光方向の直交性が保たれない。このため連続光２とパルス光の間で誘導ブリルアン散乱が生じ得ることとなる。その場合、ブリルアンゲインスペクトル形状に影響が生じ、温度や歪の分解能を低下させることとなる。 If the usual optical fiber is used instead of the polarization maintaining fiber, the above point is solved. That is, there is no problem in long-distance sensing, and the wavelength of the pulsed light may be the same as that of the continuous light 1, so that the structure of the measuring instrument can be simplified and the cost can be reduced. However, in this case, since the polarization state of each light is not maintained, the orthogonality between the polarization directions of the pulsed light and the continuous light 2 cannot be maintained. For this reason, stimulated Brillouin scattering can occur between the continuous light 2 and the pulsed light. In this case, the Brillouin gain spectrum shape is affected, and the resolution of temperature and strain is reduced.
　一方、非特許文献２に記載の方法では、ブリルアンゲインスペクトルの測定値と理論値のフィッティングに時間がかかるため、測定時間が長くなる。このため比較的短い時間での歪や温度などの変化を捉えることができない。 On the other hand, in the method described in Non-Patent Document 2, it takes a long time to fit the measured value and the theoretical value of the Brillouin gain spectrum, so that the measurement time becomes long. For this reason, changes such as strain and temperature in a relatively short time cannot be captured.
　以上のように、既知の光ファイバセンサおよびそのセンス方法では、高い位置分解能、高い測定精度、短い測定時間および低いコストを同時に満たす光ファイバセンシングは不可能であった。 As described above, with the known optical fiber sensor and its sensing method, optical fiber sensing that simultaneously satisfies high position resolution, high measurement accuracy, short measurement time, and low cost is impossible.
　本発明は上記の課題に鑑みなされたものであり、その目的は、高い位置分解能、高い測定精度、短い測定時間、および、低いコストを同時に満たすことが可能な、光ファイバセンサおよびそのセンス方法を提供することである。 The present invention has been made in view of the above problems, and an object of the present invention is to provide an optical fiber sensor and a sensing method thereof capable of simultaneously satisfying high position resolution, high measurement accuracy, short measurement time, and low cost. Is to provide.
　本発明の光ファイバセンサは、光ファイバ内を伝播する第１の光を発生する第１の発生手段と、前記光ファイバ内を前記第１の光とは逆方向に伝播し前記第１の光より周波数の低い第２の光を発生する第２の発生手段と、前記光ファイバ内を前記第２の光と同方向に伝播する第３の光を発生する第３の発生手段と、前記第３の光の散乱光の計測を行う計測手段と、を備えている。 The optical fiber sensor of the present invention includes a first generation unit that generates first light propagating in an optical fiber, and the first light that propagates in the optical fiber in a direction opposite to the first light. Second generating means for generating second light having a lower frequency; third generating means for generating third light propagating in the same direction as the second light in the optical fiber; and Measuring means for measuring the scattered light of No. 3 light.
　本発明の光ファイバセンサのセンス方法は、光ファイバ内を伝播する第１の光と、前記光ファイバ内を前記第１の光とは逆方向に伝播し前記第１の光より周波数の低い第２の光と、前記光ファイバ内を前記第２の光と同方向に伝播する第３の光とを有し、前記第３の光の散乱光を計測する。 According to the sensing method of the optical fiber sensor of the present invention, the first light propagating in the optical fiber and the first light propagating in the opposite direction to the first light in the optical fiber are lower in frequency than the first light. 2 light and third light propagating in the same direction as the second light in the optical fiber, and the scattered light of the third light is measured.
　本発明によれば、高い位置分解能、高い測定精度、短い測定時間、および、低いコストを同時に満たすことが可能な、光ファイバセンサおよびそのセンス方法を提供することができる。 According to the present invention, it is possible to provide an optical fiber sensor and a sensing method thereof that can simultaneously satisfy high position resolution, high measurement accuracy, short measurement time, and low cost.
本発明の第１の実施形態における光ファイバセンサの構成を示すブロック図である。It is a block diagram which shows the structure of the optical fiber sensor in the 1st Embodiment of this invention. 本発明の第２の実施形態における光ファイバセンサの構成を示す図である。It is a figure which shows the structure of the optical fiber sensor in the 2nd Embodiment of this invention. 本発明の第３の実施形態における光ファイバセンサの構成を示す図である。It is a figure which shows the structure of the optical fiber sensor in the 3rd Embodiment of this invention. 本発明の第４の実施形態における光ファイバセンサの構成を示す図である。It is a figure which shows the structure of the optical fiber sensor in the 4th Embodiment of this invention. 本発明の第５の実施形態における光ファイバセンサの構成を示す図である。It is a figure which shows the structure of the optical fiber sensor in the 5th Embodiment of this invention.
　以下、図を参照しながら、本発明の最良の実施形態を詳細に説明する。但し、以下に述べる実施形態には、本発明を実施するために技術的に好ましい限定がされているが、発明の範囲を以下に限定するものではない。
（第１の実施形態）
　本発明の第１の実施形態について図１を参照して説明する。図１は、本実施形態の光ファイバセンサの構成を示すブロック図である。本実施形態の光ファイバセンサは、光ファイバ１４内を伝播する第１の光を発生する第１の発生手段１０と、前記光ファイバ１４内を前記第１の光とは逆方向に伝播し前記第１の光より周波数の低い第２の光を発生する第２の発生手段１１とを備える。さらに、前記光ファイバ１４内を前記第２の光と同方向に伝播する第３の光を発生する第３の発生手段１２と、前記第３の光の散乱光の計測を行う計測手段１３とを備える。 Hereinafter, the best embodiment of the present invention will be described in detail with reference to the drawings. However, the preferred embodiments described below are technically preferable for carrying out the present invention, but the scope of the invention is not limited to the following.
(First embodiment)
A first embodiment of the present invention will be described with reference to FIG. FIG. 1 is a block diagram showing the configuration of the optical fiber sensor of the present embodiment. The optical fiber sensor of the present embodiment includes a first generation unit 10 that generates first light propagating in the optical fiber 14, and the optical fiber 14 that propagates in the opposite direction to the first light. Second generation means 11 for generating second light having a frequency lower than that of the first light. Furthermore, third generation means 12 for generating third light propagating in the same direction as the second light in the optical fiber 14, and measurement means 13 for measuring the scattered light of the third light, Is provided.
　本実施形態によれば、高い位置分解能、高い測定精度、短い測定時間、および、低いコストを同時に満たすことが可能な、光ファイバセンサを提供することができる。
（第２の実施形態）
　本発明の第２の実施形態について図面を参照して説明する。第２の実施形態では、本発明をＢＯＴＤＡ法に適用する。図２に本実施形態の光ファイバセンサの構成を示す。 According to the present embodiment, it is possible to provide an optical fiber sensor that can simultaneously satisfy high position resolution, high measurement accuracy, short measurement time, and low cost.
(Second Embodiment)
A second embodiment of the present invention will be described with reference to the drawings. In the second embodiment, the present invention is applied to the BOTDA method. FIG. 2 shows the configuration of the optical fiber sensor of this embodiment.
　本実施形態の光ファイバセンサは、以下の手段を備える。すなわち、光ファイバ１１２内を伝播する第１の光を発生する第１の発生手段１０と、光ファイバ１１２内を第１の光とは逆方向に伝播し第１の光より周波数の低い第２の光を発生する第２の発生手段１１とを備える。さらに、光ファイバ１１２内を第２の光と同方向に伝播する第３の光を発生する第３の発生手段１２と、第３の光の散乱光の計測を行う計測手段１３とを備える。 The optical fiber sensor of this embodiment includes the following means. That is, the first generating means 10 for generating the first light propagating in the optical fiber 112 and the second light having a lower frequency than the first light propagating in the optical fiber 112 in the opposite direction to the first light. And second generation means 11 for generating the light. Furthermore, a third generation unit 12 that generates third light propagating in the same direction as the second light in the optical fiber 112 and a measurement unit 13 that measures the scattered light of the third light are provided.
　第１の発生手段１０は、第１の光を次のように発生する。光源１０１から出た光は、光分岐器１０２によって分岐される。分岐した光の一方は光変調器１０３によって周波数がシフトされた後、エルビウム添加光ファイバ増幅器（ＥＤＦＡ）１０４によって増幅され、第１の光となる。ここで、光変調器１０３はマイクロ波発生器１０３ａとＳＳＢ（Ｓｉｎｇｌｅ　Ｓｉｄｅ　Ｂａｎｄ　：単側波帯）変調器１０３ｂからなり、入射光の周波数に対し、マイクロ波発生器１０３ａで発生したマイクロ波の周波数分に等しい周波数差を有する単側波帯波を発生させる。これを出力光とすることにより、光の周波数をシフトすることができる。 The first generation means 10 generates the first light as follows. The light emitted from the light source 101 is branched by the light splitter 102. One of the branched lights is shifted in frequency by the optical modulator 103 and then amplified by an erbium-doped optical fiber amplifier (EDFA) 104 to become the first light. Here, the optical modulator 103 includes a microwave generator 103a and an SSB (Single Side Band) modulator 103b, and the frequency of the microwave generated by the microwave generator 103a with respect to the frequency of the incident light. Generate a single sideband with a frequency difference equal to minutes. By using this as output light, the frequency of the light can be shifted.
　第２の発生手段１１は、第２の光を次のように発生する。光源１０１から出て光分岐器１０２によって分岐されたもう一方の光は、さらに光分岐器１０５によって２分岐される。その一方の光はＥＤＦＡ１０６により増幅され、第２の光となる。 The second generation means 11 generates the second light as follows. The other light emitted from the light source 101 and branched by the optical splitter 102 is further split into two by the optical splitter 105. One of the lights is amplified by the EDFA 106 and becomes the second light.
　第３の発生手段１２は、第３の光を次のように発生する。光分岐器１０５によって２分岐されたもう一方の光は、光変調器１０７により周波数がシフトされた後、ＥＤＦＡ１０８によって増幅され、その後、光パルス発生器１０９によってパルスを発生し、第３の光となる。ここで光変調器１０７はマイクロ波発生器１０７ａとＳＳＢ変調器１０７ｂからなり、光変調器１０３と同様に動作する。 The third generation means 12 generates the third light as follows. The other light branched into two by the optical splitter 105 is amplified by the EDFA 108 after the frequency is shifted by the optical modulator 107, and then a pulse is generated by the optical pulse generator 109, and the third light and Become. Here, the optical modulator 107 includes a microwave generator 107 a and an SSB modulator 107 b and operates in the same manner as the optical modulator 103.
　ＥＤＦＡ１０６を出た第２の光と、光パルス発生器１０９を出た第３の光は、光合波器１１０によって合波された後、光サーキュレータ１１１を通って、センサ部となる光ファイバ１１２に入射される。一方、ファイバ１１２のもう一端からは、ＥＤＦＡ１０４から出た第１の光が入射される。ここで、第１の光、第２の光、第３の光の周波数をそれぞれｆ１、ｆ２、ｆ３とすると、ｆ１＞ｆ２＞ｆ３となるように周波数をシフトさせている。 The second light exiting the EDFA 106 and the third light exiting the optical pulse generator 109 are combined by the optical multiplexer 110 and then pass through the optical circulator 111 to the optical fiber 112 serving as the sensor unit. Incident. On the other hand, the first light emitted from the EDFA 104 is incident from the other end of the fiber 112. Here, assuming that the frequencies of the first light, the second light, and the third light are f 1 , f 2 , and f 3 , the frequencies are shifted so that f 1 > f 2 > f 3 . .
　周波数ｆ１の第１の光と周波数ｆ２の第２の光は連続光であり、この両者によって形成される音響フォノンにより、周波数ｆ３のパルス光である第３の光が反射される。反射された第３の光は光サーキュレータ１１１を通り、計測手段１３である受光器１１３に到達する。受光器１１３で受光された第３の光は電気信号となり、それをアナログ－デジタル変換した後にデータとして取り込む（図２に記載なし）。このデータからファイバ１１２内での反射光強度分布が得られる。Δｆ（＝ｆ１－ｆ２）を変えて上記の測定を繰り返すことにより、ブリルアンゲインスペクトル分布が得られ、それよりファイバ１２内の歪や温度の分布を得ることができる。 First second optical light and the frequency f 2 of the frequency f 1 is continuous light, the acoustic phonon that is formed by the two, the third light is reflected is a pulsed light frequency f 3. The reflected third light passes through the optical circulator 111 and reaches the light receiver 113 as the measuring means 13. The third light received by the light receiver 113 becomes an electric signal, which is converted into data after analog-digital conversion (not shown in FIG. 2). From this data, a reflected light intensity distribution in the fiber 112 is obtained. By repeating the above measurement while changing Δf (= f 1 −f 2 ), a Brillouin gain spectrum distribution can be obtained, whereby a strain and temperature distribution in the fiber 12 can be obtained.
　本実施形態では、周波数ｆ１、ｆ２の２つの連続光によって音響フォノンが形成され、その音響フォノンによって中心周波数ｆ３のパルス光が反射されることになる。発明者は、ｆ１－ｆ２＝Δｆ＞０である周波数ｆ１、ｆ２の光で形成された音響フォノンによって、ｆ２と同じ方向に進むｆ３の光が反射されるためには、ｆ１－ｆ３がほぼ２．５Δｆに等しいことが必要となることを計算により見出した。このため、ｆ１－ｆ２＝Δｆに対し、ｆ１－ｆ３＝２．５Δｆとなるようにマイクロ波発生器１０３ａ、１０７ａの出力周波数を調整している。 In the present embodiment, an acoustic phonon is formed by the two continuous lights having the frequencies f 1 and f 2 , and the pulse light having the center frequency f 3 is reflected by the acoustic phonon. In order for the light of f 3 traveling in the same direction as f 2 to be reflected by the acoustic phonon formed by light of frequencies f 1 and f 2 where f 1 −f 2 = Δf> 0, the inventor It was found by calculation that f 1 −f 3 needs to be approximately equal to 2.5Δf. For this reason, the output frequencies of the microwave generators 103a and 107a are adjusted so that f 1 −f 3 = 2.5Δf with respect to f 1 −f 2 = Δf.
　以上、本実施形態によれば、第１と第２の光の間で誘導ブリルアン散乱が生じ、それによって生成される音響フォノンによって第３の光が散乱される。第１の光と第２の光の周波数差を掃引することによって、ファイバ内の歪または温度分布を短時間で測定することとなり、その周波数掃引の範囲は測定する温度や歪の範囲によって決まる。第３の光の周波数は第２の光の周波数と大きく離れているので、仮に石英製の光ファイバが破断もしくは軟化するほどの歪や温度範囲まで測定範囲を広げたとしても、第１と第３の光の周波数差は誘導ブリルアン散乱を生じる範囲には入らない。このため、第３の光およびそれと対向する第１の光では、両者の偏光状態に関わらず誘導ブリルアン散乱が発生しない。したがって通常の光ファイバを用い、パルス光の幅を狭くしても、変調光である第３の光が誘導ブリルアン散乱に寄与することはなくなる。したがって、高い位置分解能と高い測定精度を両立することが可能となる。 As described above, according to the present embodiment, stimulated Brillouin scattering occurs between the first and second lights, and the third light is scattered by the acoustic phonons generated thereby. By sweeping the frequency difference between the first light and the second light, the strain or temperature distribution in the fiber is measured in a short time, and the range of the frequency sweep is determined by the temperature and strain range to be measured. Since the frequency of the third light is far away from the frequency of the second light, even if the measurement range is expanded to a strain or temperature range that causes the optical fiber made of quartz to break or soften, The frequency difference of light 3 does not fall within the range where stimulated Brillouin scattering occurs. For this reason, stimulated Brillouin scattering does not occur in the third light and the first light opposite thereto, regardless of the polarization state of both. Therefore, even if a normal optical fiber is used and the width of the pulsed light is narrowed, the third light as the modulated light does not contribute to the stimulated Brillouin scattering. Therefore, it is possible to achieve both high position resolution and high measurement accuracy.
　以上のように、本実施形態によれば、高い位置分解能、高い測定精度、短い測定時間、および、低いコストを同時に満たすことが可能となる。
（第３の実施形態）
　本発明の第３の実施形態について図面を参照して説明する。第３の実施形態では、第２の実施形態と同様に本発明をＢＯＴＤＡ法に適用する。図３に本実施形態の光ファイバセンサの構成を示す。 As described above, according to the present embodiment, high position resolution, high measurement accuracy, short measurement time, and low cost can be satisfied at the same time.
(Third embodiment)
A third embodiment of the present invention will be described with reference to the drawings. In the third embodiment, the present invention is applied to the BOTDA method as in the second embodiment. FIG. 3 shows the configuration of the optical fiber sensor of this embodiment.
　光源２０１から出た光は、光分岐器２０２によって分岐される。分岐した光の一方はＥＤＦＡ２０３によって増幅され、第２の光となる。もう一方はＳＳＢ変調器２０４に入射する。ここでＳＳＢ変調器２０４は２つの出力ポートを有し、入射した光から高周波側にシフトした光と、低周波側にシフトした光の両者をそれぞれ出射する。周波数シフト量の絶対値は高周波側と低周波側で同じである。このようなＳＳＢ変調器は、例えば非特許文献３に記述がある構造において、最終段の２つの導波路を合波させず、それぞれ別の出力ポートとした構造にすることによって得ることができる。 The light emitted from the light source 201 is branched by the light splitter 202. One of the branched lights is amplified by the EDFA 203 and becomes the second light. The other is incident on the SSB modulator 204. Here, the SSB modulator 204 has two output ports, and emits both the light shifted from the incident light to the high frequency side and the light shifted to the low frequency side. The absolute value of the frequency shift amount is the same on the high frequency side and the low frequency side. Such an SSB modulator can be obtained, for example, in a structure described in Non-Patent Document 3, by using a structure in which the two waveguides in the final stage are not combined but are set as separate output ports.
　２つの出力光のうち、高周波側にシフトした光はＥＤＦＡ２０５で増幅され、第１の光となる。一方、低周波側にシフトした光は、さらに別のＳＳＢ変調器２０６に入射し、さらに低周波にシフトされる。ＳＳＢ変調器２０６から出射された光は、ＥＤＦＡ２０７で増幅された後、パルス発生器２０８によりパルス光となり、第３の光となる。 Of the two output lights, the light shifted to the high frequency side is amplified by the EDFA 205 and becomes the first light. On the other hand, the light shifted to the low frequency side is incident on another SSB modulator 206 and further shifted to a low frequency. The light emitted from the SSB modulator 206 is amplified by the EDFA 207, then becomes pulsed light by the pulse generator 208, and becomes third light.
　ＳＳＢ変調器２０４および２０６には入出力光間の周波数シフトと一致する周波数を有するマイクロ波が入力されている。マイクロ波発生器２０９から出たマイクロ波は分波器２１０により分波される。分波したマイクロ波の片方はＳＳＢ変調器２０６に入射する。もう一方は周波数逓倍器２１１に入力され、２倍の周波数のマイクロ波が出力される。 The SSB modulators 204 and 206 are input with microwaves having a frequency that matches the frequency shift between input and output light. The microwave output from the microwave generator 209 is demultiplexed by the demultiplexer 210. One of the demultiplexed microwaves enters the SSB modulator 206. The other is input to the frequency multiplier 211 and a microwave having a double frequency is output.
　光源２０１から出射される光の周波数をｆ２（第２の光の周波数）、マイクロ波発生器２０９から出射するマイクロ波の周波数を０．５Δｆ、ＳＳＢ変調器２０４から出射される高周波側の光の周波数をｆ１（第１の光の周波数）とすると、ｆ１－ｆ２＝Δｆとなる。この時ＳＳＢ変調器２０６に入射する光の周波数はｆ２－Δｆとなり、ＳＳＢ変調器２０６の出射光の周波数はｆ２－１．５Δｆとなる。これがパルス光の中心周波数となる。この周波数をｆ３（第３の光の周波数）とすれば、ｆ１－ｆ２＝Δｆに対し、ｆ３＝ｆ２－１．５Δｆ＝ｆ１－２．５Δｆとなり、先に述べた第１の実施形態と同じ関係となっている。 The frequency of the light emitted from the light source 201 is f 2 (frequency of the second light), the frequency of the microwave emitted from the microwave generator 209 is 0.5Δf, and the light on the high frequency side emitted from the SSB modulator 204 Is f 1 (frequency of the first light), f 1 −f 2 = Δf. At this time, the frequency of light incident on the SSB modulator 206 is f 2 −Δf, and the frequency of light emitted from the SSB modulator 206 is f 2 −1.5Δf. This is the center frequency of the pulsed light. If this frequency is f 3 (the frequency of the third light), f 3 = f 2 −1.5Δf = f 1 −2.5Δf with respect to f 1 −f 2 = Δf, The relationship is the same as that of the first embodiment.
　周波数ｆ１、ｆ２、ｆ３の光は光合波器２１２によって合波された後、光サーキュレータ２１３を通って光ファイバ２１４へ入射する。光ファイバ２１４の端にはＦＢＧ２１５（Ｆｉｂｅｒ　Ｂｒａｇｇ　Ｇｒａｔｉｎｇ）が接続されている。ＦＢＧ２１５は周波数ｆ１の第１の光を反射し、周波数ｆ２、ｆ３の第２の光、第３の光は透過する。ＦＢＧ２１５で反射された周波数ｆ１の第１の光は、光ファイバ２１４をサーキュレータ２１３の方向に向かって伝播する。すなわち、周波数ｆ１の第１の光が周波数ｆ２、ｆ３の第２の光、第３の光と対向して伝播することになる。対向する第１の光と第２の光によって生じる誘導ブリルアン散乱により音響フォノンが形成され、これによって第３の光が反射される。反射されたパルス光は光サーキュレータ２１３を通り、受光器２１６に到達する。 Lights having frequencies f 1 , f 2 , and f 3 are combined by the optical multiplexer 212 and then enter the optical fiber 214 through the optical circulator 213. An FBG 215 (Fiber Bragg Grating) is connected to the end of the optical fiber 214. The FBG 215 reflects the first light having the frequency f 1 and transmits the second light and the third light having the frequencies f 2 and f 3 . The first light having the frequency f 1 reflected by the FBG 215 propagates through the optical fiber 214 toward the circulator 213. That is, the first optical frequency f 1 and the second optical frequency f 2, f 3, it propagates to face the third light. Acoustic phonons are formed by stimulated Brillouin scattering caused by the opposing first light and second light, whereby the third light is reflected. The reflected pulsed light passes through the optical circulator 213 and reaches the light receiver 216.
　先に述べた第１の実施形態では、ｆ１－ｆ３＝２．５Δｆの関係を保つために、２つのマイクロ波発生器を調整する必要があったが、本実施形態では自動的にこの関係が保たれることになる。また、第２の実施形態では光ファイバの両端から光を入射する必要があるため、測定系全体の光ファイバの長さは、センサ部となる光ファイバの２倍以上が必要となる。これに対し、本実施形態では、光ファイバの片端から光を入射することになるため、全体のファイバの長さを短くすることが可能である。 In the first embodiment described above, it was necessary to adjust the two microwave generators in order to maintain the relationship of f 1 −f 3 = 2.5Δf. The relationship will be maintained. In the second embodiment, since it is necessary to make light incident from both ends of the optical fiber, the length of the optical fiber in the entire measurement system is required to be at least twice that of the optical fiber serving as the sensor unit. On the other hand, in this embodiment, since light enters from one end of the optical fiber, it is possible to shorten the length of the entire fiber.
　以上、本実施形態によれば、第２の実施形態と同様に、第１と第２の光の間で誘導ブリルアン散乱が生じ、それによって生成される音響フォノンによって第３の光が散乱される。この時、第３の光およびそれと対向する第１の光では、両者の偏光状態に関わらず誘導ブリルアン散乱が発生しない。したがって通常の光ファイバを用い、パルス光の幅を狭くしても、変調光である第３の光が誘導ブリルアン散乱に寄与することはなくなる。したがって、高い位置分解能と高い測定精度を両立することが可能となる。 As described above, according to this embodiment, similarly to the second embodiment, stimulated Brillouin scattering occurs between the first and second lights, and the third light is scattered by the acoustic phonons generated thereby. . At this time, the stimulated Brillouin scattering does not occur in the third light and the first light opposite to the third light regardless of the polarization state of the both. Therefore, even if a normal optical fiber is used and the width of the pulsed light is narrowed, the third light as the modulated light does not contribute to the stimulated Brillouin scattering. Therefore, it is possible to achieve both high position resolution and high measurement accuracy.
　以上のように、本実施形態によれば、高い位置分解能、高い測定精度、短い測定時間、および、低いコストを同時に満たすことが可能となる。
（第４の実施形態）
　本発明の第４の実施形態について図面を参照して説明する。第４の実施形態では、本発明をＢＯＦＤＡ法に適用する。図４に本実施形態の光ファイバセンサの構成を示す。本構成は第２の実施形態の構成図である図２と多くの部分で共通しているので、共通部分は図２で用いたものと同じ符号で表すものとする。 As described above, according to the present embodiment, high position resolution, high measurement accuracy, short measurement time, and low cost can be satisfied at the same time.
(Fourth embodiment)
A fourth embodiment of the present invention will be described with reference to the drawings. In the fourth embodiment, the present invention is applied to the BOFDA method. FIG. 4 shows the configuration of the optical fiber sensor of this embodiment. Since this configuration is common to many parts of FIG. 2 which is the configuration diagram of the second embodiment, common parts are represented by the same reference numerals as those used in FIG.
　光源１０１から出た周波数ｆ２の光を分岐し、ＳＳＢ変調器を用いて、周波数ｆ１、ｆ３の光を生成する。それぞれの光を、ＥＤＦＡ１０６により増幅して第２の光、ＥＤＦＡ１０４により増幅して第１の光、ＥＤＦＡ１０８により増幅して第３の光の元の光とする。以上は、第２の実施形態と同じである。ＥＤＦＡ１０８から出射された周波数ｆ３の光は、変調器３０１により、角周波数ωの正弦波によって強度変調される。変調された光は光分岐器３０２により分岐され、片方は受光器３０３に入射する。もう片方は第３の光として光合波器１１０により周波数ｆ２の第２の光と合波される。その後、光サーキュレータ１１１を通じて測定対象である光ファイバ１１２に入射する。また、光ファイバ１１２の逆の端からは周波数ｆ１の第１の光が入射される。 The light having the frequency f 2 emitted from the light source 101 is branched, and the light having the frequencies f 1 and f 3 is generated using the SSB modulator. Each light is amplified by the EDFA 106 to be the second light, amplified by the EDFA 104 to be the first light, and amplified by the EDFA 108 to be the original light of the third light. The above is the same as in the second embodiment. Light having a frequency f 3 emitted from the EDFA 108 is intensity-modulated by a modulator 301 by a sine wave having an angular frequency ω. The modulated light is branched by the optical branching device 302 and one of the light enters the light receiving device 303. The other is combined with the second light having the frequency f 2 by the optical multiplexer 110 as the third light. Thereafter, the light is incident on the optical fiber 112 to be measured through the optical circulator 111. Further, the first light having the frequency f 1 is incident from the opposite end of the optical fiber 112.
　第１の光と第２の光から生成される音響フォノンにより中心周波数ｆ３の変調光である第３の光が反射され、反射光は光サーキュレータ１１１を通り、受光器１１３に入射する。受光器３０３と受光器１１３からの出力はベクトルネットワークアナライザ（Ｖｅｃｔｏｒ　Ｎｅｔｗｏｒｋ　Ａｎａｌｙｚｅｒ　：　ＶＮＡ）３０４に入射され、両者の比から、角周波数ωにおける伝達係数が得られる。変調器３０１の変調周波数を決める角周波数ωの電気信号はＶＮＡ３０４から供給されており、ωを変えて上記のデータ取得を繰り返すことにより、伝達関数Ｈ（ω）が得られる。この伝達関数Ｈ（ω）を逆フーリエ変換することにより、光ファイバ１１２内でのブリルアン散乱による光反射の位置情報を得ることができる。Δｆ＝ｆ１－ｆ２を変えて上記の測定を繰り返すことにより、光ファイバ内の歪や温度の分布情報を得ることが可能である。 The third light that is the modulated light having the center frequency f 3 is reflected by the acoustic phonon generated from the first light and the second light, and the reflected light passes through the optical circulator 111 and enters the light receiver 113. Outputs from the light receiver 303 and the light receiver 113 are incident on a vector network analyzer (VNA) 304, and a transfer coefficient at an angular frequency ω is obtained from the ratio between the two. An electrical signal having an angular frequency ω that determines the modulation frequency of the modulator 301 is supplied from the VNA 304, and the transfer function H (ω) is obtained by repeating the above data acquisition by changing ω. By performing inverse Fourier transform on this transfer function H (ω), it is possible to obtain position information of light reflection due to Brillouin scattering in the optical fiber 112. By repeating the above measurement while changing Δf = f 1 −f 2 , it is possible to obtain strain and temperature distribution information in the optical fiber.
　本実施形態のように、本発明をＢＯＦＤＡ法に適用する場合には、第３の光は正弦波により強度変調された変調光となるが、この場合も第２の実施形態と同じ理由により、第３の光は誘導ブリルアン散乱に寄与しない。このため、測定したブリルアンゲインスペクトルと理論値とのフィッティングを行わなくても、正しいピーク位置が検出できる。したがって高い位置分解能と高い測定精度を短い測定時間で実現することが可能となる。 As in the present embodiment, when the present invention is applied to the BOFDA method, the third light is modulated light that is intensity-modulated by a sine wave. In this case as well, for the same reason as in the second embodiment, The third light does not contribute to stimulated Brillouin scattering. For this reason, the correct peak position can be detected without fitting the measured Brillouin gain spectrum and the theoretical value. Therefore, high position resolution and high measurement accuracy can be realized in a short measurement time.
　以上のように、本実施形態によれば、高い位置分解能、高い測定精度、短い測定時間、および、低いコストを同時に満たすことが可能となる。
（第５の実施形態）
　本発明の第５の実施形態について図面を参照して説明する。第５の実施形態では、本発明をＢＯＦＤＡ法に適用する。図５に本実施形態の光ファイバセンサの構成を示す。本構成は第４の実施形態の構成図である図４と多くの部分で共通しているので、共通部分は図４で用いたものと同じ符号で表すものとする。 As described above, according to the present embodiment, high position resolution, high measurement accuracy, short measurement time, and low cost can be satisfied at the same time.
(Fifth embodiment)
A fifth embodiment of the present invention will be described with reference to the drawings. In the fifth embodiment, the present invention is applied to the BOFDA method. FIG. 5 shows the configuration of the optical fiber sensor of this embodiment. Since this configuration is common to many parts in FIG. 4 which is the configuration diagram of the fourth embodiment, common parts are represented by the same reference numerals as those used in FIG.
　図５での図４の構成と異なる点は、変調器３０１に入力されている変調信号はＶＮＡから供給される正弦波ではなく、信号発生器４０１から供給される信号である。この信号は正弦波ではなく、方形波などの広い周波数スペクトルを有する信号である。したがって、受光器３０３および１１３で受信される信号も広い周波数スペクトルを有している。これらの受信信号をそれぞれアナログデジタルコンバータ（Ａｎａｌｏｇ－Ｄｉｇｉｔａｌ　Ｃｏｎｖｅｒｔｅｒ：ＡＤＣ）４０２、４０３を通じてコンピュータ４０４に取り込んだ後、フーリエ変換し、各周波数で比較することにより、中心周波数ｆ３の変調光の伝達関数Ｈ（ω）が得られる。Δｆ＝ｆ１－ｆ２を変えて上記の測定を繰り返すことにより、光ファイバ内の歪や温度の分布情報を得ることが可能である。 5 is different from the configuration of FIG. 4 in that the modulation signal input to the modulator 301 is not a sine wave supplied from the VNA but a signal supplied from the signal generator 401. This signal is not a sine wave but a signal having a wide frequency spectrum such as a square wave. Therefore, the signals received by the light receivers 303 and 113 also have a wide frequency spectrum. These received signals are analog-to-digital converter (Analog-Digital Converter: ADC) after taking the computer 404 through 402 and 403, Fourier transform, by comparing at each frequency, the transfer function of the modulated light having a center frequency f 3 H (ω) is obtained. By repeating the above measurement while changing Δf = f 1 −f 2 , it is possible to obtain strain and temperature distribution information in the optical fiber.
　本実施形態で第４の実施形態と異なる点は、角周波数ωを変えてデータ取得を繰り返す必要がないことである。したがって、測定時間を大幅に短縮できるという利点がある。 This embodiment is different from the fourth embodiment in that there is no need to repeat data acquisition by changing the angular frequency ω. Therefore, there is an advantage that the measurement time can be greatly shortened.
　本実施形態の場合も、第４の実施形態と同様に第３の光は誘導ブリルアン散乱に寄与しない。このため、測定したブリルアンゲインスペクトルと理論値とのフィッティングを行わなくても、正しいピーク位置が検出できる。したがって高い位置分解能と高い測定精度を短い測定時間で実現することが可能となる。 Also in the present embodiment, the third light does not contribute to the stimulated Brillouin scattering as in the fourth embodiment. For this reason, the correct peak position can be detected without fitting the measured Brillouin gain spectrum and the theoretical value. Therefore, high position resolution and high measurement accuracy can be realized in a short measurement time.
　以上のように、本実施形態によれば、高い位置分解能、高い測定精度、短い測定時間、および、低いコストを同時に満たすことが可能となる。 As described above, according to this embodiment, it is possible to simultaneously satisfy high position resolution, high measurement accuracy, short measurement time, and low cost.
　以上、本発明の実施形態について説明したが、本発明の実施方法は上記した形態に限定されるものではなく、その要旨を逸脱しない範囲で各種の変形が可能である。例えば、第５の実施形態では、方形波を変調周波数として例に挙げたが、広い周波数スペクトルを有していれば波形は他のものでも良く、例えば三角波などであっても良い。 As mentioned above, although embodiment of this invention was described, the implementation method of this invention is not limited to an above-described form, A various deformation | transformation is possible in the range which does not deviate from the summary. For example, in the fifth embodiment, a square wave is taken as an example of the modulation frequency, but the waveform may be other as long as it has a wide frequency spectrum, for example, a triangular wave.
　また、以上の実施形態ではセンサ部分に通常の光ファイバを用いたが、偏光保持ファイバを用いることも可能である。この場合、コスト的なメリットはやや低下するが、第１の光と第２の光を常に同じ偏光状態に保つことができるため、両者の誘導ブリルアン散乱により発生する音響フォノンの強度を一定に保つことができ、測定の安定化を図ることができる。また、先述のように本発明では第３の光の偏光状態は散乱光のスペクトルに影響しないので、第３の光を第１、第２の光と同じ偏光状態として入力することが可能である。この場合、非特許文献１の構成と異なり、２つの直交する直線偏光に対する屈折率ｎｘ，ｎｙの比の影響を受けないため、装置は比較的簡易となり、この点でコスト的なメリットが保たれる。また、測定時間も短く抑えられる。 In the above embodiment, a normal optical fiber is used for the sensor portion, but a polarization maintaining fiber can also be used. In this case, although the cost merit is slightly reduced, the first and second lights can always be kept in the same polarization state, so that the intensity of the acoustic phonon generated by the stimulated Brillouin scattering of both is kept constant. Measurement can be stabilized. Further, as described above, in the present invention, since the polarization state of the third light does not affect the spectrum of the scattered light, it is possible to input the third light as the same polarization state as the first and second light. . In this case, unlike the non-patent document 1 configuration, the refractive indices n x for the two orthogonal linear polarization, is not affected by the ratio of n y, apparatus becomes relatively simple, cost benefits in this respect Kept. Also, the measurement time can be kept short.
　一方、第３の光の偏光状態を第１と第２の光と直交させた場合には、非特許文献１と同様に第３の光の周波数を掃引する必要が生じるため、装置は複雑化し、コスト的なメリットは失われる。しかしこの場合でも、非特許文献１に比べて、以下のような利点がある。偏光保持ファイバであっても、ある程度の偏光クロストークは避けられない。このため、連続光から、変調光の散乱光と同じ方向に伝播し、同じ偏光状態を持つ光が生じる。これはノイズとなるため除去することが望ましいが、それは両者の波長差が大きいほど容易になる。本発明の方法を上記構成に適用した場合、両者の波長差を大きく取ることが可能となるため、前記ノイズの除去が容易になる。 On the other hand, when the polarization state of the third light is orthogonal to the first and second lights, the frequency of the third light needs to be swept in the same manner as in Non-Patent Document 1, so that the apparatus becomes complicated. Cost benefits are lost. However, even in this case, there are the following advantages compared with Non-Patent Document 1. Even with a polarization-maintaining fiber, some degree of polarization crosstalk is inevitable. For this reason, light having the same polarization state is generated from the continuous light in the same direction as the scattered light of the modulated light. It is desirable to remove this because it causes noise, but it becomes easier as the wavelength difference between the two is larger. When the method of the present invention is applied to the above configuration, it is possible to make a large wavelength difference between the two, so that the noise can be easily removed.
　本発明は上記実施形態に限定されることなく、請求の範囲に記載した発明の範囲内で、種々の変形が可能であり、それらも本発明の範囲内に含まれるものであることはいうまでもない。 The present invention is not limited to the above-described embodiment, and various modifications are possible within the scope of the invention described in the claims, and it goes without saying that these are also included in the scope of the present invention. Nor.
　また、上記の実施形態の一部又は全部は、以下の付記のようにも記載されうるが、以下には限られない。 Further, a part or all of the above embodiment can be described as in the following supplementary notes, but is not limited thereto.
　付記
（付記１）
　光ファイバ内を伝播する第１の光を発生する第１の発生手段と、前記光ファイバ内を前記第１の光とは逆方向に伝播し前記第１の光より周波数の低い第２の光を発生する第２の発生手段と、前記光ファイバ内を前記第２の光と同方向に伝播する第３の光を発生する第３の発生手段と、前記第３の光の散乱光の計測を行う計測手段と、を備えた、光ファイバセンサ。
（付記２）
　前記第３の光が変調光であり、前記第１の光と前記第２の光とが、前記第３の光に比べて変調速度が遅い変調光もしくは非変調光である、付記１に記載の光ファイバセンサ。
（付記３）
　前記第３の光の周波数が、前記第２の光の周波数よりも低い、付記１または２に記載の光ファイバセンサ。
（付記４）
　前記第１の光の周波数と、前記第２および第３の光の周波数との差を変化させ、前記差ごとに前記第３の光の前記散乱光を計測する、付記１から３の内の１項記載の光ファイバセンサ。
（付記５）
　前記第１の光の周波数と前記第３の光の周波数との差が、前記第１の光の周波数と前記第２の光の周波数との差の略２．５倍である、付記１から４の内の１項記載の光ファイバセンサ。
（付記６）
　前記第１の光と前記第２の光とで生じる誘導ブリルアン散乱によって発生する音響波によって、前記第３の光が散乱される、付記１から５の内の１項記載の光ファイバセンサ。
（付記７）
　前記第３の光がパルス光、あるいは、正弦波で強度変調された光である、付記１から６の内の１項記載の光ファイバセンサ。
（付記８）
　前記正弦波で強度変調された前記第３の光の変調周波数を変化させ、前記変調周波数ごとに前記第３の光とその前記散乱光との比較を行う、付記７に記載の光ファイバセンサ。
（付記９）
　前記計測を行うことで、前記光ファイバの長手方向における温度や歪の分布情報を得る、付記１から８の内の１項記載の光ファイバセンサ。
（付記１０）
　光ファイバ内を伝播する第１の光と、前記光ファイバ内を前記第１の光とは逆方向に伝播し前記第１の光より周波数の低い第２の光と、前記光ファイバ内を前記第２の光と同方向に伝播する第３の光とを有し、前記第３の光の散乱光を計測する、光ファイバセンサのセンス方法。
（付記１１）
　前記第３の光が変調光であり、前記第１の光と前記第２の光とが、前記第３の光に比べて変調速度が遅い変調光もしくは非変調光である、付記１０記載の光ファイバセンサのセンス方法。
（付記１２）
　前記第３の光の周波数が、前記第２の光の周波数よりも低い、付記１０または１１に記載の光ファイバセンサのセンス方法。
（付記１３）
　前記第１の光の周波数と、前記第２および第３の光の周波数との差を変化させ、前記差ごとに前記第３の光の前記散乱光を計測する、付記１０から１２の内の１項記載の光ファイバセンサのセンス方法。
（付記１４）
　前記第１の光の周波数と前記第３の光の周波数との差が、前記第１の光の周波数と前記第２の光の周波数との差の略２．５倍である、付記１０から１３の内の１項記載の光ファイバセンサのセンス方法。
（付記１５）
　前記第１の光と前記第２の光とで生じる誘導ブリルアン散乱によって発生する音響波によって、前記第３の光が散乱される、付記１０から１４の内の１項記載の光ファイバセンサのセンス方法。
（付記１６）
　前記第３の光がパルス光、あるいは、正弦波で強度変調された光である、付記１０から１５の内の１項記載の光ファイバセンサのセンス方法。
（付記１７）
　前記正弦波で強度変調された第３の光の周波数を変化させ、前記周波数ごとに前記第３の光とその前記散乱光との比較を行う、付記１６に記載の光ファイバセンサのセンス方法。
（付記１８）
　前記計測を行うことで、前記光ファイバの長手方向における温度や歪の分布情報を得る、付記１０から１７の内の１項記載の光ファイバセンサのセンス方法。 Appendix (Appendix 1)
First generation means for generating first light propagating in the optical fiber, and second light having a lower frequency than the first light propagating in the optical fiber in the opposite direction to the first light Second generating means for generating the third light, third generating means for generating the third light propagating in the same direction as the second light in the optical fiber, and measurement of the scattered light of the third light And an optical fiber sensor.
(Appendix 2)
The supplementary note 1, wherein the third light is modulated light, and the first light and the second light are modulated light or non-modulated light having a slower modulation speed than the third light. Fiber optic sensor.
(Appendix 3)
The optical fiber sensor according to appendix 1 or 2, wherein a frequency of the third light is lower than a frequency of the second light.
(Appendix 4)
The difference between the frequency of the first light and the frequency of the second and third lights is changed, and the scattered light of the third light is measured for each difference. 1. An optical fiber sensor according to item 1.
(Appendix 5)
From the appendix 1, the difference between the frequency of the first light and the frequency of the third light is approximately 2.5 times the difference between the frequency of the first light and the frequency of the second light. 5. The optical fiber sensor according to 1 above.
(Appendix 6)
The optical fiber sensor according to any one of appendices 1 to 5, wherein the third light is scattered by an acoustic wave generated by stimulated Brillouin scattering generated by the first light and the second light.
(Appendix 7)
7. The optical fiber sensor according to one of appendices 1 to 6, wherein the third light is pulsed light or light whose intensity is modulated with a sine wave.
(Appendix 8)
The optical fiber sensor according to appendix 7, wherein a modulation frequency of the third light intensity-modulated with the sine wave is changed, and the third light and the scattered light are compared for each modulation frequency.
(Appendix 9)
9. The optical fiber sensor according to one of appendices 1 to 8, wherein distribution information of temperature and strain in the longitudinal direction of the optical fiber is obtained by performing the measurement.
(Appendix 10)
A first light propagating in an optical fiber, a second light propagating in the optical fiber in a direction opposite to the first light and having a lower frequency than the first light, and the optical fiber in the optical fiber A sensing method for an optical fiber sensor, comprising: third light propagating in the same direction as the second light; and measuring scattered light of the third light.
(Appendix 11)
The supplementary note 10, wherein the third light is modulated light, and the first light and the second light are modulated light or non-modulated light having a modulation speed slower than that of the third light. Sense method for optical fiber sensor.
(Appendix 12)
12. The optical fiber sensor sensing method according to appendix 10 or 11, wherein the frequency of the third light is lower than the frequency of the second light.
(Appendix 13)
The difference between the frequency of the first light and the frequency of the second and third lights is changed, and the scattered light of the third light is measured for each difference. A sensing method for an optical fiber sensor according to claim 1.
(Appendix 14)
From the supplementary note 10, the difference between the frequency of the first light and the frequency of the third light is approximately 2.5 times the difference between the frequency of the first light and the frequency of the second light. 14. The sensing method for an optical fiber sensor according to one of 13 items.
(Appendix 15)
The sense of the optical fiber sensor according to any one of appendices 10 to 14, wherein the third light is scattered by an acoustic wave generated by stimulated Brillouin scattering generated by the first light and the second light. Method.
(Appendix 16)
16. The optical fiber sensor sensing method according to one of appendices 10 to 15, wherein the third light is pulsed light or light whose intensity is modulated by a sine wave.
(Appendix 17)
The optical fiber sensor sensing method according to appendix 16, wherein the frequency of the third light intensity-modulated by the sine wave is changed, and the third light and the scattered light are compared for each frequency.
(Appendix 18)
18. The sensing method for an optical fiber sensor according to one of appendices 10 to 17, wherein distribution information of temperature and strain in the longitudinal direction of the optical fiber is obtained by performing the measurement.
　この出願は、２０１２年１２月１２日に出願された日本出願特願２０１２－２７１４２３を基礎とする優先権を主張し、その開示の全てをここに取り込む。 This application claims priority based on Japanese Patent Application No. 2012-271423 filed on Dec. 12, 2012, the entire disclosure of which is incorporated herein.
　本発明は、光ファイバの長手方向における温度分布や歪分布などを測定する光ファイバセンサおよびそのセンス方法に関し、光通信システムへの利用が可能である。 The present invention relates to an optical fiber sensor for measuring temperature distribution and strain distribution in the longitudinal direction of an optical fiber and a sensing method thereof, and can be used for an optical communication system.
　１０　　第１の発生手段
　１１　　第２の発生手段
　１２　　第３の発生手段
　１３　　計測手段
　１４　　光ファイバ
　１０１　　光源
　１０２　　光分岐器
　１０３　　光変調器
　１０３ａ　　マイクロ波発生器
　１０３ｂ　　ＳＳＢ変調器
　１０４　　エルビウム添加光ファイバ増幅器（ＥＤＦＡ）
　１０５　　光分岐器
　１０６　　ＥＤＦＡ
　１０７　　光変調器
　１０７ａ　　マイクロ波発生器
　１０７ｂ　　ＳＳＢ変調器
　１０８　　ＥＤＦＡ
　１０９　　光パルス発生器
　１１０　　光合波器
　１１１　　光サーキュレータ
　１１２　　光ファイバ
　１１３　　受光器
　２０１　　光源
　２０２　　光分岐器
　２０３　　ＥＤＦＡ
　２０４　　ＳＳＢ変調器
　２０５　　ＥＤＦＡ
　２０６　　ＳＳＢ変調器
　２０７　　ＥＤＦＡ
　２０８　　パルス発生器
　２０９　　マイクロ波発生器
　２１０　　分波器
　２１１　　周波数逓倍器
　２１２　　光合波器
　２１３　　光サーキュレータ
　２１４　　光ファイバ
　２１５　　ファイバグレーティング（ＦＢＧ）
　２１６　　受光器
　３０１　　変調器
　３０２　　光分岐器
　３０３　　受光器
　３０４　　ベクトルネットワークアナライザ（ＶＮＡ）
　４０１　　信号発生器
　４０２　　アナログデジタルコンバータ（ＡＤＣ）
　４０３　　ＡＤＣ
　４０４　　コンピュータ DESCRIPTION OF SYMBOLS 10 1st generating means 11 2nd generating means 12 3rd generating means 13 Measuring means 14 Optical fiber 101 Light source 102 Optical splitter 103 Optical modulator 103a Microwave generator 103b SSB modulator 104 Erbium doped optical fiber amplifier ( EDFA)
105 Optical splitter 106 EDFA
107 optical modulator 107a microwave generator 107b SSB modulator 108 EDFA
DESCRIPTION OF SYMBOLS 109 Optical pulse generator 110 Optical multiplexer 111 Optical circulator 112 Optical fiber 113 Light receiver 201 Light source 202 Optical branching device 203 EDFA
204 SSB modulator 205 EDFA
206 SSB modulator 207 EDFA
208 Pulse generator 209 Microwave generator 210 Demultiplexer 211 Frequency multiplier 212 Optical multiplexer 213 Optical circulator 214 Optical fiber 215 Fiber grating (FBG)
216 Photoreceiver 301 Modulator 302 Optical splitter 303 Photoreceiver 304 Vector network analyzer (VNA)
401 Signal Generator 402 Analog to Digital Converter (ADC)
403 ADC
404 computer

Claims (10)

  1. 　光ファイバ内を伝播する第１の光を発生する第１の発生手段と、
    　前記光ファイバ内を前記第１の光とは逆方向に伝播し前記第１の光より周波数の低い第２の光を発生する第２の発生手段と、
    　前記光ファイバ内を前記第２の光と同方向に伝播する第３の光を発生する第３の発生手段と、
    　前記第３の光の散乱光の計測を行う計測手段と、
    を備えた、光ファイバセンサ。     First generating means for generating first light propagating in the optical fiber;
    Second generation means for generating second light having a frequency lower than that of the first light by propagating in the optical fiber in a direction opposite to the first light;
    Third generating means for generating third light propagating in the same direction as the second light in the optical fiber;
    Measuring means for measuring the scattered light of the third light;
    An optical fiber sensor comprising:
  2. 　前記第３の光が変調光であり、前記第１の光と前記第２の光とが、前記第３の光に比べて変調速度が遅い変調光もしくは非変調光である、請求項１に記載の光ファイバセンサ。 The third light is modulated light, and the first light and the second light are modulated light or non-modulated light having a slower modulation speed than the third light. The optical fiber sensor described.
  3. 　前記第３の光の周波数が、前記第２の光の周波数よりも低い、請求項１または２に記載の光ファイバセンサ。 The optical fiber sensor according to claim 1 or 2, wherein a frequency of the third light is lower than a frequency of the second light.
  4. 　前記第１の光の周波数と、前記第２および第３の光の周波数との差を変化させ、前記差ごとに前記第３の光の前記散乱光を計測する、請求項１から３の内の１項記載の光ファイバセンサ。 The difference between the frequency of the first light and the frequency of the second and third lights is changed, and the scattered light of the third light is measured for each difference. 2. An optical fiber sensor according to 1.
  5. 　前記第１の光の周波数と前記第３の光の周波数との差が、前記第１の光の周波数と前記第２の光の周波数との差の略２．５倍である、請求項１から４の内の１項記載の光ファイバセンサ。 The difference between the frequency of the first light and the frequency of the third light is approximately 2.5 times the difference between the frequency of the first light and the frequency of the second light. 5. The optical fiber sensor according to one of items 1 to 4.
  6. 　前記第３の光がパルス光、あるいは、正弦波で強度変調された光である、請求項１から５の内の１項記載の光ファイバセンサ。 6. The optical fiber sensor according to claim 1, wherein the third light is pulse light or light whose intensity is modulated with a sine wave.
  7. 　前記正弦波で強度変調された前記第３の光の変調周波数を変化させ、前記変調周波数ごとに前記第３の光とその前記散乱光との比較を行う、請求項６に記載の光ファイバセンサ。 The optical fiber sensor according to claim 6, wherein a modulation frequency of the third light intensity-modulated by the sine wave is changed, and the third light and the scattered light are compared for each modulation frequency. .
  8. 　光ファイバ内を伝播する第１の光と、前記光ファイバ内を前記第１の光とは逆方向に伝播し前記第１の光より周波数の低い第２の光と、前記光ファイバ内を前記第２の光と同方向に伝播する第３の光とを有し、前記第３の光の散乱光を計測する、光ファイバセンサのセンス方法。 A first light propagating in an optical fiber, a second light propagating in the optical fiber in a direction opposite to the first light and having a lower frequency than the first light, and the optical fiber in the optical fiber A sensing method for an optical fiber sensor, comprising: third light propagating in the same direction as the second light; and measuring scattered light of the third light.
  9. 　前記第３の光が変調光であり、前記第１の光と前記第２の光とが、前記第３の光に比べて変調速度が遅い変調光もしくは非変調光である、請求項８記載の光ファイバセンサのセンス方法。 9. The third light is modulated light, and the first light and the second light are modulated light or non-modulated light having a slower modulation speed than the third light. Sense method for optical fiber sensor.
  10. 　前記第１の光の周波数と前記第３の光の周波数との差が、前記第１の光の周波数と前記第２の光の周波数との差の略２．５倍である、請求項８または９に記載の光ファイバセンサのセンス方法。 The difference between the frequency of the first light and the frequency of the third light is approximately 2.5 times the difference between the frequency of the first light and the frequency of the second light. Or 10. A sensing method of an optical fiber sensor according to 9.
PCT/JP2013/007283 2012-12-12 2013-12-11 Optical fiber sensor and sensing method of same WO2014091754A1 (en)

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US20080013096A1 (en) * 2006-06-09 2008-01-17 Consiglio Nazionale Delle Ricerche Method for measuring the brillouin shift distribution along an optical fiber based on the optical demodulation of the signals, and relevant apparatus
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