JP2003156315A - Method and apparatus for measurement of distribution of strain and temperature - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method and an apparatus wherein both the strain and the temperature can be distinguished, so as to be measured over a long distance by a fiber sensing measuring principle, using Brillouin scattering phenomenon. SOLUTION: A strain wavelength dependence coefficient Cε (λ) of a Brillouin scattering and its temperature wavelength coefficient CT (λ) at each of wavelengths λ1 , λ2 ,..., λn in a sensing optical fiber 103 are found in advance, a change in the Brillouin frequency shift at each wavelength of pumping light which is incident on the fiber 103 is found, their measured data λ1 [νB(z)], λ2 [νB(z)],..., λn [νB(z)] are substituted into simultaneous equations having two unknowns regarding the change in the strain and the change in the temperature of the fiber 103 so as to be computed, and a change Δε in the strain and a change ΔT in the temperature generated in each position of the fiber 103 are discriminated respectively so as to be found simultaneously.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention uses an optical fiber as a medium and measures the distribution of physical quantities by capturing changes in the Brillouin scattering phenomenon occurring in the optical fiber. In particular, the physical quantities to be measured are strain and temperature. The present invention relates to a strain and temperature distribution measuring method and apparatus for distinguishing changes and measuring both distributions simultaneously.

[0002]

2. Description of the Related Art Such a measuring method can be applied to an optical fiber sensor or the like for measuring a physical quantity relating to a disturbance factor such as strain or temperature around an optical fiber.

Examples of this application are, for example, (a) maintenance and management of optical communication networks, (b) maintenance and management of large structures such as tunnels and iron bridges, and (c) failure of composite materials used in aircraft and the like. This is a self-diagnosis of defects such as fatigue.

Specifically, by embedding an optical fiber in each of the objects (a) to (c), a function of self-diagnosing a failure such as a failure or fatigue occurring in a material such as a composite material itself is obtained. It can be used as a smart material structure to be added.

In order to measure both temperature and strain distributions in such optical fiber sensing, different sensing systems having different measurement principles are required as shown in FIG.

These sensing systems use an optical pulse tester (OT) to measure Raman scattered light as temperature sensing.
DR: Raman OTDR (R-OT) using Optical Time Domain Reflectometory
DR) 101 and Brillouin OTDR (B-OT) for measuring the amount of frequency shift (called Brillouin frequency shift) of Brillouin scattering in an optical fiber as strain sensing.
DR) 102.

The Raman OTDR 101 and the Brillouin OTDR 102 are the sensing fibers 1 respectively.
03 is connected.

Among them, the Raman OTDR1 will be explained. As a method for measuring the temperature distribution in the optical fiber, a temperature distribution measuring method has been proposed which focuses on the change of the backscattering coefficient of Raman scattered light with temperature. This temperature distribution measuring method includes, for example, the document “Electron. Lett., Vol.21, N.
o.13, pp.569-570, 1985 ”.

In this temperature distribution measuring method, an optical pulse tester (OTDR) is used for measuring Raman scattered light as described above. A delay time occurs after the light pulse is incident on the sensing fiber 103 and before the scattered light is measured.
This delay time corresponds to the distance to the point where scattered light occurs (scattering point). Therefore, by measuring the scattered light and the delay time, it is possible to measure the change in the scattering coefficient of the Raman scattered light at the desired point in the sensing fiber 103, that is, the temperature change. The Raman OTDR method has already been applied to temperature distribution measurement of large structures.

On the other hand, the Brillouin OTDR 102 will be described. A strain sensing system using the sensing fiber 103 includes a sensing fiber 103.
A method of measuring strain and temperature by measuring the frequency shift amount of Brillouin scattered light along the fiber has been proposed.

This method can measure the continuous distribution of strain and temperature by combining with the optical pulse tester OTDR or a similar pulse-continuous optical counter method. For example, the document “J. Lightwave Tecnol., Vol.13, No.7, pp.12
96-1302, 1995 ”. In this method, since the Brillouin frequency shift depends on both strain and temperature, it is impossible to measure them separately.

[0012]

[Problems to be Solved by the Invention] Raman O described above
When the two methods of TDR101 and Brillouin OTDR102 are used, there are the following technical problems.

(1) Since Raman scattering is inelastic scattering, the wavelength of Raman scattered light deviates from the wavelength of incident light. This wavelength change due to Raman scattering is a large value of about 100 nm when the optical fiber is made of silica, so it deviates from the low-loss wavelength range of the optical fiber, and as a result, the propagation loss increases and measurement over a long distance is possible. Can not.

FIG. 15 shows that the range in which strain and temperature can be simultaneously measured is limited. Raman OTDR101 and Brillouin OTDR1 of sensing fiber 3
On the one end side where 02 is connected, there are measurement ranges for both temperature, strain, and distribution, but on the other end side, there is only the strain measurement range, and temperature, strain, and distribution cannot be measured at the same time.

(2) Since the Raman scattering coefficient has a small strain dependency, the strain cannot be measured by the Raman OTDR method.

(3) In the method using Brillouin scattering,
Since the Brillouin frequency shift occurs due to the effects of both strain and temperature, it is impossible to separate and identify both physical quantities with the conventional measurement method. Therefore, temperature measurement by Raman scattering is necessary.

Further, since the system configuration uses both Raman and Brillouin physical phenomena, the device configuration is complicated,
The device price is expensive.

Therefore, the present invention provides a strain and temperature distribution measuring method and apparatus capable of discriminating and measuring both strain and temperature over a long distance only by the fiber sensing measurement principle utilizing the Brillouin scattering phenomenon. The purpose is to do.

[0019]

DISCLOSURE OF THE INVENTION The present invention provides a strain and temperature distribution measuring method for detecting a change in Brillouin scattering phenomenon occurring in a sensing optical fiber to measure a change in a physical quantity to be measured. In advance, the strain wavelength dependence coefficient of the Brillouin scattering for each wavelength and its temperature wavelength coefficient are obtained in advance, and the step of obtaining the change in the Brillouin frequency shift for each wavelength of the pump light incident on the sensing optical fiber, and these measurement data By substituting into the binary simultaneous equations relating to the change in strain and the change in temperature of the sensing optical fiber, the strain change and the temperature change generated at each position of the sensing optical fiber are identified. And a step of simultaneously obtaining the strain and temperature distribution measuring method.

According to the present invention, in the strain and temperature distribution measuring method of the present invention, the two-dimensional simultaneous equation relating to the change in strain and the change in temperature of the optical fiber for sensing has a wavelength of pump light of λ _n and a wavelength dependence. The coefficient is C _ε (λ _n ), the temperature wavelength coefficient is C _T (λ _n ), and the change in Brillouin frequency shift is Δν _B (λ
_n ), the change in strain of the sensing optical fiber is Δε, and the change in temperature of the sensing optical fiber is ΔT,

[Equation 5] Is represented by

According to the present invention, in the strain and temperature distribution measuring method of the present invention, when the total number of wavelengths of pump light is 3 wavelengths or more, a change in strain and a change in temperature generated at each position of the sensing optical fiber. And add and average respectively,
The method has a step of identifying and simultaneously obtaining a change in strain and a change in temperature generated at each position of the sensing optical fiber.

In the strain and temperature distribution measuring method of the present invention described above, the equation for arithmetic mean calculation is a solution obtained by computing a binary simultaneous equation, which is a change in strain of the sensing optical fiber. Let ΔT be the change in temperature of the sensing optical fiber, and let T be the total number of combinations of these Δε and ΔT.

[Equation 6] Is represented by

The present invention provides a strain and temperature distribution measuring apparatus for measuring a change in Brillouin scattering phenomenon occurring in a sensing optical fiber to measure a change in a physical quantity to be measured,
A light source section that outputs light of a plurality of wavelength components, an optical distributor that splits the output light from the light source section into pump light and probe light, and light that modulates either pump light or probe light. A modulator, a light guide means for guiding the light modulated by the optical modulator to a sensing optical fiber, and a Brillouin scattered light having physical information of temperature and strain from the sensing optical fiber, and the light guiding means. The Brillouin frequency shift for each wavelength of the pump light that enters the sensing optical fiber by receiving the Brillouin scattered light guided by the sensor and converting it to an electrical signal, and inputting the electrical signal from this receiver. Each measurement data indicating the 2 is related to the change in strain and the change in temperature of the sensing optical fiber.
The distortion and temperature characteristics are characterized by including a signal processing unit which is calculated by substituting the original simultaneous equations and calculating the change in strain and the change in temperature generated at each position of the sensing optical fiber. It is a distribution measuring device.

According to the present invention, in the above strain and temperature distribution measuring apparatus of the present invention, the signal processing unit sets the wavelength of the pump light to λ.
_n , the wavelength dependence coefficient is C _ε (λ _n ), and the temperature wavelength coefficient is C
_T (λ _n ), the change in Brillouin frequency shift is Δν _B (λ _n ),
Letting Δε be the change in strain of the sensing optical fiber and ΔT be the change in temperature of the sensing optical fiber,

[Equation 7] Is calculated.

According to the present invention, in the strain and temperature distribution measuring apparatus of the present invention, when the total number of pumping light wavelengths is three or more, the signal processing unit detects the strain generated at each position of the sensing optical fiber. The change and the temperature change are arithmetically averaged, respectively, and the change in strain generated at each position of the sensing optical fiber and the change in temperature are identified and simultaneously obtained.

According to the present invention, in the strain and temperature distribution measuring apparatus of the present invention, the signal processing unit changes the strain of the sensing optical fiber by Δε, which is a solution obtained by calculating a binary simultaneous equation. If the temperature change of the sensing optical fiber is ΔT, and the total number of combinations of these Δε and ΔT is N, then

[Equation 8] Is calculated.

According to the present invention, in the strain and temperature distribution measuring apparatus of the present invention, the light source section is capable of continuously varying the wavelength of the light to be output, and outputs light of an arbitrary wavelength at any time by external control. To do.

According to the present invention, in the strain and temperature distribution measuring apparatus of the present invention, the light source section includes a plurality of light sources, and these light sources output lights of different wavelengths.

According to the present invention, in the strain and temperature distribution measuring apparatus of the present invention, the light source unit collects a plurality of light sources and the lights respectively output from these light sources into one optical path, and simultaneously in a single optical path. And a wavelength multiplexer that outputs light of a plurality of wavelengths.

According to the present invention, in the strain and temperature distribution measuring apparatus of the present invention, the light source section guides light having only a single wavelength, out of the lights respectively output from the plurality of light sources, to one optical path. A switch is provided, and the wavelength of light to be output is selected at any time by switching the optical path selection of this optical switch.

According to the present invention, in the above-mentioned strain and temperature distribution measuring apparatus of the present invention, the light receiving section transmits a Brillouin scattered light corresponding to an arbitrary wavelength of the pump light, and a tunable optical bandpass filter, and this wavelength. And a photodetector for converting light transmitted through the variable optical bandpass filter into an electric signal.

According to the present invention, in the strain and temperature distribution measuring apparatus of the present invention, the light receiving section is a wavelength distributor for distributing backscattered light of a plurality of wavelengths guided by a single optical path from the sensing optical fiber. , A plurality of wavelength tunable optical bandpass filters that transmit only the Brillouin scattered light corresponding to an arbitrary wavelength of the pump light for each wavelength distributed by this wavelength splitter, and these wavelength tunable optical bandpass filters are respectively transmitted. And a plurality of photodetectors for converting each light into respective electric signals.

According to the present invention, in the strain and temperature distribution measuring apparatus of the present invention, the signal processing unit extracts an Brillouin beat frequency component from the electric signal output from the light receiving unit, and the electric signal frequency filter. A first arithmetic unit that detects the peak frequency of the maximum intensity of the frequency spectrum from the frequency signal extracted by the signal frequency filter and obtains the value of this peak frequency as a Brillouin frequency, and a pump defined by this first arithmetic unit A data storage unit that stores the data of the Brillouin frequency value for each wavelength, and the above-mentioned calculation is performed using the data stored in this data storage unit, and the change in strain and temperature that occur at each position of the sensing optical fiber are changed. And a second calculation unit for simultaneously identifying and simultaneously obtaining and.

According to the present invention, in the strain and temperature distribution measuring apparatus of the present invention, when the backscattered light of a plurality of wavelengths guided by the single optical path from the sensing optical fiber is distributed, the signal processing unit is provided. Is processed in parallel by the electric signal frequency filter and the first arithmetic unit for each wavelength.

According to the present invention, in the strain and temperature distribution measuring apparatus of the present invention, when the signal processing unit has a plurality of combinations of changes in strain of the sensing optical fiber and changes in temperature of the sensing optical fiber. The calculation unit is configured to perform the arithmetic mean of the strain and the temperature, and the display unit to display the calculation result of the calculation unit as the final measurement result.

[0036]

BEST MODE FOR CARRYING OUT THE INVENTION (1) A first embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 is a block diagram of a strain and temperature distribution measuring apparatus. This strain and temperature distribution measuring device is based on Brillouin
It is a configuration to which Optical Time Domain Analysis (BOTDA) is applied. In the BOTDA method, a pulse pump light having a variable frequency ν and a continuous wave probe light are respectively incident from both ends of the sensing optical fiber 103, and a change in power proportional to the Brillouin gain of the probe light due to the Brillouin scattering phenomenon is changed with time. Is measured as a function of, and the temperature and strain distribution are obtained from the amount of change.

The overall structure of the strain and temperature distribution measuring apparatus will be described. The light source section 1 is connected to an optical distributor 3 via an optical fiber 2-1.

This optical distributor 3 has two optical fibers 2
-2, 2-3 are connected, and the optical circulator 5 is connected to one optical fiber 2-2 via the optical modulator 4. Between the optical modulator 4 and the optical circulator 5,
It is connected by an optical fiber 2-4. The optical modulator 6 is connected to the other optical fiber 2-3.

A sensing optical fiber 103 is connected between the optical circulator 5 and the optical modulator 6 via the optical fibers 2-5 and 2-6. The sensing optical fiber 103 is for detecting actual strain and temperature.

The optical circulator 5 has an optical fiber 2-
A light receiving unit 7 is connected via 7, and a signal processing unit 8 is connected to an output terminal of the light receiving unit 7.

The light source section 1 outputs light of a plurality of wavelength components, and comprises a variable wavelength light source 10 and a wavelength controller power source 11 as shown in FIG.

The variable wavelength light source 10 has a wavelength range of λ _{1 to} λn.
To output the light P by changing the wavelength at, for example, a semiconductor laser (LD) is used. An optical distributor 3 is connected to the wavelength variable light source 2 via an optical fiber 2-1.

The wavelength controller power supply 11 drives the variable wavelength light source 2 and sets the wavelength of the output light P to the wavelength range λ _{1 to} λ.
has a function of a wavelength variable control in n, for example, the center wavelength lambda ₁ to the wavelength of output light _P, λ _2,
..., λn is controlled.

The light distributor 3 distributes the output light P of the light source unit 1 into the pump light P ₁ and the probe light P _2, and is preferably an optical coupler, a beam splitter, a half mirror, or the like. Two optical fibers 2-for pump light P ₁ and probe light P ₂ are provided on the branch output side of the optical distributor 5.
2, 2-3 are connected.

In this embodiment, the optical fiber 2-
2, the pump light P ₁ is guided, and the probe light P ₂ is guided to the optical fibers 2-2 and 2-3. On the contrary, the probe light P ₂ is guided to the optical fiber 2-2 and the optical fiber 2 is guided. -2,
The pump light P ₁ may be guided to 2-3.

The optical modulator 6 modulates the probe light P ₂ to the vicinity Brillouin frequency, i.e. has a function of modulating the frequency of the Puropu light P _2. The optical fiber 2-
When the led probe light P ₂ to 2 modulates the probe light P ₂ to the vicinity of the Brillouin frequency by the optical modulator 4.

This optical modulator 6 has, for example, a wavelength of 1.55 μm.
Brillouin shift frequency ν of quartz optical fiber at m
An example is a waveguide type modulator that uses the electric field effect of _B (= 10 to 11 GHz equivalent) that can be modulated. This optical modulator 6
Alternatively, a modulation element using an acoustic effect, a bulk type modulation element based on both effects, or the like may be used.

The optical circulator 5 has an input port 5-1.
And two output ports 5-2 and 5-3, of which the input port 5-1 has an optical fiber 2-4 for the pump light P _1.
, And the sensing optical fiber 103 is connected to the output port 5-2 via the optical fiber 2-5.
Further, the light receiving unit 7 is connected to the output port 5-3 via the optical fiber 2-7. This optical circulator 5
For example, an optical coupler, a beam splitter, a half mirror, etc. are suitable.

The pump light P ₁ enters the sensing optical fiber 103 from one end and propagates in the sensing optical fiber 103, and the probe light P ₂ enters from the other end and the pump light P ₁ propagates. Propagate in the opposite direction (opposite excitation).

As a result, the sensing optical fiber 10
In 3, the power of the probe light P ₂ is partially transferred to the probe light P ₂ via the SBS phenomenon generated by the pump light P ₁ .
From the perspective of this probe light P ₂ , it behaves as propagating light due to Brillouin amplification.

Probe light P having this SBS information
₂ again enters the output port 5-2 of the optical circulator 5, propagates from the output port 5-2 through the output port 5-3 and the optical fiber 2-7, and enters the light receiving unit 7.

The light receiving section 7 has a function of receiving the Brillouin scattered light of the probe light P ₂ propagating through the optical fiber 2-7 and converting it into an electric signal, and as shown in FIG. It includes a pass filter 12 and a photodetector 13.

The wavelength tunable optical bandpass filter 12 has a function of transmitting only the Brillouin scattered light corresponding to the arbitrary wavelengths λ ₁ , λ ₂ , ..., λn of the pump light P ₁ , and for example, the light source section 1 0.0 than the wavelength λn of the output light P
8 to 0.1 nm (This value is 1.
(In the case of 55 μm), it has a function of extracting only the wavelength of Brillouin scattered light detuned.

The photodetector 13 has a function of converting the light transmitted through the variable wavelength optical bandpass filter 12 into an electric signal.

The signal processing unit 8 receives the electric signal from the light receiving unit 7 and performs Brillouin frequency shift for each wavelength λ ₁ , λ ₂ , ..., λn of the pump light P ₁ incident on the sensing optical fiber 103. Each measurement data indicating the change is substituted into a binary simultaneous equation concerning the change in strain and the change in temperature of the sensing optical fiber 103, and the calculated data is calculated, and the change in strain generated at each position of the sensing optical fiber 103 and the temperature It has a function of identifying changes and requesting them at the same time.

The signal processor 8 has a wavelength of the pump light P ₁ of λn, a wavelength dependence coefficient of C _ε (λn), and a temperature wavelength coefficient of C n.
_T (λn), the change of Brillouin frequency shift is Δν _B (λ
n), the change in strain of the sensing optical fiber 103 is Δ
ε, the temperature change of the sensing optical fiber 103 is ΔT
Then, the following binary simultaneous equations,

[Equation 9] And a change Δε in strain and a change ΔT in temperature generated at each position of the sensing optical fiber 103 are identified and simultaneously obtained.

FIG. 4 shows the relationship between the physical quantity of strain and temperature at an arbitrary wavelength and the Brillouin frequency shift. The change in the Brillouin frequency shift, Δν _B , increases proportionally to the change in strain Δε and the change in temperature ΔT.

When the total number of wavelengths of the pump light P ₁ is 3 wavelengths or more, the signal processor 8 detects the optical fiber 1 for sensing.
03, the change in strain and the change in temperature generated at each position are arithmetically averaged to obtain the sensing optical fiber 10
3 has a function of discriminating a change in strain generated at each position and a change in temperature, and simultaneously obtaining the same.

The signal processing unit 8 calculates the change in strain of the sensing optical fiber 103, which is a solution obtained by calculating the above-mentioned simultaneous equations (equation (1)), by Δε, and the temperature of the sensing optical fiber 103. Let ΔT be the change in Δ, and let N be the total number of combinations of these Δε and ΔT.

[Equation 10] Is calculated and the change in strain and the change in temperature generated at each position of the sensing optical fiber 103 when the total number of wavelengths of the pump light P ₁ is 3 wavelengths or more are respectively identified and simultaneously obtained.

Specifically, the signal processor 8 includes an electric signal frequency filter 14 and an A / D converter 15 as shown in FIG.
A first arithmetic unit 16, a data storage unit 17, a second arithmetic unit (hereinafter referred to as a separation arithmetic unit) 18, a total wavelength determination unit 19, an arithmetic mean arithmetic unit 20, and a display unit 21. And have.

The electric signal frequency filter 14 includes the light receiving portion 7
It has a function of reducing noise and the like of the electric signal output from the.

The A / D converter 15 has a function of converting the noise-reduced analog signal transmitted through the electric signal frequency filter 14 into a digital signal.

The first arithmetic unit 16 has a digital signal waveform of each modulation frequency ν of the optical modulator 6 which has passed through the electric signal frequency filter 14 and the A / D converter 15, that is, this digital signal waveform is the optical signal of the optical modulator 6. It is waveform data in which three parameters (three-dimensional) of the modulation frequency ν, the waveform time t, and the waveform intensity I are related. Brillouin frequency ν _B
To detect as. Then, the Brillouin frequency distribution (two-dimensional) ν _B (t) in the time domain is obtained by performing the process of obtaining the Brillouin frequency over the entire waveform time. That is, since the time domain and the distance domain are equivalent, as a result, it has a function of obtaining the Brillouin frequency distribution ν _B (z) at each distance. Again, the role and action of the first calculation unit 16 are as described above.

The data storage unit 17 includes the first calculation unit 16
Wavelength lambda ₁ of the pump light _{P 1} detected by, λ _2, ...,
Brillouin frequency value data (measurement data of Brillouin frequency distribution) for each λn is stored. These measurement data are, for example, the data λ ₁ [ν of the peak frequency ν _B
B (z)], λ ₂ [ν _B (z)], ..., λn [ν _B (z)]. The data storage unit 17 stores the measurement data λ ₁ [ν
_B (z)], λ ₂ [ν _B (z)], ..., λn [ν _B (z)] can be written and read.

The separation / calculation unit 18 measures the measurement data λ ₁ [ν _B (z)] and λ ₂ [ν stored in the data storage unit 17.
_B (z)], ..., λn [ν _B (z)] is used to calculate the change in strain Δε and the change in temperature ΔT of the strain generated at each position of the sensing optical fiber 103. Has a function of identifying each of them and simultaneously obtaining them.

Here, the method using Brillouin scattering, which is the basic principle of the present invention, causes the frequency component of the scattered light to change due to the influence of the disturbance factors (physical quantity to be measured) “distortion” and “temperature”. Amount of change (Brillouin frequency shift)
Is measured and the measured physical quantity is calculated from the measured value. The relation of Brillouin frequency ν _B in the light wave of wavelength λ is

[Equation 11] Is represented by

Here, n is the sensing optical fiber 10.
Refractive index of 3, λ is the light in the sensing optical fiber 103
Is the wavelength of. v_aOf the sensing optical fiber 103
Is the speed of sound, and is the temperature around the sensing optical fiber 103.
Sound velocity ν when degree and distortion change _aChanges and the final result
From the relation of the above equation (3), the Brillouin frequency ν_BBut
Change.

Incidentally, this sound velocity ν _A is a value obtained depending on the physical property value unique to the sensing optical fiber 103 in the surrounding environment, and is given by the Young's modulus, Poisson's ratio, and density of the sensing optical fiber 103.

The above formula (3) is specifically expressed by a wavelength of 1.55 μm.
The calculation coefficient C _T (λ) and C _ε (λ) for the temperature and strain of the Brillouin frequency ν _B of the UV (ultraviolet) coated single mode quartz fiber in the following equations (4) and (5) are respectively obtained. Is known to be.

[0071]

[Equation 12]

Another wavelength λ = 1.3 μ in the same optical communication band
Similar coefficients described above for m are expressed by the following equations (6) and (7).

[0073]

[Equation 13]

As described above, each coefficient of temperature and strain has wavelength dependence, and can be treated as a coefficient unique to each wavelength.

The separation calculation section 18 uses the equation (1),
According to (2), both the measured physical quantity of the strain change Δε and the temperature change ΔT are calculated from the measured value of the Brillouin frequency shift obtained by the actual measurement, and therefore the above equations (4)- Calculation coefficient value C as in (7)
_T (λ) and C _ε (λ) are converted into data as calculation parameters and prepared as existing values.

FIG. 6 shows the wavelength dependence of each physical quantity change coefficient. From the figure, changes in the temperature change coefficient (calculation coefficient value) C _T (λ) and the strain change coefficient (calculation coefficient value) C _ε (λ) with respect to the wavelength λ can be seen.

The total wavelength determining unit 19 determines the wavelength λ of the light source unit 1.
_It has a function of determining whether or not the total number of ₁ , ₁ , λ ₂ , ..., λn is, for example, 3 or more (n ≧ 3).

The averaging unit 20 calculates the wavelength λ of the light source unit 1.
_When the total number of ₁ , λ ₂ , ..., λn is, for example, 3 or more (n ≧ 3), the arithmetic mean of the respective values of the strain change Δε and the temperature change ΔT obtained by the calculation of the separation calculation unit 18 is calculated. Have the function to do.

More specifically, the averaging unit 20 calculates the change in strain of the sensing optical fiber 103, which is a solution obtained by computing the above simultaneous binary equations (equation (1)), Δε, and the sensing optical fiber. The temperature change of 103 is ΔT, and these Δ
When the total number of combinations of ε and ΔT is N, the above equation (2) is calculated to change the strain generated at each position of the sensing optical fiber 103 when the total number of wavelengths of the pump light P ₁ is 3 wavelengths or more. And the change in temperature are identified and simultaneously determined.

The display unit 21 displays the strain change Δε and the temperature change ΔT calculated by the separation calculation unit 18, or the strain change Δε and the temperature change calculated by averaging by the arithmetic mean calculation unit 20. Display and output ΔT.

Next, the operation of the apparatus configured as described above will be described.

From the light source unit 1, wavelengths λ ₁ , λ ₂ , ..., λ
n lights are output. The output light P is distributed by the light distributor 3 into the pump light P ₁ and the probe light P ₂ .

Of these, the pump light P ₁ propagates from the optical modulator 4 through the optical circulator 5 and enters the sensing optical fiber 103.

Probe light P_TwoEnters the light modulator 6
It This optical modulator 6 uses the probe light P _TwoBrillouin Zhou
Modulates up to near wave number, that is, the probe light P_TwoFrequency
Modulate a number. This modulated probe light P_TwoIs Sen
It is incident on the optical fiber 103 for singing.

In this sensing optical fiber 103,
The pump light P ₁ enters from one end and propagates in the sensing optical fiber 103, and the probe light P ₂ enters from the other end and propagates in a direction opposite to the propagation direction of the pump light P ₁ (opposite excitation). To do.

As a result, the sensing optical fiber 10
In 3, the power of the probe light P ₂ is partially transferred to the probe light P ₂ via the SBS phenomenon generated by the pump light P ₁ .
From the perspective of this probe light P ₂ , it behaves as propagating light due to Brillouin amplification.

Probe light P having this SBS information
₂ again enters the output port 5-2 of the optical circulator 5, propagates from the output port 5-2 through the output port 5-3 and the optical fiber 2-7, and enters the light receiving unit 7.

As a result, the sensing optical fiber 10
3, the pump light P from one end₁Incident and the same sensing
Propagating in the optical fiber 103 for use and a probe from the other end
Light P _TwoIs incident on the pump light P₁Opposite to the propagation direction of
Propagate (opposite excitation).

In the sensing optical fiber 103, a part of its power is transferred to the probe light P ₂ via the SBS phenomenon generated by the pump light P ₁ . From the perspective of this probe light P ₂ , it behaves as propagating light due to Brillouin amplification.

Probe light P having this SBS information
₂ again enters the output port 5-2 of the optical circulator 5, propagates from the output port 5-2 through the output port 5-3 and the optical fiber 2-7, and enters the light receiving unit 7.

The light receiving section 7 causes the Brillouin scattered light of the probe light P ₂ propagating through the optical fiber 2-7 to enter the wavelength tunable optical bandpass filter 12 as shown in FIG.

This wavelength tunable optical bandpass filter 12
Transmits only the Brillouin scattered light corresponding to the arbitrary wavelengths λ ₁ , λ ₂ , ..., λn of the pump light P ₁ . For example, the wavelength of the output light P of the light source unit 1 is 0.08 to 0.1
Only the Brillouin scattered light wavelength detuned by m (this value is a quartz fiber having a wavelength of 1.55 μm) is extracted and incident on the photodetector 13.

The photodetector 13 converts the light having only the wavelength of the Brillouin scattered light transmitted through the variable wavelength optical bandpass filter 12 into an electric signal. This electric signal is sent to the signal processing unit 8.

The signal processing section 8 sends the electric signal sent from the light receiving section 7 to the electric signal frequency filter 14.
The electric signal frequency filter 14 reduces noise and the like of the electric signal output from the light receiving unit 7.

Next, the A / D converter 15 converts the noise-reduced analog signal transmitted through the electric signal frequency filter 14 into a digital signal.

Next, the first calculation unit 16 passes through the electric signal frequency filter 14 and the A / D converter 15 and the optical modulator 6
Of each modulation frequency ν, that is, this digital signal waveform is the modulation frequency ν of the optical modulator 6 and the waveform time t.
And waveform strength I are three parameters (three-dimensional) related to each other, and the frequency value (peak frequency) at which the strength is maximized when the waveform data is viewed from the relationship between the frequency and the waveform strength at each time from the waveform data. Value) is detected as the Brillouin frequency ν _B. The Brillouin frequency distribution (two-dimensional) ν _B (t) in the time domain is obtained by performing the process of obtaining the Brillouin frequency over the entire waveform time.
Is required. That is, since the time domain and the distance domain are equivalent, as a result, the Brillouin frequency distribution ν at each distance is
_B (z) is obtained.

The data storage unit 17 includes the first arithmetic unit 16
Wavelength lambda ₁ of the pump light _{P 1} detected by, λ _2, ...,
The measurement data of the Brillouin frequency distribution for each λn is stored. These data are, for example, measurement data λ ₁ [ν _B (z)], λ ₂ [ν _B (z)], ..., λn [ν of the peak frequency ν _B.
B (z)]. In FIG. 7, each wavelength λ ₁ , λ ₂ , ..., λn
The measurement data of the Brillouin frequency distribution for each is shown.

Next, the demultiplexing operation unit 18 is connected to the data storage unit 1
Measurement data λ stored in 7₁[Ν _B(z)], λ_Two[Ν
_B(z)], ..., λn [ν_B(z)] and read these measurements
Data λ₁[Ν_B(z)], λ_Two[Ν_B(z)], ..., λn
[Ν_B(z)] is used to calculate the above equation (1) and
Of the distortion generated at each position of the optical fiber 103 for
Separate the change Δε and the temperature change ΔT from each other at the same time.
Ask.

The separation calculation unit 18 uses the above equation (1),
According to (2), both the measured physical quantity of the strain change Δε and the temperature change ΔT are calculated from the measured value of the Brillouin frequency shift obtained by the actual measurement, and therefore the above equations (4)- Calculation coefficient value C as in (7)
_T (λ) and C _ε (λ) are converted into data as calculation parameters and prepared as existing values.

Next, the total wavelength determining unit 19 determines that the total number of wavelengths λ ₁ , λ ₂ , ..., λn of the light source unit 1 is, for example, 3 or more (n ≧ 1).
It is determined whether or not 3).

As a result of this judgment, the wavelengths λ ₁ and λ of the light source unit 1 are
_If the total number of ₂ , ..., λn is 3 or less, for example, the display unit 2
As shown in FIG. 7, 1 displays and outputs the strain change Δε and the temperature change ΔT obtained by the calculation of the separation calculation unit 18.

However, the wavelengths λ ₁ , λ _{2 of} the light source unit 1,
If the total number of λn is, for example, 3 or more (n ≧ 3), the averaging calculation unit 20 is a solution obtained by calculating the above simultaneous binary equations (equation (1)). 10
The change in strain of 3 is Δε, the sensing optical fiber 103
The temperature change of ΔT, the total number of combinations of these Δε and ΔT is N, the arithmetic mean of the respective values of the strain change Δε and the temperature change ΔT, that is, the above formula (2) is calculated to calculate the pump light P ₁ When the total number of wavelengths is 3 or more, the change in strain generated at each position of the sensing optical fiber 103 and the change in temperature are identified and simultaneously obtained.

Next, the display unit 21 outputs the change Δε in strain and the change ΔT in temperature, which are obtained by adding and averaging by the adding and averaging unit 20, as shown in FIG.

As described above, in the first embodiment, the distortion wavelength dependence coefficient C _ε (λ) of Brillouin scattering for each wavelength λ ₁ , λ ₂ , ..., λn in the sensing optical fiber 103 and its temperature. The wavelength coefficient C _T (λ) is obtained in advance, the change of the Brillouin frequency shift for each wavelength of the pump light incident on the sensing optical fiber 103 is obtained, and these measurement data λ ₁ [ν _B (z)], λ ₂ [ν
_B (z)], ..., λn [ν _B (z)] is substituted into a binary simultaneous equation relating to a change in strain and a change in temperature of the sensing optical fiber 103, and calculation is performed to calculate the sensing optical fiber 103. Since the change Δε in strain generated at each position and the change ΔT in temperature are identified and obtained simultaneously, both the strain and temperature can be measured over a long distance using only the fiber sensing measurement principle that utilizes the Brillouin scattering phenomenon. Differentiate and measure simultaneously. Further, the device structure is simple, and the device price can be fixed.

When the total number of pump light wavelengths is 3 or more, the strain change Δε and the temperature change ΔT generated at each position of the sensing optical fiber 103 are arithmetically averaged to obtain the sensing light. Since the strain change Δε and the temperature change ΔT generated at each position of the fiber 103 are respectively identified and simultaneously obtained, the sensing optical fiber 1
03 strain change Δε and temperature change Δ
Both T and T can be separated and identified, and both physical quantities can be displayed simultaneously with high accuracy.

Furthermore, by using Brillouin scattered light whose wavelength shift amount is much smaller than that of Raman scattering, it is possible to measure only within the range of 1.3 to 1.55 μm of the low loss wavelength band of the optical fiber, and it is possible to measure further. The measurement range can be expanded up to.

Distortion and temperature are distinguished and simultaneous distribution measurement is performed by solving simultaneous equations using strain wavelength dependence coefficient and temperature wavelength dependence coefficient among Brillouin scattering coefficients and parameters of respective Brillouin frequency shift amount at two or more wavelengths. it can.

Moreover, the accuracy of measurement of strain and temperature can be improved by averaging a plurality of solutions of strain and temperature of simultaneous equations using respective parameters relating to that of three or more wavelengths.

Therefore, an optical fiber sensor or the like for measuring a physical quantity relating to a disturbance factor such as strain or temperature around the optical fiber is installed, for example, (a) maintenance of an optical communication network, (b) tunnel or iron bridge, etc. Maintenance of large structures in
(C) It is most suitable for self-diagnosis of failures such as failure and fatigue of composite materials used in aircraft and the like.

(2) Next, a second embodiment of the present invention will be described with reference to the drawings. The same parts as those in FIG. 1 are designated by the same reference numerals, and detailed description thereof will be omitted.

FIG. 8 is a block diagram of a strain and temperature distribution measuring apparatus. This strain and temperature distribution measuring device is based on Brillouin
This is a configuration to which Optical Time Domain Reflectometory (BOTDR) is applied. In this BOTDR method, only the pump pulse light is incident from the measured fiber and measured as a time function (positional function on the fiber) of the Brillouin gain spectrum g _B (ν) of the backscattered light component power due to the natural Brillouin scattering phenomenon, The distribution of temperature and strain is obtained from the amount of change.

The overall configuration of the strain and temperature distribution measuring apparatus will be described. The light source section 1 is connected to the optical distributor 3 via the optical fiber 2-1. Two optical fibers 2-2 and 2-3 are connected in parallel to this optical distributor 3, and an optical circulator 5 is connected to one optical fiber 2-2 via an optical modulator 4. And this optical circulator 5
The sensing optical fiber 103 is connected to the output port 5-2 of the.

An optical multiplexer 22 is connected to the other optical fiber 2-3 of the optical distributor 3 via an optical modulator 6. The output port 5-3 of the optical circulator 5 is connected to the optical multiplexer 22 via an optical fiber 2-7.

Therefore, when the pump light P ₁ is incident on the sensing optical fiber 103, the sensing optical fiber 1
In 03, backscattered light including natural Brillouin scattered light and Rayleigh scattered light is generated by the pump light P ₁ . This backscattered light is output to the output port 5 of the optical circulator 5 again.
-2, propagates through the optical fibers 2-7 from the output ports 5-2, 5-3, and is guided to the optical multiplexer 22.

The optical multiplexer 22 multiplexes the probe light P ₂ from the optical distributor 3 and the backscattered light from the sensing optical fiber 103.

The light multiplexed by the optical multiplexer 22 is
It is sent to the light receiving unit 7. The signal processing unit 8 is connected to the light receiving unit 7.

Next, the operation of the apparatus configured as described above will be described.

From the light source unit 1, wavelengths λ ₁ , λ ₂ , ..., λ
n lights are output. The output light P is distributed by the light distributor 3 into the pump light P ₁ and the probe light P ₂ .

Of these, the pump light P ₁ propagates through the optical circulator 5 and enters the sensing optical fiber 103.

When the pump light P ₁ enters the sensing optical fiber 103, the sensing optical fiber 103
In the inside, backscattered light including natural Brillouin scattered light and Rayleigh scattered light is generated by the pump light P ₁ . This backscattered light is output to the output port 5-2 of the optical circulator 5 again.
To the optical multiplexer 22 through the optical fibers 2-7 from the output ports 5-2 and 5-3.

On the other hand, the probe light P ₂ is modulated by the optical modulator 6 up to near the Brillouin frequency. That is, the frequency of the probe light P ₂ is modulated. The modulated probe light P ₂ is guided to the optical multiplexer 22.

The optical multiplexer 22 multiplexes the probe light P ₂ from the optical distributor 3 and the backscattered light from the sensing optical fiber 103, and sends the combined light to the light receiving section 7.

Hereinafter, as in the first embodiment, the light receiving section 7 receives the combined light from the optical multiplexer 22 and converts it into an electric signal.

The signal processing unit 8 receives the electric signal from the light receiving unit 7 and performs Brillouin frequency shift for each wavelength λ ₁ , λ ₂ , ..., λn of the pump light P ₁ incident on the sensing optical fiber 103. Each measurement data showing change λ ₁ [ν _B
(z)], λ ₂ [ν _B (z)], ..., λn [ν _B (z)] are _binary elements of the above equation (1) relating to changes in strain and temperature of the sensing optical fiber 103. Substituting into the simultaneous equations for calculation, the change Δε in strain generated at each position of the sensing optical fiber 103 and the change ΔT in temperature are identified and simultaneously determined.

When the total number of wavelengths of the pump light P ₁ is 3 wavelengths or more, the signal processor 8 detects the optical fiber 1 for sensing.
03 strain change Δε and temperature change Δ
T and T are respectively calculated by addition and averaging using the above equation (2), and a change Δε in strain generated at each position of the sensing optical fiber 103 and a change ΔT in temperature are respectively identified and simultaneously obtained.

The display unit 21 displays the strain change Δε and the temperature change ΔT obtained by the calculation of the separation calculation unit 18, or the strain change Δε and the temperature change obtained by the averaging by the arithmetic mean calculation unit 20. Display and output ΔT.

As described above, according to the second embodiment, even if the BOTDR method is applied, both strain and temperature can be distinguished and measured simultaneously over a long distance. Further, the device structure is simple, and the device price can be fixed.

Further, when the total number of wavelengths of the pump light is three or more wavelengths, the change Δε of strain generated at each position of the sensing optical fiber 103 and the change ΔT of temperature are respectively calculated by averaging, so that the sensing light is used. The change Δε of strain and the change ΔT of temperature generated at each position of the fiber 103 can be separated and identified, and both physical quantities can be simultaneously displayed with high accuracy.

Furthermore, by using Brillouin scattered light whose wavelength shift amount is much smaller than that of Raman scattering, it is possible to measure only within the range of 1.3 to 1.55 μm in the low loss wavelength band of the optical fiber, and it is possible to measure further. The measurement range can be expanded up to.

Distortion and temperature are distinguished and simultaneous distribution measurement is performed by solving simultaneous equations using strain wavelength dependence coefficient and temperature wavelength dependence coefficient among Brillouin scattering coefficients and parameters of respective Brillouin frequency shift amounts at two or more wavelengths. it can.

In addition, the accuracy of measurement of strain and temperature can be improved by averaging a plurality of solutions of the strain and temperature of the simultaneous equations using the respective parameters related to that of three wavelengths or more.

(3) Next, a third embodiment of the present invention will be described with reference to the drawings.

In the third embodiment, the configurations of each light source unit 1, each light receiving unit 7 and each signal processing unit 8 in the strain and temperature distribution measuring apparatus shown in FIGS. 1 and 8 are changed. is there.

FIG. 9 is a block diagram of the light source unit 1. The light source unit 1 is provided with a plurality of light sources 30-1 to 30-n. The light sources 30-1 to 30-n have different oscillation wavelengths λ ₁ , λ ₂ , ..., λn. Each of the light sources 30-1 to 30-n includes an optical fiber 3
It is connected in parallel to the wavelength multiplexer 32 via 1-1 to 31-n.

The light source controller 33 is arranged so that each light source 30-1
.About.30-n independently of the individual wavelengths λ ₁ , λ ₂ ,
..., and to stabilize the lambda] n, and outputs their respective light _P 1 to PN, made of n-channel for driving and controlling the light sources 30-1 to 30-n.

FIG. 10 is a block diagram of the light receiving section 7. The light receiving unit 7 receives, for example, the wavelength-division-multiplexed Brillouin scattered light from the optical multiplexer 22 shown in FIG. 8, and the Brillouin scattered light is divided by the number of wavelengths λ ₁ , λ ₂ , ... ).

The wavelength divider 34 includes the same number of optical bandpass filters 35-1 to 35-n as the number of wavelengths λ ₁ , λ ₂ , ..., λn of the output lights P _{1 to} Pn of the light source section 1. Are provided in parallel. These optical bandpass filters 35-1
~ 35-n are the respective wavelengths λ of the pump light P _1.
It has an effect of transmitting only Brillouin scattered light corresponding to ₁ , λ ₂ , ..., λn.

The optical receivers 36-1 to 36-n are provided corresponding to the respective optical bandpass filters 35-1 to 35-n. Each of the optical receivers 36-1 to 36-n has a function of converting each light transmitted through each optical bandpass filter 35-1 to 35-n into each electric signal.

FIG. 11 is a block diagram of the signal processor 8. Na
It should be noted that the same parts as those in FIG.
The description is omitted. The signal processing unit 8 uses the electric signal frequency
The filter 37, the A / D converter 38, and the first arithmetic unit 39
Output light P of each light source unit 1 ₁~ Each wavelength λ of Pn₁, Λ
_Two, ..., Parallel processing by the same number of channels n as λn.
It makes sense.

Of these, the electric signal frequency filter 37 is
It has a function of reducing noise and the like of each of the n-channel electric signals output from the light receiving unit 7.

The A / D converter 38 has a function of converting each noise-reduced analog signal transmitted through the n-channel electric signal frequency filter 37 into a digital signal.

The first arithmetic unit 39 calculates the digital signal waveform of each modulation frequency ν of the optical modulator 6 that has passed through the n-channel electric signal frequency filter 37 and the A / D converter 38, that is, this digital signal waveform. It is waveform data in which three parameters (three-dimensional) of the modulation frequency ν of the optical modulator 6, the waveform time t, and the waveform intensity I are related. The frequency value (peak frequency value) at which the intensity is maximized is detected as the Brillouin frequency ν _B. Then, the Brillouin frequency distribution (two-dimensional) ν _B (t) in the time domain is obtained by performing the process of obtaining the Brillouin frequency over the entire waveform time. That is, since the time domain and the distance domain are equivalent, as a result, it has a function of obtaining the Brillouin frequency distribution ν _B (z) at each distance.

Next, the operation of the apparatus configured as described above will be described.

As shown in FIG. 9, the light source unit 1 has a plurality of light sources 30-1 to 30-n which have different oscillation wavelengths λ ₁ , respectively.
The lights P _{1 to} Pn of λ ₂ , ..., λn are output. These lights P _{1 to} Pn are multiplexed by the wavelength multiplexer 32 and propagated to the optical distributor 3.

By the way, the Brillouin scattered light from the sensing optical fiber 103, regardless of whether the device using the BOTDA method shown in FIG. 1 or the BOTDR method shown in FIG. Each oscillation wavelength λ of n
_The wavelength-division-multiplexed Brillouin scattered light corresponding to ₁ , λ ₂ , ..., λn.

As shown in FIG. 10, the light receiving section 7 is an optical multiplexer.
Injecting wavelength-division-multiplexed Brillouin scattered light from 22,
Each wavelength of the Brillouin scattered light is determined by the wavelength distributor 34.
λ₁, Λ _Two, ..., λn (n) are distributed.

These n distributed Brillouin scattered lights are respectively passed through the bandpass filters 35-1 to 35-35.
incident on n. Bandpass filters 35-1 to 35-3
5-n, each arbitrary wavelength λ ₁ , λ ₂ , of the pump light P ₁ ,
..., only Brillouin scattered light corresponding to λn is transmitted.

Each of the optical receivers 36-1 to 36-n supplies the light corresponding to each of the wavelengths λ ₁ , λ ₂ , ..., λn transmitted through each of the optical bandpass filters 35-1 to 35-n to each of the electrical receivers. Convert to signal.

Next, the signal processing section 8 outputs the output light P _{1 to} Pn of the light source section 1 in the electric signal frequency filter 37, the A / D converter 38 and the first calculating section 39 as shown in FIG.
, Λn of the respective wavelengths λ ₁ , λ ₂ , ...

Of these, the electric signal frequency filter 37 is
It has a function of reducing noise and the like of each of the n-channel electric signals output from the light receiving unit 7.

The A / D converter 38 has a function of converting each noise-reduced analog signal transmitted through the n-channel electric signal frequency filter 37 into a digital signal.

The first arithmetic unit 39 calculates the digital signal waveform of each modulation frequency ν of the optical modulator 6 that has passed through the n-channel electric signal frequency filter 37 and the A / D converter 38, that is, this digital signal waveform. It is waveform data in which three parameters (three-dimensional) of the modulation frequency ν of the optical modulator 6, the waveform time t, and the waveform intensity I are related. The frequency value (peak frequency value) at which the intensity is maximized is detected as the Brillouin frequency ν _B. Then, the Brillouin frequency distribution (two-dimensional) ν _B (t) in the time domain is obtained by performing the process of obtaining the Brillouin frequency over the entire waveform time. That is, since the time domain and the distance domain are equivalent, the Brillouin frequency distribution ν _B (z) at each distance is obtained as a result.

Hereinafter, similar to the above-described first embodiment, the data storage unit 17 stores, for each wavelength λ ₁ , λ ₂ , ..., λn of the pump light P ₁ detected by the first arithmetic unit 39. Brillouin frequency distribution measurement data λ ₁ [ν _B (z)], λ
₂ [ν _B (z)], ..., λn [ν _B (z)] are stored.

Next, the demultiplexing operation unit 18 is connected to the data storage unit 1
Measurement data λ stored in 7₁[Ν _B(z)], λ_Two[Ν
_B(z)], ..., λn [ν_B(z)] and read these measurements
Data λ₁[Ν_B(z)], λ_Two[Ν_B(z)], ..., λn
[Ν_B(z)] is used to calculate the above equation (1) and
Of the distortion generated at each position of the optical fiber 103 for
Separate the change Δε and the temperature change ΔT from each other at the same time.
Ask.

Next, the total wavelength determining unit 19 determines that the total number of wavelengths λ ₁ , λ ₂ , ..., λn of the light source unit 1 is, for example, 3 or more (n ≧ 1).
3) is determined, and as a result of this determination, the light source unit 1
If the total number of wavelengths λ ₁ , λ ₂ , ..., λn is 3 or less, the display unit 21 displays the separation calculation unit 18 as shown in FIG.
Strain change Δε and temperature change Δ
Display and output T.

If the total number of wavelengths λ ₁ , λ ₂ , ..., λn of the light source unit 1 is, for example, 3 or more (n ≧ 3), the averaging arithmetic unit 20 causes the binary simultaneous equations (Equation (1)) The change in strain of the sensing optical fiber 103, which is the solution obtained by computing the above, is Δε, the change in temperature of the sensing optical fiber 103 is ΔT, and the total number of combinations of these Δε and ΔT is N. The arithmetic mean of the respective values of the temperature change ΔT and the temperature change ΔT is calculated by calculating the above formula (2), and the change of the strain generated at each position of the sensing optical fiber 103 and the change of the temperature are identified and simultaneously. Ask.

Next, as shown in FIG. 7, the display unit 21 displays and outputs the change Δε in strain and the change ΔT in temperature which are obtained by the averaging by the arithmetic mean calculator 20.

As described above, according to the third embodiment, it is needless to say that the same effect as that of the first embodiment can be obtained, and further, a plurality of light sources 30-1 to 30 having different wavelengths are used. By arranging -n in parallel and configuring the light-receiving unit 7 and the signal processing unit 8 corresponding thereto in parallel, it is possible to measure at higher speed and shorten the measurement time.

(4) Next, a fourth embodiment of the present invention will be described with reference to the drawings.

In the fourth embodiment, the configurations of each light source unit 1, each light receiving unit 7 and each signal processing unit 8 in the strain and temperature distribution measuring apparatus shown in FIGS. 1 and 8 are changed. is there.

The light source unit 1 has the same structure as the light source unit 1 shown in FIG. 9 described in the third embodiment, and has a plurality of light sources 30-1 to 30-n and respective light sources as shown in FIG. Fiber 3
1-1 to 31-n, a wavelength multiplexer 32, and a light source controller 33.

The light receiving section 7 has the same structure as the light receiving section 7 shown in FIG. 3 described in the first embodiment, and as shown in FIG. 13, the variable wavelength optical bandpass filter 12 and the photodetector 1 are used.
3 and 3.

The signal processing unit 8 has the same configuration as that of the signal processing unit 8 shown in FIG. 5 described in the first embodiment and has the same configuration as that shown in FIG.
As shown in FIG. 1, the electric signal frequency filter 14, the A / D converter 15, the first arithmetic unit 16, and the data storage unit 17
And a second calculation unit (separation calculation unit) 18, a wavelength total number determination unit 19, an arithmetic mean calculation unit 20, and a display unit 21.

With such a configuration, the light source section 1 has the respective light beams P having different oscillation wavelengths λ ₁ , λ ₂ , ..., λn from the plurality of light sources 30-1 to 30-n as shown in FIG. ₁
~ Pn is output. These lights P _{1 to} Pn are multiplexed by the wavelength multiplexer 32 and propagated to the optical distributor 3.

By the way, in any of the devices to which the BOTDA method shown in FIG. 1 or the BOTDR method shown in FIG. 8 is applied, the Brillouin scattered light from the sensing optical fiber 103 has a plurality of light sources 30-1 to 30-. Each oscillation wavelength λ of n
_The wavelength-division-multiplexed Brillouin scattered light corresponding to ₁ , λ ₂ , ..., λn.

Hereinafter, as in the first embodiment, the light receiving section 7 receives the combined light from the optical multiplexer 22 and converts it into an electric signal.

The signal processing unit 8 receives the electric signal from the light receiving unit 7 and performs Brillouin frequency shift for each wavelength λ ₁ , λ ₂ , ..., λn of the pump light P ₁ incident on the sensing optical fiber 103. Each measurement data showing change λ ₁ [ν _B
(z)], λ ₂ [ν _B (z)], ..., λn [ν _B (z)] are _binary elements of the above equation (1) relating to changes in strain and temperature of the sensing optical fiber 103. Substituting into the simultaneous equations for calculation, the change Δε in strain generated at each position of the sensing optical fiber 103 and the change ΔT in temperature are identified and simultaneously determined.

If the total number of wavelengths of the pump light P ₁ is 3 or more, the signal processing section 8 detects the optical fiber 1 for sensing.
03 strain change Δε and temperature change Δ
T and T are respectively calculated by addition and averaging using the above equation (2), and a change Δε in strain generated at each position of the sensing optical fiber 103 and a change ΔT in temperature are respectively identified and simultaneously obtained.

The display unit 21 displays the strain change Δε and the temperature change ΔT obtained by the calculation of the separation calculation unit 18, or the strain change Δε and the temperature change obtained by the averaging by the arithmetic mean calculation unit 20. Display and output ΔT.

As described above, according to the fourth embodiment, it is needless to say that the same effect as that of the first embodiment can be obtained, and further, a plurality of light sources 30-1 to 30 having different wavelengths are used. By arranging -n in parallel,
High-speed measurement is possible and measurement time can be shortened.

Further, a plurality of light sources 30-1 to 30-3 having different wavelengths are used.
The light receiving unit 7 and the signal processing unit 8 are arranged while 0-n are arranged in parallel.
By serially configuring the devices, the entire system becomes cheaper by simplifying the device configuration.

The present invention is not limited to the above-described first to fourth embodiments, and can be variously modified at the stage of implementation without departing from the spirit of the invention.

Further, the above embodiments include inventions at various stages, and various inventions can be extracted by appropriately combining a plurality of disclosed constituent elements. For example, even if some constituent elements are deleted from all the constituent elements shown in the embodiment, the problem described in the section of the problem to be solved by the invention can be solved, and it is described in the section of the effect of the invention. When the effect of being obtained is obtained, a configuration in which this constituent element is deleted can be extracted as an invention.

For example, according to the present invention, FM light is divided into pump light and probe light, the pump light is made incident from one end of the sensing optical fiber, the probe light is modulated to near the Brillouin frequency, and The incident Brillouin, which is generated when the pump light and the probe light are incident from the other end and propagated in the sensing optical fiber from opposite directions, receives the information of the physical quantity to be measured and propagates as the light to be measured. The location of the physical quantity to be measured is specified from the frequency value of the beat signal in the combined light of the light and the probe light, and the physical quantity to be measured is calculated based on the intensity change of the beat signal when the detuning width of the probe light is changed. It can also be applied to an optical fiber distributed measuring method and its apparatus.

[0175]

As described above in detail, according to the present invention, it is possible to measure strain and temperature by distinguishing both strain and temperature over a long distance only by the measurement principle of fiber sensing utilizing the Brillouin scattering phenomenon. It is possible to provide a method for measuring the distribution and a device therefor.

[Brief description of drawings]

FIG. 1 is a configuration diagram showing a first embodiment of a strain and temperature distribution measuring apparatus according to the present invention.

FIG. 2 is a specific configuration diagram of a light source unit in the strain and temperature distribution measuring apparatus according to the first embodiment of the present invention.

FIG. 3 is a specific configuration diagram of a light receiving section in the strain and temperature distribution measuring apparatus according to the first embodiment of the present invention.

FIG. 4 is a diagram showing a relationship between a physical quantity of strain and temperature at an arbitrary wavelength and a Brillouin frequency shift in the first embodiment of the strain and temperature distribution measuring apparatus according to the present invention.

FIG. 5 is a specific configuration diagram of a signal processing unit in the first embodiment of the strain and temperature distribution measuring apparatus according to the present invention.

FIG. 6 is a diagram showing wavelength dependence of each physical quantity change coefficient in the first embodiment of the strain and temperature distribution measuring apparatus according to the present invention.

FIG. 7 is a diagram showing a processing process of a signal processing unit in the strain and temperature distribution measuring apparatus according to the first embodiment of the present invention.

FIG. 8 is a configuration diagram showing a second embodiment of a strain and temperature distribution measuring apparatus according to the present invention.

FIG. 9 is a configuration diagram of a light source unit in a strain and temperature distribution measuring apparatus according to a third embodiment of the present invention.

FIG. 10 is a configuration diagram of a light receiving section in a strain and temperature distribution measuring apparatus according to a third embodiment of the present invention.

FIG. 11 is a configuration diagram of a signal processing unit in a strain and temperature distribution measuring apparatus according to a third embodiment of the present invention.

FIG. 12 is a configuration diagram of a light source section in a strain and temperature distribution measuring apparatus according to a fourth embodiment of the present invention.

FIG. 13 is a configuration diagram of a light receiving unit in a strain and temperature distribution measuring apparatus according to a fourth embodiment of the present invention.

FIG. 14 is a configuration diagram of a signal processing unit in a strain and temperature distribution measuring apparatus according to a fourth embodiment of the present invention.

FIG. 15 is a diagram showing a measurement principle when measuring both temperature and strain distributions in the related art.

[Explanation of symbols]

103: Optical fiber for sensing 1: Light source section 2-1, 2-2, 2-3, 2-4, 2-5, 2-6, 2
-7: Optical fiber 3: Optical distributors 4, 6: Optical modulator 5: Optical circulator 7: Light receiving unit 8: Signal processing unit 10: Wavelength variable light source 11: Wavelength controller power supply 12: Wavelength variable optical bandpass filter 13: Photodetector 14: Electric signal frequency filter 15: A / D converter 16: First calculation unit 17: Data storage unit 18: Second calculation unit (separation calculation unit) 19: Total wavelength determination unit 20: Addition average Operation unit 21: Display unit 22: Optical multiplexers 30-1 to 30-n: Light sources 31-1 to 31-n: Optical fiber 32: Wavelength multiplexer 33: Light source controller 34: Wavelength distributors 35-1 to 35 -N: Optical bandpass filters 36-1 to 36-n: Optical receiver 37: Electric signal frequency filter 38: A / D converter 39: First arithmetic unit

   ─────────────────────────────────────────────────── ─── Continued front page    F term (reference) 2F056 VF03 VF12                 2F065 AA65 FF00 GG06 GG23 JJ01                       LL00 LL02 LL23 LL46 LL53                       LL57 NN06 NN08 QQ00 QQ03                       QQ17 QQ23 QQ27 QQ33 QQ34                       QQ42                 2F103 BA41 BA43 CA07 EB02 EB05                       EB11 EB19 EC09 EC10 EC16                       ED27 ED37 FA02                 2G086 DD04 DD05

Claims (17)

[Claims] 1. A strain and temperature distribution measuring method for detecting a change in Brillouin scattering phenomenon occurring in a sensing optical fiber to measure a change in a physical quantity to be measured, comprising: Brillouin scattering for each wavelength in the sensing optical fiber. Strain wavelength dependence coefficient and its temperature wavelength coefficient are obtained in advance, the step of obtaining the change of Brillouin frequency shift for each wavelength of the pump light incident on the sensing optical fiber, and these measurement data By substituting into a two-dimensional simultaneous equation relating to a change in fiber strain and a change in temperature, the change in strain generated at each position of the sensing optical fiber and the change in temperature are identified and simultaneously performed. A method for measuring distribution of strain and temperature, comprising: 2. The binary simultaneous equations relating to a change in strain and a change in temperature of the sensing optical fiber are: the wavelength of the pump light is λ _n , the wavelength dependence coefficient is C _ε (λ _n ),
The temperature wavelength coefficient is C _T (λ _n ), the Brillouin frequency shift change is Δν _B (λ _n ), the strain change of the sensing optical fiber is Δε, and the temperature change of the sensing optical fiber is ΔT. Then, The method for measuring strain and temperature distribution according to claim 1, wherein: 3. When the total number of wavelengths of the pump light is 3 wavelengths or more, the change of the strain generated at each position of the sensing optical fiber and the change of the temperature are arithmetically averaged to obtain the sensing value. 2. The strain and temperature distribution measuring method according to claim 1, further comprising a step of identifying and simultaneously obtaining the change in the strain and the change in the temperature generated at each position of the optical fiber for use. 4. The equation for calculating the arithmetic mean is the above-mentioned 2
Let Δε be the change in strain of the sensing optical fiber, which is the solution obtained by computing the simultaneous equations, ΔT be the change in temperature of the sensing optical fiber, and let N be the total number of combinations of these Δε and ΔT. [Equation 2] The strain and temperature distribution measuring method according to claim 3, wherein 5. A strain and temperature distribution measuring device for measuring a change in Brillouin scattering phenomenon occurring in a sensing optical fiber to measure a change in a physical quantity to be measured, and a light source section for outputting light of a plurality of wavelength components. An optical distributor that splits the output light from the light source unit into a pump light and a probe light, an optical modulator that modulates the pump light or the probe light, and an optical modulator that modulates with the optical modulator. Guiding light to the sensing optical fiber and guiding Brillouin scattered light having physical information of temperature and strain from the sensing optical fiber, and the Brillouin scattered light guided by the light guiding means. A light-receiving part that receives the light and converts it into an electric signal, and a block for each wavelength of the pump light that inputs the electric signal from the light-receiving part and is incident on the sensing optical fiber. Each measurement data indicating the change of the Liluan frequency shift is substituted into a binary simultaneous equation concerning the change of the strain and the change of the temperature of the sensing optical fiber, and the strain is generated at each position of the sensing optical fiber. And a signal processing unit for simultaneously determining the change in the temperature and the change in the temperature, and measuring the distribution of strain and temperature. 6. The signal processing unit, wherein the wavelength of the pump light is λ _n , the wavelength dependence coefficient is C _ε (λ _n ), the temperature wavelength coefficient is C _T (λ _n ), and the Brillouin frequency shift is changed. Δ
ν _B (λ _n ), the change in strain of the sensing optical fiber is Δε, and the change in temperature of the sensing optical fiber is ΔT
Then, The strain and temperature distribution measuring device according to claim 5, wherein 7. The signal processing unit, when the total number of wavelengths of the pump light is 3 wavelengths or more, adds and averages the change of the strain generated at each position of the sensing optical fiber and the change of the temperature, respectively. 6. The strain and temperature distribution measuring apparatus according to claim 5, wherein the strain and temperature distribution measuring apparatus calculates and simultaneously determines the strain change and the temperature change generated at each position of the sensing optical fiber. 8. The signal processing unit, wherein the change in strain of the sensing optical fiber, which is a solution obtained by computing the simultaneous binary equations, is Δε, the change in temperature of the sensing optical fiber is ΔT, If the total number of combinations of these Δε and ΔT is N, then The strain and temperature distribution measuring device according to claim 7, wherein 9. The distortion according to claim 5, wherein the light source section is capable of continuously changing the wavelength of the light to be output, and outputs light of an arbitrary wavelength at any time by external control. Temperature distribution measuring device. 10. The strain and temperature distribution measuring apparatus according to claim 5, wherein the light source unit includes a plurality of light sources, and the light sources output lights of different wavelengths. 11. The light source unit collects a plurality of light sources and lights respectively output from the light sources into one optical path,
11. The strain and temperature distribution measuring device according to claim 10, comprising a wavelength multiplexer that outputs light of a plurality of wavelengths simultaneously in a single optical path. 12. The light source unit includes an optical switch for guiding light of an arbitrary single wavelength out of lights respectively output from a plurality of light sources to one optical path, and outputs by switching optical path selection of the optical switch. 11. The strain and temperature distribution measuring apparatus according to claim 10, wherein the wavelength of light to be selected is selected at any time. 13. The light receiving section includes a wavelength tunable optical bandpass filter for transmitting only Brillouin scattered light corresponding to an arbitrary wavelength of the pump light, and light transmitted through the wavelength tunable optical bandpass filter as an electric signal. 6. A strain and temperature distribution measuring device according to claim 5, further comprising a photodetector for converting. 14. The light receiving unit distributes backscattered light of a plurality of wavelengths guided by a single optical path from the sensing optical fiber, and a wavelength distributor for each wavelength distributed by the wavelength distributor. A plurality of wavelength tunable optical bandpass filters for transmitting only Brillouin scattered light corresponding to an arbitrary wavelength of the pump light, and a plurality of wavelength variable optical bandpass filters for converting each light respectively transmitted through these wavelength tunable optical bandpass filters into respective electric signals. The strain and temperature distribution measuring device according to claim 5, comprising a photodetector. 15. The signal processing unit includes an electric signal frequency filter that extracts only Brillouin beat frequency components from the electric signal output from the light receiving unit, and a frequency spectrum from the frequency signal extracted by the electric signal frequency filter. Of the peak intensity of the maximum intensity, and a value of the peak frequency is obtained as a Brillouin frequency, and a first calculation unit, and data of the Brillouin frequency value for each pump wavelength defined by the first calculation unit are stored. And a change in the strain generated at each position of the sensing optical fiber by performing the calculation according to claim 6 using the data storage unit that stores the data and the data stored in the data storage unit. 6. The strain and temperature of claim 5, characterized by comprising: Distribution measuring device. 16. When the backscattered light of a plurality of wavelengths guided by a single optical path from the optical fiber for sensing is respectively distributed, the signal processing unit is configured to operate with the electric signal frequency filter for each wavelength. The strain and temperature distribution measuring apparatus according to claim 15, wherein the first arithmetic unit performs parallel processing. 17. The signal processing unit, when there are a plurality of combinations of a change in strain of the sensing optical fiber and a change in temperature of the sensing optical fiber, adds the respective values of strain and temperature. The strain and temperature distribution measuring device according to claim 5, further comprising: an arithmetic unit that performs averaging, and a display unit that displays the arithmetic result of the arithmetic unit as a final measurement result.