JP2007240294A - Apparatus for measuring optical fiber distortion - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To shorten the measuring time and to measure the distortion accurately. <P>SOLUTION: The optical fiber distortion measuring device for measuring the distortion of an optical fiber using Brillouin scattering light occurring in an optical fiber to be measured comprises an optical source for emitting pulse light, an optical branching means for making the pulse light come into one end of the optical fiber, branching the back-scattering light coming from one end of the optical fiber every wavelength band, and making it go out, a distortion detecting means for making the branch light of the wavelength band including Brillouin scattering light from the optical branching means, detecting the Brillouin scattering light, and measuring the distortion, a temperature detecting means for making the branch light of the wavelength band including Raman scattering light from the optical branching means, detecting the Raman scattering light, and measuring the temperature, and an arithmetic controlling means for extracting measuring data of distortion from the distortion detecting means, extracting measuring data of temperature from the temperature detecting means, and compensating the measuring data of distortion with temperature data. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an optical fiber strain measuring apparatus that measures strain of an optical fiber by using Brillouin scattered light (back-scattered light that has been Brillouin scattered) generated in an optical fiber to be measured. The present invention relates to an optical fiber strain measuring apparatus capable of accurately measuring the above.

  Part of the light propagating in the optical fiber is absorbed as the kinetic energy of the glass structural molecules. The absorbed energy is released as an acoustic phonon when it exceeds a certain value. Brillouin scattering is a phenomenon in which Stokes light that is shifted by the frequency of the acoustic phonon (Brillouin frequency shift) is generated due to the mutual interference between the emitted acoustic phonon and the transmitted light.

  Prior art documents related to an optical fiber strain measuring apparatus for measuring strain of an optical fiber using Brillouin scattered light generated in an optical fiber to be measured are as follows.

Japanese Patent Laid-Open No. 04-248426 Japanese Patent Laid-Open No. 04-276518 Japanese Patent Laid-Open No. 05-231923 Japanese Patent Laid-Open No. 11-257828 JP 2001-281471 A JP 2002-221407 A Japanese Patent Laid-Open No. 2002-340531

  In an optical fiber strain measuring apparatus that measures strain of an optical fiber using Brillouin scattered light generated in the optical fiber, the change in Brillouin frequency shift does not depend only on the change in strain, but is also caused by a change in temperature. A change occurs in the frequency shift.

  For this reason, it is necessary to accurately measure the strain by separately measuring the temperature in the optical fiber and compensating for the temperature. As a method of measuring the temperature in the optical fiber, there is a method of measuring the temperature using Raman scattered light.

  Here, the Raman scattered light generates Raman scattered light having a frequency shifted based on vibration and rotation of glass constituent molecules as backscattered light simultaneously with generation of Brillouin scattered light. This Raman scattered light is generated simultaneously with anti-Stokes light whose light intensity is highly sensitive to temperature and Stokes light with low sensitivity, and the temperature is obtained from the light intensity ratio of the generated anti-Stokes light and Stokes light. be able to.

  FIG. 15 is a configuration block diagram showing an example of a conventional optical fiber strain measuring apparatus that performs temperature compensation of strain described in “Patent Document 4”. In FIG. 15, 1 is an optical fiber to be measured for strain, 2 is an optical path switching means for switching the optical path of incident light such as an optical switch, 3 is a strain detection means for detecting the Brillouin scattered light and measuring the strain, 4 is Temperature detection means 5 for detecting the Raman scattered light and measuring the temperature, 5 controls the optical path switching means, and controls the arithmetic processing of a CPU (Central Processing Unit) etc. that takes in and processes the measurement data from the strain detection means 3 and the temperature detection means 4 Means.

  One end of the optical fiber 1 is connected to the incident end of the optical path switching means 2. The output light from one exit end of the optical path switching means 2 is incident on the incident end of the strain detection means 3, and the output light from the other exit end of the optical path switching means 2 is incident on the incident end of the temperature detection means 4. Is done.

  The outputs of the strain detection means 3 and the temperature detection means 4 are respectively connected to the calculation control means 5, and the control signal of the calculation control means 5 is connected to the control terminal of the optical path switching means 2.

  Here, the operation of the conventional example shown in FIG. 15 will be described. Backscattered light (Brillouin scattered light and Raman scattered light) generated by light incident on one end of the optical fiber 1 to be measured from means such as a light source (not shown) propagates as indicated by “LG01” in FIG. The light is emitted from one end of the optical fiber 1 and enters the optical path switching means 2.

  Then, the arithmetic control unit 5 switches the optical path of the incident backscattered light as shown by “LG01” in FIG. 15 by the control signal shown by “CT01” in FIG. 15 to the strain detecting unit 3 or the temperature detecting unit 4. Make it incident.

  For example, the arithmetic control unit 5 controls the optical path switching unit 2 to cause the backscattered light to enter the strain detecting unit 3 as indicated by “LG02” in FIG. 15, and the strain detecting unit 3 performs Brillouin scattering of the backscattered light. Strain is measured based on light to obtain strain measurement data.

  Thereafter, the arithmetic control means 5 controls the optical path switching means 2 to cause the backscattered light to enter the temperature detecting means 4 as indicated by “LG03” in FIG. Temperature is measured based on light, temperature measurement data is acquired, and distortion data acquired previously is compensated with the temperature data to obtain accurate distortion.

  As a result, the temperature of the Brillouin scattered light is measured by measuring the strain based on the Brillouin scattered light out of the backscattered light emitted from the optical fiber to be measured and compensating the strain at the temperature measured based on the Raman scattered light. It becomes possible to measure the distortion with high accuracy by removing the influence of.

  However, in the conventional example shown in FIG. 15, since the backscattered light is sequentially switched by the optical path switching means 2 to measure the strain and temperature, the strain and temperature are measured based on the Brillouin scattered light and the Raman scattered light at the same time. There was a problem that it was not possible.

  For example, even if temperature compensation is used for strain, it cannot be compensated for at the same time. If the strain measurement time or temperature measurement time is long, the accuracy of temperature compensation may deteriorate. .

Further, since the total time of the strain measurement time and the temperature measurement time is the total measurement time, there is a problem that the time required for the measurement becomes long.
Therefore, the problem to be solved by the present invention is to realize an optical fiber strain measuring device capable of shortening the measuring time and measuring the strain with high accuracy.

In order to achieve such a problem, the invention according to claim 1 of the present invention is:
In an optical fiber strain measuring apparatus that measures strain of an optical fiber using Brillouin scattered light generated in an optical fiber to be measured,
A light source that emits pulsed light, light branching means for causing the pulsed light to enter one end of the optical fiber, branching backscattered light emitted from one end of the optical fiber for each wavelength band, and emitting the light. A branching light of a wavelength band including Brillouin scattered light is incident from the branching means, a strain detecting means for detecting the Brillouin scattered light and measuring the strain, and a branched light of a wavelength band including Raman scattered light is incident from the light branching means. Temperature detection means for detecting the Raman scattered light and measuring the temperature; strain measurement data from the strain detection means; temperature measurement data from the temperature detection means; and strain measurement data compensated by the temperature data By providing the calculation control means, it is possible to accurately measure the distortion. In addition, since the measurement of strain and the measurement of temperature are performed simultaneously, the measurement time can be shortened.

The invention according to claim 2
In the optical fiber strain measuring device which is the invention according to claim 1,
The light branching means is
An optical directional coupler for causing the pulsed light to enter one end of the optical fiber and branching backscattered light emitted from the one end of the optical fiber, and the branched light of the optical directional coupler in two wavelength bands The first optical filter that divides and emits separately, and the second optical filter that divides and emits one branched light of the first optical filter into two wavelength bands, thereby enabling distortion to be accurately detected. It becomes possible to measure well. Further, since the measurement of strain and the measurement of temperature are performed simultaneously, the measurement time can be shortened.

The invention described in claim 3
In the optical fiber strain measuring device which is the invention according to claim 2,
The first optical filter is divided into a wavelength band including anti-Stokes light of the Raman scattered light and a wavelength band including Stokes light of the Raman scattered light and the Brillouin scattered light, and the second optical filter. However, it is possible to measure the distortion with high accuracy by separately emitting the wavelength band including the Stokes light of the Raman scattered light and the wavelength band including the Brillouin scattered light. In addition, since the measurement of strain and the measurement of temperature are performed simultaneously, the measurement time can be shortened.

The invention according to claim 4
In the optical fiber strain measuring device which is the invention according to claim 2,
The first optical filter is divided into a wavelength band including the Stokes light of the Raman scattered light and an anti-Stokes light of the Raman scattered light and a wavelength band including the Brillouin scattered light, respectively, and the second optical filter However, it is possible to measure the distortion with high accuracy by separately emitting the wavelength band including the anti-Stokes light of the Raman scattered light and the wavelength band including the Brillouin scattered light. In addition, since the measurement of strain and the measurement of temperature are performed simultaneously, the measurement time can be shortened.

The invention according to claim 5
In the optical fiber strain measuring device according to any one of claims 2 to 4,
The first and second optical filters are
By using a reflection type, etalon type, or diffraction grating type optical filter, distortion can be measured with high accuracy. In addition, since the measurement of strain and the measurement of temperature are performed simultaneously, the measurement time can be shortened.

The invention described in claim 6
In the optical fiber strain measuring device according to any one of claims 2 to 4,
The first and second optical filters are
By using a fiber coupler type or spatial light type optical filter, it becomes possible to measure distortion with high accuracy. In addition, since the measurement of strain and the measurement of temperature are performed simultaneously, the measurement time can be shortened.

The present invention has the following effects.
According to the first, second, third, fourth, and fifth aspects of the present invention, the backscattered light generated by making the pulsed light incident on the optical fiber is branched into Brillouin scattered light and Raman scattered light by the light branching means. By measuring the strain based on the Brillouin scattered light, measuring the temperature based on the Raman scattered light, and compensating the strain measurement data with the temperature data, the strain can be accurately measured. In addition, since the measurement of strain and the measurement of temperature are performed simultaneously, the measurement time can be shortened.

  Hereinafter, the present invention will be described in detail with reference to the drawings. FIG. 1 is a block diagram showing an embodiment of an optical fiber strain measuring apparatus according to the present invention for performing temperature compensation of strain.

  In FIG. 1, 6 is a light source that emits pulsed light as output light, 7 is an incident light from an incident end that is emitted from an incident / exit end, and the incident light from the incident / exit end is branched into three wavelength bands and emitted. 8 is an optical fiber to be measured for strain, 9 is a strain detection unit for detecting Brillouin scattered light and measuring strain, and 10 is for detecting Raman scattered light (anti-Stokes light and Stokes light). A temperature detection means 11 for measuring the temperature, and 11 is an arithmetic control means such as a CPU for fetching and processing measurement data from the strain detection means 9 and the temperature detection means 10.

  The pulsed light that is the output light of the light source 6 is incident on the incident end of the light branching means 7 as indicated by “LG11” in FIG. 1 propagates through the optical fiber 8 as indicated by “LG12” in FIG.

  As shown by “LG12” in FIG. 1, the back scattered light (Brillouin scattered light and Raman scattered light) generated by the pulse light propagating in the optical fiber 8 propagates as shown by “LG13” in FIG. The light is emitted from one end of the fiber 8 and is incident on the incident / exit end of the light branching means 7.

  In the light branching means 7, the Brillouin scattered light of the incident backscattered light is branched and made incident on the strain detecting means 9 as indicated by “LG 14” in FIG. 1, and the Raman scattered light (anti-Stokes light) of the backscattered light. ) And is incident on the temperature detecting means 10 as indicated by “LG15” in FIG. 1, and Raman scattered light (Stokes light) of the backscattered light is branched and the temperature is indicated by “LG16” in FIG. The light is incident on the detection means 10.

  The arithmetic control unit 11 causes the strain detection unit 9 to measure strain based on Brillouin scattered light among the backscattered light incident as indicated by “LG14” in FIG. 1, and obtains strain measurement data.

  Similarly, the calculation control means 11 causes the temperature detection means 10 to measure the temperature based on the Raman scattered light among the backscattered light incident as indicated by “LG15” in FIG. 1 and “LG16” in FIG. In addition to acquiring the measurement data, the distortion measurement data acquired previously is compensated with the temperature data to obtain accurate distortion.

  Here, the operation of the optical branching means 7 will be described with reference to FIGS. 2, 3, 4, 5, 6, 7, 8, 8, 9, 10, 11, 12, 13, and 14. Will be described in detail.

  2 is an explanatory diagram for explaining the configuration of the optical branching means, FIG. 3 is a characteristic curve diagram showing an example of the spectrum of the pulsed light incident on the optical fiber 8, and FIG. 4 is a diagram of the backscattered light emitted from the optical fiber 8. FIG. 5 is an explanatory diagram illustrating the configuration of the optical filter, FIGS. 6 and 9 are explanatory diagrams illustrating an example of the characteristics of the optical filter, and FIGS. 7, 8, 10 and 11 are optical diagrams. FIG. 12 is a characteristic curve diagram showing an example of strain measurement data, FIG. 13 is a characteristic curve diagram showing an example of temperature measurement data, and FIG. 14 is temperature compensated. It is a characteristic curve figure which shows an example of the measured data of the distortion.

  In FIG. 2, “LG11”, “LG12”, “LG13”, “LG14”, “LG15”, and “LG16” are assigned the same reference numerals as in FIG. 1, and 12 indicates the incident light from the incident end. The optical directional couplers 13 and 14 are configured to emit light from the light input and output light from the light input / output end, and are reflection type and fiber coupler type optical filters using a reflection film. In addition, 12, 13 and 14 constitute an optical branching means 50.

  The pulsed light from the light source 6 indicated by “LG11” in FIG. 2 enters the incident end of the optical directional coupler 12, and the emitted light and the incident light indicated by “LG12” and “LG13” in FIG. The light is emitted or incident from the incident / exit end of the vessel 12.

  The outgoing light from the outgoing end of the optical directional coupler 12 is incident on the incident end of the optical filter 13, and the Raman scattered light (anti-Stokes light) as indicated by “LG 15” in FIG. Is emitted.

  Further, light emitted from the reflection end of the optical filter 13 is incident on the incident end of the optical filter 14, and Brillouin scattered light as indicated by “LG 14” in FIG. 2 is emitted from the transmission end of the optical filter 14. Further, Raman scattered light (Stokes light) as indicated by “LG16” in FIG. 2 is emitted from the reflection end of the optical filter.

  For example, assuming that a pulsed light having a spectrum (output wavelength: 1550 nm band) as shown in “SP21” in FIG. 3 is incident from one end of the optical fiber 8, the spectral distribution of the backscattered light generated by the pulsed light Is as shown in FIG.

  That is, Rayleigh scattered light / Fresnel scattered light (1550 nm band) having the same wavelength as the incident light (pulse light) as indicated by “SP31” in FIG. 4, Brillouin scattering as indicated by “SP32” and “SP33” in FIG. Backscattered light consisting of the Raman scattered light (anti-Stokes light: 1450 nm band) shown in FIG. 4 and the Raman scattered light (Stokes light: 1650 nm band) shown in FIG. The light is incident on the incident end of the optical filter 13 through the optical directional coupler 12.

  Here, in the optical filter shown in FIG. 5, light is incident from the incident end indicated by “IP41” in FIG. 5, and light having a certain wavelength or less is transmitted through the reflection film and transmitted from the transmission end indicated by “TP41” in FIG. The emitted light having a certain wavelength or longer is reflected by the reflective film and emitted from the reflection end indicated by “RP41” in FIG.

  For example, when the characteristics of the optical filter 13 are the characteristics shown in FIG. 6, the light in the wavelength band indicated by “TB51” in FIG. 6 is emitted from the transmission end, and the light in the wavelength band indicated by “TB52” in FIG. The light is emitted from the end.

  For this reason, the Raman scattered light (anti-Stokes light: 1450 nm band) is transmitted through the reflection film and emitted from the transmission end as indicated by “LG15” in FIG. 2, and the remaining backscattered light is reflected by the reflection film and reflected at the reflection end. It is emitted from.

  Therefore, the spectrum of the light emitted from the transmission end of the optical filter 13 indicated by “LG15” in FIG. 2 is as shown in FIG. 7, and the Raman scattered light (anti-Stokes light: 1450 nm indicated by “SP34” in FIG. Band) components are extracted.

  On the other hand, the spectrum of the light emitted from the reflection end of the optical filter 13 is as shown in FIG. 8, and Rayleigh scattered light / Fresnel scattered light having the same wavelength as the incident light (pulsed light) as indicated by “SP31” in FIG. Back-scattered light consisting of light, Brillouin scattered light as indicated by “SP32” and “SP33” in FIG. 8, and Raman scattered light (Stokes light: 1650 nm band) indicated by “SP35” in FIG.

  For example, when the characteristics of the optical filter 14 are the characteristics shown in FIG. 9, the light in the wavelength band indicated by “TB61” in FIG. 9 is emitted from the transmission end, and the light in the wavelength band indicated by “TB62” in FIG. Is emitted from the reflection end.

  For this reason, Rayleigh scattered light / Fresnel scattered light (1550 nm band) and Brillouin scattered light are transmitted through the reflective film and emitted from the transmission end as indicated by “LG14” in FIG. 2, and the remaining backscattered light is reflected by the reflective film. Reflected and emitted from the reflection end.

  Therefore, the spectrum of the light emitted from the transmission end of the optical filter 14 indicated by “LG14” in FIG. 2 is as shown in FIG. 10, and the incident light (pulse light) as indicated by “SP31” in FIG. Rayleigh scattered light / Fresnel scattered light (1550 nm band) of the same wavelength, Brillouin scattered light components as indicated by “SP32” and “SP33” in FIG. 10 are extracted.

  On the other hand, the spectrum of the light emitted from the reflection end of the optical filter 14 indicated by “LG16” in FIG. 2 is as shown in FIG. 11, and Raman scattered light (Stokes light: 1650 nm band) indicated by “SP35” in FIG. Are extracted.

  In this way, as described above, the distortion of each extracted backscattered light is measured based on the Brillouin scattered light of the incident backscattered light as indicated by “LG14” in FIG. The arithmetic control unit 11 acquires strain measurement data from the strain detection unit 3.

  For example, it is assumed that the strain measurement data acquired by the arithmetic control unit 11 from the strain detection unit 3 has a characteristic as indicated by “CH71” in FIG.

  Similarly, the temperature detection means 4 measures the temperature based on the Raman scattered light among the backscattered light incident as indicated by “LG15” in FIG. 2 and “LG16” in FIG. 2, and the arithmetic control means 11 detects the temperature. The temperature measurement data is acquired from the means 4 and the distortion measurement data acquired previously is compensated with the temperature data to obtain an accurate distortion.

  Similarly, for example, it is assumed that the temperature measurement data acquired by the arithmetic control unit 11 from the temperature detection unit 4 has a characteristic as indicated by “CH81” in FIG.

Here, the frequency shift of the Brillouin scattered light changes according to the strain “δε” of the optical fiber, as shown in the following formula (1). However, “∂ν _b / ∂ε” is a Brillouin frequency shift distortion coefficient, and “∂ν _b / ∂T” is a Brillouin frequency shift temperature coefficient.

For this reason, it is said that the strain amount “δε” can be obtained by detecting the amount of change “δν _b ” of the frequency, but as can be seen from the equation (1), the temperature parameter is included, A frequency shift also occurs due to the temperature change “δT”.

Since “δT” is a temperature change amount, if the temperature of the temperature distribution waveform obtained from the Raman scattered light is “T _R ” and the reference temperature is “T _REF ”,
δT = T _R −T _REF (2)
It becomes.

If the distortion coefficient and temperature coefficient of the Brillouin frequency shift are measured in advance, the frequency shift “δν _b (ε, T)” of the Brillouin scattered light and the temperature “T _R ” of the Raman scattered light are measured. In other words, a strain amount that is not affected by temperature can be obtained by temperature compensation.

  Similarly, for example, by compensating the strain measurement data acquired by the arithmetic control unit 11 from the strain detection unit 3 with the temperature measurement data acquired from the temperature detection unit 4, as indicated by “CH 91” in FIG. 14. Characteristics that are not affected by temperature can be obtained.

  That is, the temperature as indicated by “CH91” in FIG. 14 is obtained by removing the characteristic of the temperature measurement data as indicated by “CH81” in FIG. 13 from the characteristic of the strain measurement data as indicated by “CH71” in FIG. The characteristics of the compensated distortion measurement data can be obtained.

  As a result, the backscattered light generated when the pulsed light is incident on the optical fiber is branched into Brillouin scattered light and Raman scattered light by the light branching means, the strain is measured based on the Brillouin scattered light, and the temperature is measured based on the Raman scattered light. By measuring and compensating the distortion measurement data with the temperature data, the distortion can be accurately measured. In addition, since the measurement of strain and the measurement of temperature are performed simultaneously, the measurement time can be shortened.

  In the embodiment shown in FIG. 2, Raman scattering light (anti-Stokes light: 1450 nm band), Brillouin scattered light (including Rayleigh scattered light / Fresnel scattered light (1550 nm band)), and Raman scattered light (Stokes light) are used in the light branching means. : 1650 nm band), the scattered light is separated and extracted. Of course, the order of separation and extraction may be any order.

  For example, first, Raman scattered light (Stokes light: 1650 nm band) is extracted, Brillouin scattered light (including Rayleigh scattered light / Fresnel scattered light (1550 nm band)), and Raman scattered light (anti-Stokes light: 1450 nm band). Alternatively, the scattered light may be separated and extracted.

  Further, as the optical filter, a reflective optical filter using a reflective film has been illustrated, but of course, an etalon optical filter or a diffraction grating optical filter may be used.

  Further, as the optical filter, a fiber coupler type optical filter is exemplified, but it is needless to say that a spatial light type optical filter may be used.

1 is a configuration block diagram showing an embodiment of an optical fiber strain measuring apparatus according to the present invention. It is explanatory drawing explaining the structure of an optical branching means. It is a characteristic curve figure which shows an example of the spectrum of the pulsed light which injected into an optical fiber. It is a characteristic curve figure which shows an example of the backscattered light radiate | emitted from an optical fiber. It is explanatory drawing explaining the structure of an optical filter. It is explanatory drawing which shows an example of the characteristic of an optical filter. It is a characteristic curve figure which shows an example of the spectrum of the output light of an optical filter. It is a characteristic curve figure which shows an example of the spectrum of the output light of an optical filter. It is explanatory drawing which shows an example of the characteristic of an optical filter. It is a characteristic curve figure which shows an example of the spectrum of the output light of an optical filter. It is a characteristic curve figure which shows an example of the spectrum of the output light of an optical filter. It is a characteristic curve figure which shows an example of the measurement data of distortion. It is a characteristic curve figure which shows an example of the measurement data of temperature. It is a characteristic curve figure which shows an example of the measurement data of distortion compensated for temperature. It is a configuration block diagram showing an example of a conventional optical fiber strain measurement device that performs temperature compensation of strain.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1,8 Optical fiber 2 Optical path switching means 3,9 Strain detection means 4,10 Temperature detection means 5,11 Operation control means 6 Light source 7,50 Optical branching means 12 Optical directional coupler 13,14 Optical filter

Claims (6)

In an optical fiber strain measuring apparatus that measures strain of an optical fiber using Brillouin scattered light generated in an optical fiber to be measured,
A light source that emits pulsed light;
Light branching means for causing the pulsed light to enter one end of the optical fiber, branching backscattered light emitted from one end of the optical fiber for each wavelength band, and emitting the branched light;
Strain detecting means for measuring the strain by detecting the Brillouin scattered light when the branched light in the wavelength band including the Brillouin scattered light is incident from the light branching means,
Temperature detecting means for measuring the temperature by detecting the Raman scattered light when the branched light in the wavelength band including the Raman scattered light is incident from the light branching means;
An optical fiber strain measuring apparatus comprising: strain measurement data from the strain detection means; temperature control data from the temperature detection means; and calculation control means for compensating the strain measurement data with temperature data. . The light branching means is
An optical directional coupler for causing the pulsed light to enter one end of the optical fiber and branching backscattered light emitted from one end of the optical fiber;
A first optical filter that divides the branched light of the optical directional coupler into two wavelength bands and emits the divided light;
2. The optical fiber strain measuring apparatus according to claim 1, further comprising: a second optical filter that divides one branched light of the first optical filter into two wavelength bands and outputs the divided light. The first optical filter comprises:
Separated into a wavelength band containing anti-Stokes light of the Raman scattered light and a Stokes light of the Raman scattered light and a wavelength band containing the Brillouin scattered light, respectively,
The second optical filter comprises:
3. The optical fiber strain measuring device according to claim 2, wherein the optical fiber strain measuring device emits the light by dividing it into a wavelength band including the Stokes light of the Raman scattered light and a wavelength band including the Brillouin scattered light. The first optical filter comprises:
Dividing into a wavelength band including the Stokes light of the Raman scattered light and an anti-Stokes light of the Raman scattered light and a wavelength band including the Brillouin scattered light, respectively,
The second optical filter comprises:
3. The optical fiber strain measuring apparatus according to claim 2, wherein the optical fiber strain measuring apparatus emits the light by dividing it into a wavelength band including the anti-Stokes light of the Raman scattered light and a wavelength band including the Brillouin scattered light. The first and second optical filters are
5. The optical fiber strain measuring device according to claim 2, wherein the optical fiber strain measuring device is a reflection type, etalon type, or diffraction grating type optical filter. The first and second optical filters are
5. The optical fiber strain measuring apparatus according to claim 2, wherein the optical fiber strain measuring apparatus is a fiber coupler type or a spatial light type optical filter.

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