WO2014091755A1 - Optical fiber sensing device and optical fiber sensing method - Google Patents

Optical fiber sensing device and optical fiber sensing method Download PDF

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Publication number
WO2014091755A1
WO2014091755A1 PCT/JP2013/007284 JP2013007284W WO2014091755A1 WO 2014091755 A1 WO2014091755 A1 WO 2014091755A1 JP 2013007284 W JP2013007284 W JP 2013007284W WO 2014091755 A1 WO2014091755 A1 WO 2014091755A1
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light
optical fiber
frequency
fiber sensing
optical
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PCT/JP2013/007284
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French (fr)
Japanese (ja)
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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
    • 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
    • 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
    • G01M11/33—Testing of optical devices, constituted by fibre optics or optical waveguides with a light emitter being disposed at one fibre or waveguide end-face, and a light receiver at the other end-face

Definitions

  • the present invention relates to an optical fiber sensing device and an optical fiber sensing method for measuring temperature distribution and strain distribution in the longitudinal direction of an optical fiber.
  • Optical fiber sensing measures characteristics such as temperature and strain distribution in the longitudinal direction of an optical fiber by making continuous light or pulse light incident on the optical fiber and receiving scattered light or reflected light generated in the optical fiber. Is.
  • BOFDA Bacillouin Optical Frequency Domain Analysis
  • continuous light is incident from one end of an optical fiber, and modulated light whose intensity is modulated by a sine wave is incident from the other end, and light which is scattered by stimulated Brillouin scattering is measured.
  • the frequency of sinusoidal modulation is swept to obtain a transfer function between the modulated light and the scattered light, and the distribution of stimulated Brillouin scattering in the optical fiber is obtained from the inverse Fourier transform of the transfer function.
  • the Brillouin gain spectrum distribution in the optical fiber can be obtained, and the distribution of strain and temperature can be calculated from the peak position. .
  • the BOFDA method since it is necessary to sweep the frequency of the sine wave modulation, it takes a long time to measure. On the other hand, if a modulation signal including a plurality of frequency components is used instead of a sine wave and frequency separation is performed after receiving scattered light, the measurement time may be shortened. On the other hand, in the BOFDA method, unnecessary components are superimposed on the measured Brillouin gain spectrum, so that the peak position detection accuracy is lowered, and as a result, the distortion and temperature measurement accuracy is lowered.
  • Non-Patent Document 1 discloses a method for removing the unnecessary components and improving the peak position detection accuracy by performing an appropriate signal correction process on the measured value of the Brillouin gain spectrum. Yes.
  • this method is possible when the modulation frequency is single, but cannot be applied when a modulation signal including a plurality of frequency components is used as described above. Therefore, when the measurement time is shortened by the above-described method, the measurement accuracy of strain and temperature is lowered, and both have a trade-off relationship.
  • 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 sensing device and an optical fiber sensing method that can reduce measurement time without reducing measurement accuracy of strain and temperature in the BOFDA method. It is to provide.
  • the optical fiber sensing device of the present invention includes a first generating means for generating first light propagating in an optical fiber, and the first light propagating in the optical fiber in a direction opposite to the first light.
  • Second generation means for generating second light having a frequency lower than that of light, and third light having a plurality of modulation frequencies whose modulation speed is faster than that of the first and second light propagating in the optical fiber.
  • third comparison means for comparing the third light and the scattered light of the third light for each of the plurality of modulation frequencies.
  • the BOFDA method it is possible to provide an optical fiber sensing device and an optical fiber sensing method that can shorten the measurement time without reducing the measurement accuracy of strain and temperature.
  • FIG. 1 is a block diagram showing the configuration of the optical fiber sensing device of the present embodiment.
  • the optical fiber sensing device of this embodiment propagates in the optical fiber 14 in the direction opposite to the first light, and the first generation means 10 for generating the first light propagating in the optical fiber 14.
  • Second generating means 11 for generating second light having a frequency lower than that of the first light.
  • third generation means 12 for generating third light having a plurality of modulation frequencies faster than the first and second lights propagating in the optical fiber 14, and the third light And comparing means 13 for comparing the scattered light of the third light for each of the plurality of modulation frequencies.
  • FIG. 2 is a diagram showing a configuration of an optical fiber sensing device according to the second embodiment of the present invention.
  • the first generation means 10 for generating the first light propagating in the optical fiber 113, and the first light propagating in the optical fiber 113 in the opposite direction to the first light.
  • Second generation means 11 for generating a second light having a frequency lower than that of the first light, and a third modulation frequency having a plurality of modulation frequencies faster than the first and second lights propagating in the optical fiber 113.
  • Third generation means 12 for generating light, and comparison means 13 for comparing the third light and the scattered light of the third light for each of a plurality of modulation frequencies are provided.
  • the first generation means 10 generates the first light as follows.
  • the light having the frequency f1 emitted from the light source 101 is branched by the optical branching device 102.
  • One of the lights branched by the splitter 102 is further split into two by the optical splitter 105, and one of them is amplified by the EDFA 106 and becomes the first light.
  • the second generation means 11 generates the second light as follows.
  • the light having the frequency f 1 emitted from the light source 101 is branched by the optical branching unit 102.
  • One of the branched lights is amplified by an erbium-doped optical fiber amplifier (EDFA) 104 after the frequency is shifted to f 2 by the optical modulator 103 to the low frequency side. Further, the light passes through the polarization controller 114 (Polarization Controller: PC) and becomes the second light.
  • 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.
  • the third generation means 12 generates the third light as follows.
  • the light having the frequency f1 emitted from the light source 101 is branched by the optical branching device 102.
  • One of the branched lights is further branched into two by the optical branching unit 105, and one of them is intensity-modulated by the optical modulator 107.
  • a square wave is supplied from the signal generator 108 to the optical modulator 107, and light is modulated by the signal.
  • the light output from the optical modulator 107 is amplified by the EDFA 109 to become third light.
  • the third light is branched by the optical branching device 110.
  • One of the branched lights is incident on a polarization beam splitter 111 (Polarization Beam Splitter: PBS).
  • PBS Polarization Beam Splitter
  • the first light amplified by the EDFA 106 also enters the PBS 111.
  • all the optical paths from the light source 101 to the PBS 111 are coupled by a polarization maintaining optical fiber.
  • the EDFA 106 and the EDFA 109 also use a polarization maintaining type.
  • the polarizations of the first light and the third light are incident on the PBS 111 so as to be orthogonal, and the two polarizations are combined here. Thereafter, the light enters the optical fiber 113 through the polarization-independent optical circulator 112.
  • the second light amplified by the EDFA 104 enters from the opposite end of the optical fiber 113.
  • a polarization controller 114 (Polarization Controller: PC) is inserted between the EDFA 104 and the optical fiber 113.
  • Light having a frequency f 1 is incident on the optical fiber 113 from the PBS 111 and light having a frequency f 2 is incident on the PC 114.
  • the light emitted from the PBS 111 includes continuous light f 1 emitted from the EDFA 106 (first light) and modulated light (third light) emitted from the optical branching device 110.
  • the continuous light and the modulated light have the same frequency, but the polarizations are orthogonal to each other.
  • the polarization is adjusted by the PC 114 so that the polarization of the continuous light of the frequency f 1 (first light) matches the polarization of the continuous light of the frequency f 2 (second light) as much as possible.
  • stimulated Brillouin scattering occurs due to the continuous light of the frequencies f 1 and f 2 , and the continuous light (first light) and the modulated light (third light) of the frequency f 1 are generated by the acoustic phonons generated thereby. Are scattered together.
  • the scattered light passes through the optical circulator 112 and enters the light receiver 115 provided in the comparison means 13.
  • one of the lights branched by the optical branching device 110 is directly incident on the light receiver 116 provided in the comparison means 13.
  • Outputs from the light receiver 115 and the light receiver 116 are taken into a computer 119 provided in the comparison means 13 through an analog-digital converter (ADC) 117 and an analog-digital converter 118, respectively.
  • ADC analog-digital converter
  • the transfer function H ( ⁇ ) of the modulated light is obtained by performing Fourier transform on each data and comparing the values at each frequency. If this is subjected to inverse Fourier transform, a pulse response function h (t) of the optical fiber can be obtained.
  • the polarization of the continuous light of the second light having the frequency f 2 matches the polarization of the continuous light of the first light having the frequency f 1 as much as possible, and is orthogonal to the modulated light of the third light. Adjusted to Therefore, stimulated Brillouin scattering due to the modulated light is suppressed, and unnecessary components can be prevented from being superimposed on the Brillouin gain spectrum.
  • the stimulated Brillouin scattering is generated by the first and second lights, which are slow light, preferably unmodulated continuous light, and acoustic phonons are generated.
  • This acoustic phonon is hardly modulated and can be considered to have an almost single frequency.
  • the modulated light which is the third light, is scattered, but in this case, unnecessary components do not occur. Therefore, the peak position of the Brillouin spectrum becomes clear without performing signal correction processing after measurement. Since the signal correction processing after the measurement is unnecessary, even if the modulation signal includes a large number of frequency components, the measurement accuracy of the distortion and temperature is not lowered.
  • FIG. 3 is a diagram showing a configuration of an optical fiber sensing device according to a third embodiment of the present invention. Since this configuration is common to many parts in FIG. 2 which is the configuration diagram of the second embodiment, the common parts are denoted by the same reference numerals as those used in FIG.
  • the light having the frequency f 1 emitted from the light source 101 is branched by the optical branching device 102, and one of the branched lights is amplified by the EDFA 106 to be the first light.
  • the light having the frequency f 2 is generated from the other branched light using the SSB modulator 103, the light is amplified by the EDFA 104 to be the second light.
  • the above is the same as in the second embodiment.
  • the modulated light that is the third light is generated by modulating the branched light from the light source 101 in the second embodiment, but in this embodiment, the frequency emitted from the light source 201 that is another light source.
  • light of f 3 is modulated, it is generated is amplified by EDFA109.
  • the continuous light having the frequency f 1 that is the first light exiting the EDFA 106 and the modulated light having the center frequency f 3 that is the third light are combined by the PBS 111 and pass through the polarization-independent optical circulator 112. Is incident on the optical fiber 202. Continuous light of a frequency f 2 which is the second light exiting the EDFA104 from opposite ends of the optical fiber 202 is incident.
  • the optical fiber 202 is a polarization maintaining optical fiber, and has a fast axis and a slow axis.
  • the continuous lights of frequencies f 1 and f 2 are incident so that the polarization is fast axis or both are parallel to the slow axis.
  • modulated light having a center frequency f 3 the polarization is to be incident in parallel to the different axes from these continuous light.
  • the optical paths from the light source 101 and the light source 201 to the polarization maintaining optical fiber 202 are all coupled by the polarization maintaining fiber.
  • the modulated light scattered by the polarization maintaining optical fiber 202 is received by the light receiver 115, and the light branched by the optical branching device 110 is directly received by the light receiver 116.
  • the strain and temperature distribution in the polarization-maintaining optical fiber 202 can be obtained.
  • stimulated Brillouin scattering occurs due to continuous light of frequencies f 1 and f 2 , and the modulated light and continuous light of frequency f 1 are both generated by the acoustic phonons generated thereby. Scattered.
  • the sensor unit is a conventional optical fiber 113, the frequency of the modulated light whereas it if f 1, in the present embodiment has the sensor unit is a polarization maintaining optical fiber 202 In order to have birefringence, the frequency of the modulated light needs to be different from that of continuous light.
  • the polarization is adjusted by the PC 114 so that the polarizations of the continuous lights having the frequencies f 1 and f 2 coincide as much as possible. Ideally, both polarizations coincide with each other, and the polarization of the modulated light is orthogonal to them. However, polarization may be disturbed in the optical fiber 113 that is a sensor unit. For this reason, a part of the light having the frequency f 2 and the modulated light may have the same polarization, and in this case, an unnecessary component is superimposed on the Brillouin spectrum. On the other hand, since the polarization maintaining optical fiber 202 is used in the present embodiment, the polarization of the continuous light and the modulated light is kept orthogonal to each other.
  • FIG. 4 is a diagram showing a configuration of an optical fiber sensing device according to a fourth embodiment of the present invention. Since this configuration is also common to many parts of FIG. 2 which is the configuration diagram of the second embodiment, the common parts are represented by the same reference numerals as those used in FIG.
  • 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, amplified by the EDFA 104, adjusted in polarization by the PC 114, and becomes the first light.
  • the frequency is shifted to the low frequency side by the optical modulator 103, but in this embodiment, the frequency is shifted to the high frequency side.
  • the frequency of light emitted from the light source is f 2
  • the other split light of the optical splitter 102 is further split into two by the subsequent optical splitter 105.
  • One of them is amplified by the EDFA 106 and becomes the second light.
  • the other is incident on the optical modulator 120.
  • the optical modulator 120 includes a microwave generator 120a and an SSB (Single Side Band) modulator 120b, and the frequency of the microwave generated by the microwave generator 120a 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.
  • SSB Single Side Band
  • the frequency is shifted to the low frequency side.
  • the intensity is modulated by the modulator 107, and is amplified again by the EDFA 109 to become third light.
  • the optical splitter 110 After being branched by the optical splitter 110 is combined with the second optical frequency f 2 from the optical multiplexer 302 EDFA106, through the optical circulator 112, it enters the optical fiber 113 is a sensor unit
  • the PC 114 is adjusted so that the polarizations of the continuous lights having the frequencies f 1 and f 2 match as much as possible.
  • the modulated light that is the third light scattered in the optical fiber passes through the optical circulator 112 and is received by the light receiver 115. Also, one of the modulated lights branched by the optical branching device 110 is received by the light receiver 116.
  • the strain and temperature distribution in the optical fiber 113 can be obtained.
  • the microwave generator 120a is also set so that f 2 ⁇ f 3 becomes 1.5 ⁇ f (ie, f 1 ⁇ f 3 is 2.5 ⁇ f). Adjust at the same time.
  • continuous light frequency is a second light having a lower, i.e. the same as that of the optical frequency f 2 ing.
  • the modulated light, which is the third light is scattered by the continuous light of the frequencies f 1 and f 2 , that is, the acoustic phonon formed by the first light and the second light.
  • the center frequency of f needs to be f 3 shown above, not f 1 .
  • ⁇ f which is the difference between the first and second frequencies
  • the frequency sweep range is determined by the temperature to be measured and the range of strain. Since the frequency f 3 of the third light is far away from the frequency f 2 of the second light, even if the measurement range is expanded to a strain or temperature range that causes the quartz optical fiber to break or soften, The frequency difference between the first and third lights does not fall within a range where stimulated Brillouin scattering occurs.
  • the modulated light of the third light and the polarization of the continuous light of the first light propagating opposite thereto are not necessarily orthogonal, but for the above reasons, the modulated light and the modulated light Stimulated Brillouin scattering does not occur between continuous light. Therefore, even if a normal optical fiber that is not a polarization maintaining optical fiber is used for the sensor unit, an unnecessary component is not superimposed on the Brillouin spectrum, and stable measurement is possible.
  • a square wave is used as an example of the modulation frequency, but the waveform may be other as long as it has a wide frequency spectrum, such as a triangular wave.
  • the successive optical frequency f 1 was combined with PBS111 modulated light frequency f 3, it is made incident on the polarization maintaining fiber 202 which is a sensor portion through a polarization-independent optical circulator 112
  • the respective light beams may be combined with PBS after passing through the polarization maintaining optical circulator and incident on the optical fiber.
  • the stimulated Brillouin scattering is generated by the continuous light of the frequencies f 1 and f 2. However, these are not necessarily complete continuous light, that is, completely unmodulated light, There may be fluctuations.
  • 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 And second generation means for generating third light having a plurality of modulation frequencies faster than the first and second lights propagating in the optical fiber.
  • An optical fiber sensing device comprising: comparing means for comparing the third light and the scattered light of the third light for each of the plurality of modulation frequencies.
  • Appendix 2 The optical fiber sensing device according to appendix 1, wherein the third light propagates in the same direction as the second light.
  • Appendix 3) The optical fiber sensing device according to appendix 1 or 2, wherein the frequency of the third light is lower than that of the second light.
  • 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.
  • the optical fiber sensing device according to 1. (Appendix 5) The third light is propagated in the same direction as the first light, and the polarization states of the first light and the third light at the time of incidence on the optical fiber are substantially orthogonal to each other.
  • Optical fiber sensing device. (Appendix 6) The optical fiber sensing device according to appendix 5, wherein the optical fiber is a polarization maintaining optical fiber.
  • the optical fiber sensing device 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 comparison.
  • 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 frequency lower than that of the first light, and the first and second A third light having a plurality of modulation frequencies whose modulation speed is faster than that of the light, and comparing the third light and the scattered light of the third light for each of the plurality of modulation frequencies Fiber sensing method.
  • Appendix 11 The optical fiber sensing method according to appendix 10, wherein the third light propagates in the same direction as the second light.
  • the present invention relates to an optical fiber sensing device and an optical fiber sensing method for measuring temperature distribution and strain distribution in the longitudinal direction of an optical fiber, and can be used for an optical communication system.
  • SYMBOLS 10 1st generation means 11 2nd generation means 12 3rd generation means 13 Comparison means 14 Optical fiber 101 Light source 102 Optical splitter 103 Optical modulator 103a Microwave generator 103b SSB modulator 104 EDFA 105 Optical splitter 106 EDFA 107 optical modulator 108 signal generator 109 EDFA DESCRIPTION OF SYMBOLS 110 Optical splitter 111 Polarizing beam splitter 112 Polarization-independent optical circulator 113 Optical fiber 114 Polarization controller 115, 116 Light receiver 117, 118 Analog-digital converter 119 Computer 120 Optical modulator 120a Microwave generator 120b SSB modulator 201 Light source 202 Polarization-maintaining fiber 301 EDFA 302 Optical multiplexer

Abstract

This optical fiber sensing device comprises: a means of generating first light that propagates within an optical fiber; a means for generating second light that has a lower frequency than the first light and which propagates in the opposite direction to the first light; a means for generating third light having a plurality of modulating frequencies and which has a modulation speed which is faster than that of the first and second light; and a means of comparing, for each modulation frequency, the third light and the scattered light of the third light. As a result of this configuration, it is possible to shorten the measurement time without detriment to measurement accuracy.

Description

光ファイバセンシング装置および光ファイバセンシング方法Optical fiber sensing device and optical fiber sensing method
　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シング装置および光ファイバセンシング方法に関する。 The present invention relates to an optical fiber sensing device and an optical fiber sensing method for measuring temperature distribution and strain distribution in the longitudinal direction of an optical fiber.
　光ファイバセンシングは、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。 Optical fiber sensing measures characteristics such as temperature and strain distribution in the longitudinal direction of an optical fiber by making continuous light or pulse light incident on the optical fiber and receiving scattered light or reflected light generated in the optical fiber. Is.
　ＢＯＦＤＡ（Ｂｒｉｌｌｏｕｉｎ　Ｏｐｔｉｃａｌ　Ｆｒｅｑｕｅｎｃｙ　Ｄｏｍａｉｎ　Ａｎａｌｙｓｉｓ）は、そのような光ファイバセンシングの一方式であり、特許文献１に開示されている。これは光ファイバの一方の端から連続光を、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、この変調光が誘導ブリルアン散乱によって散乱される光を測定するものである。正弦波変調の周波数を掃引して、変調光とその散乱光の間の伝達関数を求め、その伝達関数の逆フーリエ変換から、光ファイバ内の誘導ブリルアン散乱の分布が得られる。連続光と変調光の周波数の差を掃引して、上記の測定を繰り返すことにより、光ファイバ内でのブリルアンゲインスペクトル分布が得られ、そのピーク位置から歪や温度の分布を算出することができる。 BOFDA (Brillouin Optical Frequency Domain Analysis) is one type of such optical fiber sensing, and is disclosed in Patent Document 1. In this method, continuous light is incident from one end of an optical fiber, and modulated light whose intensity is modulated by a sine wave is incident from the other end, and light which is scattered by stimulated Brillouin scattering is measured. The frequency of sinusoidal modulation is swept to obtain a transfer function between the modulated light and the scattered light, and the distribution of stimulated Brillouin scattering in the optical fiber is obtained from the inverse Fourier transform of the transfer function. By sweeping the difference between the frequency of continuous light and modulated light and repeating the above measurement, the Brillouin gain spectrum distribution in the optical fiber can be obtained, and the distribution of strain and temperature can be calculated from the peak position. .
米国特許第７５１５２７３号明細書US Pat. No. 7,515,273
　一般にＢＯＦＤＡ法では、正弦波変調の周波数を掃引する必要があるため、測定に時間がかかった。これに対し、正弦波の代わりに複数の周波数成分を含む変調信号を用い、散乱光の受信後に周波数分離を行えば、測定時間を短縮する可能性がある。一方、ＢＯＦＤＡ法では測定されるブリルアンゲインスペクトルに不要な成分が重畳するため、ピーク位置の検出精度が低下し、その結果歪や温度の測定精度が低下する。 Generally, in the BOFDA method, since it is necessary to sweep the frequency of the sine wave modulation, it takes a long time to measure. On the other hand, if a modulation signal including a plurality of frequency components is used instead of a sine wave and frequency separation is performed after receiving scattered light, the measurement time may be shortened. On the other hand, in the BOFDA method, unnecessary components are superimposed on the measured Brillouin gain spectrum, so that the peak position detection accuracy is lowered, and as a result, the distortion and temperature measurement accuracy is lowered.
　これに対し、非特許文献１には、ブリルアンゲインスペクトルの測定値に適切な信号補正処理を施すことにより、上記の不要な成分を除去し、ピーク位置の検出精度を向上させる方法が示されている。しかしながら、この方法は変調周波数が単一である場合には可能であるが、上述のように複数の周波数成分を含む変調信号を用いると適用できなくなる。したがって、上述の方法で測定時間を短縮すると、歪や温度の測定精度が低下することとなり、両者はトレードオフの関係にあった。 On the other hand, Non-Patent Document 1 discloses a method for removing the unnecessary components and improving the peak position detection accuracy by performing an appropriate signal correction process on the measured value of the Brillouin gain spectrum. Yes. However, this method is possible when the modulation frequency is single, but cannot be applied when a modulation signal including a plurality of frequency components is used as described above. Therefore, when the measurement time is shortened by the above-described method, the measurement accuracy of strain and temperature is lowered, and both have a trade-off relationship.
　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、ＢＯＦＤＡ法において、歪や温度の測定精度を低下させることなく、測定時間を短縮する、光ファイバセンシング装置および光ファイバセンシング方法を提供することにある。 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 sensing device and an optical fiber sensing method that can reduce measurement time without reducing measurement accuracy of strain and temperature in the BOFDA method. It is to provide.
　本発明の光ファイバセンシング装置は、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伝播する前記第１および第２の光よりも変調速度が速い複数の変調周波数を有する第３の光を発生する第３の発生手段と、前記第３の光と前記第３の光の散乱光とを、前記複数の変調周波数ごとに比較を行う比較手段と、を備えている。 The optical fiber sensing device of the present invention includes a first generating means for generating first light propagating in an optical fiber, and the first light propagating in the optical fiber in a direction opposite to the first light. Second generation means for generating second light having a frequency lower than that of light, and third light having a plurality of modulation frequencies whose modulation speed is faster than that of the first and second light propagating in the optical fiber. And third comparison means for comparing the third light and the scattered light of the third light for each of the plurality of modulation frequencies.
　本発明の光ファイバセンシング方法は、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、前記第１および第２の光よりも変調速度が速い複数の変調周波数を有する第３の光とを有し、前記第３の光と前記第３の光の散乱光とを前記複数の変調周波数ごとに比較する。 In the optical fiber sensing method of the present invention, the first light propagating in the optical fiber and the second light propagating in the optical fiber in the opposite direction to the first light and having a frequency lower than that of the first light. Light, and third light having a plurality of modulation frequencies whose modulation speeds are faster than those of the first and second lights, and the plurality of the third light and the scattered light of the third light. Compare for each modulation frequency.
　本発明によれば、ＢＯＦＤＡ法において、歪や温度の測定精度を低下させることなく、測定時間を短縮する、光ファイバセンシング装置および光ファイバセンシング方法を提供することができる。 According to the present invention, in the BOFDA method, it is possible to provide an optical fiber sensing device and an optical fiber sensing method that can shorten the measurement time without reducing the measurement accuracy of strain and temperature.
本発明の第１の実施形態の光ファイバセンシング装置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 sensing apparatus of the 1st Embodiment of this invention. 本発明の第２の実施形態の光ファイバセンシング装置の構成を示す図である。It is a figure which shows the structure of the optical fiber sensing apparatus of the 2nd Embodiment of this invention. 本発明の第３の実施形態の光ファイバセンシング装置の構成を示す図である。It is a figure which shows the structure of the optical fiber sensing apparatus of the 3rd Embodiment of this invention. 本発明の第４の実施形態の光ファイバセンシング装置の構成を示す図である。It is a figure which shows the structure of the optical fiber sensing apparatus of the 4th 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シング装置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シング装置は、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内を伝播する前記第１および第２の光よりも変調速度が速い複数の変調周波数を有する第３の光を発生する第３の発生手段１２と、前記第３の光と前記第３の光の散乱光とを前記複数の変調周波数ごとに比較を行う比較手段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 sensing device of the present embodiment. The optical fiber sensing device of this embodiment propagates in the optical fiber 14 in the direction opposite to the first light, and the first generation means 10 for generating the first light propagating in the optical fiber 14. Second generating means 11 for generating second light having a frequency lower than that of the first light. Further, third generation means 12 for generating third light having a plurality of modulation frequencies faster than the first and second lights propagating in the optical fiber 14, and the third light And comparing means 13 for comparing the scattered light of the third light for each of the plurality of modulation frequencies.
　本実施形態によれば、ＢＯＦＤＡ法において、歪や温度の測定精度を低下させることなく、測定時間を短縮する、光ファイバセンシング装置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。図２は本発明の第２の実施形態における光ファイバセンシング装置の構成を示す図である。 According to this embodiment, in the BOFDA method, it is possible to provide an optical fiber sensing device that shortens the measurement time without reducing the measurement accuracy of strain and temperature.
(Second Embodiment)
A second embodiment of the present invention will be described with reference to the drawings. FIG. 2 is a diagram showing a configuration of an optical fiber sensing device according to the second embodiment of the present invention.
　本実施形態の光ファイバセンシング装置は、光ファイバ１１３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１１３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、光ファイバ１１３内を伝播する第１および第２の光よりも変調速度が速い複数の変調周波数を有する第３の光を発生する第３の発生手段１２と、第３の光と第３の光の散乱光とを、複数の変調周波数ごとに比較を行う比較手段１３とを備える。 In the optical fiber sensing device of the present embodiment, the first generation means 10 for generating the first light propagating in the optical fiber 113, and the first light propagating in the optical fiber 113 in the opposite direction to the first light. Second generation means 11 for generating a second light having a frequency lower than that of the first light, and a third modulation frequency having a plurality of modulation frequencies faster than the first and second lights propagating in the optical fiber 113. Third generation means 12 for generating light, and comparison means 13 for comparing the third light and the scattered light of the third light for each of a plurality of modulation frequencies 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から出た周波数ｆ１の光は、光分岐器１０２によって分岐される。分岐器１０２によって分岐された光の一方は、さらに、光分岐器１０５によって２つに分岐され、その一方はＥＤＦＡ１０６により増幅され第１の光となる。 The first generation means 10 generates the first light as follows. The light having the frequency f1 emitted from the light source 101 is branched by the optical branching device 102. One of the lights branched by the splitter 102 is further split into two by the optical splitter 105, and one of them is amplified by the EDFA 106 and becomes the first light.
　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から出た周波数ｆ１の光は、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によって低周波側へ周波数がｆ２にシフトされた後、エルビウム添加光ファイバ増幅器（ＥＤＦＡ）１０４によって増幅される。さらに、偏光コントローラ１１４（Ｐｏｌａｒｉｚａｔｉｏｎ　Ｃｏｎｔｒｏｌｌｅｒ：ＰＣ）を通って第２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 second generation means 11 generates the second light as follows. The light having the frequency f 1 emitted from the light source 101 is branched by the optical branching unit 102. One of the branched lights is amplified by an erbium-doped optical fiber amplifier (EDFA) 104 after the frequency is shifted to f 2 by the optical modulator 103 to the low frequency side. Further, the light passes through the polarization controller 114 (Polarization Controller: PC) and becomes the second 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３の発生手段１２は、第３の光を次のように発生する。光源１０１から出た周波数ｆ１の光は、光分岐器１０２によって分岐される。分岐した光の一方は、さらに、光分岐器１０５によって２つに分岐され、その一方は、光変調器１０７により強度変調される。光変調器１０７には信号発生器１０８より方形波が供給されており、その信号によって光が変調される。光変調器１０７から出力された光はＥＤＦＡ１０９で増幅されて、第３の光となる。 The third generation means 12 generates the third light as follows. The light having the frequency f1 emitted from the light source 101 is branched by the optical branching device 102. One of the branched lights is further branched into two by the optical branching unit 105, and one of them is intensity-modulated by the optical modulator 107. A square wave is supplied from the signal generator 108 to the optical modulator 107, and light is modulated by the signal. The light output from the optical modulator 107 is amplified by the EDFA 109 to become third light.
　第３の光は、光分岐器１１０によって分岐される。分岐された光の片方は偏光ビームスプリッタ１１１（Ｐｏｌａｒｉｚａｔｉｏｎ　Ｂｅａｍ　Ｓｐｌｉｔｔｅｒ：ＰＢＳ）に入射する。また、ＥＤＦＡ１０６で増幅された第１の光もＰＢＳ１１１に入射する。 The third light is branched by the optical branching device 110. One of the branched lights is incident on a polarization beam splitter 111 (Polarization Beam Splitter: PBS). The first light amplified by the EDFA 106 also enters the PBS 111.
　ここで、光源１０１からＰＢＳ１１１に至る光路は全て偏光保持型光ファイバで結合されている。また、ＥＤＦＡ１０６とＥＤＦＡ１０９も偏光保持型を用いることが望ましい。第１の光と第３の光の偏光は直交するようにＰＢＳ１１１に入射され、ここで２つの偏光が結合される。その後、偏光無依存の光サーキュレータ１１２を通じて光ファイバ１１３に入射される。 Here, all the optical paths from the light source 101 to the PBS 111 are coupled by a polarization maintaining optical fiber. In addition, it is desirable that the EDFA 106 and the EDFA 109 also use a polarization maintaining type. The polarizations of the first light and the third light are incident on the PBS 111 so as to be orthogonal, and the two polarizations are combined here. Thereafter, the light enters the optical fiber 113 through the polarization-independent optical circulator 112.
　一方、光ファイバ１１３の逆の端からは、ＥＤＦＡ１０４で増幅された第２の光が入射される。ここでＥＤＦＡ１０４と光ファイバ１１３の間には、偏光コントローラ１１４（Ｐｏｌａｒｉｚａｔｉｏｎ　Ｃｏｎｔｒｏｌｌｅｒ：ＰＣ）が挿入されている。ここで光源１０１から出射された光の周波数ｆ１、光変調器１０３で周波数シフトされた後の光の周波数ｆ２は、ｆ１－ｆ２＝Δｆ＞０とする。ＰＢＳ１１１からは周波数ｆ１の光、ＰＣ１１４からは周波数ｆ２の光が光ファイバ１１３に入射する。 On the other hand, the second light amplified by the EDFA 104 enters from the opposite end of the optical fiber 113. Here, a polarization controller 114 (Polarization Controller: PC) is inserted between the EDFA 104 and the optical fiber 113. Here, the frequency f 1 of the light emitted from the light source 101 and the frequency f 2 of the light after the frequency shift by the optical modulator 103 are assumed to be f 1 −f 2 = Δf> 0. Light having a frequency f 1 is incident on the optical fiber 113 from the PBS 111 and light having a frequency f 2 is incident on the PC 114.
　ＰＢＳ１１１から出射される光は、ＥＤＦＡ１０６から出射される連続光ｆ１と（第１の光）と、光分岐器１１０から出射される変調光（第３の光）とを含む。この連続光と変調光とは周波数は同じだが、偏光は互いに直交している。周波数ｆ１の連続光（第１の光）と、周波数ｆ２の連続光（第２の光）の偏光が極力一致するようにＰＣ１１４により偏光を調整する。これにより、周波数ｆ１とｆ２の連続光により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、周波数ｆ１の連続光（第１の光）と変調光（第３の光）とがともに散乱される。散乱された光は光サーキュレータ１１２を通り、比較手段１３に備えられた受光器１１５に入射する。一方、光分岐器１１０で分岐された光の片方は、比較手段１３に備えられた受光器１１６に直接入射する。 The light emitted from the PBS 111 includes continuous light f 1 emitted from the EDFA 106 (first light) and modulated light (third light) emitted from the optical branching device 110. The continuous light and the modulated light have the same frequency, but the polarizations are orthogonal to each other. The polarization is adjusted by the PC 114 so that the polarization of the continuous light of the frequency f 1 (first light) matches the polarization of the continuous light of the frequency f 2 (second light) as much as possible. As a result, stimulated Brillouin scattering occurs due to the continuous light of the frequencies f 1 and f 2 , and the continuous light (first light) and the modulated light (third light) of the frequency f 1 are generated by the acoustic phonons generated thereby. Are scattered together. The scattered light passes through the optical circulator 112 and enters the light receiver 115 provided in the comparison means 13. On the other hand, one of the lights branched by the optical branching device 110 is directly incident on the light receiver 116 provided in the comparison means 13.
　受光器１１５と受光器１１６からの出力は、それぞれ、アナログ・デジタル・コンバータ１１７（Ａｎａｌｏｇ－Ｄｉｇｉｔａｌ　Ｃｏｎｖｅｒｔｅｒ：ＡＤＣ）とアナログ・デジタル・コンバータ１１８を通じて、比較手段１３に備えられたコンピュータ１１９に取り込まれる。それぞれのデータをフーリエ変換し、各周波数における値を比較することにより、変調光の伝達関数Ｈ（ω）が得られる。これを逆フーリエ変換すれば、光ファイバのパルス応答関数ｈ（ｔ）を得ることができる。 Outputs from the light receiver 115 and the light receiver 116 are taken into a computer 119 provided in the comparison means 13 through an analog-digital converter (ADC) 117 and an analog-digital converter 118, respectively. The transfer function H (ω) of the modulated light is obtained by performing Fourier transform on each data and comparing the values at each frequency. If this is subjected to inverse Fourier transform, a pulse response function h (t) of the optical fiber can be obtained.
　光ファイバの屈折率をｎ、高速をｃ、光ファイバ内の位置をｚで表すとすれば、ｔ＝２ｎｚ／ｃを代入することにより、Δｆに対するブリルアン利得の光ファイバ内の位置依存性が得られる。Δｆ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。 Assuming that the refractive index of the optical fiber is n, the high speed is c, and the position in the optical fiber is z, by substituting t = 2 nz / c, the position dependence of Brillouin gain with respect to Δf is obtained in the optical fiber. It is done. By repeating the above measurement while changing Δf, it is possible to obtain strain and temperature distribution information in the optical fiber.
　本実施形態では、周波数ｆ２の第２の光の連続光の偏光は、周波数ｆ１の第１の光の連続光の偏光と極力一致し、第３の光の変調光とは直交するように調整される。したがって、変調光による誘導ブリルアン散乱は抑制され、ブリルアンゲインスペクトルには、不要な成分が重畳するのを防止できる。 In the present embodiment, the polarization of the continuous light of the second light having the frequency f 2 matches the polarization of the continuous light of the first light having the frequency f 1 as much as possible, and is orthogonal to the modulated light of the third light. Adjusted to Therefore, stimulated Brillouin scattering due to the modulated light is suppressed, and unnecessary components can be prevented from being superimposed on the Brillouin gain spectrum.
　以上、本実施形態の構成では、変調速度が遅い、望ましくは非変調の連続光である第１および第２の光により誘導ブリルアン散乱が生じ、音響フォノンが生成される。この音響フォノンはほとんど変調を受けず、ほぼ単一の周波数を有すると見なすことができる。これにより第３の光である変調光が散乱されるが、この場合には不要な成分が生じない。したがって、測定後の信号補正処理をせずともブリルアンスペクトルのピーク位置は明瞭となる。測定後の信号補正処理が不要であるので、変調信号が多数の周波数成分を含んでいても、歪や温度の測定精度が下がることはない。一方、多数の周波数成分を含む変調信号を用いることにより、変調周波数の掃引を行う必要がなくなるため、測定時間を大幅に短縮することができる。すなわち、ＢＯＦＤＡ法の課題であった測定時間と精度のトレードオフを解消する光ファイバセンシングが可能となる。
（第３の実施形態）
　本発明の第３の実施形態について説明する。図３は本発明の第３の実施形態の光ファイバセンシング装置の構成を示す図である。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し、説明も省略する。 As described above, in the configuration of the present embodiment, the stimulated Brillouin scattering is generated by the first and second lights, which are slow light, preferably unmodulated continuous light, and acoustic phonons are generated. This acoustic phonon is hardly modulated and can be considered to have an almost single frequency. As a result, the modulated light, which is the third light, is scattered, but in this case, unnecessary components do not occur. Therefore, the peak position of the Brillouin spectrum becomes clear without performing signal correction processing after measurement. Since the signal correction processing after the measurement is unnecessary, even if the modulation signal includes a large number of frequency components, the measurement accuracy of the distortion and temperature is not lowered. On the other hand, by using a modulation signal including a large number of frequency components, it is not necessary to sweep the modulation frequency, so that the measurement time can be greatly shortened. That is, optical fiber sensing that eliminates the trade-off between measurement time and accuracy, which was a problem of the BOFDA method, can be performed.
(Third embodiment)
A third embodiment of the present invention will be described. FIG. 3 is a diagram showing a configuration of an optical fiber sensing device according to a third embodiment of the present invention. Since this configuration is common to many parts in FIG. 2 which is the configuration diagram of the second embodiment, the common parts are denoted by the same reference numerals as those used in FIG.
　光源１０１から出た周波数ｆ１の光を光分岐器１０２で分岐し、その一方の分岐光をＥＤＦＡ１０６で増幅し第１の光とする。もう一方の分岐光からＳＳＢ変調器１０３を用いて周波数ｆ２の光を生成した後、ＥＤＦＡ１０４により増幅し第２の光とする。以上は第２の実施形態と同じである。 The light having the frequency f 1 emitted from the light source 101 is branched by the optical branching device 102, and one of the branched lights is amplified by the EDFA 106 to be the first light. After the light having the frequency f 2 is generated from the other branched light using the SSB modulator 103, the light is amplified by the EDFA 104 to be the second light. The above is the same as in the second embodiment.
　第３の光である変調光は、第２の実施形態では光源１０１からの分岐光が変調されることにより生成されたが、本実施形態では、別の光源である光源２０１から出射される周波数ｆ３の光が変調され、ＥＤＦＡ１０９により増幅されて生成される。 The modulated light that is the third light is generated by modulating the branched light from the light source 101 in the second embodiment, but in this embodiment, the frequency emitted from the light source 201 that is another light source. light of f 3 is modulated, it is generated is amplified by EDFA109.
　ＥＤＦＡ１０６を出た第１の光である周波数ｆ１の連続光と、第３の光である中心周波数ｆ３の変調光は、ＰＢＳ１１１で合波され、偏光無依存光サーキュレータ１１２を通ってセンサ部分である光ファイバ２０２に入射する。光ファイバ２０２の逆端からはＥＤＦＡ１０４を出た第２の光である周波数ｆ２の連続光が入射される。ここで光ファイバ２０２は偏光保持型光ファイバであり、速軸と遅軸を有する。周波数ｆ１とｆ２の連続光が共に偏光が速軸、または共に偏光が遅軸と平行になるように入射させる。この時、中心周波数がｆ３の変調光は、これらの連続光とは異なる軸に偏光が平行となるように入射することになる。 The continuous light having the frequency f 1 that is the first light exiting the EDFA 106 and the modulated light having the center frequency f 3 that is the third light are combined by the PBS 111 and pass through the polarization-independent optical circulator 112. Is incident on the optical fiber 202. Continuous light of a frequency f 2 which is the second light exiting the EDFA104 from opposite ends of the optical fiber 202 is incident. Here, the optical fiber 202 is a polarization maintaining optical fiber, and has a fast axis and a slow axis. The continuous lights of frequencies f 1 and f 2 are incident so that the polarization is fast axis or both are parallel to the slow axis. In this case, modulated light having a center frequency f 3, the polarization is to be incident in parallel to the different axes from these continuous light.
　ここで、光源１０１および光源２０１から偏光保持型光ファイバ２０２に至る光路は全て偏光保持ファイバで結合されている。偏光保持型光ファイバ２０２で散乱された変調光は受光器１１５で受光され、光分岐器１１０で分岐された光は直接受光器１１６で受光される。受光器１１５と１１６の信号を第１の実施形態と同様の方法で処理することにより、偏光保持型光ファイバ２０２内の歪や温度の分布を得ることができる。 Here, the optical paths from the light source 101 and the light source 201 to the polarization maintaining optical fiber 202 are all coupled by the polarization maintaining fiber. The modulated light scattered by the polarization maintaining optical fiber 202 is received by the light receiver 115, and the light branched by the optical branching device 110 is directly received by the light receiver 116. By processing the signals of the light receivers 115 and 116 in the same manner as in the first embodiment, the strain and temperature distribution in the polarization-maintaining optical fiber 202 can be obtained.
　本実施形態でも、第２の実施形態と同様に、周波数ｆ１とｆ２の連続光により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、変調光と周波数ｆ１の連続光がともに散乱される。ただし、第２の実施形態ではセンサ部は通常の光ファイバ１１３であるため、変調光の周波数はｆ１とすれば良いのに対し、本実施形態ではセンサ部が偏光保持型光ファイバ２０２であり、複屈折性を持つため、変調光の周波数は連続光と異なるものにする必要がある。これについては非特許文献２に記載があり、連続光の偏光方向をｘ、変調光の偏光方向をｙとし、それぞれの方向に対する偏光保持型光ファイバの屈折率をｎｘ、ｎｙとすれば、ｎｘ・ｆ１＝ｎｙ・ｆ３を満たすようにｆ３を調整する必要がある。 In this embodiment as well, as in the second embodiment, stimulated Brillouin scattering occurs due to continuous light of frequencies f 1 and f 2 , and the modulated light and continuous light of frequency f 1 are both generated by the acoustic phonons generated thereby. Scattered. However, in the second embodiment the sensor unit is a conventional optical fiber 113, the frequency of the modulated light whereas it if f 1, in the present embodiment has the sensor unit is a polarization maintaining optical fiber 202 In order to have birefringence, the frequency of the modulated light needs to be different from that of continuous light. This will have described in Non-Patent Document 2, the polarization direction of the continuous light x, the polarization direction of the modulated light and y, if the refractive index of the polarization-maintaining optical fiber for each direction n x, and n y , it is necessary to adjust the f 3 to satisfy the n x · f 1 = n y · f 3.
　第２の実施形態では、周波数ｆ１とｆ２の連続光の偏光が極力一致するようにＰＣ１１４により偏光を調整している。理想的には両者の偏光は一致し、変調光の偏光はこれらと直交する。しかし、センサ部である光ファイバ１１３内で偏光が乱れることが起こりうる。このため周波数ｆ２の光の一部と変調光が同じ偏光になることがあり、その場合にはブリルアンスペクトルに不要な成分が重畳することとなる。これに対し、本実施形態では偏光保持型光ファイバ２０２を用いているため、連続光と変調光の偏光は互いに直交した状態に保たれる。したがって、より安定した測定が可能となる。
（第４の実施形態）
　本発明の第４の実施形態について説明する。図４は本発明の第４の実施形態の光ファイバセンシング装置の構成を示す図である。本構成も、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し、説明も省略する。 In the second embodiment, the polarization is adjusted by the PC 114 so that the polarizations of the continuous lights having the frequencies f 1 and f 2 coincide as much as possible. Ideally, both polarizations coincide with each other, and the polarization of the modulated light is orthogonal to them. However, polarization may be disturbed in the optical fiber 113 that is a sensor unit. For this reason, a part of the light having the frequency f 2 and the modulated light may have the same polarization, and in this case, an unnecessary component is superimposed on the Brillouin spectrum. On the other hand, since the polarization maintaining optical fiber 202 is used in the present embodiment, the polarization of the continuous light and the modulated light is kept orthogonal to each other. Therefore, more stable measurement is possible.
(Fourth embodiment)
A fourth embodiment of the present invention will be described. FIG. 4 is a diagram showing a configuration of an optical fiber sensing device according to a fourth embodiment of the present invention. Since this configuration is also common to many parts of FIG. 2 which is the configuration diagram of the second embodiment, the common parts are represented by the same reference numerals as those used in FIG.
　光源１０１から出た光は光分岐器１０２で分岐される。一方の分岐光は、光変調器１０３によって周波数がシフトされた後、ＥＤＦＡ１０４で増幅され、ＰＣ１１４により偏光を調整されて第１の光となる。第１および第２の実施形態では、光変調器１０３によって低周波側に周波数をシフトしていたが、本実施形態では高周波側に周波数をシフトする。本実施形態では、光源から出た光の周波数をｆ２、光変調器１０３でシフトされた光の周波数をｆ１とする。また、ｆ１－ｆ２＝Δｆ＞０とする。 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, amplified by the EDFA 104, adjusted in polarization by the PC 114, and becomes the first light. In the first and second embodiments, the frequency is shifted to the low frequency side by the optical modulator 103, but in this embodiment, the frequency is shifted to the high frequency side. In the present embodiment, the frequency of light emitted from the light source is f 2 , and the frequency of light shifted by the optical modulator 103 is f 1 . Further, it is assumed that f 1 −f 2 = Δf> 0.
　光分岐器１０２のもう片方の分岐光は、後続の光分岐器１０５でさらに２分岐される。その一方はＥＤＦＡ１０６で増幅され、第２の光となる。もう一方は光変調器１２０に入射する。ここで、光変調器１２０はマイクロ波発生器１２０ａとＳＳＢ（Ｓｉｎｇｌｅ　Ｓｉｄｅ　Ｂａｎｄ　：単側波帯）変調器１２０ｂからなり、入射光の周波数に対し、マイクロ波発生器１２０ａ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 other split light of the optical splitter 102 is further split into two by the subsequent optical splitter 105. One of them is amplified by the EDFA 106 and becomes the second light. The other is incident on the optical modulator 120. Here, the optical modulator 120 includes a microwave generator 120a and an SSB (Single Side Band) modulator 120b, and the frequency of the microwave generated by the microwave generator 120a 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.
　光変調器１２０では、低周波側に周波数がシフトされる。シフト後の光の周波数をｆ３とすると、ｆ２－ｆ３＝１．５Δｆ（すなわち、ｆ１－ｆ３＝２．５Δｆ）となるように周波数シフト量を調整している。ＥＤＦＡ３０１で増幅された後、変調器１０７で強度変調され、ＥＤＦＡ１０９で再度増幅されて、第３の光となる。 In the optical modulator 120, the frequency is shifted to the low frequency side. When the frequency of the light after the shift and f 3, f 2 -f 3 = 1.5Δf ( i.e., f 1 -f 3 = 2.5Δf) is adjusted the frequency shift amount so that. After being amplified by the EDFA 301, the intensity is modulated by the modulator 107, and is amplified again by the EDFA 109 to become third light.
　その後、光分岐器１１０によって分岐された後、光合波器３０２でＥＤＦＡ１０６からの周波数ｆ２の第２の光と合波され、光サーキュレータ１１２を通って、センサ部である光ファイバ１１３に入射される。光ファイバ１１３の他端からは、ＥＤＦＡ１０４で増幅された周波数ｆ１の光がＰＣ１１４を通った後に入射される。周波数ｆ１およびｆ２の連続光の偏光が極力一致するようにＰＣ１１４を調整する。 Then, after being branched by the optical splitter 110 is combined with the second optical frequency f 2 from the optical multiplexer 302 EDFA106, through the optical circulator 112, it enters the optical fiber 113 is a sensor unit The From the other end of the optical fiber 113, light having a frequency f 1 amplified by the EDFA 104 is incident after passing through the PC 114. The PC 114 is adjusted so that the polarizations of the continuous lights having the frequencies f 1 and f 2 match as much as possible.
　光ファイバ内で散乱された第３の光である変調光は、光サーキュレータ１１２を通って受光器１１５で受光される。また、光分岐器１１０で分岐された変調光の片方は受光器１１６で受光される。受光器１１５と１１６の信号を第１の実施形態と同様の方法で処理することにより、光ファイバ１１３内の歪や温度の分布を得ることができる。ただし、マイクロ波発生器１０３ａの周波数を変えてΔｆを掃引する際、ｆ２－ｆ３が１．５Δｆ（すなわち、ｆ１－ｆ３が２．５Δｆ）となるようにマイクロ波発生器１２０ａも同時に調整する。 The modulated light that is the third light scattered in the optical fiber passes through the optical circulator 112 and is received by the light receiver 115. Also, one of the modulated lights branched by the optical branching device 110 is received by the light receiver 116. By processing the signals from the light receivers 115 and 116 in the same manner as in the first embodiment, the strain and temperature distribution in the optical fiber 113 can be obtained. However, when sweeping Δf by changing the frequency of the microwave generator 103a, the microwave generator 120a is also set so that f 2 −f 3 becomes 1.5Δf (ie, f 1 −f 3 is 2.5Δf). Adjust at the same time.
　本実施形態では、第２の実施形態と異なり、第３の光である変調光の伝播方向が、周波数が低い方の第２の光である連続光、すなわち周波数ｆ２の光と同じとなっている。この場合、周波数ｆ１およびｆ２の連続光、すなわち、第１の光と第２の光で形成される音響フォノンで、第３の光である変調光が散乱されるためには、変調光の中心周波数はｆ１ではなく、上記に示したｆ３である必要がある。 In the present embodiment, unlike the second embodiment, is the direction of propagation of the modulated light which is the third light, continuous light frequency is a second light having a lower, i.e. the same as that of the optical frequency f 2 ing. In this case, the modulated light, which is the third light, is scattered by the continuous light of the frequencies f 1 and f 2 , that is, the acoustic phonon formed by the first light and the second light. The center frequency of f needs to be f 3 shown above, not f 1 .
　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となるように調整している。 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, it is adjusted so that f 1 −f 3 = 2.5Δf with respect to f 1 −f 2 = Δf.
　なお、上記のように測定時には、第１と第２の周波数の差であるΔｆを掃引することとなるが、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ｆ３は第２の光の周波数ｆ２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の光の周波数差が誘導ブリルアン散乱を生じる範囲に入ることはない。 As described above, during measurement, Δf, which is the difference between the first and second frequencies, is swept, and the frequency sweep range is determined by the temperature to be measured and the range of strain. Since the frequency f 3 of the third light is far away from the frequency f 2 of the second light, even if the measurement range is expanded to a strain or temperature range that causes the quartz optical fiber to break or soften, The frequency difference between the first and third lights does not fall within a range where stimulated Brillouin scattering occurs.
　本実施形態では、第３の光の変調光とそれに対向して伝播する第１の光の連続光の偏光は必ずしも直交しないが、上記の理由により、変調光の偏光状態に関わらず変調光と連続光の間で誘導ブリルアン散乱は発生しない。したがって、センサ部に偏光保持型光ファイバではない通常の光ファイバを用いても、ブリルアンスペクトルに不要な成分が重畳することなく、安定した測定が可能となる。 In the present embodiment, the modulated light of the third light and the polarization of the continuous light of the first light propagating opposite thereto are not necessarily orthogonal, but for the above reasons, the modulated light and the modulated light Stimulated Brillouin scattering does not occur between continuous light. Therefore, even if a normal optical fiber that is not a polarization maintaining optical fiber is used for the sensor unit, an unnecessary component is not superimposed on the Brillouin spectrum, and stable measurement is possible.
　以上、本発明の実施形態について説明したが、本発明は上記した実施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。 As mentioned above, although embodiment of this invention was described, this invention is not limited to above-described embodiment, In the range which does not deviate from the summary, various deformation | transformation are possible.
　例えば、上記の実施形態では、変調周波数として方形波を例に挙げたが、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。また、第３の実施形態では、周波数ｆ１の連続光と、周波数ｆ３の変調光をＰＢＳ１１１で合波した後、偏光無依存光サーキュレータ１１２を通してセンサ部となる偏光保持ファイバ２０２に入射させたが、それぞれの光を偏光保持型の光サーキュレータを通した後にＰＢＳで合波し、光ファイバに入射するという構成にしても良い。また、上記の実施形態では周波数ｆ１およびｆ２の連続光により誘導ブリルアン散乱を生じさせる構成としたが、これらは必ずしも完全な連続光、すなわち完全な非変調光である必要はなく、僅かな変動があっても良い。 For example, in the above embodiment, a square wave is used as an example of the modulation frequency, but the waveform may be other as long as it has a wide frequency spectrum, such as a triangular wave. In the third embodiment, between the successive optical frequency f 1, was combined with PBS111 modulated light frequency f 3, it is made incident on the polarization maintaining fiber 202 which is a sensor portion through a polarization-independent optical circulator 112 However, the respective light beams may be combined with PBS after passing through the polarization maintaining optical circulator and incident on the optical fiber. In the above embodiment, the stimulated Brillouin scattering is generated by the continuous light of the frequencies f 1 and f 2. However, these are not necessarily complete continuous light, that is, completely unmodulated light, There may be fluctuations.
　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伝播する前記第１および第２の光よりも変調速度が速い複数の変調周波数を有する第３の光を発生する第３の発生手段と、前記第３の光と前記第３の光の散乱光とを前記複数の変調周波数ごとに比較を行う比較手段と、を備えた、光ファイバセンシング装置。
（付記２）
　前記第３の光は前記第２の光と同じ方向に伝播する、付記１に記載の光ファイバセンシング装置。
（付記３）
　前記第３の光は前記第２の光よりも周波数が低い、付記１または２に記載の光ファイバセンシング装置。
（付記４）
　前記第１の光の周波数と前記第３の光の周波数の差が、第１の光の周波数と前記第２の光の周波数の差の略２．５倍である、付記１から３の内の１項記載の光ファイバセンシング装置。
（付記５）
　前記第３の光は前記第１の光と同じ方向に伝播し、かつ前記第１の光と前記第３の光は前記光ファイバ入射時の偏光状態が互いに略直交する、付記１に記載の光ファイバセンシング装置。
（付記６）
　前記光ファイバは偏光保持型光ファイバである、付記５に記載の光ファイバセンシング装置。
（付記７）
　前記第１の光の周波数と前記第２の光の周波数との差、および、前記第１の光の周波数と前記第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の光と前記第３の光の前記散乱光とを比較する、付記１から６の内の１項記載の光ファイバセンシング装置。
（付記８）
　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７の内の１項記載の光ファイバセンシング装置。
（付記９）
　前記比較を行うことで、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シング装置。
（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、前記第１および第２の光よりも変調速度が速い複数の変調周波数を有する第３の光とを有し、前記第３の光と前記第３の光の散乱光とを前記複数の変調周波数ごとに比較する、光ファイバセンシング方法。
（付記１１）
　前記第３の光は前記第２の光と同じ方向に伝播する、付記１０に記載の光ファイバセンシング方法。
（付記１２）
　前記第３の光は前記第２の光よりも周波数が低い、付記１０または１１に記載の光ファイバセンシング方法。
（付記１３）
　前記第１の光の周波数と前記第３の光の周波数の差が、前記第１の光の周波数と前記第２の光の周波数の差の略２．５倍である、付記１０から１２の内の１項記載の光ファイバセンシング方法。
（付記１４）
　前記第３の光は前記第１の光と同じ方向に伝播し、かつ前記第１の光と前記第３の光は前記光ファイバ入射時の偏光状態が互いに略直交する、付記１０に記載の光ファイバセンシング方法。
（付記１５）
　前記光ファイバは偏光保持型光ファイバである、付記１４に記載の光ファイバセンシング方法。
（付記１６）
　前記第１の光の周波数と前記第２の光の周波数との差、および、前記第１の光の周波数と前記第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の光と前記第３の光の前記散乱光とを比較する、付記１０から１５の内の１項記載の光ファイバセンシング方法。
（付記１７）
　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１６の内の１項記載の光ファイバセンシング方法。
（付記１８）
　前記比較を行うことで、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シング方法。 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 And second generation means for generating third light having a plurality of modulation frequencies faster than the first and second lights propagating in the optical fiber. An optical fiber sensing device comprising: comparing means for comparing the third light and the scattered light of the third light for each of the plurality of modulation frequencies.
(Appendix 2)
The optical fiber sensing device according to appendix 1, wherein the third light propagates in the same direction as the second light.
(Appendix 3)
The optical fiber sensing device according to appendix 1 or 2, wherein the frequency of the third light is lower than that of the second light.
(Appendix 4)
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. The optical fiber sensing device according to 1.
(Appendix 5)
The third light is propagated in the same direction as the first light, and the polarization states of the first light and the third light at the time of incidence on the optical fiber are substantially orthogonal to each other. Optical fiber sensing device.
(Appendix 6)
The optical fiber sensing device according to appendix 5, wherein the optical fiber is a polarization maintaining optical fiber.
(Appendix 7)
The difference between the frequency of the first light and the frequency of the second light, and the difference between the frequency of the first light and the frequency of the third light are changed, and the third is changed for each difference. The optical fiber sensing device according to any one of appendices 1 to 6, which compares the light of the third light and the scattered light of the third light.
(Appendix 8)
The optical fiber sensing device according to one of appendices 1 to 7, 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 9)
9. The optical fiber sensing device 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 comparison.
(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 frequency lower than that of the first light, and the first and second A third light having a plurality of modulation frequencies whose modulation speed is faster than that of the light, and comparing the third light and the scattered light of the third light for each of the plurality of modulation frequencies Fiber sensing method.
(Appendix 11)
The optical fiber sensing method according to appendix 10, wherein the third light propagates in the same direction as the second light.
(Appendix 12)
The optical fiber sensing method according to appendix 10 or 11, wherein the third light has a frequency lower than that of the second light.
(Appendix 13)
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. 2. An optical fiber sensing method according to item 1.
(Appendix 14)
The third light propagates in the same direction as the first light, and the polarization states of the first light and the third light when entering the optical fiber are substantially orthogonal to each other. Optical fiber sensing method.
(Appendix 15)
The optical fiber sensing method according to appendix 14, wherein the optical fiber is a polarization maintaining optical fiber.
(Appendix 16)
The difference between the frequency of the first light and the frequency of the second light, and the difference between the frequency of the first light and the frequency of the third light are changed, and the third is changed for each difference. 16. The optical fiber sensing method according to one of appendices 10 to 15, wherein the first light and the scattered light of the third light are compared.
(Appendix 17)
17. The optical fiber sensing method according to one of appendices 10 to 16, 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 18)
18. The optical fiber sensing method according to any one of appendices 10 to 17, wherein information of temperature and strain distribution in the longitudinal direction of the optical fiber is obtained by performing the comparison.
　この出願は、２０１２年１２月１２日に出願された日本出願特願２０１２－２７１４２４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. 2012-271424 filed on December 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シング装置および光ファイバセンシング方法に関し、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 sensing device and an optical fiber sensing method for measuring temperature distribution and strain distribution in the longitudinal direction of an optical fiber, 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　　比較手段
　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　　ＥＤＦＡ
　１０５　　光分岐器
　１０６　　ＥＤＦＡ
　１０７　　光変調器
　１０８　　信号発生器
　１０９　　ＥＤＦＡ
　１１０　　光分岐器
　１１１　　偏光ビームスプリッタ
　１１２　　偏光無依存光サーキュレータ
　１１３　　光ファイバ
　１１４　　偏光コントローラ
　１１５、１１６　　受光器
　１１７、１１８　　アナログ・デジタル・コンバータ
　１１９　　コンピュータ
　１２０　　光変調器
　１２０ａ　　マイクロ波発生器
　１２０ｂ　　ＳＳＢ変調器
　２０１　　光源
　２０２　　偏光保持ファイバ
　３０１　　ＥＤＦＡ
　３０２　　光合波器 DESCRIPTION OF SYMBOLS 10 1st generation means 11 2nd generation means 12 3rd generation means 13 Comparison means 14 Optical fiber 101 Light source 102 Optical splitter 103 Optical modulator 103a Microwave generator 103b SSB modulator 104 EDFA
105 Optical splitter 106 EDFA
107 optical modulator 108 signal generator 109 EDFA
DESCRIPTION OF SYMBOLS 110 Optical splitter 111 Polarizing beam splitter 112 Polarization-independent optical circulator 113 Optical fiber 114 Polarization controller 115, 116 Light receiver 117, 118 Analog-digital converter 119 Computer 120 Optical modulator 120a Microwave generator 120b SSB modulator 201 Light source 202 Polarization-maintaining fiber 301 EDFA
302 Optical multiplexer

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伝播する前記第１および第２の光よりも変調速度が速い複数の変調周波数を有する第３の光を発生する第３の発生手段と、
    　前記第３の光と前記第３の光の散乱光とを前記複数の変調周波数ごとに比較を行う比較手段と、を備えた、光ファイバセンシング装置。     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 having a plurality of modulation frequencies whose modulation speed is faster than that of the first and second light propagating in the optical fiber;
    An optical fiber sensing device comprising: comparing means for comparing the third light and the scattered light of the third light for each of the plurality of modulation frequencies.
  2. 　前記第３の光は前記第２の光と同じ方向に伝播する、請求項１に記載の光ファイバセンシング装置。 The optical fiber sensing device according to claim 1, wherein the third light propagates in the same direction as the second light.
  3. 　前記第３の光は前記第２の光よりも周波数が低い、請求項１または２に記載の光ファイバセンシング装置。 The optical fiber sensing device according to claim 1 or 2, wherein the frequency of the third light is lower than that of the second light.
  4. 　前記第１の光の周波数と前記第３の光の周波数の差が、第１の光の周波数と前記第２の光の周波数の差の略２．５倍である、請求項１から３の内の１項記載の光ファイバセンシング装置。 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. 2. An optical fiber sensing device according to item 1.
  5. 　前記第３の光は前記第１の光と同じ方向に伝播し、かつ前記第１の光と前記第３の光は前記光ファイバ入射時の偏光状態が互いに略直交する、請求項１に記載の光ファイバセンシング装置。 The third light propagates in the same direction as the first light, and the polarization states of the first light and the third light when they enter the optical fiber are substantially orthogonal to each other. Optical fiber sensing device.
  6. 　前記光ファイバは偏光保持型光ファイバである、請求項５に記載の光ファイバセンシング装置。 The optical fiber sensing device according to claim 5, wherein the optical fiber is a polarization maintaining optical fiber.
  7. 　前記第１の光の周波数と前記第２の光の周波数との差、および、前記第１の光の周波数と前記第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の光と前記第３の光の前記散乱光とを比較する、請求項１から６の内の１項記載の光ファイバセンシング装置。 The difference between the frequency of the first light and the frequency of the second light, and the difference between the frequency of the first light and the frequency of the third light are changed, and the third is changed for each difference. The optical fiber sensing device according to claim 1, wherein the light of the third light is compared with the scattered light of the third light.
  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、前記第１および第２の光よりも変調速度が速い複数の変調周波数を有する第３の光とを有し、前記第３の光と前記第３の光の散乱光とを前記複数の変調周波数ごとに比較する、光ファイバセンシング方法。 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 frequency lower than that of the first light, and the first and second A third light having a plurality of modulation frequencies whose modulation speed is faster than that of the light, and comparing the third light and the scattered light of the third light for each of the plurality of modulation frequencies Fiber sensing method.
  9. 　前記第３の光は前記第２の光と同じ方向に伝播し、前記第１の光の周波数と前記第３の光の周波数の差が、前記第１の光の周波数と前記第２の光の周波数の差の略２．５倍である、請求項８記載の光ファイバセンシング方法。 The third light propagates in the same direction as the second light, and the difference between the frequency of the first light and the frequency of the third light is the frequency of the first light and the second light. The optical fiber sensing method according to claim 8, which is approximately 2.5 times the difference in frequency.
  10. 　前記第３の光は前記第１の光と同じ方向に伝播し、かつ前記第１の光と前記第３の光は前記光ファイバ入射時の偏光状態が互いに略直交する、請求項８に記載の光ファイバセンシング方法。 9. The third light propagates in the same direction as the first light, and the polarization states of the first light and the third light when entering the optical fiber are substantially orthogonal to each other. Optical fiber sensing method.
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