JPH09203665A - Optical-fiber sensor system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a system, which can demodulate the signal including the physical quantity detected by an optical-fiber sensor without the effects of the fluctuation in frequency shift and the like, and can output the result. SOLUTION: A modulating-signal generator 10 outputs the sine wave signal having the angular frequency ω0 and a reset signal in synchronization with the sine wave signal. A light source 20 outputs the frequency modulated optical signal based on the sine wave signal from the generator 10. A frequency-shift measuring instrument 30 receives the optical signal from the light source 20, receives the reset signal from the generator 10 and obtains the signal indicating the maximum frequency shift νd of the optical signal from the reset signal. An interferometer 40 outputs the optical- intensity signal based on the phase difference between two optical fibers in accordance with the optical signal from the measuring instrument 30. An OE converter 50 outputs the electric signal I=A+Bcos [Ccos ω0 t+ϕ(t)] based on the optical intensity signal from the interferometer 40. A demodulator 60 receives the sine wave signal from the generator 10, receives the I signal from the converter 50 and receives the νd signal from the measuring instrument 30, obtains the signal of X=B<2> .J1 (C).J2 (C).ϕ(t) in accordance with the νd and the I signal, obtains the signal of Y=J1 (C).J2 (C) corresponding to the Νd and I signals, divided X by Y and outputs the signal of Z=B<2> .ϕ(t).

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical fiber sensor system, and more particularly to a PGC (Phase Generated Carrier).
The present invention relates to an optical fiber sensor system using a homodyne demodulation method.

[0002]

2. Description of the Related Art Conventionally, physical quantities such as sound pressure and magnetic field are detected by an optical fiber sensor, and the detected physical quantities are demodulated by A. Danderidge, ABTveten and TGGiallorenz.
i, "Homodyne demodulation scheme for fiber-optic se
nsors using phase generated carrier ", IEEE J.Quant
um Electron., Vol. QE-18, No. 10, pp1647-1653 (1982). There is a PGC homodyne demodulation method.

An optical fiber sensor system using the PGC homodyne demodulation method according to this document will be described with reference to FIG. The frequency of the laser constituting the light source 20 is frequency-modulated (FM) in a sinusoidal wave by the modulation signal sent from the modulation signal generator 5, and the FM-generated optical signal is an interferometer in which an optical fiber has an optical path difference. The light intensity signal of the interferometer 40 is sent to the O / E converter 50, and an electric signal represented by the following equation (1) is obtained from the O / E converter 50.

I = A + Bcos [Ccos ω _o t + φ (t)] (1) C = 2πΔL nν _d / c ₀ (2) where A is the average power of the light input to the O / E converter 50,
B is determined by the average power of light input to the O / E converter 50, the power of light passing through the interferometer, and the polarization state, and is usually treated as a constant. ω _o is the angular frequency of the sine wave that modulates the laser, φ (t) is the phase difference of the light that has passed through the interferometer 40, and the signal to be detected is included here. ΔL is the optical path difference of the interferometer 40, n is the refractive index of the optical fiber that is the arm of the interferometer, and ν
_d is the maximum frequency shift of the laser, and c ₀ is the speed of light in vacuum.

Next, the output of the O / E converter 50 is the demodulation processor 20.
It is sent to the synchronous detectors 62 and 64 (multiplier and LPF) that make up 0, and this detector 62 extracts the odd order of ω ₀ of the signal sent from the O / E converter 50, and the detector 64 Extracts even-order components. When the first-order component is extracted, the synchronous detector 62
The signal expressed by the following equation (3) is obtained from, and when the second-order component is extracted, the following (4) is obtained from the synchronous detector 64.
The signal represented by the equation is obtained.

2B ・ J ₁ (C) ・ sin φ (t) ・ ・ ・ ・ ・ ・ ・ (3) -2B ・ J ₂ (C) ・ cos φ (t) ・ ・ ・ ・(4) Here, J ₁ (C) is a first-order Bessel function of the first kind with C as an argument, and J ₂ (C) is a second-order Bessel function of the second kind with C as an argument.

Next, these signals are sent to the sin / cos demodulator 66 which constitutes the demodulation processor 200, and differential cross multiplication, subtraction and integration are performed to obtain a signal represented by the following equation (5).

B ² · J ₁ (C) · J ₂ (C) · φ (t) ···· (5) Therefore, from the sin / cos demodulator 66, φ including the signal to be detected An output proportional to (t) is obtained.

A system that multiplex-transmits signals detected by a plurality of sensors includes ADKersey, A. Danderidge an
d ABTveten, "Time-division multiplexing of interf
erometoric fiber sensors using passive phase gener
ated carrier interrogation ", OPTICS LETTERS Vol.12,
No.10, pp775-777 (1987).

The system according to this document sends pulsed laser light to an interferometric optical fiber sensor array composed of a plurality of optical fiber sensors and a plurality of delay lines, and is time-divisionally detected by each sensor of this array ( A pulse trained signal is transmitted, the transmitted and received pulse train is separated for each channel by a demultiplexer, and then demodulated by the conventional PGC homodyne system described above.

[0011]

However, since C depends on the optical path difference of the interferometer in the conventional system as described above, C changes due to the error of the optical path difference of the interferometer, and (5)
There is a problem that an error occurs in the demodulation output expressed by the formula. Further, when the frequency shift of the frequency modulation of the laser fluctuates, C also fluctuates, so that the demodulation output becomes unstable. Further, there is a problem that the demodulation output becomes unstable due to the fluctuation of B due to the polarization dependent loss fluctuation of the optical coupler forming the interferometer and the fluctuation of B that occurs when a single mode fiber is used for the interferometer.

An object of the present invention is to solve the above-mentioned drawbacks of the prior art and to provide an optical fiber sensor system capable of obtaining a stable demodulated output without error.

[0013]

In order to solve the above-mentioned problems, the present invention provides an optical fiber sensor system for detecting a certain quantity, which system outputs a sinusoidal signal having an angular frequency of ω _0. At the same time, a modulation signal generating means for outputting a reset signal synchronized with the sine wave signal, and a light source means for receiving a sine wave signal from the modulation signal generating means and outputting an optical signal frequency-modulated based on the signal. ,
Receives an optical signal from the light source means, outputs the received optical signal, and receives the optical signal from the frequency deviation measuring means for obtaining a signal indicating the maximum frequency deviation ν _d of the received optical signal and the frequency deviation measuring means. , An interferometer means for outputting a light intensity signal based on the phase difference between the two optical fibers according to the received optical signal, and an optical signal I = based on the light intensity signal received from the interferometer means A first optical / electrical conversion means for outputting A + Bcos [Ccosω _o t + φ (t)], and A is the first optical / electrical conversion means.
The average power of the light input to the electrical conversion means, and B is a constant determined by the average power of the light input to the first optical / electrical conversion means, the power of the light when passing through the interferometer means, and the polarization state. , C is 2πΔL nν _d / c ₀ , and ΔL
Is the optical path difference between the two optical fibers of the interferometer means, n is the refractive index of the two optical fibers serving as the arms of the interferometer means, c ₀ is the speed of light in vacuum, and φ (t) is It is the phase difference of the light when passing through the interferometer means, and the amount of signal to be detected is included here, and the sinusoidal signal from the modulation signal generating means and the signal from the first optical / electrical converting means I Signal
Receiving a [nu _d signal from the frequency shift measuring means, the received sine wave X = B ² · J ₁ corresponding to the signal and I signal _{(C) · J 2 (C} ) · φ
The signal of (t) is obtained, and the signal of Y = J ₁ (C) ・ J ₂ (C) or U = B ²・ J ₁ (C) ・ J ₂ (according to the received ν _d signal and I signal C), and X is divided by Y to obtain a signal of Z = B ² · φ (t) or X is divided by U to obtain a signal of V = φ (t). , J ₁ (C) is a first-order Bessel function with C as an argument when the second item of the I signal is analyzed, and J ₂ (C) is 2
It is characterized by the following Bessel function.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of an optical fiber sensor system according to the present invention will be described in detail with reference to the accompanying drawings.

FIG. 1 shows a first embodiment of an optical fiber sensor system according to the present invention. FIG. 1 shows an interferometer which is not affected by the fluctuation of the frequency shift of the frequency modulation of the laser used for the light source 20 from the demodulation processor 60.
It is a system that can obtain 40 demodulation outputs. FIG.
Referring to this system, the modulation signal generator 10, the light source
It is composed of 20, a frequency deviation measuring device 30, an interferometer 40, an O / E converter 50 and a demodulation processor 60.

The modulation signal generator 10 is composed of a circuit that oscillates a sine wave signal having an angular frequency of ω _o and a circuit that generates a reset signal based on this sine wave signal. And outputs this generated reset signal to its output 104 and 104, respectively.
Output to The output 102 is connected to the light source 20, the output 104 is connected to the frequency shift measuring device 30, and the output 106 is connected to the demodulation processor 60.

The light source 20 is composed of a semiconductor laser and its drive circuit, and sends a signal input from its input 102 to the semiconductor laser through the drive circuit, and changes the drive current of the semiconductor laser by the sent modulation signal. FM
Optical FM that outputs this FM optical signal from its output 108
Circuit. The output 108 is connected to the frequency deviation measuring device 30 by an optical fiber.

The frequency deviation measuring device 30 is, as shown in FIG.
Optical coupler 310, frequency shift measurement interferometer 320, O / E converter 33
It consists of 0 and a counter 340.

The input 108 of the optical coupler 310 is connected to the output 108 of the light source 20 by an optical fiber, and the optical coupler 310 branches the optical signal input from the input 108 and outputs the optical signal to its outputs 110 and 362. The add / drop function unit outputs the light intensity signal from the interferometer 320 for measuring the frequency shift input from 362 to the output 364 thereof. The output 110 is connected to the interferometer 40 by an optical fiber, the input / output 362 is connected to the interferometer 320 by an optical fiber, and the output 364 is connected to the O / E converter 330 by an optical fiber.

As shown in FIG. 2, the frequency shift measuring interferometer 320 comprises an optical coupler 320a, optical fibers 320b and 320c, and reflecting mirrors 320d and 320e, which constitute a Michelson interferometer. The arm of this interferometer is composed of a first arm composed of an optical fiber 320b and a second arm composed of an optical fiber 320c.

The input 362 of the optical coupler 320a is connected to the output 362 of the optical coupler 310 by an optical fiber. Optical coupler 320a
Splits the optical signal input from its input 362 and outputs it.
Outputs to 366 and 368, and also from its input 366 to the first
Input the reflected light signal from the arm of the
The add / drop function unit receives the reflected light signal from the second arm from 368 and outputs a light intensity signal based on the phase difference between the inputted reflected light signals to its output 362. Output 366
Is connected to the input of optical fiber 320b and the output 368 is connected to the input of optical fiber 320c.

In this example, single mode fibers are used as the optical fibers 320b and 320c.
In the case of the Michelson interferometer, the optical path difference between 0b and the optical fiber 320c is set to be equal to or less than the coherence length of the semiconductor laser. The interferometer arm is molded (fixed) so that the phase of the interference output does not change significantly due to vibration or the like. The output of the optical fiber 320b is the reflecting mirror 32.
The output of the optical fiber 320c is connected to the reflecting mirror 320e.

When a polarization maintaining fiber is used between the light source and the reflecting mirror 320d and the reflecting mirror 320e, a light intensity signal based on the phase difference between the first arm and the second arm is shown in FIG. Alternatively, the output may be output to the output 370 of the optical coupler 320a, and this output may be directly input to the input of the O / E converter 330 as shown by the dotted line in FIG.

In this example, Faraday rotator mirrors are used as the reflecting mirrors 320d and 320e.
The optical signal that has passed through 320b is reflected by the mirror 320d, is sent again to the input 366 of the optical coupler 320a through the optical fiber 320b, and the optical signal that has passed through the optical fiber 320c is reflected by the mirror 320e and is again sent to the optical fiber. It is sent to the input 368 of the optical coupler 320a through 320c. These transmitted reflected light signals are combined by the optical coupler 320a to generate a light intensity signal.

The O / E converter 330 is composed of a light receiving element and an amplifier. The light intensity signal input to the input 362 of the O / E converter 330 is received by the light receiving element and converted into an electric signal, and the converted electric signal is predetermined by the amplifier. It is a photoelectric conversion circuit that amplifies to the level and outputs it to the output 372. From this circuit, for example, FIG.
And a signal as shown in FIG. 4 is output. Output 372 is connected to counter 340. For details, see O / E converter 33.
From 0, an electric signal as expressed by the following equation (6) is output.

I ₁ = A ₁ + B ₁ cos [C ₁ cos ω _o t + φ ₁ (t)] ・ ・ ・ ・ ・ ・ (6) C ₁ = 2πΔL ₁ n ₁ ν _d / c ₀・ ・ ・(7) where A ₁ is the average power of light input to the O / E converter 330, and B ₁ is the average power of light input to the O / E converter 330 and the light passed through the interferometer. Determined by the power of light and the state of polarization, usually
Treated as a constant. ω _o is the angular frequency of the sine wave modulating the laser, φ ₁ (t) is the phase difference of the light that has passed through the interferometer 320, and the signal to be detected is included here. ΔL ₁ is the optical path difference of the interferometer 320, n ₁ is the refractive index of the optical fiber serving as the arm of the interferometer 320, ν _d is the maximum frequency shift of the laser, and c ₀ is the speed of light in vacuum.

The counter 340 is composed of a counter (binary counting) circuit, a flip-flop, a timing generation circuit, etc., and based on the reset signal input from the input 104, the signal input from the input 372 (of the formula (6)). This is a counting circuit that counts the number of vibrations of the second term) and outputs the count value to its output 112. In this case, in the present embodiment, the number of frequencies of the half cycle period of the sine wave having the angular frequency ω _o is counted. The output 112 is connected to the modulation / function calculator 68 of the demodulation processor 60 described later. Details this counter 34
From 0, a data value (binary code) of the frequency N as represented by the following equation (8) is output.

N = (2ΔL ₁ n ₁ ν _d / c ₀ ) + R ₁ (8) where ΔL ₁ is the optical path difference of the interferometer 320, and n ₁ is the interferometer 320.
Is the refractive index of the optical fiber that is the arm of ν, ν _d is the maximum frequency shift of the laser, and c ₀ is the speed of light in a vacuum. R ₁ is an error and is a fraction that takes a value within ± 1. Therefore, the counter 340 outputs integer count data.
In this case, the optical path difference ΔL _{1 of} the frequency shift measuring interferometer 320
The maximum frequency shift ν _d of the laser can be accurately obtained from the above equation (8) if it is obtained by measuring in advance. In addition,
In this example, the period for counting the frequency N is a half cycle period of the sine wave, but it may be an integral multiple thereof.

The frequency deviation measuring device 30 may have a circuit configuration in which a calculating circuit 68a of a modulation degree / function calculating device 68, which will be described later, for obtaining the maximum frequency deviation ν _d is connected after the counter 340.

Returning to FIG. 1, the interferometer 40 is an interferometer which serves as a sensor for detecting physical quantities such as sound pressure and magnetic field as touched a little before, and the optical path difference of the interferometer is detected by the physical detection. A signal is taken in the phase of light by changing it. Therefore, this interferometer 40 receives the optical signal input to its input 110 and outputs an optical intensity signal based on the phase difference between the arms of this interferometer to its output 114. The output 114 is connected to the O / E converter 50.

The O / E converter 50 has the same structure as the above-mentioned O / E converter 330. The light intensity signal input to the input 114 of the O / E converter 50 is received by the light receiving element and converted into an electric signal. The signal is amplified by an amplifier to a predetermined level and its output 11
It is a photoelectric conversion circuit that outputs to 6. As mentioned before, the O / E converter 50 outputs the electric signal represented by the above equation (1). Output 116 is a demodulator 60 synchronous detector
Connected to 62 and 64.

As shown in FIG. 1, the demodulation processor 60 comprises a synchronous detector 62, a synchronous detector 64, a sin / cos demodulator 66, a modulation / function calculator 68 and a divider 70.

The synchronous detector 62 is a multiplier and a low pass filter.
(LPF), this multiplier multiplies the signal input from its input 116 by the signal whose angular frequency is ω ₀ input from its input 106, and then obtains the signal of the first-order component by LPF. Is a circuit for outputting the obtained signal of the first-order component to its output 118. As mentioned before, the synchronous detector 62 outputs the electric signal represented by the above equation (3). The output 118 is connected to the differentiating circuit 66a and the multiplier 66d of the sin / cos demodulator 66 which will be described later.

The synchronous detector 64 is composed of a multiplier, an LPF and a doubling circuit. The doubling circuit multiplies the angular frequency ω ₀ input from its input 106 by 2 and outputs a signal having an angular frequency of 2ω ₀ to the multiplier. Input and then its input by the multiplier 116
It is a circuit that multiplies the signal input from the signal 2 and a signal of 2ω ₀ that has been doubled, then obtains the signal of the second-order component by LPF, and outputs the obtained signal of the second-order component to its output 122. As mentioned above, the synchronous detector 64 outputs the electric signal represented by the above equation (4). Output 122
Is the differential circuit 66b and multiplier 66 of the sin / cos demodulator 66, which will be described later.
connected to c.

As shown in FIG. 5, the sin / cos demodulator 66 includes differentiating circuits 66a and 66b, multipliers 66c and 66d, a subtractor 66e and an integrator.
It consists of 66f.

The differentiating circuit 66a constitutes a differentiating circuit using, for example, an operational amplifier, and this circuit differentiates the signal of the formula (3) inputted from the input 118 thereof to obtain the signal of the following formula (9). Output signal at its output 600. This output 60
0 is connected to the multiplier 66c.

2B · J ₁ (C) · d φ / dt · cos φ (t) ···· (9) Differentiating circuit 66b has the same circuit configuration as that of differentiating circuit 66a. The signal of formula (4) input from the input 122 is differentiated to obtain the signal of formula (10) below, and the obtained signal is output 60
Output to 2. This output 602 is connected to the multiplier 66d.

2B · J ₂ (C) · d φ / dt · sin φ (t) ····· (10) As the multiplier 66c, for example, an analog type multiplication device is used. The device multiplies the signal of equation (9) input from its input 600 with the signal of equation (4) input from its input 122 to obtain the signal of equation (11) below, and outputs this obtained signal to its output. Output to 604. This output 604
Is connected to one input of the subtractor 66e.

4B ² · J ₁ (C) · J ₂ (C) · dφ / dt · cos ² φ (t) ··· (11) The multiplier 66d has the same circuit configuration as the multiplier 66c. ,
The signal of Eq. (10) input from its input 602 and its input 118
Multiply the signal of equation (3) input from
The signal of the equation is obtained and the obtained signal is output at its output 606. This output 606 is connected to the other input of the subtractor 66e.

-4B ² · J ₁ (C) · J ₂ (C) · dφ / dt · sin ² φ (t) (12) The subtractor 66e is a subtraction circuit using an operational amplifier, for example. This circuit subtracts the signal of equation (12) input from its input 606 from the signal of equation (11) input from its input 604 to obtain the signal of equation (13) below. To its output 608. Output 608 is connected to integrator 66f.

[0041]

[Equation 1] The integrator 66f forms an integrating circuit using, for example, an operational amplifier, and this circuit integrates the signal of the equation (13) input from its input 608 to obtain the signal of the above equation (5), and obtains this obtained signal. It outputs to its output 124. The output 124 is connected to the divider 70.

As shown in FIG. 6, the modulation / function calculator 68 is composed of calculation circuits 68a, 68b, 68c and 68d. The calculation circuit 68a is a circuit for performing the calculation of the above equation (8). The value (integer) of the frequency N input from the input 112 and the optical path difference ΔL _{1 of} the interferometer 320, which is obtained in advance, the interferometer 320
This is a circuit for obtaining the maximum frequency deviation ν _d from the refractive index n _{1 of the} optical fiber that serves as the arm and the speed of light c _{0 in} vacuum, and sending it to the arithmetic circuit 68b.

The arithmetic circuit 68b is a circuit for performing the arithmetic operation of the equation (2), and this circuit calculates the value of ν _d that has been sent, the optical path difference ΔL of the interferometer 40, and the arm of the interferometer 40 which are obtained in advance. Refractive index n of the optical fiber and the speed of light c ₀ to C in vacuum
This is a circuit for obtaining (modulation degree) and transmitting the obtained value of C to the arithmetic circuit 68c.

The arithmetic circuit 68c is an arithmetic circuit for obtaining the above J ₁ (C) and J ₂ (C), and this circuit substitutes the value of C which has been sent into C of the above equation (1) into (1 ) Find the signal of the second term of the equation,
Next, the signal of the second term is converted into a Bessel function and J ₁ (C)
And J ₂ (C) and sends them to the arithmetic circuit 68d.

The arithmetic circuit 68d is a multiplication circuit. This circuit multiplies the sent J ₁ (C) and J ₂ (C) to obtain the signal of the following equation (14), and the obtained signal is Output to output 126.

J ₁ (C) · J ₂ (C) ····· (14) Further, the value (integer) of the frequency N input from the input 112 and the interferometer 320 previously obtained Optical path difference ΔL ₁ , interferometer 320
Equation (14) may be directly obtained from the refractive index n _{1 of the} optical fiber serving as the arm and the speed of light c _{0 in} vacuum.

The divider 70 constitutes a division circuit using, for example, a multiplication circuit and a subtraction circuit, which circuit has its input 124.
Input the signal of equation (5) from the input 126
It is divided by the signal of equation (14) to obtain the signal of equation (15) below, and the obtained signal is output to its output 128. As can be seen from the equation (15), a demodulation output independent of C can be obtained.

B ² · φ (t) (15) The operation of the first embodiment will be described. When the modulation signal generator 10 sends a sine wave of angular frequency ω _{o to} the light source 20 by the start of measurement,
The light source 20 sends an FM optical signal 108 based on the sinusoidal signal 102 to the frequency shift measuring device 30. The frequency shift measuring device 30 receives the FM optical signal 108, sends the FM optical signal 110 to the interferometer 40, and uses the FM optical signal 108 and the reset signal 104 sent from the generator 10 to determine the frequency N. It counts and sends this data 112 to the modulation / function calculator 68. The interferometer 40 receives the FM optical signal 110 from the measuring device 30 and forms an optical intensity signal 114 based on the phase difference between the arms of this interferometer to form an O / E converter 50.
Send to

The O / E converter 50 receives the light intensity signal 114, converts it into an electric signal 116 (equation (1)), and outputs it to the synchronous detector 62 and
Send to 64. The synchronous detector 62 receives the electric signal 116 and the signal 106 of the angular frequency ω ₀ from the modulation signal generator 10 and outputs 1 of ω ₀ .
The signal of the next component (Equation (3)) is formed and sent to the sin / cos demodulator 66. Further, the synchronous detector 64 receives the electric signal 116 and the signal 106 of the angular frequency ω ₀ from the modulation signal generator 10 to form a signal of the second-order component of ω ₀ (Equation (4)) and sin / cos Demodulator 66
Send to The sin / cos demodulator 66 receives the signals of equations (3) and (4), forms the signal of equation (5), and sends it to the divider 70.

On the other hand, the modulation / function calculator 68 receives the data 112 of the frequency N from the frequency deviation measuring device 30, forms a signal of the equation (14), and sends it to the divider 70. The divider 70 outputs the signal of equation (5)
It is divided by the signal of Eq. (14) to form the signal of Eq. (15) and output from its output 128. As can be seen from the equation (15), a demodulation output independent of C can be obtained.

According to the system of the first embodiment, the modulation signal generator 5 of the conventional system is replaced with the modulation signal generator.
Change to 10 and add frequency deviation measuring instrument to conventional system 3
0, since the modulation / function calculator 68 and the divider 70 are provided, the instability of the demodulation output due to the fluctuation of the frequency deviation of the frequency modulation of the laser can be improved.

FIG. 7 shows a second embodiment of the optical fiber sensor system according to the present invention. FIG. 7 shows the output amplitude B of the O / E converter 50 that occurs when the frequency shift of the frequency modulation of the laser used for the light source 20 fluctuates and when a single mode fiber is used for the interferometer 40. This is a system that can obtain the demodulation output of the interferometer 40 that is not affected by the fluctuation from the demodulation processor 80 even if the fluctuation occurs. Referring to FIG. 7, the difference from the configuration of FIG.
Is changed to the demodulation processor 80.Specifically, the synchronous detector 62 of the demodulation processor 60 is changed to the synchronous detector 82, the synchronous detector 64 is changed to the synchronous detector 84, and the modulation degree is changed. The function calculator 68 is changed to the modulation / function calculator 86, and the divider 70 is changed to the divider 88. 7, elements similar to the elements shown in FIG. 1 are designated by the same reference numerals, and the description of the same reference numerals is omitted.

The synchronous detector 82 is different from the synchronous detector 62 in that an output 119 is added in addition to the output 118. From the output 119, the same output (118) is output. The signal of equation 3) is output. The output 119 is connected to the corresponding input of the modulation / function calculator 86. The difference between the synchronous detector 84 and the synchronous detector 64 is that the output 12
In addition to 2, output 123 is added, and this output 123
Outputs the same signal of the above equation (4) as that output to the output 122. The output 123 is connected to the corresponding input of the modulation / function calculator 86.

As shown in FIG. 8, the modulation / function calculator 86 is composed of the same calculation circuits 68a, 68b, 68c as those described in the modulation / function calculator 68 in addition to the calculation circuits 86a, 86b. ing. Therefore, the description of the arithmetic circuits 68a, 68b, 68c is omitted.

The arithmetic circuit 86a inputs from its input 119.
The signal of equation (3) is the signal J sent from the arithmetic circuit 68c.
₁ ) Divide by (C) to obtain the signal of equation (16) below, and then input that signal.
The signal of equation (4) input from 123 is divided by J ₂ (C) sent from the arithmetic circuit 68c to obtain the signal of equation (17) below, and the obtained signal is sent to the arithmetic circuit 86b.

B · sinφ (t) ································································································································ (() The signal of equation (18) below is obtained by performing the square sum of the signal of equation (17) and the signal of equation (18) and J ₁ (C) sent from the arithmetic circuit 68c.
And J ₂ (C) are multiplied to obtain the signal of the following equation (19), and the obtained signal is output to its output 130.

B ²・ ・ ・ ・ ・ ・ ・ ・ (18) B ²・ J ₁ (C) ・ J ₂ (C) ・ ・ ・ ・ ・ ・ ・ ・ (19) The divider 88 has its input 124 The signal of Eq. (5) input from the input 130 is divided by the signal of Eq.
The signal of equation (0) is obtained and the obtained signal is output to its output 132. As can be seen from the equation (20), it is possible to obtain a demodulation output that does not depend on B and C.

Φ (t) (20) The operation of the second embodiment will be described. The frequency deviation measuring instrument 30 sends the optical signal 110 sent to the interferometer 40, and the frequency N is calculated from the equation (8) and this data is output to its output 112 and the O / E converter. The operation up to the point where the light intensity signal 114 receives the light intensity signal 114 and converts it into the electric signal 116 of the equation (1) and outputs it to the output 116 is the same as the operation of the first embodiment. The synchronous detector 82 receives the electric signal 116 and the signal 10 of the angular frequency ω ₀ from the modulation signal generator 10.
6 is received to form a signal of the first-order component of ω ₀ (Equation (3)) and si
It is sent to the n / cos demodulator 66 and the modulation factor / function calculator 86. Also,
The synchronous detector 84 receives the electric signal 116 and the signal 106 of the angular frequency ω ₀ from the modulation signal generator 10 to form a signal of the second-order component of ω ₀ (Equation (4)) to generate a sin / cos demodulator. 66 and the modulation / function calculator 86. Next, the sin / cos demodulator 66
The signal of equation (4) is received and the signal of equation (5) is formed and sent to the divider 88.

On the other hand, the modulation / function calculator 86 receives the data 112 of the frequency N from the frequency shift measuring device 30, forms a signal of the equation (19) and sends it to the divider 88. The divider 88 outputs the signal of equation (5).
It is divided by the signal of equation (19) to form the signal of equation (20), which is output from its output 128. As can be seen from the equation (20), it is possible to obtain a demodulation output that does not depend on B and C.

According to the system of the second embodiment, the modulation signal generator 5 of the conventional system is replaced with the modulation signal generator.
Change to 10 and add frequency deviation measuring instrument to conventional system 3
0, the synchronous detectors 82 and 84, the modulation / function calculator 86 and the divider 88 are provided, so that the instability of the demodulation output due to the fluctuation of the frequency deviation of the frequency modulation of the laser is improved and it also serves as a sensor. The instability of the demodulation output due to the fluctuation of the output amplitude B of the O / E converter 50 that occurs when a single mode fiber is used for the interferometer 40 can be improved.

FIG. 9 shows a third embodiment of the optical fiber sensor system according to the present invention. In FIG. 9, the laser light from the light source 20 pulsed by the optical pulse gate 91 is sent to the interferometric optical fiber sensor array 400, and then detected by each of the interferometers 40-1 to 40-M of the array 400. The pulsed light intensity signal is sent to the O / E converter 50 via the optical coupler 92, and the sent light intensity signal is converted into an electric signal by the O / E converter 50, and the demultiplexer 95 is provided.
To the interferometers 40-1 to 40-M sent by the demultiplexer 95.
~ 40-M and the corresponding demodulation processors 80-1 to 80-M are separated and sent, whereby the respective demodulation processors 80-1 to 80-M are sent.
It is a system that can obtain stable demodulation output from ~ 80-M.

Referring to FIG. 9, this system includes a modulation signal generator 10, a light source 20, a frequency shift measuring device 30, and an interferometer 40-1.
~ 40-M, O / E converter 50, Demodulation processor 80-1 ~ 80-M, Gate signal generator 90, Optical pulse gate 91, Optical coupler 92, Optical coupler
93-1 to 93-M, delay lines 94-1 to 94- (M-1), and a demultiplexer 95. Of these, interferometers 40-1 to 40
-M, the optical couplers 93-1 to 93-M, and the delay lines 94-1 to 94- (M-1) form an interference type optical fiber sensor array 400. Each of the demodulation processors 80-1 to 80-M receives a sine wave signal having an angular frequency of ω ₀ from the modulation signal generator 10 via the signal line 106, and a frequency deviation measuring device via the signal line 112. 30 to frequency N
Is configured to be supplied.

In the above configuration, the characters following the interferometer 40, the demodulation processor 80, the optical coupler 93 and the delay line 94 are the interferometer 40, the demodulation processor 80, the optical coupler 93 and the delay line 94.
The number of constituents of 94 is shown by a number, and M (natural number) is the final number. 9, the same elements as those shown in FIGS. 1 and 7 are designated by the same reference numerals, and the description of the same reference numerals will be omitted.

The gate signal generator 90 comprises a reference signal generator and a gate pulse generator. The reference signal generator sends the reference signal oscillated by this generator to the gate pulse generator, and the gate pulse generator A gate pulse as shown in FIG. 10a is generated from the sent reference signal and is output to its output 140, and a demultiplexer trigger signal synchronized with this gate pulse is output to its output 142.

Specifically, the repetition period T of the gate pulse 140 is a time larger than Mτ _{0 in} this example, and its pulse width τ ₁ (700-1 in FIG. 10a) is a time smaller than τ _0. is there. The period between each pulse of the gate pulse group 142 is τ
_{It is 0} hours, and the pulse width of each pulse is τ ₁ hour. Also, the time τ ₂ from the rise of pulse 700 to the rise of pulse 702-1 is from optical coupler 93-1 to optical coupler 9-1.
2. The propagation time of light from the O / E converter 50 to the demultiplexer 95. Here, τ ₀ is the round trip delay time of the delay line 94. The output 140 is connected to the optical pulse gate 91, and the output 142 is connected to the demultiplexer 95.

The input 110 of the optical pulse gate 91 is connected to the output 110 of the frequency deviation measuring device 30, and the optical pulse gate 91 receives the high level of the gate pulse input from its input 140 (see FIG.
10a 700-1) is turned on during the period, and during that period, input 110
It outputs the optical signal input from the output to its output 144, and is “OFF” during the period of low level (700-2 in Fig. 10a).
Do not output the optical signal input from 140 to its output 144 1:
This is an optical switch with one configuration. The output 144 is connected to the optical coupler 92 by an optical fiber.

The optical coupler 92 outputs the optical signal input from its input 144 to its output 146, and outputs the optical intensity signal from the interferometric optical fiber sensor array 400 input from its input 146 to its output 148. It is an insertion function unit.
Output 146 is an optical fiber and an interferometric fiber optic sensor array
The output 148 is connected to the O / E converter 50 by an optical fiber.

The optical coupler 93-1 branches the optical signal input from its input 146 and outputs it to its output 150 and output 152, and the optical intensity signal from its interferometer 40-1 input from its input 152 and its optical intensity signal. The add / drop function unit outputs the light intensity signal from the delay line 94-1 input from the input 150 to the output 146. The signal passing through this delay line 94-1 is an interferometer 40-2 to 40-40.
-The light intensity signal from M. Therefore, the output 146 of the optical coupler 93-1 outputs the light intensity signals from the interferometers 40-1 to 40-M. The output 150 is connected to the input of the delay line 94-1 by an optical fiber, and the output 152 is connected to the interferometer 40-1 by an optical fiber.

The optical couplers 93-2 to 93-M are also the optical couplers 93.
-1 has the same configuration as that of -1, and the first input / output of each optical coupler 93-2 to 93-M corresponds to each delay line 94-1 to 94- (M-1) corresponding to each optical coupler. And the second input / output of each of the optical couplers 93-2 to 93-M is connected to the input / output of the interferometers 40-2 to 40-M corresponding to each of the optical couplers. The third input / output of each optical coupler 93-2 to 93- (M-1) is connected to the input of each delay line 94-2 to 94- (M-1) corresponding to each optical coupler. .

[0070] The delay line 94-1 is an optical delay line for outputting from the output 154 of the optical signal inputted from the input 150 is delayed tau _0/2 hours. The output 154 is connected to the optical coupler 93-2. The delay lines 94-2 to 94- (M-1) also have the same configuration as the delay line 94-1.
-2 to 94- (M-1) input is connected to the output of each optical coupler 93-2 to 93- (M-1) corresponding to each delay line.
The outputs of 94-2 to 94- (M-1) are connected to the inputs of the optical couplers 93-3 to 93-M corresponding to the respective delay lines.

The input 162 of the demultiplexer 95 is connected to the output 162 of the O / E converter 50, and the demultiplexer 95 converts the electrical signal input from its input 162 into the trigger signal input from its input 142 and τ ₂ + nτ. It is an analog switch of 1: N configuration which selectively outputs to any one of outputs 164-1 to 164-M based on a delay time of ₀ (n = 1 to M). The outputs 164-1, 164-2, 164-3 to 164-M are connected to the corresponding demodulation processors 80-1, 80-2, 80-3 to 80-M, respectively.

In this way, the light intensity signals from the interferometers 40-1 to 40-M are sent to the corresponding demodulation processors 80-1 to 80-M, demodulated and output.

Next, the operation of the third embodiment will be described. When the modulation signal generator 10 sends a sine wave having an angular frequency ω _{0 to} the light source 20 by the start of measurement, the light source 20 sends an FM optical signal 108 based on the sine wave signal 102 to the frequency shift measuring device 30. The frequency deviation measuring device 30 receives the FM optical signal 108 and outputs it to the optical pulse gate 91.
The FM optical signal 110 is sent, and the frequency N is calculated from the equation (8) using the FM optical signal 108 and the reset signal 104 sent from the generator 10, and this data 112 is demodulated and processed.
Send to each of 80-1 to 80-M.

Further, in parallel with this, the gate signal generator 90
Outputs the gate pulse 140 shown in FIG. 10a to the optical pulse gate 91 and sends this trigger signal 142 to the demultiplexer 95. The optical pulse gate 91 passes the FM optical signal 110 during the high level of the gate pulse 140 (700-1 in FIG. 10a) and sends the pulsed FM optical signal 144 to the optical coupler 92. The optical coupler 92 receives the FM optical signal 144, sends it to the pulsed FM optical signal 146 to the interferometric optical fiber sensor array 400, and sends this FM optical signal 146 to the array 400 to form an interferometer 40. -1 to 40-M, the time-division multiplexed light intensity signal 1 shown in Fig. 10b is sent back.
Send 48 to O / E converter 50.

The O / E converter 50 converts the time-division multiplexed (pulsed) light intensity signal 148 into an electric signal 162 and sends it to the demultiplexer 95. The demultiplexer 95 receives the electric signals 162 from the interferometers 40-1 to 40-M, which are sent in a pulsed form, by the trigger signal 142 sent from the gate signal generator 90. 40-M and the corresponding demodulation processors 80-1 to 80-M are separately sent. The demodulators 80-1 to 80-M each receive an electric signal 16
2 and the sine wave 106 of the angular frequency ω ₀ sent from the modulation signal generator 10 and the data 112 of the frequency N sent from the frequency shift measuring device 30 to form a signal of equation (20), respectively. Output to 166-1 to 166-M. This makes it possible to obtain a demodulation output that does not depend on B and C.

According to the system of the third embodiment, the conventional modulation signal generator 5 is changed to the modulation signal generator 10, and the frequency deviation measuring device 30 and the demodulation processor 80 are newly added to the conventional system. -1 to 80-M is provided, so the instability of the demodulation output due to the fluctuation of the frequency deviation of the frequency modulation of the laser is improved,
Interferometer 40-1 to 40-M of the interferometric optical fiber sensor array 400
Dependent Loss Variation and Interferometers 40-1 to 40 in Optical Couplers
The instability of the demodulation output due to the fluctuation of the output amplitude B of the O / E converter 50 which occurs when a single mode fiber is used for -M can be improved.

FIG. 11 shows a fourth embodiment of the optical fiber sensor system according to the present invention. In FIG.
The difference from the configuration of FIG. 9 is that the modulation signal generator 10 is changed to a modulation signal generator 12.
This is a point in which 30 is changed to a frequency deviation measuring device 32. Further, since the frequency shift measuring device 32 is configured not to send the data of the frequency N to the demodulation processors 80-1 to 80-M, the demodulation processor is provided.
Since 80-1 to 80-M operate differently from the operation of the demodulation processor 80, this will be described later.

The modulation signal generator 12 is composed of a circuit for oscillating a sine wave signal having an angular frequency of ω ₀ , an automatic gain control circuit, and a reset signal generating circuit. The sine wave oscillating circuit outputs a sine wave signal at its output 106. The automatic gain control circuit controls the level of the sine wave signal input from the sine wave oscillation circuit based on the difference between the reference voltage in this control circuit and the voltage input from its input 190, and outputs it to its output 102. The reset signal generating circuit generates a reset signal based on the sine wave signal input from the sine wave oscillating circuit, and outputs the reset signal.
Output to The output 102 is connected to the light source 20, the output 104 is connected to the frequency deviation measuring device 32, and the output 106 is the demodulation processor.
It is connected to 80-1 to 80-M.

Referring to FIG. 12, in addition to the optical coupler 310 used in the frequency deviation measuring device 30, the frequency deviation measuring interferometer 320, the O / E converter 330 and the counter 340, the frequency deviation measuring device 32 is used. It has a configuration including an arithmetic circuit 350. Therefore, the description of the optical coupler 310, the frequency shift measuring interferometer 320, the O / E converter 330, and the counter 340 is omitted.

The input of the arithmetic circuit 350 is the output of the counter 340.
The calculation circuit 350 is basically a circuit that is connected to the circuit 112 and performs the calculation of the above equation (8). This circuit interferes with the value (integer) of the frequency N input from the input 112 of the circuit. optical path difference meter 320 △ L _1, determine the maximum frequency deviation [nu _d from the light velocity c ₀ of the refractive index n ₁ and a vacuum of optical fiber as the arm of the interferometer 320, the maximum frequency deviation [nu _d this that obtained It outputs the corresponding voltage on its output 190.

Therefore, in this system, if the voltage of this maximum frequency deviation ν _d is a predetermined voltage, it becomes the same as the reference voltage in the modulation signal generator 12, and the voltage difference between them becomes 0. The output 102 of the modulation signal generator 12 is output at the same level as the level of the sine wave signal so far. If the voltage with the maximum frequency deviation ν _d is lower than the reference voltage, the level of the sine wave signal is raised, and if the voltage with the maximum frequency deviation ν _d is higher than the reference voltage, the level of the sine wave signal is lowered and the reference voltage is lowered. And the voltage of the maximum frequency shift ν _d are controlled so as to match.

Next, the demodulation processor 80 used in the system of FIG. 11 will be described. In detail, the modulation factor / function calculator 86 of the demodulation processor 80 will be described. As described above, the modulation / function calculator 86 includes the calculation circuits 68a, 68b, 68c and the calculation circuit.
Comprised of 86a and 86b, of which the arithmetic circuit 68
For a, the maximum frequency deviation ν _d was obtained from the value of the frequency N, but in the case of the system of FIG. 11, the maximum frequency deviation ν _d is kept at a constant value, so this value is calculated in advance. circuit
It should be set to the output of 68a. Other arithmetic circuits
The operations 68b and 68c and the arithmetic circuits 86a and 86b perform the same operations as those described above, and thus the description thereof is omitted.

Regarding the operation of the fourth embodiment, the difference from the third embodiment will be described. When the modulation signal generator 12 sends a sine wave having an angular frequency ω ₀ to the light source 20, the light source 20 sends an FM optical signal 108 having a maximum frequency shift ν _d based on the sine wave signal 102 to the frequency shift measuring device 32. send. The frequency shift measuring device 32 receives the FM optical signal 108, sends the FM optical signal 110 to the optical pulse gate 91, and uses the FM optical signal 108 and the reset signal 104 sent from the generator 10 to generate a frequency N. Is calculated from the equation (8), the voltage of the maximum frequency deviation ν _d of the light source 20 is calculated from the value of the frequency N, and the voltage is sent to the modulation signal generator 12. The modulation signal generator 12 compares the internal reference voltage value with this sent voltage value of the maximum frequency deviation ν _d , and controls the level of the sine wave output from this output 102 based on this comparison value. , Sends the level-controlled sine wave again to the light source 20.
This loop circuit ensures that the maximum frequency deviation of the laser is always ν _d
To a predetermined value.

The modulation factor / function calculator 86 of each of the demodulation processors 80-1 to 80-M uses the value of the predetermined maximum frequency deviation ν _d preset in the output of the calculation circuit 68a (19). The formula signal is formed and sent to the divider 70. The divider 88 of each of the demodulation processors 80-1 to 80-M divides the signal of equation (5) by the signal of equation (19) to form the signal of equation (20), and outputs the respective outputs 166-1. Output from ~ 166-M. As can be seen from equation (20), each demodulation processor 80-1
A demodulation output independent of B and C can be obtained from .about.80-M.

According to the system of the fourth embodiment, the conventional modulation signal generator 5 is changed to the modulation signal generator 12, and the frequency shift measuring device 32 and the demodulation processor 80 are newly added to the conventional system. -1 to 80-M is provided, so the instability of the demodulation output due to the fluctuation of the frequency deviation of the frequency modulation of the laser is improved,
Interferometer 40-1 to 40-M of the interferometric optical fiber sensor array 400
Dependent Loss Variation and Interferometers 40-1 to 40 in Optical Couplers
The instability of the demodulation output due to the fluctuation of the output amplitude B of the O / E converter 50 which occurs when a single mode fiber is used for -M can be improved.

In the first to fourth embodiments, the Michelson interferometer is used as the frequency shift measuring interferometer 320 of the frequency shift measuring devices 30 and 32, but the Mach-Zehnder interferometer is used. Other types of interferometers, such as Further, in the demodulation processors 60 and 80 of the first to fourth embodiments, sin / co
s The example of dividing J ₁ (C) J ₂ (C) from the output of demodulator 66 has been explained, but J ₁ (C) and J ₂ (J) at the output of synchronous detector 62 or 82 and synchronous detector 64 or 84. (C) may be divided.

Further, in the third and fourth embodiments, the case where the sensors constituted by Michelson interferometers are arranged in a cascade connection and time division multiplex transmission is explained, but other sensors such as a Mach-Zehnder interferometer are used as the sensors. Type interferometer may be used, the array method may be another array such as parallel connection, and the multiplex transmission method may be another method such as frequency multiplex. Furthermore, in the third and fourth embodiments, the frequency shift measuring devices 30 and 32 are connected to the light source 20.
However, it may be arranged anywhere between the light source 20 and the sensor 400.

Furthermore, in the first to fourth embodiments, if the variation of the frequency deviation is within the allowable range, the frequency deviation measuring device 3
Instead of providing 0 and 32, the demodulation processors 60 and 80 may be configured to use the degree of modulation obtained from the set frequency deviation and the optical path difference of the interferometer.

[0089]

As described above, according to the present invention, the modulation signal generating means outputs a sine wave signal having an angular frequency of ω ₀ and a reset signal synchronized with this sine wave signal. The light source means receives a sine wave signal from the modulation signal generating means and outputs a frequency-modulated optical signal based on this signal. The frequency deviation measuring means receives the optical signal from the light source means, receives the reset signal from the modulation signal generating means, outputs the received optical signal, and outputs the maximum frequency deviation v _d of the received optical signal based on the received reset signal. Is obtained. The interferometer means receives the optical signal from the frequency shift measuring means and outputs a light intensity signal based on the phase difference between the two optical fibers according to the received optical signal. The first optical / electrical converting means receives the light intensity signal from the interferometer means and outputs an electric signal I = A + Bcos [Ccosω _o t + φ (t)] based on the light intensity signal. The demodulation processing means outputs a sinusoidal signal from the modulated signal generating means, an I signal from the first optical / electrical converting means, and a ν _d from the frequency deviation measuring means.
Receiving a signal and responding to the received sine wave signal and I signal
X = B ² · J ₁ (C) · J ₂ (C) · φ (t) signal is obtained, and the received ν
Signal of Y = J ₁ (C) ・ J ₂ (C) or U = depending on _d signal and I signal
Find the signals of B ² · J ₁ (C) · J ₂ (C), divide X by Y, and Z = B ²
• Divide the φ (t) signal or X by U to obtain the V = φ (t) signal.

Therefore, it is possible to effectively obtain a demodulation output including a stable physical quantity that is not affected by the C signal or the B and C signals.

[Brief description of drawings]

FIG. 1 is a functional block diagram of an optical fiber sensor system according to a first embodiment of the present invention.

FIG. 2 is a block diagram of a frequency deviation measuring device included in the optical fiber sensor system shown in FIGS.

FIG. 3 is a diagram showing a first example of output waveforms of an O / E converter included in the optical fiber sensor system shown in FIGS. 1, 7, and 13 and output waveforms of the demultiplexers of FIGS.

FIG. 4 is a diagram showing a second example of output waveforms of the O / E converter included in the optical fiber sensor system shown in FIGS. 1, 7, and 13 and output waveforms of the demultiplexers of FIGS.

5 is a block diagram of a sin / cos demodulator included in the fiber optic sensor system shown in FIGS. 1, 7, 9, 11, and 13. FIG.

6 is a block diagram of a modulation / function calculator included in the optical fiber sensor system shown in FIG.

FIG. 7 is a functional block diagram of an optical fiber sensor system according to a second embodiment of the present invention.

FIG. 8 is a block diagram of a modulation / function calculator included in the optical fiber sensor system shown in FIGS.

FIG. 9 is a functional block diagram of an optical fiber sensor system according to a third embodiment of the present invention.

FIG. 10 is a timing chart of signals appearing at various parts of the optical fiber sensor system shown in FIGS.

FIG. 11 is a functional block diagram of an optical fiber sensor system according to a fourth embodiment of the present invention.

FIG. 12 is a block diagram of a frequency deviation measuring device included in the optical fiber sensor system shown in FIG.

FIG. 13 is a functional block diagram of a conventional optical fiber sensor system.

[Explanation of symbols]

 10, 12 Modulation signal generator 20 Light source 30, 32 Frequency deviation measuring device 40, 40-1 to 40-M Interferometer 50 O / E converter 60, 80, 80-1 to 80-M Demodulation processor 62, 64, 82, 84 Synchronous detector 66 sin / cos Demodulator 68, 86 Modulation factor / function calculator 70, 88 Divider 90 Gate signal generator 91 Optical pulse gate 92, 93-1 to 93-M Optical coupler 94- 1 to 94- (M-1) Delay line 95 Demultiplexer 400 Interferometric fiber optic sensor array

Claims (12)

[Claims] 1. An optical fiber sensor system for detecting a physical quantity, wherein the system outputs a sine wave signal having an angular frequency of ω ₀ and a modulation signal generation for outputting a reset signal synchronized with the sine wave signal. Means, a light source means for receiving a sine wave signal from the modulation signal generating means, and outputting an optical signal frequency-modulated based on the signal, an optical signal from the light source means, and a reset signal from the modulation signal generating means Frequency shift measuring means for receiving the received optical signal, outputting the received optical signal, and obtaining a signal indicating the maximum frequency shift ν _d of the received optical signal based on the received reset signal, and the frequency shift measuring means. Interferometer means for receiving an optical signal from the means and outputting an optical intensity signal based on a phase difference between two optical fibers according to the received optical signal; and an optical intensity signal from the interferometer means for receiving the optical signal Average a first optical / electrical converting means for outputting an electrical signal _{I = A + Bcos [Ccosω o} t + φ (t)] based on the degree signal, wherein A is of the light input to the first optical / electrical conversion means Is a constant, B is a constant determined by the average power of light input to the first optical / electrical conversion means, the power of light when passing through the interferometer means, and the polarization state, and C is 2πΔL nν _d / c ₀ , ΔL is the optical path difference between the two optical fibers of the interferometer means, n is the refractive index of the two optical fibers serving as the arm of the interferometer means, and c ₀ Is the speed of light in vacuum, and φ (t)
Is the phase difference of the light when passing through the interferometer means,
The signal of the physical quantity to be detected is included here, and the sine wave signal from the modulation signal generating means, the I signal from the first optical / electrical converting means, and the ν _d signal from the frequency shift measuring means. And the received sinusoidal signal and I
Calculate the signal of X = B ²・ J ₁ (C) ・ J ₂ (C) ・ φ (t) according to the signal,
A signal of Y = J ₁ (C) · J ₂ (C) or a signal of U = B ² · J ₁ (C) · J ₂ (C) corresponding to the received ν _d signal and the I signal is obtained, And a demodulation processing means for obtaining a signal of Z = B ² · φ (t) by dividing the X by the Y or a signal of V = φ (t) by dividing the X by the U. ₁ (C) is a first-order Bessel function with C as an argument when the second item of the I signal is analyzed, and J (
₂ (C) is a second-order Bessel function, which is an optical fiber sensor system. 2. The optical fiber sensor system according to claim 1, wherein the frequency deviation measuring means includes a first input terminal, a first output terminal, a second input / output terminal, and a third output terminal. The optical signal from the light source means is input from the first input terminal, the input optical signal is branched and output to the first and second input / output terminals, and the second input / output is provided. First optical coupler means for inputting a light intensity signal from the terminal and outputting the input light intensity signal to the third output terminal; and an optical signal received from the second input / output terminal for receiving the received light signal. An interferometer unit for measuring frequency deviation, which generates a light intensity signal based on a phase difference between two optical fibers corresponding to a signal, and outputs the generated light intensity signal to the second input / output terminal; The light intensity signal is received from the output terminal of _{No. 3, and the} electric signal I ₁ = A ₁ + B ₁ cos based on the light intensity signal [C ₁ cos ω _o t ＋ φ ₁ (t)]
A second optical / electrical converting means, and A ₁ is an average power of light input to the second optical / electrical converting means, and B ₁ is a second optical / electrical converting means. A constant determined by the average power of the input light and the power of the light when passing through the frequency shift measuring interferometer means and the polarization state, and C ₁ is 2πΔL ₁ n ₁ ν _d / c ₀ , and ΔL ₁ is the optical path difference between the two optical fibers of the frequency shift measuring interferometer means, and n ₁ is the refractive index of the two optical fibers forming the arm of the frequency shift measuring interferometer means. , Φ ₁ (t) is the phase difference of the light when passing through the frequency shift measuring interferometer means, and the I ₁ signal from the second optical / electrical converting means and the modulation signal generating means from the second optical / electrical converting means receiving a reset signal, a half cycle of the sine wave of the angular frequency omega ₀ on the basis of the reset signal or Of generating a signal indicating a period of integral multiple counts the frequency of the received I ₁ signal within the period thus generated, a counter means for outputting a signal indicating the frequency, frequency from said counter means And a first arithmetic means for obtaining the ν _d signal according to the received signal. 3. The optical fiber sensor system according to claim 2, wherein the frequency deviation measuring interferometer means includes a fourth input / output terminal, a fifth input / output terminal, and a sixth input / output terminal. , The optical signal output from the second input / output terminal is input from the fourth input / output terminal, the input optical signal is branched and output to the fifth and sixth input / output terminals, Fifth
And a reflected light signal from each of the sixth input / output terminals, a light intensity signal based on the phase difference between the two optical fibers is generated from the input reflected light signal, and the reflected light signal is generated via the fourth input / output terminal. Second optical coupler means for outputting to the second input / output terminal, and an optical signal input from the fifth input / output terminal, transmitting the input optical signal, and transmitting the optical signal. A first optical fiber means having a first predetermined length for transmitting the reflected optical signal, and an optical signal input from the sixth input / output terminal, transmitting the input optical signal, and transmitting the optical signal. Second optical fiber means having a second predetermined length for transmitting a reflected optical signal of the received optical signal, and the optical path difference ΔL based on the first predetermined length and the second predetermined length ₁ is equal to or less than the coherence length of the light source A first reflecting mirror configured to form the reflected light signal of the optical signal transmitted from the first optical fiber means, and the reflected light of the optical signal transmitted from the second optical fiber means A fiber optic sensor system including a second reflector for forming a signal. 4. The optical fiber sensor system according to claim 1, wherein the demodulation processing means receives a sine wave signal from the modulation signal generation means and an I signal from the first optical / electrical conversion means. A first demodulation means for obtaining the X signal corresponding to the received sinusoidal signal and the I signal, and a ν _d signal from the frequency deviation measuring means are set in advance with the received ν _d signal. The second optical operation means for obtaining the C signal from the signal of the optical path difference ΔL and the refractive index n of the interferometer means and the signal of the light speed c _{0 in} the vacuum which is preset, and the first optical / electrical The signal of the second item of the I signal received from the converting means is converted into a Bessel function, and the converted Bessel functions J ₁ (C) and J ₂ (C) based on the C signal from the second calculating means. ) And a third calculation means for calculating the signal A fourth computing means J ₁ (C) and for multiplying J ₂ and (C) determining the Y signal, the Y signal from the arithmetic means of said 4 receives the X signal from the first demodulating means , A first division unit for dividing the X by the Y to obtain the Z signal. 5. The optical fiber sensor system according to claim 1, wherein the demodulation processing means receives a sinusoidal signal from the modulation signal generation means and an I signal from the first optical / electrical conversion means, A signal of P = 2B · J ₁ (C) · sin φ (t) corresponding to the received sine wave signal and I signal, a signal of Q = −2B · J ₂ (C) · cos φ (t) and the above The second demodulation means for obtaining the X signal and the ν _d signal from the frequency shift measuring means, and the received ν _d signal and the preset optical path difference ΔL and refractive index n of the interferometer means. A second arithmetic means for obtaining a C signal from a signal and a signal of a light speed c _{0 in} a preset vacuum, and a signal of the second item of the I signal received from the first optical / electrical converting means Is converted into a Bessel function, and the converted Bessel functions J ₁ (C) and J _{2 are} converted based on the C signal from the second calculating means. A third computing means for obtaining the signal of (C), P and Q signals from the second demodulating means, J ₁ (C) and J ₂ (C) signals from the third computing means, and Divide the P signal by the J ₁ (C) signal to obtain the signal of R = B · sin φ (t),
Fifth computing means for dividing the Q signal by the J ₂ (C) signal to obtain a signal of S = −B · cos φ (t), and R and S signals from the fifth computing means, The R and S
The signal of B ² is obtained by performing the sum of squares of the signal of
A sixth arithmetic means for obtaining the U signal is multiplied by J ₁ and (C) J ₂ and (C) from ² signal and the third computing means, the U signal from the arithmetic means of said 6 , A division means for receiving the X signal from the first demodulation means and dividing the X by the U to obtain the V signal. 6. An optical fiber sensor system for detecting a physical quantity, wherein the system inputs a comparison voltage and outputs a sine wave signal having an angular frequency ω _{0 at} a level based on a difference between the input comparison voltage and a reference voltage. A modulation signal generating unit that outputs a reset signal in synchronization with the sine wave signal and a sine wave signal from the modulation signal generating unit, and outputs an optical signal that is frequency-modulated based on the signal. The light source means receives an optical signal from the light source means, receives a reset signal from the modulation signal generating means, outputs the received optical signal, and outputs a maximum frequency deviation of the received optical signal based on the received reset signal. A frequency deviation measuring means for obtaining a signal indicating the shift ν _d and outputting the comparison voltage according to the obtained signal; and the modulation signal generating means, the light source means and the frequency deviation measuring means. The maximum frequency deviation ν _d is configured to have a predetermined constant value, receives the optical signal from the frequency deviation measuring means, and determines the phase difference between the two optical fibers according to the received optical signal. An interferometer means for outputting a light intensity signal based on the interferometer means, and a first signal for receiving the light intensity signal from the interferometer means and outputting an electric signal I = A + Bcos [Ccosω _o t + φ (t)] based on the light intensity signal. Optical / electrical conversion means, A is the average power of light input to the first optical / electrical conversion means, and B is the average power of light input to the first optical / electrical conversion means and the Is a constant determined by the power and polarization state of light passing through the interferometer means, C is 2πΔL nν _d / c ₀ , and ΔL is an optical path difference between two optical fibers of the interferometer means, The n is the refractive index of the two optical fibers serving as the arm of the interferometer means, c ₀ is the speed of light in vacuum, wherein phi (t)
Is the phase difference of the light when passing through the interferometer means,
The signal of the physical quantity to be detected is included here. The sine wave signal is received from the modulation signal generating means, the I signal is received from the first optical / electrical converting means, and the received sine wave signal and I signal are received. A signal of X = B ² · J ₁ (C) · J ₂ (C) · φ (t) corresponding to the signal is obtained, and Y corresponding to the preset predetermined ν _d signal and the received I signal is obtained. = J ₁ (C) ・ J ₂ (C) signal or U =
Calculate the signals of B ² · J ₁ (C) · J ₂ (C) and divide the X by the Y
Z = B ² · φ (t) signal or the X is divided by the U to obtain V = φ
demodulation processing means for obtaining the signal of (t), wherein J ₁ (C) is a first-order Bessel function with C as an argument when the second item of the I signal is analyzed.
₂ (C) is a second-order Bessel function, which is an optical fiber sensor system. 7. The optical fiber sensor system according to claim 6, wherein the frequency deviation measuring means includes a first input terminal, a first output terminal, a second input / output terminal, and a third output terminal. The optical signal from the light source means is input from the first input terminal, the input optical signal is branched and output to the first and second input / output terminals, and the second input / output is provided. First optical coupler means for inputting a light intensity signal from the terminal and outputting the input light intensity signal to the third output terminal; and an optical signal received from the second input / output terminal for receiving the received light signal. An interferometer unit for measuring frequency deviation, which generates a light intensity signal based on a phase difference between two optical fibers corresponding to a signal, and outputs the generated light intensity signal to the second input / output terminal; The light intensity signal is received from the output terminal of _{No. 3, and the} electric signal I ₁ = A ₁ + B ₁ cos based on the light intensity signal [C ₁ cos ω _o t ＋ φ ₁ (t)]
A second optical / electrical converting means, and A ₁ is an average power of light input to the second optical / electrical converting means, and B ₁ is a second optical / electrical converting means. A constant determined by the average power of the input light and the power of the light when passing through the frequency shift measuring interferometer means and the polarization state, and C ₁ is 2πΔL ₁ n ₁ ν _d / c ₀ , and ΔL ₁ is the optical path difference between the two optical fibers of the frequency shift measuring interferometer means, and n ₁ is the refractive index of the two optical fibers forming the arm of the frequency shift measuring interferometer means. , Φ ₁ (t) is the phase difference of the light when passing through the frequency shift measuring interferometer means, and the I ₁ signal from the second optical / electrical converting means and the modulation signal generating means from the second optical / electrical converting means receiving a reset signal, a half cycle of the sine wave of the angular frequency omega ₀ on the basis of the reset signal or Of generating a signal indicating a period of integral multiple counts the frequency of the received I ₁ signal within the period thus generated, a counter means for outputting a signal indicating the frequency, frequency from said counter means An optical fiber for receiving the signal indicating the above, obtaining the ν _d signal corresponding to the received signal, and outputting the comparison voltage according to the obtained ν _d signal. Sensor system. 8. The optical fiber sensor system according to claim 7, wherein the frequency deviation measuring interferometer means includes a fourth input / output terminal, a fifth input / output terminal, and a sixth input / output terminal. , The optical signal output from the second input / output terminal is input from the fourth input / output terminal, the input optical signal is branched and output to the fifth and sixth input / output terminals, Fifth
And a reflected light signal from each of the sixth input / output terminals, a light intensity signal based on the phase difference between the two optical fibers is generated from the input reflected light signal, and the reflected light signal is generated via the fourth input / output terminal. Second optical coupler means for outputting to the second input / output terminal, and an optical signal input from the fifth input / output terminal, transmitting the input optical signal, and transmitting the optical signal. A first optical fiber means having a first predetermined length for transmitting the reflected optical signal, and an optical signal input from the sixth input / output terminal, transmitting the input optical signal, and transmitting the optical signal. Second optical fiber means having a second predetermined length for transmitting a reflected optical signal of the received optical signal, and the optical path difference ΔL based on the first predetermined length and the second predetermined length ₁ is equal to or less than the coherence length of the light source A first reflecting mirror configured to form the reflected light signal of the optical signal transmitted from the first optical fiber means, and the reflected light of the optical signal transmitted from the second optical fiber means A fiber optic sensor system including a second reflector for forming a signal. 9. The optical fiber sensor system according to claim 6, wherein the demodulation processing means receives a sinusoidal signal from the modulation signal generation means and an I signal from the first optical / electrical conversion means. First demodulating means for obtaining the X signal in accordance with the received sinusoidal signal and the I signal; a signal indicating the preset 2π and a signal indicating ΔL;
The calculation of 2πΔL nν _d / c ₀ is performed from the signal indicating n, the signal indicating ν _d, and the signal indicating c ₀ , and C indicating the modulation degree is obtained.
Modulation degree means for forming a signal, and a signal of the second item of the I signal received from the first optical / electrical conversion means to a Bessel function, and the conversion based on the C signal from the modulation degree means Bessel function
J ₁ and (C) a second computing means for obtaining a signal J ₂ (C), calculated in the second calculating means J ₁ and (C) J ₂ the Y signal by multiplying the (C) Third calculating means for obtaining, Y signal from the third calculating means, X signal from the first demodulating means, first dividing means for dividing the X by the Y to obtain the Z signal An optical fiber sensor system comprising: 10. The optical fiber sensor system according to claim 6, wherein the demodulation processing means receives a sine wave signal from the modulation signal generation means and an I signal from the first optical / electrical conversion means, A signal of P = 2B · J ₁ (C) · sin φ (t) corresponding to the received sine wave signal and I signal, a signal of Q = −2B · J ₂ (C) · cos φ (t) and the above Second demodulation means for obtaining an X signal; a signal indicating the preset 2π, a signal indicating ΔL,
modulation degree means for performing the calculation of 2πΔL nν _d / c ₀ using the signal indicating n, the signal indicating ν _d and the signal indicating c ₀ , and a modulation degree means for forming the C signal indicating the modulation degree; The signal of the second item of the I signal received from the electrical conversion means is converted into a Bessel function, and the converted Bessel function based on the C signal from the modulation degree means
Second computing means for obtaining signals of J ₁ (C) and J ₂ (C), P and Q signals from the second demodulating means, and J ₁ (C) and J ₂ from the second computing means. (C) signal is received, the P signal is divided by the J ₁ (C) signal to obtain a signal of R = B · sin φ (t),
Fourth computing means for dividing the Q signal by the J ₂ (C) signal to obtain a signal S = −B · cos φ (t), and R and S signals from the fourth computing means, The R and S
The signal of B ² is obtained by performing the sum of squares of the signal of
A fifth arithmetic means for obtaining the U signal is multiplied by J ₁ and (C) J ₂ and (C) from ² signal and the second calculating means, a U signal from the arithmetic means of the fifth A second division means for receiving the X signal from the demodulation means and dividing the X by the U to obtain the V signal. 11. An optical fiber sensor system for detecting a physical quantity, wherein the system outputs a sine wave signal having an angular frequency of ω ₀ and a modulation signal generation for outputting a reset signal synchronized with the sine wave signal. Means, a light source means for receiving a sine wave signal from the modulation signal generating means, and outputting an optical signal frequency-modulated based on the signal, an optical signal from the light source means, and a reset signal from the modulation signal generating means Receiving the optical signal, outputting the received optical signal, and determining a signal indicating the maximum frequency deviation ν _d of the received optical signal based on the received reset signal, frequency deviation measuring means, and a predetermined first A plurality of pulse signals having a predetermined second pulse width that outputs a gate pulse signal having a predetermined first pulse width that repeats in a cycle and repeats a predetermined second cycle in the first cycle A gate signal generating means for outputting a gate pulse signal group, and a gate pulse signal from the gate signal generating means, an optical signal from the frequency deviation measuring means, and the first pulse of the received gate pulse signal. An optical pulse gate means for outputting the received optical signal during a width period, a first input terminal, a second input / output terminal and a third output terminal are provided, and the optical signal is output from the first input terminal. A pulsed optical signal is input from the pulse gate means, the input optical signal is output to the second input / output terminal, a light intensity signal group is input from the second input / output terminal, and the input signal is input. Optical coupler means for outputting a light intensity signal group to the third output terminal, and pulsed optical signals from the second input / output terminal, and a plurality of interferometers in response to the input optical signals. Intensity of time-division multiplexed light transmitted from Optical fiber sensor array means for outputting a signal group to the second input / output terminal, a light intensity signal group from the optical fiber sensor array means, and an electrical signal I based on each light intensity signal of the light intensity signal group. = A + Bcos [Ccosω _o t + φ (t)] is output, and A is an average power of light input to the optical / electrical converting means, and B is the optical / electrical converting means. Is a constant determined by the average power of the light input to the optical fiber, the power of the light when passing through each interferometer of the optical fiber sensor array means, and the polarization state, C is 2πΔL nν _d / c ₀ , and ΔL is The optical path difference between the two optical fibers of each interferometer of the optical fiber sensor array means, the n is the refractive index of the two optical fibers serving as the arms of the interferometer, and the c ₀ is in vacuum. Is the speed of light, and φ (t) is the interference Is the phase difference of the light when passing through, and the signal of the physical quantity to be detected is included here. It is provided with a plurality of output terminals, and the electric signal I time-division multiplexed from the optical / electrical conversion means is provided. Receiving the gate pulse signal group from the gate signal generating means, receiving the received electric signals I which are time-division-multiplexed and sent, and sequentially sending the received pulse signal of the received gate pulse signal group. Demultiplexer means that gates in the period of the second pulse width and outputs respectively from the corresponding plurality of output terminals, and is connected to each of the plurality of output terminals of the demultiplexer, and outputs a sine wave from the modulation signal generating means. Signal of the
The I signal is received from the demultiplexer and the ν _d signal is received from the frequency shift measuring means, and X = B ² · J ₁ (C) · J ₂ (C) corresponding to the received sine wave signal and I signal.・ A signal of φ (t) is obtained, and Y = J ₁ (C) ・ J corresponding to the received ν _d signal and the I signal.
₂ (C) signal or U = B ² · J ₁ (C) · J ₂ (C) signal,
Demodulation processing means group comprising a plurality of demodulation processing means for dividing the X by the Y to obtain a signal of Z = B ² · φ (t) or the X to obtain a signal of V = φ (t) And J ₁ (C) is a first-order Bessel function with C as an argument when the second item of the I signal is analyzed.
₂ (C) is a second-order Bessel function, which is an optical fiber sensor system. 12. An optical fiber sensor system for detecting a physical quantity, wherein the system inputs a comparison voltage and outputs a sine wave signal having an angular frequency ω _{0 at} a level based on a difference between the input comparison voltage and a reference voltage. A modulation signal generating unit that outputs a reset signal in synchronization with the sine wave signal and a sine wave signal from the modulation signal generating unit, and outputs an optical signal that is frequency-modulated based on the signal. The light source means receives an optical signal from the light source means, receives a reset signal from the modulation signal generating means, outputs the received optical signal, and outputs a maximum frequency deviation of the received optical signal based on the received reset signal. The frequency deviation measuring means for obtaining a signal indicating the shift ν _d and outputting the comparison voltage according to the obtained signal; and the modulation signal generating means, the light source means and the frequency deviation measuring means. Is configured such that the maximum frequency deviation ν _d becomes a predetermined constant value, and a gate pulse signal having a predetermined first pulse width that repeats in a predetermined first cycle is output, Gate signal generating means for outputting a gate pulse signal group consisting of a plurality of pulse signals having a predetermined second pulse width, which repeats in a predetermined second cycle within a cycle; and a gate pulse signal from the gate signal generating means, An optical pulse gate means for receiving an optical signal from the frequency shift measuring means and outputting the received optical signal during a period of the first pulse width of the received gate pulse signal; a first input terminal; Two optical input / output terminals and a third output terminal are provided, the pulsed optical signal is input from the optical pulse gate means from the first input terminal, and the input optical signal is input to the second input / output. Output to the terminal and the second input / output An optical coupler means for inputting a light intensity signal group from the terminal and outputting the input light intensity signal group to the third output terminal; and inputting a pulsed optical signal from the second input / output terminal, Optical fiber sensor array means for outputting to the second input / output terminal a light intensity signal group that is time-division multiplexed and sent from a plurality of interferometers in response to the input optical signal, and the optical fiber sensor. An optical / electrical conversion means for receiving a light intensity signal group from the array means and outputting an electric signal I = A + Bcos [Ccosω _o t + φ (t)] based on each light intensity signal of the light intensity signal group; Is the average power of the light input to the optical / electrical conversion means, and B is the average power of the light input to the optical / electrical conversion means and the light when passing through each interferometer of the optical fiber sensor array means. Is a constant determined by the power and polarization state of C is 2πΔL nν _d / c _0, wherein ΔL is an optical path difference between the two optical fibers of each interferometer of the optical fiber sensor array means, wherein n is two optical fibers comprising the arms of the respective people interferometer Is the refractive index, c ₀ is the speed of light in vacuum, φ (t) is the phase difference of the light when passing through each interferometer, and the signal of the physical quantity to be detected is included here. A plurality of output terminals, and receives the time-division multiplexed electrical signal I from the optical / electrical conversion means, receives the gate pulse signal group from the gate signal generation means, and receives the time-division multiplexed electrical signal. The respective electrical signals I sent in sequence are gated in the period of the second pulse width of the respective pulse signals of the received gate pulse signal group sequentially transmitted, and are respectively output from the corresponding plurality of output terminals. Demultiplexer means, and Is connected to each of the plurality of output terminals of the multiplexer, the sine wave signal from said modulation signal generating means,
The I signal is obtained from the demultiplexer, and a signal of X = B ² · J ₁ (C) · J ₂ (C) · φ (t) corresponding to the received sine wave signal and the I signal is obtained and preset. In addition, a signal of Y = J ₁ (C) · J ₂ (C) or U = corresponding to the predetermined ν _d signal and the received I signal.
The signals of B ² · J ₁ (C) · J ₂ (C) are obtained, and the X is divided by the Y to obtain Z
= B ² · φ (t) signal or the X is divided by the U to obtain V = φ (t)
A group of demodulation processing means for obtaining the signal of J ₁ (C) is a first-order Bessel function with C as an argument when the second item of the I signal is analyzed. , Said J
₂ (C) is a second-order Bessel function, which is an optical fiber sensor system.