JP5761765B2 - Interferometric fiber optic sensor - Google Patents

Description

  The present invention relates to an interference-type optical fiber sensor, and more particularly to an interference-type optical fiber sensor that suppresses the influence of disturbance received by a delay compensator by providing two arms that suppress the influence of disturbance at different phases.

  The interference type optical fiber sensor includes a sensing fiber, and converts a signal to be detected into a strain of the sensing fiber. Next, the interference type optical fiber sensor changes the phase of the sensing light passing through the sensing fiber due to distortion of the sensing fiber. Next, the interference type optical fiber sensor demodulates and detects the phase of the sensing light. In this way, the interference optical fiber sensor can detect various physical quantities.

  For example, there is one that detects an acoustic signal by using an interference type optical fiber sensor (for example, see Non-Patent Document 1). Further, for example, there is one that detects a magnetic signal by using an interference type optical fiber sensor (see, for example, Non-Patent Document 2). Moreover, for example, there is an interference type optical fiber sensor that enables multiplex transmission by configuring a sensor array with a plurality of sensing fibers (see, for example, Non-Patent Document 3).

  In the above, an outline has been described of an example in which the phase of the sensing light passing through the sensing fiber is changed by various signals. By the way, the phase of the sensing light also changes due to other factors. For example, the phase of the sensing light changes even when the temperature of the installation environment changes or the pressure of the installation environment changes. Since the frequency of the signal accompanying the temperature change or pressure change is low, the interference type optical fiber sensor detects the signal by using the difference in frequency between the signal to be detected and the signal accompanying the temperature change or pressure change, and Signals associated with temperature or pressure changes can be separated.

  However, when there is an error in demodulation, high-frequency noise is generated, which hinders detection of various signals. For example, when temperature or pressure changes greatly, phase drift of sensing light occurs, and the frequency of noise reaches the signal band and cannot be separated. Therefore, there is an interference type optical fiber sensor that suppresses noise due to phase drift of sensing light by canceling the phase change of sensing light (see, for example, Patent Document 1).

  In general, it is known that a range in which the phase change of sensing light is canceled can be expanded by using a combination of a Peltier element and a heat sink. For example, FIG. 4 is a diagram illustrating an example of a schematic configuration of the interference type optical fiber sensor 3 in the related art. As shown in FIG. 4, the light pulse output from the pulse light source 11 is divided into two pulses by the optical coupler 37. One of the two pulses is immediately reflected by the mirror 35 and sent to the optical coupler 51. The other of the two pulses is reflected by the mirror 33 after passing through the sensing fiber 31 and immediately sent to the optical coupler 51 later than the first pulse reflected by the mirror 35.

  Next, the pulse input to the optical coupler 51 is divided into a plurality. One of the divided pulses is immediately reflected by the mirror 73 and sent to an O / E (Optical / Electrical) converter 17_1 and an O / E converter 17_2. Of the pulses divided into a plurality of pulses, the other pulse passes through the delay compensation fiber 76 and is reflected by the mirror 71, and immediately after the first pulse reflected by the mirror 73, O / E conversion is performed. To the device 17_1 and the O / E converter 17_2.

  As a result, a pulse that has passed through the sensing fiber 31 but has not passed through the delay compensation fiber 76 interferes with a pulse that has not passed through the sensing fiber 31 but has passed through the delay compensation fiber 76. Next, the interference type optical fiber sensor 3 detects various signals from the interfered pulses by using the O / E converter 17_1, the O / E converter 17_2, and the demodulator 19.

  Next, the phase change of the sensing light in FIG. 4 will be described. A part of the delay compensation fiber 76 is wound around the bobbin 61. A portion wound around the bobbin 61 is bonded to the bobbin 61 so that heat from the Peltier element 57 is transmitted to the bobbin 61. The bobbin 61 is provided with a Peltier element 57. On the premise of this configuration, the output of the demodulator 19 is supplied to the Peltier element 57.

  Specifically, first, the output of the demodulator 19 includes a phase change associated with a temperature change or pressure change of the sensing fiber 31 and a phase change associated with a temperature change or pressure change of the delay compensation fiber 76. . Then, the output of the demodulator 19 is supplied to the Peltier element 57 via the amplifier 23. Thereby, the phase change accompanying the temperature change or pressure change of the sensing fiber 31 and the phase change accompanying the temperature change or pressure change of the delay compensation fiber 76 are converted into a temperature change of the Peltier element 57.

  As a result, the bobbin 61 and a part of the delay compensation fiber 76 wound around and bonded to the bobbin 61 undergo a temperature change. As a result, a part of the delay compensation fiber 76 causes a phase change with a temperature change, so that a feedback system is configured. Since such a feedback system suppresses the phase change accompanying the temperature change or pressure change of the sensing fiber 31 and the phase change accompanying the temperature change or pressure change of the delay compensation fiber 76, noise due to such a phase change is suppressed. Is resolved.

  More specifically, first, the output of the demodulator 19 is expressed by Expression (1) as shown below.

Here, O represents the output of the demodulator 19. X _S represents a signal input from the sensing fiber 31. X _N represents a disturbance input from the sensing fiber 31. Y represents a disturbance applied to the delay compensation fiber 76. Z represents a control signal wound around the bobbin 61 and applied to a part of the delay compensation fiber 76.

Most of the disturbance X _N and the disturbance Y, is a variation of the long period due to temperature change or pressure change. Therefore, in the case where feedback control is performed on the long-period variation of the output O of the demodulator 19, the control signal Z is expressed by the following equation (2) as shown below.

  By substituting equation (2) into equation (1), equation (3) shown below is derived.

Therefore, by feedback-controlling the variation in the long period, since X _N and Y is a variation of the long period is canceled, and the variation of the long period, and the high frequency noise generated by the demodulation error is suppressed The

  Patent Document 1 described above discloses a technique for preventing saturation of the amplifier 23 and failure of the Peltier element 57 by providing a filter in the feedback system. On the other hand, in FIG. 4, the heat generated by the Peltier element 57 is radiated to the outside through the heat sink 59 by bringing the heat sink 59 into contact with the surface of the Peltier element 57 on the side where the bobbin 61 is not provided. Yes. Thereby, saturation of the amplifier 23 and failure of the Peltier element 57 are prevented. In addition, as a kind of the heat sink 59, there is one that radiates heat by using fins or the like, but here, an example of radiating heat by flowing a medium such as water or antifreeze is shown.

Japanese Patent No. 4930068

Ryotaku SATO et al. "Expansion of Dynamic Range in Interferometric Fiber Optical Hydrophone", Japan Journal of Applied Physics, Vol. 52,2013,012501 Ryotaku SATO et al. "Design of Fiber-Optic Magnetometer Utilizing Magnetostriction", Japan Journal of Applied Physics, Vol. 46, no. 2, 2007, p. 817-820 Ryozawa Sato, 3 others, “Development of optical fiber hydrophone”, IEICE Technical Report, May 1995, OPE95-2, p. 7-12

  However, when the temperature of the bobbin 61 fluctuates by other than the control by the feedback system, the suppression of the long-period fluctuation and the high frequency noise generated by the demodulation error is insufficient. Specifically, when the temperature of the bobbin 61 increases due to a factor other than the feedback system, or when the temperature change of the bobbin 61 increases due to a factor other than the feedback system, the temperature should be sufficiently controlled by the feedback system. Thus, Equation (2) shown above is not established. In this state, it becomes impossible to suppress the phase change accompanying the temperature change or pressure change of the delay compensation fiber 76.

  That is, when the temperature of the bobbin 61 increases due to a factor other than the feedback system, or when the temperature change of the bobbin 61 increases due to a factor other than the feedback system, high frequency noise is generated. Reach the signal band. Therefore, noise and a signal cannot be separated using a difference in frequency, and signal detection is hindered.

  In other words, the influence of the disturbance that the delay compensator 15 including the delay compensation fiber 76 receives may not be suppressed. Therefore, an interference type optical fiber sensor that can suppress the influence of disturbance received by the delay compensator 15 has been desired.

The interference type optical fiber sensor of the present invention is a first optical coupler that outputs a sensing fiber that detects a physical quantity, a pulse that causes a delay difference in the sensing fiber, and a pulse that does not cause a delay difference in the sensing fiber. When a pulse that caused the delay difference, a second optical coupler to supply and does not cause the delay difference pulses, to the first arm and the second arm, supplied from said second optical coupler to said first arm A demodulator for outputting an output signal including the physical quantity from an interference pulse obtained by interfering the first pulse thus generated and the second pulse supplied from the second optical coupler to the second arm; and Correspondingly, a first surface, and two first member for generating a temperature difference and a second surface, the sandwiched two first member, a second member for radiating heat of the two first member , Wherein the first arm, one of the two first member having a first optical fiber disposed in one of said first surface, said second arm, a delay in the sensing fiber A delay compensating fiber for compensation, and a second optical fiber disposed on the other second surface of the two first members , wherein the first optical fiber is formed on one of the first surfaces. The phase is displaced according to a temperature change, the phase of the second optical fiber is displaced according to a temperature change of the other second surface, and the phase difference between the first pulse and the second pulse is: It is displaced in accordance with the difference between the temperature change of one of the first surfaces and the temperature change of the other second surface .

  In the interference-type optical fiber sensor of the present invention, the first member is formed of a Peltier element.

  In the interference-type optical fiber sensor of the present invention, the demodulator outputs the physical quantity as a current and supplies the current to the Peltier element.

  The interference type optical fiber sensor of the present invention is a first optical coupler that outputs a sensing fiber that detects a physical quantity, a pulse that causes a delay difference in the sensing fiber, and a pulse that does not cause a delay difference in the sensing fiber. A pulse that causes the delay difference and a pulse that does not cause the delay difference are supplied to the first arm and the second arm, the first pulse that reciprocates the first arm, and the second arm A second optical coupler that causes the reciprocated second pulse to interfere with each other, and outputs the interfered interference pulse; a demodulator that outputs an output signal including the physical quantity from the interference pulse; Two first members that generate a temperature difference between the first surface and the second surface; and a second member that is sandwiched between the two first members and dissipates heat from the two first members. The first arm has a first optical fiber disposed on one of the two first members, and the second arm compensates for delay in the sensing fiber. A second optical fiber disposed on the second surface of the other of the two first members, the first optical fiber responding to a temperature change of one of the first surfaces. The phase of the second optical fiber is displaced according to the temperature change of the other second surface, and the phase difference between the first pulse and the second pulse is one of the first optical fibers. It is displaced according to the difference between the temperature change of one surface and the temperature change of the other second surface.

  In the interference-type optical fiber sensor of the present invention, each of the two first members is formed of a Peltier element.

  In the interference-type optical fiber sensor of the present invention, the demodulator outputs the physical quantity as a current and supplies the current to the Peltier element.

  The interference type optical fiber sensor of the present invention is a first optical coupler that outputs a sensing fiber that detects a physical quantity, a pulse that causes a delay difference in the sensing fiber, and a pulse that does not cause a delay difference in the sensing fiber. A pulse that causes the delay difference and a pulse that does not cause the delay difference are supplied to the first arm and the second arm, the first pulse that reciprocates the first arm, and the second arm A second optical coupler for causing the reciprocated second pulse to interfere with each other and outputting the interfered interference pulse; a demodulator for outputting an output signal including the physical quantity from the interference pulse; and at least a first surface, In accordance with the output signal output from the demodulator, the two first members that heat the first surface and the two first members are sandwiched between the two first members. A second member that radiates heat, wherein the first arm has a first optical fiber disposed on one of the two first members, and the second arm is A delay compensating fiber that compensates for a delay in the sensing fiber; and a second optical fiber disposed on the first surface of the other of the two first members, the first optical fiber comprising: The phase of the second optical fiber is displaced in accordance with a temperature change of one of the first surfaces, and the phase of the second optical fiber is displaced in accordance with a temperature change of the other first surface. The phase difference from the pulse is displaced in accordance with the difference between the temperature change of one of the first surfaces and the temperature change of the other first surface.

  In the interference-type optical fiber sensor of the present invention, each of the two first members is formed by a heater.

  In the interference-type optical fiber sensor of the present invention, the demodulator outputs the physical quantity as a current and supplies the current to the heater.

  The interference type optical fiber sensor according to the present invention includes two diodes, each of the two diodes having a different orientation, and one of the two diodes is the demodulator and the two second diodes. One is provided between one of the members, and the other is provided between the demodulator and the other of the two first members.

  The present invention has an effect that the influence of the disturbance received by the delay compensator 15 can be suppressed by providing two arms that suppress the influence of the disturbance with different phases.

It is a figure which shows an example of schematic structure of the interference type optical fiber sensor 1 in Embodiment 1 of this invention. It is a figure which shows an example of schematic structure of the interference type optical fiber sensor 1 in Embodiment 2 of this invention. It is a figure which shows an example of schematic structure of the interference type optical fiber sensor 1 in Embodiment 3 of this invention. It is a figure which shows an example of schematic structure of the interference type optical fiber sensor 3 in a prior art.

  Hereinafter, Embodiments 1 to 3 of the present invention will be described in detail with reference to the drawings. In the following drawings, the size relationship of each component may be different from the actual one. In the following drawings, the same reference numerals are added to the same or corresponding parts, and this is common throughout the entire specification. Furthermore, the forms of the constituent elements described in the entire specification are merely examples, and are not limited to these descriptions.

Embodiment 1 FIG.
<Overview>
As a high-frequency noise is generated and the frequency of the noise reaches the signal band, the noise and the signal cannot be separated using the difference in frequency. It is assumed that the ambient temperature exceeds the controllable range of the Peltier element 57 (described later).

  Specifically, this is a case where the ambient temperature of the place where the bobbin 61 and the bobbin 63 (both described later) are placed changes faster than the temperature change caused by the Peltier element 57 (described later). This is also the case where the magnitude of the change in ambient temperature at the place where the bobbin 61 and the bobbin 63 (both will be described later) are larger than the temperature control range of the Peltier element 57 (described later). In these cases, the control of the Peltier element 57 (described later) may be insufficient. In the first embodiment, a configuration and operation that can cope with such a case will be described.

<Description of configuration>
FIG. 1 is a diagram showing an example of a schematic configuration of an interference optical fiber sensor 1 according to Embodiment 1 of the present invention. As shown in FIG. 1, the interference type optical fiber sensor 1 includes a pulse light source 11, a sensor unit 13, a delay compensator 15, an O / E (Optical / Electrical) converter 17_1, an O / E converter 17_2, and a demodulator 19. , A filter 21 and an amplifier 23.

The pulse light source 11 generates a pulse of light having a constant wavelength and supplies it to the sensor unit 13. Sensor unit 13 is provided, for example, under the water surface to detect a signal X _S. The signal _XS is a physical quantity. Further, the sensor unit 13, the disturbance _{X N} is detected. Sensor unit 13 supplies a signal _{X S,} a disturbance _{X N} to the delay compensator 15. The delay compensator 15 compensates for the delay of the sensor unit 13. Although the delay compensator 15 is affected by the disturbance Y ₁ , the influence of the disturbance X _N and the disturbance Y ₁ is suppressed by the control signal Z ₁ , and the signal is sent to the O / E converter 17_1 and the O / E converter 17_2. It supplies the interference pulses including X _S.

The O / E converter 17 </ b> _ <b> 1 and the O / E converter 17 </ b> _ <b> 2 convert light pulses into electrical signals and supply them to the demodulator 19. Demodulator 19, by a variety of processes, detecting a signal X _S from electrical signal corresponding to the interference pulses, and supplies to the filter 21. Filter 21 extracts the electrical signal of a specific frequency from the electric signal corresponding to the signal X _S, supplied to the amplifier 23. The amplifier 23 amplifies the supplied signal and supplies the amplified signal to the delay compensator 15. In the following description, both the O / E converter 17_1 and the O / E converter 17_2 are referred to as an O / E converter 17.

  Specifically, the sensor unit 13 includes a sensing fiber 31, a mirror 33, a mirror 35, and an optical coupler 37. The delay compensator 15 includes an optical coupler 51, a first arm 53, a second arm 55, and a Peltier element 57. The first arm 53 includes a bobbin 63, an optical fiber 67, and a mirror 73. The second arm 55 includes a bobbin 61, an optical fiber 65, a delay compensation fiber 75, and a mirror 71.

More specifically, the light pulse output from the pulse light source 11 is divided into two pulses by the optical coupler 37. Of the divided pulses, one pulse is immediately reflected by the mirror 35 and sent to the optical coupler 51 via the optical coupler 37. On the other hand, of the divided pulses, the other pulse passes through the sensing fiber 31 and is reflected by the mirror 33, and is sent to the optical coupler 51 via the optical coupler 37 later than the first pulse. It is done. At this time, the sensing fiber 31 outputs a pulse whose phase is displaced in the signal X _S or disturbance X _N.

  The pulse sent to the optical coupler 51 is divided into a plurality. Of the pulses divided into a plurality of pulses, one pulse is immediately reflected by the mirror 73 to reciprocate through the optical fiber 67 and sent to the O / E converter 17 via the optical coupler 51. On the other hand, of the pulses divided into a plurality of pulses, the other one pulse passes through the delay compensation fiber 75 and then reflects to the mirror 71 so as to reciprocate through the optical fiber 65, via the optical coupler 51, It is sent to the O / E converter 17.

Here, the pulse sent from the optical coupler 51 to the O / E converter 17 does not pass through the sensing fiber 31, passes through the delay compensation fiber 75, passes through the sensing fiber 31, and passes through the delay compensation fiber 75. This is a pulse that interferes with a pulse that has not passed. O / E converter 17 and the demodulator 19 detects a signal _{X S} from the interference pulses. The delay compensation fiber 75 is an optical fiber that compensates for the delay of the sensing fiber 31.

  The configuration related to the pulse of the interference type optical fiber sensor 1 has been described above. Next, a configuration related to the phase change of the interference type optical fiber sensor 1 will be described. First, as a precondition, it is assumed that when the bobbin 61 is heated by the Peltier element 57, the bobbin 63 is cooled, and when the bobbin 61 is cooled by the Peltier element 57, the bobbin 63 is heated. Further, it is assumed that the delay compensation fiber 75 is placed in a place where the temperature change and the pressure change are small. Although an example in which the Peltier element 57 is used as a member that generates a temperature difference between the first surface and the second surface has been described here, the present invention is not particularly limited thereto.

  Further, it is assumed that each of the bobbin 61, the bobbin 63, the optical fiber 65, and the optical fiber 67 has a configuration in which the magnitude of the phase change due to the ambient temperature is equal. For example, the same material is used for each of the bobbin 61, the bobbin 63, the optical fiber 65, and the optical fiber 67, and the length of the portion of the optical fiber 65 that is wound and bonded to the bobbin 61 and the bobbin 63 are wound. It is assumed that the lengths of the portions of the optical fiber 67 bonded together are equal. By doing in this way, each of the bobbin 61, the bobbin 63, the optical fiber 65, and the optical fiber 67 can make the magnitude | size of the phase change by ambient temperature equal.

  An optical fiber 65 is provided between the optical coupler 51 and the mirror 71. The optical fiber 65 is wound around the bobbin 61, and the wound part is bonded to the bobbin 61. Thereby, the heat of the Peltier element 57 is transmitted to the bobbin 61, whereby the heat of the Peltier element 57 is also transmitted to the optical fiber 65 via the bobbin 61.

  An optical fiber 67 is provided between the optical coupler 51 and the mirror 73. The optical fiber 67 is wound around the bobbin 63, and the wound portion is bonded to the bobbin 63. As a result, the heat of the Peltier element 57 is transmitted to the bobbin 63, whereby the heat of the Peltier element 57 is also transmitted to the optical fiber 67 via the bobbin 63.

  As a result, various temperature changes or pressure changes included in the output of the demodulator 19 are converted into temperature changes by the amplifier 23 and the Peltier element 57. For example, the output of the demodulator 19 includes a phase change associated with a temperature change or pressure change of the sensing fiber 31, a phase change associated with a temperature change or pressure change of the delay compensation fiber 75, and a temperature included in the optical fiber 65. The phase change accompanying the change or pressure change and the phase change accompanying the temperature change or pressure change included in the optical fiber 67 are included.

  Therefore, since these temperature changes or pressure changes are converted into temperature changes by the amplifier 23 and the Peltier element 57, they are converted into temperature changes between the bobbin 61 and the optical fiber 65 wound around and bonded to the bobbin 61. The temperature change between the bobbin 63 and the optical fiber 67 wound around and bonded to the bobbin 63 is converted.

  Therefore, when the temperature of the optical fiber 65 changes, the phase change of the pulse passing through the optical fiber 65 is converted, and when the temperature of the optical fiber 67 changes, the phase change of the pulse passing through the optical fiber 67 is converted. . For example, when the optical fiber 65 or the optical fiber 67 is heated, the material expands, so that a transmission distance of a pulse passing through the optical fiber 65 or the optical fiber 67 becomes long, and the optical fiber 65 or the optical fiber 67 passes through. Therefore, the phase of the pulse passing through the optical fiber 65 or the optical fiber 67 is delayed. Further, for example, when the optical fiber 65 or the optical fiber 67 is cooled, the material contracts, so that a transmission distance of a pulse passing through the optical fiber 65 or the optical fiber 67 is shortened, and the optical fiber 65 or the optical fiber 67 is reduced. Since the arrival of the pulse passing through the optical fiber becomes faster, the phase of the pulse passing through the optical fiber 65 or the optical fiber 67 advances.

  From the above description, the interference optical fiber sensor 1 is configured with a feedback system. That is, the phase change accompanying the temperature change or pressure change of the sensing fiber 31, the phase change accompanying the temperature change or pressure change of the delay compensation fiber 75, the phase change accompanying the temperature change or pressure change included in the optical fiber 65, light Each of the phase changes accompanying the temperature change or pressure change included in the fiber 67 is canceled by the phase change of the optical fiber 65 and the optical fiber 67 generated by being fed back from the output of the demodulator 19. Is configured.

  The filter 21 is provided between the demodulator 19 and the amplifier 23. However, when the amplifier 23 is saturated, an overcurrent flows through the Peltier element 57, and the Peltier element 57 fails. It is attached when assumed.

  The optical coupler 37 corresponds to the first optical coupler in the present invention. The pulse reciprocating the first arm 53 corresponds to the first pulse in the present invention. The pulse reciprocating the second arm 55 corresponds to the second pulse in the present invention. The optical coupler 51 corresponds to the second optical coupler in the present invention. The Peltier element 57 corresponds to the first member in the present invention. The optical fiber 67 corresponds to the first optical fiber in the present invention. The optical fiber 65 corresponds to the second optical fiber in the present invention.

<Description of operation>
Sensing fiber 31 by a signal X _S for detecting distortion are modulated sensing light phase passing through the sensing fiber 31 by the strain of the sensing fiber 31, the signal X _S is detected by the demodulator 19 and the like. Phase change associated with temperature change or pressure change of sensing fiber 31, phase change associated with temperature change or pressure change of delay compensation fiber 75, phase change associated with temperature change or pressure change included in optical fiber 65, optical fiber 67 Each of the phase changes accompanying the temperature change or pressure change included in the signal is canceled by the feedback of the output of the demodulator 19 to the optical fiber 65 and the optical fiber 67.

  That is, the phase change of light due to temperature change or pressure change, that is, long-period fluctuation such as temperature change or pressure change is canceled, so that noise generated by the phase change is eliminated.

  Further, the phase change of the first arm 53 and the phase change of the second arm 55 include a phase change accompanying a change in ambient temperature and a phase change accompanying a current flowing through the Peltier element 57. The phase change accompanying the change in the ambient temperature is canceled because the optical fiber 65 and the optical fiber 67 are feedback-controlled. Therefore, if the phase of one pulse before the interference by the optical coupler 51 advances, the phase of the other pulse before the interference by the optical coupler 51 also advances, so that the timings of the amplitudes of the interfering pulses coincide with each other. The phase change is canceled by the applied pulse.

  On the other hand, the phase change accompanying the current flowing through the Peltier element 57 is such that when the optical fiber 65 is warmed, the optical fiber 67 is cooled, so the phase of the pulse passing through the optical fiber 65 is delayed and passes through the optical fiber 67. When the optical fiber 65 is cooled, the optical fiber 67 is warmed, so that the phase of the pulse passing through the optical fiber 65 advances and the phase of the pulse passing through the optical fiber 67 is delayed. . That is, the phase difference between the pulse passing through the optical fiber 65 and the pulse passing through the optical fiber 67 is displaced according to the temperature difference between the first surface and the second surface of the Peltier element 57. Therefore, if the phase of one pulse before the interference by the optical coupler 51 is advanced, the phase of the other pulse before the interference by the optical coupler 51 is delayed. As a result, the phase of the pulse in which the pulse reciprocating through the first arm 53 interferes with the pulse reciprocating through the second arm 55 is displaced, so that the phase of the pulse can be adjusted by feedback by the Peltier element 57.

Specifically, a signal inputted to the sensing fiber 31 and the signal X _S, the disturbance is input to the sensing fiber 31 and the disturbance X _N. Further, the disturbance applied to the optical fiber 65 wound on the bobbin 61 to apply a change in temperature as a disturbance Y _1, to the disturbance applied to the optical fiber 67 wound around a bobbin 63 to apply a temperature change and disturbance Y _2. That is, the disturbance applied to the delay compensator 15 is referred to as disturbance Y ₁ and disturbance Y ₂ . Further, the optical fiber 65, a control signal applied to the delay compensation fiber 75 and Z _1, when the control signal applied to the optical fiber 67 and -Z _2, output O, which is the output of the demodulator 19, the following formula It is represented by (4).

The disturbance X _N , the disturbance Y ₁ , and the disturbance Y ₂ are mostly long-period fluctuations associated with temperature changes or pressure changes. The third term of Expression (4) represents a phase change applied to the second arm 55. Further, the fourth term of the equation (4) represents a phase change applied to the first arm 53. Therefore, the sign of the third term and the sign of the fourth term are inverted. Of the output O of the demodulator 19, the feedback control of the variation of the long cycle, the control signal Z is the sum of the control signal Z ₁ and the control signal Z ₂ is represented by the following formula (5).

  By substituting equation (5) into equation (4), the following equation (6) is derived.

That is, the output O of the demodulator 19 at this time is as shown in Expression (6). Thereby, X _N + Y ₁ -Y _2, which is a long-period fluctuation, is canceled out, and a long-period fluctuation and high-frequency noise generated by a demodulation error are suppressed.

  When Y1 and Y2 match, the output O of the demodulator 19 is represented by the following equation (4 '), and the control signal Z is represented by the following equation (5').

As a result, the disturbance Y ₁ and the disturbance Y ₂ disappear from the control signal Z. This is also a disturbance Y ₁ and disturbance Y ₂ is changed, become independent of the control, which means that it is possible to suppress the fluctuation of the long-period only control to cancel the disturbance X _N. Even if the disturbance Y ₁ and the disturbance Y ₂ do not completely coincide with each other, the disturbance Y ₁ and the disturbance Y ₂ are weakened, and the operation of the control signal Z ₁ + Z ₂ for canceling the disturbance X _N The range can be reduced. In other words, the disturbance Y ₁ applied to the delay compensator 15 is provided by providing the first arm 53 and the second arm 55 and suppressing the influence of the disturbance at a phase different between the first arm 53 and the second arm 55. and the influence of the disturbance Y ₂ is suppressed.

<Description of effects>
In the prior art, high frequency noise is generated and the noise frequency reaches the signal band, so that noise and signal cannot be separated using the difference in frequency, and signal detection is hindered. For example, the case where the ambient temperature exceeds the controllable range of the Peltier element 57 is assumed.

  Specifically, this is a case where the ambient temperature of the place where the bobbin 61 and the bobbin 63 are placed changes faster than the temperature change by the Peltier element 57. In addition, the magnitude of the change in ambient temperature at the place where the bobbin 61 and the bobbin 63 are placed is larger than the temperature control range of the Peltier element 57. In these cases, the control of the Peltier element 57 may be insufficient. Therefore, in the first embodiment, as a configuration and operation that can cope with such a case, the delay compensator 15 including the delay compensation fiber 75 is provided by providing two arms that suppress the influence of disturbance at different phases. The influence of the disturbance received can be suppressed.

  Thereby, the phase change accompanying the change in the ambient temperature is canceled out by the pulse in which the pulse reciprocating the first arm 53 and the pulse reciprocating the second arm 55 interfere with each other, so that stable control can be performed. As a result, the state where the control becomes unstable is eliminated, and it is possible to prevent the detection of signals due to the occurrence of high frequency noise from being hindered.

  As described above, in the first embodiment, the light that outputs the sensing fiber 31 that detects the physical quantity, the pulse that causes the delay difference in the sensing fiber 31, and the pulse that does not cause the delay difference in the sensing fiber 31 are output. The coupler 37, a pulse that causes a delay difference, and a pulse that does not cause a delay difference are supplied to the first arm 53 and the second arm 55, and the first pulse that reciprocates the first arm 53 and the second arm The optical pulse 51 that outputs the interference pulse that interferes with the second pulse that reciprocates 55 and outputs the interference pulse, the demodulator 19 that outputs the output signal including the physical quantity from the interference pulse, and the first according to the output signal. And a Peltier element 57 that generates a temperature difference between the first surface and the second surface, the first arm 53 includes an optical fiber 67 disposed on the first surface, and the second arm 55 includes: A delay compensating fiber 75 that compensates for a delay in the sensing fiber 31, and an optical fiber 65 disposed on the second surface, and the optical fiber 67 has a phase displaced according to a temperature change of the first surface, The phase of the optical fiber 65 is displaced according to the temperature change of the second surface, and the phase difference between the first pulse and the second pulse is displaced according to the temperature difference.

  Thereby, the phase change accompanying the change in the ambient temperature is canceled out by the pulse in which the pulse reciprocating the first arm 53 and the pulse reciprocating the second arm 55 interfere with each other, so that stable control can be performed. As a result, the state where the control becomes unstable is eliminated, and it is possible to prevent the detection of signals due to the occurrence of high frequency noise from being hindered.

Embodiment 2. FIG.
<Overview>
FIG. 2 is a diagram showing an example of a schematic configuration of the interference optical fiber sensor 1 according to Embodiment 2 of the present invention. As shown in FIG. 2, the difference from the first embodiment is that a plurality of Peltier elements 57 and 58 are used, and a heat sink 59 is provided between the Peltier element 57 and the Peltier element 58.

  For example, high-frequency noise is generated and the noise frequency reaches the signal band, so that noise and signal cannot be separated using the difference in frequency, which is a factor that hinders signal detection. For example, it is assumed that the ambient temperature exceeds the controllable range of the Peltier element 57 and the Peltier element 58.

  Specifically, this is a case where the ambient temperature of the place where the bobbin 61 and the bobbin 63 are placed changes faster than the temperature change by the Peltier element 57 and the Peltier element 58. Further, the magnitude of the change in the ambient temperature at the place where the bobbin 61 and the bobbin 63 are placed is larger than the temperature control range of the Peltier element 57 and the Peltier element 58. In these cases, the control of the Peltier element 57 and the Peltier element 58 may be insufficient.

  In addition, when high-frequency noise is generated and the noise frequency reaches the signal band, the noise and the signal cannot be separated using the difference in frequency, and the signal detection is hindered. As a factor, it is assumed that the temperature change of the medium of the heat sink 59 exceeds the controllable range of the Peltier element 57 and the Peltier element 58.

  Specifically, when a medium for heat dissipation such as water or antifreeze liquid is passed through the heat sink 59, when the temperature change of the medium is faster than the temperature change of the Peltier element 57 and the Peltier element 58, or the magnitude of the temperature change of the medium Is larger than the temperature control range of the Peltier element 57 and the Peltier element 58, the control may be insufficient.

  In addition, when high-frequency noise is generated and the noise frequency reaches the signal band, the noise and the signal cannot be separated using the difference in frequency, and the signal detection is hindered. As a factor, it is assumed that the bobbin 61 and the bobbin 63 do not operate normally due to condensation or the like.

  Specifically, when the temperature of the Peltier element 57 and the Peltier element 58 or the temperature of the bobbin 61 and the bobbin 63 is lower than the ambient temperature and the bobbin 61 and the bobbin 63 are condensed, It is assumed that the temperature of the bobbin 61 and the bobbin 63 is lower than the freezing point and the condensed moisture is frozen. In this case, since the temperature change of the bobbin 61 and the bobbin 63 is slowed by the solidification heat, the control may be insufficient.

  Further, it is assumed that the temperature is higher than the melting point in a state where the Peltier element 57 and the Peltier element 58 or the bobbin 61 and the bobbin 63 are frozen. In this case, since the temperature change of the bobbin 61 and the bobbin 63 is slowed by the heat of fusion, the control may be insufficient.

  In the second embodiment, a configuration and operation that can cope with such a case will be described.

<Description of configuration>
Although the outline has been described above, in FIG. 2, a Peltier element 57 for heating and cooling the bobbin 61 and a Peltier element 58 for heating and cooling the bobbin 63 are provided. A heat sink 59 is sandwiched between 57 and the Peltier element 58. Here, as a setting of the Peltier element 57 and the Peltier element 58, when the Peltier element 57 heats a surface close to the bobbin 61, the Peltier element 58 cools the surface close to the bobbin 63, and the Peltier element 57 closes to the bobbin 61. , It is assumed that the Peltier element 58 heats the surface close to the bobbin 63.

  The temperature changes in the Peltier element 57 and the Peltier element 58 include a temperature change due to heat absorption and heat release due to the Peltier effect, and a temperature change due to Joule heat generated by flowing current. Therefore, by providing the heat sink 59, Joule heat generated in the Peltier element 57 and the Peltier element 58 is released. Thereby, the temperature around the Peltier element 57 and the Peltier element 58 and the periphery of the Peltier element 57 and the Peltier element 58 is prevented from becoming excessively high or low.

  Specifically, the heat sink 59 includes a Peltier element 57 and a Peltier element 58, a bobbin 61 and a bobbin 63, an optical fiber 65 wound around the bobbin 61 and bonded thereto, and an optical fiber wound around and bonded to the bobbin 63. In order to prevent the temperature of each of 67 from becoming below freezing point, the heat sink 59 of its own is heated, or the medium flowing through the heat sink 59 is heated. Here, the heat sink 59 has been described as an example of a member that dissipates the Peltier element 57 and the Peltier element 58, but the heat sink 59 is not particularly limited thereto.

  The Peltier element 57 and the Peltier element 58 correspond to the two first members in the present invention.

<Description of operation>
Sensing fiber 31 by a signal X _S for detecting distortion are modulated sensing light phase passing through the sensing fiber 31 by the strain of the sensing fiber 31, the signal X _S is detected by the demodulator 19 and the like. Phase change associated with temperature change or pressure change of sensing fiber 31, phase change associated with temperature change or pressure change of delay compensation fiber 75, phase change associated with temperature change or pressure change included in optical fiber 65, optical fiber 67 The phase change accompanying the temperature change or the pressure change included in is canceled by the feedback of the output of the demodulator 19 to the optical fiber 65 and the optical fiber 67.

  That is, the phase change of light due to temperature change or pressure change, that is, long-period fluctuation such as temperature change or pressure change is canceled, so that noise generated by the phase change is eliminated.

  Further, the phase change of the first arm 53 and the phase change of the second arm 55 include a phase change accompanying a change in ambient temperature and a phase change accompanying a current flowing in the Peltier element 57 and the Peltier element 58. The phase change accompanying the change in the ambient temperature is canceled because the optical fiber 65 and the optical fiber 67 are feedback-controlled. Therefore, if the phase of one pulse before the interference by the optical coupler 51 advances, the phase of the other pulse before the interference by the optical coupler 51 also advances, so that the timings of the amplitudes of the interfering pulses coincide with each other. The phase change is canceled by the applied pulse.

  On the other hand, the phase change accompanying the current flowing through the Peltier element 57 and the Peltier element 58 is such that when the optical fiber 65 is warmed, the optical fiber 67 is cooled, so the phase of the pulse passing through the optical fiber 65 is delayed. The phase of the pulse passing through the fiber 67 advances, and when the optical fiber 65 is cooled, the optical fiber 67 is warmed, so the phase of the pulse passing through the optical fiber 65 advances and the phase of the pulse passing through the optical fiber 67 is It is set to be delayed. Therefore, if the phase of one pulse before the interference by the optical coupler 51 is advanced, the phase of the other pulse before the interference by the optical coupler 51 is delayed. As a result, the phase of the pulse in which the pulse reciprocating the first arm 53 and the pulse reciprocating the second arm 55 interfere with each other, so that the phase of the pulse is adjusted by feedback using the Peltier element 57 and the Peltier element 58. Can do.

Specifically, as described above, the disturbances applied to the delay compensator 15 are the disturbance Y ₁ and the disturbance Y ₂ , and the output O which is the output of the demodulator 19 is expressed by the above equation (4). expressed. Further, as described above, the outputs O of the demodulator 19, the feedback control of the variation of the long period, which is the sum control signal Z to the control signal Z ₁ and the control signal Z _2, the above formula ( 5).

That is, the output O of the demodulator 19 at this time is expressed by the above equation (6). Thereby, X _N + Y ₁ -Y _2, which is a long-period fluctuation, is canceled out, and a long-period fluctuation and high-frequency noise generated by a demodulation error are suppressed. Further, when the disturbance Y ₁ and the disturbance Y ₂ coincide, the output O of the demodulator 19 becomes as in the above equation (4 ′), and the control signal Z becomes as in the above equation (5 ′).

As a result, also in the second embodiment, the disturbance Y ₁ and the disturbance Y ₂ are eliminated from the control signal Z. This is also a disturbance Y ₁ and disturbance Y ₂ is changed, become independent of the control, which means that it is possible to suppress the fluctuation of the long-period only control to cancel the disturbance X _N. Even if the disturbance Y ₁ and the disturbance Y ₂ do not completely coincide with each other, the disturbance Y ₁ and the disturbance Y ₂ are weakened, and the operation of the control signal Z ₁ + Z ₂ for canceling the disturbance X _N The range can be reduced. In other words, the disturbance Y ₁ applied to the delay compensator 15 is provided by providing the first arm 53 and the second arm 55 and suppressing the influence of the disturbance at a phase different between the first arm 53 and the second arm 55. and the influence of the disturbance Y ₂ is suppressed.

  The heat sink 59 releases Joule heat generated from the Peltier element 57 and the Peltier element 58. Accordingly, the temperatures of the Peltier element 57 and the Peltier element 58, the bobbin 61 and the bobbin 63, the optical fiber 65 wound around the bobbin 61 and bonded thereto, and the optical fiber 67 wound around and bonded to the bobbin 63 are changed. It doesn't get too high or too low.

<Description of effects>
In the prior art, high frequency noise is generated and the noise frequency reaches the signal band, so that noise and signal cannot be separated using the difference in frequency, and signal detection is hindered. For example, the case where the ambient temperature exceeds the controllable range of the Peltier element 57 and the Peltier element 58 is assumed.

  Specifically, this is a case where the ambient temperature of the place where the bobbin 61 and the bobbin 63 are placed changes faster than the temperature change by the Peltier element 57 and the Peltier element 58. Further, the magnitude of the change in the ambient temperature at the place where the bobbin 61 and the bobbin 63 are placed is larger than the temperature control range of the Peltier element 57 and the Peltier element 58. In these cases, the control of the Peltier element 57 and the Peltier element 58 may be insufficient.

  Therefore, also in the second embodiment, as a configuration and operation that can cope with such a case, the delay compensator 15 including the delay compensation fiber 75 is provided by providing two arms that suppress the influence of disturbance with different phases. It was made possible to suppress the influence of the disturbance that is affected.

  Thereby, the phase change accompanying the change in the ambient temperature is canceled out by the pulse in which the pulse reciprocating the first arm 53 and the pulse reciprocating the second arm 55 interfere with each other, so that stable control can be performed. As a result, it is possible to prevent the detection of the signal from being hindered due to generation of high-frequency noise by eliminating the state where the control becomes unstable.

  In the second embodiment, since the Joule heat of the Peltier element 57 and the Peltier element 58 is released as compared with the first embodiment, the two average temperatures of the bobbin 61 and the bobbin 63 do not change greatly. Therefore, the operation is more stable in the second embodiment than in the first embodiment.

  In addition, when high-frequency noise is generated and the noise frequency reaches the signal band, the noise and the signal cannot be separated using the difference in frequency, and the signal detection is hindered. As a factor, it is assumed that the temperature change of the medium of the heat sink 59 exceeds the controllable range of the Peltier element 57 and the Peltier element 58.

  Specifically, when a medium for heat dissipation such as water or antifreeze liquid is passed through the heat sink 59, when the temperature change of the medium is faster than the temperature change of the Peltier element 57 and the Peltier element 58, or the magnitude of the temperature change of the medium May be insufficient when the temperature is larger than the temperature control range of the Peltier element 57 and the Peltier element 58.

  Therefore, in the second embodiment, even if the temperature of the medium changes, the phase change of the pulse that interferes with the pulse that reciprocates the first arm 53 and the pulse that reciprocates the second arm 55 is canceled out. , Can be controlled stably. Therefore, since the state where the control becomes unstable is eliminated, it is possible to prevent the detection of the signal from being hindered by the occurrence of high frequency noise.

  In addition, when high-frequency noise is generated and the noise frequency reaches the signal band, the noise and the signal cannot be separated using the difference in frequency, and the signal detection is hindered. As a factor, it is assumed that the bobbin 61 and the bobbin 63 do not operate normally due to condensation or the like.

  Specifically, when the temperature of the Peltier element 57 and the Peltier element 58 or the temperature of the bobbin 61 and the bobbin 63 is lower than the ambient temperature and the bobbin 61 and the bobbin 63 are condensed, It was assumed that the temperature of the bobbin 61 and the bobbin 63 became lower than the freezing point, and the condensed moisture was frozen. In this case, since the temperature change of the bobbin 61 and the bobbin 63 is slowed by the heat of solidification, the control may be insufficient.

  Further, it was assumed that the temperature became higher than the melting point in a state where the Peltier element 57 and the Peltier element 58 or the bobbin 61 and the bobbin 63 were frozen. In this case, since the temperature change of the bobbin 61 and the bobbin 63 is slowed by the heat of fusion, the control may be insufficient.

  Therefore, in the second embodiment, by using the heat sink 59, the Peltier element 57 and the Peltier element 58, the bobbin 61 and the bobbin 63, the optical fiber 65 bonded to the bobbin 61, and the optical fiber 67 bonded to the bobbin 63 are used. Is prevented from becoming below freezing. Thereby, stable control can be performed. Therefore, since the state where the control becomes unstable is eliminated, it is possible to prevent the detection of the signal from being hindered by the occurrence of high frequency noise.

  As described above, in the second embodiment, the light that outputs the sensing fiber 31 that detects the physical quantity, the pulse that causes the delay difference in the sensing fiber 31, and the pulse that does not cause the delay difference in the sensing fiber 31 are output. The coupler 37, a pulse that causes a delay difference, and a pulse that does not cause a delay difference are supplied to the first arm 53 and the second arm 55, and the first pulse that reciprocates the first arm 53 and the second arm The optical pulse 51 that outputs the interference pulse that interferes with the second pulse that reciprocates 55 and outputs the interference pulse, the demodulator 19 that outputs the output signal including the physical quantity from the interference pulse, and the first according to the output signal. The Peltier element 57 and the Peltier element 58 that generate a temperature difference between the surface and the second surface, and the Peltier element 57 and the Peltier element 58 are sandwiched between the Peltier element 5 and the second surface. And a heat sink 59 that dissipates heat from the Peltier element 58. The first arm 53 includes an optical fiber 67 disposed on one first surface of the Peltier element 57 and the Peltier element 58, and a second The arm 55 includes a delay compensation fiber 75 that compensates for a delay in the sensing fiber 31, and an optical fiber 65 disposed on the other second surface of the Peltier element 57 and the Peltier element 58. The phase of the optical fiber 65 is displaced according to the temperature change of one of the first surfaces, and the phase of the optical fiber 65 is displaced according to the temperature change of the other second surface. The phase difference is displaced according to the difference between the temperature change of one of the first surfaces and the temperature change of the other second surface.

  Thereby, the phase change accompanying the change in the ambient temperature is canceled out by the pulse in which the pulse reciprocating the first arm 53 and the pulse reciprocating the second arm 55 interfere with each other, so that stable control can be performed. As a result, the state where the control becomes unstable is eliminated, and it is possible to prevent the detection of signals due to the occurrence of high frequency noise from being hindered.

Embodiment 3 FIG.
<Overview>
The difference between the first embodiment and the second embodiment is that a heater 81 and a heater 82 are used as members that cause a temperature difference between the bobbin 61 and the bobbin 63 instead of the Peltier element 57 and the Peltier element 58. is there. In addition, a circuit using a diode 85 and a diode 86 is configured between the amplifier 23 and the heater 81 and the heater 82.

<Description of configuration>
FIG. 3 is a diagram showing an example of a schematic configuration of the interference optical fiber sensor 1 according to Embodiment 3 of the present invention. As shown in FIG. 3, the diode 85 and the diode 86 are provided in different directions. The diode 85 and the heater 81 are connected in series, and the diode 86 and the heater 82 are connected in series. The diode 85 and the heater 81, the diode 86 and the heater 82 are connected in parallel, and each is connected to the amplifier 23. The heater 81 and the heater 82 are heated when a current flows. Here, if the bobbin 61 is heated when the output of the amplifier 23 is positive, the bobbin 63 is heated when the output of the amplifier 23 is negative, and the bobbin 63 is heated when the output of the amplifier 23 is positive. For example, it is assumed that the bobbin 61 is heated when the output of the amplifier 23 is negative.

  In addition, although the heater 81 and the heater 82 were demonstrated as an example of the member which heats the bobbin 61 and the bobbin 63 here, it is not specifically limited to these.

  The heater 81 and the heater 82 correspond to the two first members in the present invention.

<Description of operation>
The phase change of the first arm 53 and the phase change of the second arm 55 include a phase change accompanying a change in ambient temperature and a phase change accompanying a current flowing through the heater 81 and the heater 82. The phase change accompanying the change in the ambient temperature is canceled because the optical fiber 65 and the optical fiber 67 are feedback-controlled. Therefore, if the phase of one pulse before the interference by the optical coupler 51 advances, the phase of the other pulse before the interference by the optical coupler 51 also advances, so that the timings of the amplitudes of the interfering pulses coincide with each other. The phase change is canceled by the applied pulse.

On the other hand, the phase change due to the current flowing through the heater 81 and the heater 82 is not heated when the optical fiber 65 is warmed. Therefore, the phase of the pulse passing through the optical fiber 67 is higher than that of the optical fiber 65. The phase of the pulse passing through the optical fiber 67 is delayed, and when the optical fiber 67 is warmed, the optical fiber 65 is not warmed. Therefore, the phase of the pulse passing through the optical fiber 67 is delayed from the phase of the pulse passing through the optical fiber 65. Is set to Accordingly, since one of the pulses before the interference by the optical coupler 51 is displaced, the phase of the pulse can be adjusted by the heater 81 and the heater 82 by feedback.

  In the heat sink 59, the temperatures of the heater 81 and the heater 82, the bobbin 61 and the bobbin 63, the optical fiber 65 wound and bonded to the bobbin 61, and the optical fiber 67 wound and bonded to the bobbin 63 are excessive. The heat is dissipated so that it is not too high.

Next, a specific description will be given. A signal input to the sensing fiber 31 and the signal X _S, the disturbance is input to the sensing fiber 31 and the disturbance X _N. Further, the disturbance applied to the optical fiber 65 wound on the bobbin 61 to apply a change in temperature as a disturbance Y _1, to the disturbance applied to the optical fiber 67 wound around a bobbin 63 to apply a temperature change and disturbance Y _2.

That is, the disturbance applied to the delay compensator 15 is referred to as disturbance Y ₁ and disturbance Y ₂ . Further, the optical fiber 65, a control signal applied to the delay compensation fiber 75 and _{Z p,} the control signal applied to the optical fiber 67 and -Z _n. In such an _assumption, the output _{O p} is the output of the demodulator 19 when X _{N +} Y 1 -Y ₂ is increased is expressed by the following formula _{(7a), X N + Y} 1 -Y 2 There the output O _n which is the output of the demodulator 19 when reduced is expressed by the following formula (7b).

The disturbance X _N , the disturbance Y ₁ , and the disturbance Y ₂ are mostly long-period fluctuations associated with temperature changes or pressure changes. The third term of each of the equations (7a) and (7b) represents a phase change applied to the second arm 55. Further, the fourth term of each of the equations (7a) and (7b) represents a phase change applied to the first arm 53. Therefore, the sign of the third term and the sign of the fourth term are inverted. Of the output O of the demodulator 19, the feedback control of the variation of the long _cycle, the control signal _{Z p} when X _{N +} Y 1 -Y ₂ is increased is expressed by the following formula (8a), _{X N} + control signal _{Z n when Y} 1 -Y ₂ is reduced is represented by the following formula (8b).

In this case, the output _{O p} of the demodulator 19 is expressed by the following formula (9a), the output _{O n} of the demodulator 19 is expressed by the following formula (9b).

That is, the disturbances X _N + Y ₁ -Y ₂ both when X _N + Y ₁ -Y ₂ is increasing and when X _N + Y ₁ -Y ₂ is decreasing are canceled out. Thereby, X _N + Y ₁ -Y _2, which is a long-period fluctuation, is canceled out, and a long-period fluctuation and high-frequency noise generated by a demodulation error are suppressed.

When the disturbance Y ₁ and the disturbance Y ₂ match, the output Op of the demodulator 19 is expressed by the following equation (7a ′), and the output On of the demodulator 19 is expressed by the following equation (7b ′). The control signal Z _p is expressed by the following equation (8a ′), and the control signal Z _n is expressed by the following equation (8b ′).

As a result, the disturbance Y ₁ and the disturbance Y ₂ are eliminated from the control signal Z _p and the control signal Z _n . This is also a disturbance Y ₁ and disturbance Y ₂ is changed, become independent of the control, which means that it is possible to suppress the fluctuation of the long-period only control to cancel the disturbance X _N. Even if the disturbance Y ₁ and the disturbance Y ₂ do not completely coincide with each other, the disturbance Y ₁ and the disturbance Y ₂ will weaken each other, and the control signal Z _p and the control signal Z for canceling the disturbance X _N The operating range of _n can be reduced. In other words, the disturbance Y ₁ is applied to the delay compensator 15 by including the first arm 53 and the second arm 55 and suppressing the influence of the disturbance at a phase different between the first arm 53 and the second arm 55. and the influence of the disturbance Y ₂ is suppressed.

  The heat sink 59 releases Joule heat generated from the Peltier element 57 and the Peltier element 58. Accordingly, the temperatures of the Peltier element 57 and the Peltier element 58, the bobbin 61 and the bobbin 63, the optical fiber 65 wound around the bobbin 61 and bonded thereto, and the optical fiber 67 wound around and bonded to the bobbin 63 are changed. It doesn't get too high or low.

<Description of effects>
In the third embodiment, the bobbin 61 and the bobbin 63, and the optical fiber 65 wound around and bonded to the bobbin 61 and the optical fiber 67 wound around and bonded to the bobbin 63 are cooled only by being heated. There is nothing. Therefore, a delay in temperature change due to condensation and freezing does not occur. Therefore, since the state where the control becomes unstable is eliminated, it is possible to eliminate the state where the detection of the signal is hindered by the generation of high-frequency noise.

  As described above, in the third embodiment, the light that outputs the sensing fiber 31 that detects the physical quantity, the pulse that causes the delay difference in the sensing fiber 31, and the pulse that does not cause the delay difference in the sensing fiber 31 are output. The coupler 37, a pulse that causes a delay difference, and a pulse that does not cause a delay difference are supplied to the first arm 53 and the second arm 55, and the first pulse that reciprocates the first arm 53 and the second arm An optical coupler 51 for causing the second pulse reciprocating through 55 to interfere with each other and outputting the interfered pulse, a demodulator 19 for outputting an output signal including a physical quantity from the interference pulse, and at least a first surface, In response to the output signal output from the demodulator 19, the heater 81 and the heater 82 for heating the first surface, and the heater 81 and the heater 82 are sandwiched. The first arm 53 includes an optical fiber 67 disposed on one first surface of the heater 81 and the heater 82, and the second arm 55 includes a delay compensation fiber 75 that compensates for a delay in the sensing fiber 31, and an optical fiber 65 disposed on the other first surface of the heater 81 and the heater 82. The phase of the optical fiber 65 is displaced according to the temperature change of the first surface of the optical fiber 65, the phase of the optical fiber 65 is displaced according to the temperature change of the other first surface, and the phase difference between the first pulse and the second pulse is It is displaced according to the difference between the temperature change of one first surface and the temperature change of the other first surface.

  Thereby, since the state where control becomes unstable is eliminated, it is possible to eliminate the state where the detection of the signal is hindered by the occurrence of high-frequency noise.

<Description of usage pattern>
The phase demodulation method described in the first to third embodiments is an example, and the present invention is not particularly limited to this. For example, other phase demodulation methods may be used.

  In the first to third embodiments, an example of configuring a Michelson interferometer using the optical coupler 37, the optical coupler 51, the mirror 33, the mirror 35, the mirror 71, and the mirror 73 has been described. However, as in the Mach-Zehnder interferometer, Other interferometers may be used.

  In the first to third embodiments, an example in which a pulse is branched by the optical coupler 37 and the optical coupler 51 has been described. However, the present invention is not particularly limited thereto. For example, a sensor array including a plurality of sensing fibers 31 may be used. When such a sensor array is applied, it is desirable to input the average value of the outputs of all the sensing fibers 31 constituting the sensor array to the Peltier element 57 and the Peltier element 58. You may use only one to do.

  In the first to third embodiments, an example in which the bobbin 61 and the bobbin 63 are used has been described. However, the phase of the light may be changed only by the change in the refractive index associated with the temperature change of the optical fiber 65 and the optical fiber 67.

  In the first to third embodiments, the configuration of feedback from the output of the demodulator 19 has been described. However, the temperature or pressure of the sensing fiber 31 is detected, and based on the detection result, the Peltier element 57, the Peltier element 58, the heater 81, and It is good also as a structure which sends an electric current to the heater 82. FIG.

  In the second embodiment, an example of heating the heat sink 59 or the medium flowing through the heat sink 59 has been described. However, heating may be omitted when there is no risk of condensation and freezing.

  1, 3 interference type optical fiber sensor, 11 pulse light source, 13 sensor unit, 15 delay compensator, 17, 17_1, 17_2 O / E converter, 19 demodulator, 21 filter, 23 amplifier, 31 sensing fiber, 33, 35 , 71, 73 Mirror, 37, 51 Optical coupler, 53 First arm, 55 Second arm, 57, 58 Peltier element, 59 Heat sink, 61, 63 Bobbin, 65, 67 Optical fiber, 75, 76 Delay compensation fiber, 81 , 82 Heater, 85, 86 Diode.

Claims (10)

A sensing fiber that detects physical quantities;
A first optical coupler that outputs a pulse that causes a delay difference in the sensing fiber and a pulse that does not cause a delay difference in the sensing fiber;
A pulse that caused the delay difference, a second optical coupler for supplying a pulse that does not cause the delay difference, the the first and second arms,
An output including the physical quantity from an interference pulse obtained by causing the first pulse supplied from the second optical coupler to the first arm and the second pulse supplied from the second optical coupler to the second arm to interfere with each other. A demodulator that outputs a signal;
Two first members that generate a temperature difference between the first surface and the second surface in response to the output signal;
A second member sandwiched between the two first members and radiating the heat of the two first members;
With
The first arm has a first optical fiber disposed on one of the first surfaces of the two first members ,
The second arm includes a delay compensation fiber that compensates for a delay in the sensing fiber, and a second optical fiber disposed on the other second surface of the two first members ,
Wherein the first optical fiber, phase displaced in accordance with a change in temperature of one of said first surface,
The phase of the second optical fiber is displaced according to the temperature change of the other second surface,
The phase difference between the first pulse and the second pulse is displaced according to the difference between the temperature change of one of the first surfaces and the temperature change of the other second surface. Type optical fiber sensor. The interference type optical fiber sensor according to claim 1, wherein the first member is formed of a Peltier element. The demodulator
The interference type optical fiber sensor according to claim 2, wherein the physical quantity is output as a current, and the current is supplied to the Peltier element. A sensing fiber that detects physical quantities;
A first optical coupler that outputs a pulse that causes a delay difference in the sensing fiber and a pulse that does not cause a delay difference in the sensing fiber;
The pulse causing the delay difference and the pulse not causing the delay difference are supplied to the first arm and the second arm, the first pulse reciprocating the first arm, and the second arm reciprocating. A second optical coupler for causing the second pulse to interfere with each other and outputting the interfered pulse,
A demodulator that outputs an output signal including the physical quantity from the interference pulse;
Two first members that generate a temperature difference between the first surface and the second surface in response to the output signal;
A second member sandwiched between the two first members and radiating the heat of the two first members;
With
The first arm has a first optical fiber disposed on one of the first surfaces of the two first members,
The second arm includes a delay compensation fiber that compensates for a delay in the sensing fiber, and a second optical fiber disposed on the other second surface of the two first members,
The phase of the first optical fiber is displaced according to the temperature change of one of the first surfaces,
The phase of the second optical fiber is displaced according to the temperature change of the other second surface,
The phase difference between the first pulse and the second pulse is displaced according to the difference between the temperature change of one of the first surfaces and the temperature change of the other second surface. Type optical fiber sensor. The interference type optical fiber sensor according to claim 4, wherein each of the two first members is formed of a Peltier element. The demodulator
The interference type optical fiber sensor according to claim 5, wherein the physical quantity is output as a current and the current is supplied to the Peltier element. A sensing fiber that detects physical quantities;
A first optical coupler that outputs a pulse that causes a delay difference in the sensing fiber and a pulse that does not cause a delay difference in the sensing fiber;
The pulse causing the delay difference and the pulse not causing the delay difference are supplied to the first arm and the second arm, the first pulse reciprocating the first arm, and the second arm reciprocating. A second optical coupler for causing the second pulse to interfere with each other and outputting the interfered pulse,
A demodulator that outputs an output signal including the physical quantity from the interference pulse;
At least two first members that comprise a first surface and heat the first surface in response to the output signal output from the demodulator;
A second member sandwiched between the two first members and radiating the heat of the two first members;
With
The first arm has a first optical fiber disposed on one of the first surfaces of the two first members,
The second arm includes a delay compensation fiber that compensates for a delay in the sensing fiber, and a second optical fiber disposed on the other first surface of the two first members,
The phase of the first optical fiber is displaced according to the temperature change of one of the first surfaces,
The phase of the second optical fiber is displaced according to the temperature change of the other first surface,
The phase difference between the first pulse and the second pulse is displaced according to the difference between the temperature change of one of the first surfaces and the temperature change of the other first surface. Type optical fiber sensor. The interference type optical fiber sensor according to claim 7, wherein each of the two first members is formed by a heater. The demodulator
9. The interference type optical fiber sensor according to claim 8, wherein the physical quantity is output as a current and the current is supplied to the heater. With two diodes,
Each of the two diodes is
In different directions,
One of the two diodes is provided between the demodulator and one of the two first members, and the other is the other of the demodulator and the two first members. The interference type optical fiber sensor according to claim 9, which is provided between

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