JPH08145695A - Optical fiber gyro - Google Patents

Abstract

PURPOSE: To provide a highly accurate and reliable optical fiber gyro in which the total cost is reduced by decreasing the number of components. CONSTITUTION: In the optical fiber gyro for detecting the rotational state of an object optically, a second light receiving means 15 delivers a second output signal P2 to a light source output control means 16 in order to control the current being injected to a light source 11 to be at a constant level. Since fluctuation in the zero point output can be suppressed regardless of temperature variation, the rotational angular speed can be detected with high accuracy. Furthermore, the number of optical components can be decreased because phase modulation is not employed and the cost can be reduced significantly.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical fiber gyro used as a rotational angular velocity sensor.

[0002]

2. Description of the Related Art A gyroscope is a rotational angular velocity sensor with respect to an inertial space. Among them, an optical fiber gyro (hereinafter referred to as FOG) has high sensitivity because it utilizes optical interference to detect rotational angular velocity. It has excellent features such as no moving parts and short start-up time. Especially, development of a phase modulation type optical gyro with a phase modulator installed in the sensing loop is active. However, as a rotation sensor, an FOG that has a simpler configuration and is easier to manufacture is desired, and an optical fiber coupler (hereinafter referred to as 3 × 3 coupler) having three input and output ports is required. The research and development of the used FOG (hereinafter referred to as 3 × 3 FOG) has also been made.

The principle of the optical fiber gyro is based on a phenomenon called the Sagnac effect. When light is propagated to the left and right using a beam splitter in a circular optical path, and the system is rotating at an angular velocity of rotation Ω with respect to inertial space.

[0004]

[Equation 1]

The phase difference given by is generated between the lights in both directions. This is the Sagnac effect. Here, φ is the Sagnac phase, R is the radius of the circular optical path, L is the fiber length of the sensing loop, and λ is the light source wavelength. Therefore, when the two lights are made to interfere with each other, the output I is changed according to the rotational angular velocity.

[0006]

[Equation 2]

[0007] Here, when the output I is differentiated by the Sagnac phase φ,

[0008]

(Equation 3)

As can be seen from the above, the sensitivity is poor near φ = 0. Therefore, in order to increase the sensitivity, a configuration is adopted in which a phase modulator is installed in the sensing loop.

A piezo element is used for this phase modulator, and by applying an AC signal of several tens to several hundreds of kHz (this frequency is referred to as a fundamental frequency), substantially π / is applied to the left and right light. A phase difference of 2 is given so that the output is proportional to the sin function. This improves the sensitivity in the vicinity of φ = 0, so that the rotational angular velocity can be detected. However, as a result of applying the phase modulation, the gyro output becomes an AC component of the fundamental frequency and its harmonic frequency, and a lock-in amplifier must be used for its detection, so the structure was very complicated.

On the other hand, a major advantage of the 3 × 3 FOG is that it does not require phase modulation due to the phase bias that occurs in the 3 × 3 coupler. 3 × using FIG.
The operating principle of 3FOG will be briefly described.

In FIG. 6, 61 is a light source, 62 is an optical branching / coupling means, 63 is a sensing loop, 64 is a first light receiving means, 65 is a second light receiving means, 66 is a third light receiving means,
67 is a light source output control means, 68 is an arithmetic processing means, 69 is a depolarization means, P1, P2 and P3 are respectively a first output signal output from the first light receiving means 64 and a second light receiving means 65. Second output signal output, third output signal output from third light receiving means 66, 601 to 606
Indicate the first to sixth branches, respectively.

The operation will be briefly described below. Light source 6
The light emitted from No. 1 passes through the first branch 601, enters the optical branching / coupling means 62 composed of an optical fiber coupler, and enters the second branch 602, the third branch 603, and the sixth branch 606. Branched. The light branched to the sixth branch 606 enters the third light receiving means 66. The light incident on the second branch 602 is depolarized by the depolarizing means 69 composed of an optical fiber type depolarizer, and then the sensing loop 6 is emitted.
The light is incident on one end of 3 and becomes clockwise light, and again enters the optical branching / coupling means 62. The light incident on the third branch 603 is
The light enters the other end of the sensing loop 63, becomes counterclockwise light, is emitted from the sensing loop 63, is depolarized by the depolarizing means 69, and is incident on the optical branching / coupling means 62 again. The two-way light propagating in the clockwise and counterclockwise loops respectively is combined in the optical branching / coupling means 62, and branched into the sixth branch 604, the fifth branch 605, and the first branch 601. The lights branched into the sixth branch 604 and the fifth branch 605 are incident on the first light receiving means 64 and the second light receiving means 65, respectively, and output signals P1 of the first light receiving means 64 and The output signal P2 of the second light receiving means 65 is input to the arithmetic processing means 68, and the output signal P3 of the third light receiving means 66 is input to the light source output control means 67. When this optical fiber gyro rotates, a phase difference φ proportional to the rotational angular velocity occurs between the two-direction light due to the Sagnac effect. In the optical fiber gyro having such a configuration, if the branching ratio of the optical branching / coupling means is always 1/3 and the loss is negligible, the phase bias received by the branched light in the optical branching / coupling means becomes 120 °, 1
When the light intensity from the light source is K, the output signal P1, the second output signal P2, and the third output signal P3 of

[0014]

[Equation 4]

[0015]

(Equation 5)

[0016]

(Equation 6)

## EQU1 ## Here, the second output signal P2,
Taking the difference of the first output signal P1,

[0018]

(Equation 7)

And is proportional to sin φ. From such a relationship, the phase due to the Sagnac effect can be obtained,
The rotational angular velocity can be calculated from the value.

In this prior art example, the output signal P3 of the third light receiving means 66 is input to the light source output control means 67, but the monitor PD output of the light source 61 is used as the light source output control means 6.
You may enter in 7. In the case of this configuration, since the third output signal P3 represented by (Equation 6) is proportional to the light source output,
It may be used to standardize (Equation 7).

As described above, in this configuration, there is no need to perform phase modulation for the phase bias in the optical branching / coupling means. Therefore, the phase modulator, the lock-in amplifier, etc. are unnecessary, and the price can be greatly reduced.

[0022]

However, in the above-mentioned conventional configuration, the zero-point output of the gyro greatly fluctuates when the temperature fluctuates. First, when the light source output is controlled by the third output signal P3, the wavelength characteristic of the 3 × 3 optical fiber coupler has an effect. The reason why light is branched by the 3 × 3 optical fiber coupler is that mode coupling occurs, and the coupling coefficient changes as the wavelength changes. For example, when the temperature rises and the light source wavelength increases, the second branch 6
02, the component branched to the third branch 603 increases, and the component propagating the incident light as it is to the sixth branch 606 decreases. As a result, the value of the third output signal P3 decreases, so that the value of the injection current to the light source 61 in the light source output control means increases, and the component branched to the second branch 602 and the third branch 603 becomes It will increase even more. Next, when the light source output is controlled by the monitor PD output of the light source, the coupling efficiency between the light source and the first branch 601 fluctuates due to the deviation of the optical axis when the temperature fluctuates. Fluctuates. That is, there is a problem that the zero-point output of the gyro is not constant regardless of which light source output control method is used when the temperature changes.

Further, it is said that it is desirable that the 3 × 3 optical fiber coupler has a regular triangular cross section. As a result, even if light is incident from any port, it is divided into three equal parts, and the phase bias at the time of branching is always 120 °. However, in reality, there is a problem that it is very difficult to form the cross-sectional shape into an equilateral triangle.

Further, the optical fiber gyro is composed of various optical parts, but the temperature varies depending on the parts. For example, since the light source generates heat, the temperature is slightly higher than other parts. Further, the output linearity of the optical fiber gyro changes because the light source wavelength, the 3 × 3 optical fiber coupler branching ratio, and the like change depending on the temperature, but since the temperature characteristics of each optical component are different, find an appropriate correction method. Is difficult. As described above, there is a problem that sufficient temperature correction cannot be performed because the temperature and the temperature characteristic of each optical component are different.

The present invention solves the above-mentioned conventional problems, and an object of the present invention is to provide an optical fiber gyro which can be easily manufactured, has excellent output linearity, small drift, and is guaranteed to operate in a wide temperature range. .

[0026]

In order to solve the above-mentioned problems, firstly, a light source for emitting light and an optical fiber are formed by winding, and the light is incident from both ends thereof to produce a Sagnac effect. A loop, and light emitted from the light source enters from a first branch, branches into second and third branches, enters both ends of the sensing loop, and propagates through the sensing loop, and then both ends thereof. Ejected from 2
Two beams of light are incident from the second and third branches, are coupled and branched to be emitted from the fourth and fifth branches, and are emitted from the fourth and fifth branches. First and second light receiving means for respectively receiving light, arithmetic processing means for deriving a rotational angular velocity using a first output signal output from the first light receiving means, and second light receiving means. Light source output control means for controlling the light output intensity of the light source using the second output signal that is output is provided.

Secondly, a light source which emits light, a sensing loop which is formed by winding an optical fiber and which has a Sagnac effect when light is incident from both ends thereof, and the light emitted from the light source Of light from the second branch, the third branch and the sixth branch, and the lights from the second and third branches are incident on both ends of the sensing loop, and after propagating through the sensing loop. 2 which is ejected from both ends
From the fourth, fifth and sixth branches, there are optical branching and coupling means for inputting two lights from the second and third branches, coupling and branching and emitting the light from the fourth and fifth branches. First, second and third light receiving means for respectively receiving the emitted light, a first output signal output from the first light receiving means and a third output signal output from the third light receiving means. Arithmetic processing means for deriving the rotational angular velocity using at least one of the output signals, and light source output control means for controlling the light output intensity of the light source using the second output signal output from the second light receiving means. It is equipped with.

Thirdly, a light source for emitting light, a sensing loop formed by winding an optical fiber and receiving light from both ends thereof to generate a Sagnac effect, and a light emitted from the light source for the first. Incident from the branch of the second and third
The light is branched into two branches and is made incident on both ends of the sensing loop, and two lights emitted from both ends after propagating through the sensing loop are made incident from the second and third branches and are combined and branched. Optical branching / coupling means for emitting light from the fourth and fifth branches, and first and second light receiving means for receiving light emitted from the fourth and fifth branches, respectively.
Light source output control means for controlling the light output intensity of the light source using at least one of a first output signal output from the first light receiving means and a second output signal output from the second light receiving means. And a calculation processing means for deriving a rotation angular velocity using the current value injected into the light source by the light source output control means.

Fourthly, the light emitted from the light source and incident on the first branch is branched by the optical branching / coupling means, and then passes through the sensing loop to be transmitted by the optical branching / coupling means. Depolarization means is disposed at at least one of the paths until the light is coupled, or between the light source and the light splitting / coupling means.

Fifth, a plurality of temperature detecting means are provided, and the output signal is corrected by using a plurality of correction coefficients based on each of a plurality of temperature values output from the plurality of temperature detecting means. .

[0031]

With this configuration, firstly, only the left-right symmetry of the light from the second and third branches of the 3 × 3 optical fiber coupler becomes important, and the cross-sectional shape is not necessarily an equilateral triangle,
Since an isosceles triangular shape will do, it is easy to obtain a desired 3 × 3 optical fiber coupler. Further, if the 3 × 3 optical fiber coupler has excellent left-right symmetry, the temperature characteristics of the first and second output signals are the same, so that even if there is a temperature fluctuation, the 3 × 3 optical fiber coupler The zero point output of the gyro can be stabilized without being affected by the change in the branch ratio, the drift can be significantly reduced, and the rotational angular velocity is derived from one output signal, which simplifies the signal processing. The number of parts can be reduced.

Secondly, by using the third output signal as the rotational angular velocity derivation term or the output correction term, the rotational angular velocity can be derived with high accuracy.

Thirdly, by measuring the injection current value to the light source, the rotational angular velocity can be measured with high accuracy.

Fourthly, the depolarizing means forcibly depolarizes the propagating light, and an unnecessary interference noise component due to the change of the polarization plane in the optical fiber, or an optical branching / coupling means due to the change of the polarization plane. It is possible to eliminate the fluctuation of the branching ratio at.

Fifthly, even if the temperature values and temperature characteristics of the optical components constituting the optical fiber gyro are different,
Highly accurate temperature correction can be performed.

[0036]

Embodiments of the present invention will be described below in detail with reference to the drawings.

(Embodiment 1) FIG. 1 is a block diagram of an optical rotation detector in a first embodiment of the present invention.

In FIG. 1, 11 is a light source for emitting light to the first branch, 12 is a second light source for receiving light from the first branch,
Optical branching / coupling means for branching into the third branch, 13 is a sensing loop for receiving the light from the second and third branches to produce the Sagnac effect, and 14 is a first for receiving the light from the fourth branch.
Light receiving means, 15 second light receiving means for receiving light from the fifth branch, 16 light source output control means for controlling the output of the light source, 17 arithmetic processing means for calculating the rotational angular velocity, P1,
P2 is an output signal from the first light receiving means 14, respectively.
Output signals 101 to 106 from the second light receiving means 15 indicate first to sixth branches, respectively.

The operation will be described below. The light emitted from the light source 11 passes through the first branch 101, enters the optical branching / coupling means 12 composed of an optical fiber coupler, and the second branch 1
02, a third branch 103, and a sixth branch 106. The light that has entered the second branch 102 and the third branch 103 respectively enters both ends of the sensing loop 13, becomes clockwise light and counterclockwise light, respectively, and propagates through the loop. The bidirectional light emitted from the sensing loop 13 is again incident on the optical branching / coupling means 12, is combined, and is branched into the fourth branch 104, the fifth branch 105, and the first branch 101. The light branched into the fourth branch 104 and the fifth branch 105 enters the first light receiving means 14 and the second light receiving means 15, respectively, and the output signal P1 of the first light receiving means 14 is calculated. The processing means 17 converts the rotational angular velocity, and the second
The output signal P2 of the light receiving means 15 of the
The light source output is controlled so that P2 becomes constant. When this optical fiber gyro rotates, a phase difference φ proportional to the rotational angular velocity occurs between the two-direction light due to the Sagnac effect. In the optical fiber gyro having such a configuration, the first output signal P1 is [1
It is proportional to + sin (φ−π / 6)] / [1-sin (φ + π / 6)]. Therefore, the phase due to the Sagnac effect can be obtained from such a relationship, and the rotational angular velocity can be calculated from the value. As a result of performance evaluation of the optical fiber gyro having this configuration at 0 to 75 ° C., it was possible to make a great improvement over the conventional one.

As shown above, with this configuration,
The zero-point output of the optical fiber gyro is stable even when the temperature fluctuates, and the number of parts is small, so that it is possible to provide a highly accurate optical fiber gyro at low cost.

In the present embodiment, the optical branching / coupling means is composed of an optical fiber coupler, but it may be an integrated optical waveguide.

(Embodiment 2) FIG. 2 is a block diagram of an optical rotation detector in a second embodiment of the present invention.

In FIG. 2, 21 is a light source for emitting light to the first branch, 22 is a second light source for receiving light from the first branch,
Optical branching / coupling means for branching into the third branch, 23 is a sensing loop for receiving the light from the second and third branches to produce the Sagnac effect, and 24 is a first for receiving light from the fourth branch.
Light receiving means, 25 is second light receiving means for receiving light from the fifth branch, 26 is third light receiving means for receiving light from the sixth branch, and 27 is a light source output for controlling the output of the light source. The control means 28 is an arithmetic processing means for calculating the rotational angular velocity, P1,
P2 and P3 are the output signal from the first light receiving means 24, the output signal from the second light receiving means 25, the output signal from the third light receiving means 26, and 201 to 206 are the first to sixth signals, respectively. Indicates a branch.

The operation will be described below. The light emitted from the light source 21 passes through the first branch 201, enters the optical branching / coupling means 22 formed of an optical fiber coupler, and then the second branch 2
02, a third branch 203, and a sixth branch 206. The light branched into the sixth branch 206 enters the third light receiving means 26. Second branch 202 and third branch 2
The light incident on 03 enters the both ends of the sensing loop 23, respectively, and becomes clockwise light and counterclockwise light,
Propagate the loop. The bidirectional light emitted from the sensing loop 23 again enters the optical branching / coupling means 22, is combined, and is branched into the fourth branch 204, the fifth branch 205, and the first branch 201. The light branched into the fourth branch 204 and the fifth branch 205 is respectively received by the first light receiving means 24.
And the second light receiving means 25, and the third light receiving means 26
The output signal P3 of the above is converted into the rotational angular velocity by the arithmetic processing means 28, the output signal P2 of the second light receiving means 25 is input to the light source output control means 27, and the light source output is controlled so that P2 becomes constant. Has become. When this optical fiber gyro rotates, a phase difference φ proportional to the rotational angular velocity occurs between the two-direction light due to the Sagnac effect. In the optical fiber gyro having such a configuration, the third output signal P
3 is proportional to 1 / [1-sin (φ + π / 6)]. Therefore, the phase due to the Sagnac effect can be obtained from such a relationship, and the rotational angular velocity can be calculated from the value. The optical fiber gyro of this configuration is 0-75
As a result of performance evaluation at ℃, it was able to be improved significantly compared to the past.

As shown above, with this configuration,
The zero-point output of the optical fiber gyro is stable even when the temperature fluctuates, and the number of parts is small, so that it is possible to provide a highly accurate optical fiber gyro at low cost.

In this embodiment, the output signal P3 of the third light receiving means 26 is converted into the rotational angular velocity by the arithmetic processing means 28. However, the output signal P1 of the first light receiving means 24 and the The output signal P3 of the light receiving means 26 of No. 3 may be used to convert the rotational angular velocity by the arithmetic processing means 28.

In the present embodiment, the output signal P2 of the second light receiving means 25 is input to the light source output control means 27, but the output signal P1 of the first light receiving means 24 and the second It is also possible to input the output signal P2 of the light receiving means 25 to the light source output control means 27 and drive the light source 21 so that the average value of both is constant.

In the present embodiment, the optical branching / coupling means is composed of an optical fiber coupler, but it may be an integrated optical waveguide.

(Embodiment 3) FIG. 3 is a block diagram of an optical rotation detector in a third embodiment of the present invention.

In FIG. 3, 31 is a light source for emitting light to the first branch, 32 is a second light source for receiving light from the first branch,
Optical branching / coupling means for branching into the third branch, 33 is a sensing loop for receiving the light from the second and third branches to produce the Sagnac effect, and 34 is a first for receiving the light from the fourth branch.
, 35 is a second light receiving means for receiving the light from the fifth branch, 36 is a third light receiving means for receiving the light from the sixth branch, and 37 is a light source output for controlling the output of the light source. A control means, 38 is an arithmetic processing means for calculating the rotational angular velocity, C1 is an injection current value to the light source 31, P1, P2, and P3 are respectively a first output signal output from the first light receiving means 34, and a second output signal. Second output signal output from the light receiving means 35, output signal from the third light receiving means 36, 301 to 30
Reference numerals 6 denote first to sixth branches, respectively.

The operation will be described below. The light emitted from the light source 31 passes through the first branch 301, enters the optical branching / coupling means 32 formed of an optical fiber coupler, and the second branch 3
02, a third branch 303, and a sixth branch 306. The light branched to the sixth branch 306 enters the third light receiving means 36. Second branch 302 and third branch 3
The light that has entered 03 is incident on both ends of the sensing loop 33, and becomes clockwise light and counterclockwise light, respectively.
Propagate the loop. The bidirectional light emitted from the sensing loop 33 is again incident on the optical branching / coupling means 32, is combined, and is branched into the fourth branch 304, the fifth branch 305, and the first branch 301. The light branched into the fourth branch 304 and the fifth branch 305 are respectively received by the first light receiving means 34.
And incident on the second light receiving means 35, and the second light receiving means 35
The output signal P2 is input to the light source output control means 37, and the light source output is controlled so that P2 becomes constant. The injection current value C1 to the light source 31 in the light source output control means 37 is input to the arithmetic processing means 38, and is converted into the rotational angular velocity by the arithmetic processing means 38. When this optical fiber gyro rotates, a phase difference φ proportional to the rotational angular velocity occurs between the two-direction light due to the Sagnac effect. In the optical fiber gyro having such a configuration, the injection current value C1 to the light source 31 depends on 1 / [1-sin (φ + π / 6)]. Therefore, the phase due to the Sagnac effect can be obtained from such a relationship, and the rotational angular velocity can be calculated from the value. As a result of performance evaluation of the optical fiber gyro having this configuration at 0 to 75 ° C., it was possible to make a great improvement over the conventional one.

As described above, with this configuration,
The zero-point output of the optical fiber gyro is stable even when the temperature fluctuates, and the number of parts is small, so that it is possible to provide a highly accurate optical fiber gyro at low cost.

In the present embodiment, the output signal P2 of the second light receiving means 35 is input to the light source output control means 37, but the output signal P1 of the first light receiving means 34 and the second The output signal P3 of the light receiving means 35 may be input to the light source output control means 37, and the light source 31 may be driven so that the average value of both is constant.

In this embodiment, the optical branching / coupling means is composed of an optical fiber coupler, but it may be an integrated optical waveguide.

(Embodiment 4) FIG. 4 is a block diagram of an optical rotation detector in a fourth embodiment of the present invention.

In FIG. 4, reference numeral 41 denotes a light source for emitting light to the first branch, 42 denotes second light receiving the light from the first branch,
Optical branching / coupling means for branching into the third branch, 43 is a sensing loop for receiving the light from the second and third branches to produce the Sagnac effect, and 44 is a first for receiving the light from the fourth branch.
Light receiving means, 45 is second light receiving means for receiving light from the fifth branch, 46 is light source output control means for controlling output of the light source, 47 is arithmetic processing means for calculating rotational angular velocity, and 48 is light. Depolarization depolarizing means for depolarizing, P1 and P2, respectively, are a first output signal output from the first light receiving means 44, a second output signal output from the second light receiving means 45, and 401 to 406. The first to sixth branches are shown respectively.

The operation will be described below. The light emitted from the light source 41 passes through the first branch 401, enters the optical branching / coupling means 42 composed of an optical fiber coupler, and then the second branch 4
02, a third branch 403, and a sixth branch 406. The light incident on the second branch 402 is depolarized by the depolarizer 48 composed of an optical fiber type depolarizer, and then enters one end of the sensing loop 43.
The light becomes clockwise light and enters the optical branching / coupling means 42 again.
The light incident on the third branch 403 is detected by the sensing loop 4
The light enters the other end of 3 and becomes counterclockwise light, which is emitted from the sensing loop 43, is depolarized by the depolarizing means 48, and is incident on the optical branching / coupling means 42 again. The two-way light propagating in the clockwise and counterclockwise loops respectively is combined in the optical branching / coupling means 42 and branched into the fourth branch 404, the fifth branch 405, and the first branch 401. The light branched into the fourth branch 404 and the fifth branch 405 enters the first light receiving means 44 and the second light receiving means 45, respectively, and the output signal P1 of the first light receiving means 44 is processed. The output signal P2 of the second light receiving means 45 is converted into the rotational angular velocity by the means 47, and is input to the light source output control means 46 so that the light source output is controlled so that P2 becomes constant. When this optical fiber gyro rotates, a phase difference φ proportional to the rotational angular velocity occurs between the two-direction light due to the Sagnac effect. In the optical fiber gyro having such a configuration, the first output signal P1 is [1 + sin (φ−π /
6)] / [1-sin (φ + π / 6)]. Therefore, the phase due to the Sagnac effect can be obtained from such a relationship, and the rotational angular velocity can be calculated from the value. The optical fiber gyro of this configuration is
As a result of performance evaluation in, it was possible to improve significantly compared with the conventional one.

In the above structure, when a single mode optical fiber is used as the optical fiber, two modes polarized in two orthogonal directions can propagate within the cross section of the optical fiber. If the fiber structure is truly axially symmetric, there will be no dispersion in these two modes, but in a real optical fiber there will always be some non-axial symmetry, so there will be some polarization dispersion. I will end up. In this case, energy is exchanged between the two modes to cause mode coupling, resulting in polarization dispersion. Experimentally, if such polarization fluctuations occur, the output signal becomes very unstable and becomes noise, such as the branching ratio of the optical branching / coupling means becoming unstable and the interference noise component being generated. It has been confirmed. Therefore, in order to reduce such noise, it is necessary to lower the polarization characteristic of the propagating light.

From the above, in the present embodiment, as a result of conducting an experiment by configuring the optical fiber gyro in which the depolarizing means 48 is inserted at one end of the sensing loop as described above,
Since the both-direction light in the sensing loop is depolarized by the depolarizer 48, output noise due to polarization fluctuation of light in the optical fiber is significantly reduced, and the zero-point output of the optical fiber gyro is stabilized. I was able to.

Further, the depolarizer 48 is connected to the second branch 40.
It was inserted in one place between 2 and the sensing loop 43,
Even if it is inserted between the third branch 403 and the sensing loop 43, in the sensing loop 43, or between the light source 41 and the optical branching / coupling means 42 at one or more places, the same as described above. It has been confirmed that it has the effect of reducing output noise due to polarization fluctuation.

In this embodiment, the optical branching / coupling means is composed of an optical fiber coupler, but it may be an integrated optical waveguide.

(Embodiment 5) A fifth embodiment of the present invention will be described below with reference to FIGS.

The description of FIG. 1 is the same as that of the first embodiment, and will be omitted. FIG. 5 is a conceptual diagram showing a part of arithmetic processing means in the optical fiber gyro of the fifth embodiment of the present invention.

In FIG. 5, reference numeral 51 is a first arithmetic processing unit, 5
2 is a second arithmetic processing unit, 53 is a first temperature detecting means, 5
Reference numeral 4 is the second temperature detecting means, P1 and P1 ′ are the first input signal input to the first arithmetic processing unit 51, and the first input signal is the first input signal.
The second input signals T1 and T2 input from the arithmetic processing unit 51 to the second arithmetic processing unit 52 are the measured temperature value output from the first temperature detecting unit and the second input signal from the second temperature detecting unit, respectively. Indicates the output temperature value.

The operation will be described below. In FIG. 1, the first output signal P1 input to the arithmetic processing means 17
Is the same as the first input signal P1 in FIG. The first arithmetic processing unit 51 includes a first input signal P
1, and the first temperature measurement value T1 output from the first temperature detection means installed in the light source is input, and the correction coefficient depending on the first temperature measurement value T1 is multiplied by P1 to obtain the first temperature measurement value T1. The second input signal P is input from the first arithmetic processing unit 51 to the second arithmetic processing unit 52 after the temperature correction of 1 is performed.
1'is obtained. The second input signal P1 ′ and the temperature measurement value T2 output from the second temperature detection means 54 installed in the arithmetic processing circuit are input to the second arithmetic processing unit 52, and the second temperature measurement is performed. The correction coefficient depending on the value T2 is P1 '
Is multiplied to perform the second temperature correction, and the value after the multiplication is output.

As described above, with this configuration,
It becomes possible to perform temperature correction depending on the temperature value and temperature characteristic of each optical component, and the rotational angular velocity can be derived with high accuracy.

In this embodiment, the first temperature detecting means is installed in the light source and the second temperature detecting means is installed in the arithmetic processing means, but it is installed in the optical branch coupling means, the sensing loop, etc. Is also good.

Although the first temperature detecting means 53 and the second temperature detecting means 54 are installed in this embodiment, the first temperature detecting means 54 and the second temperature detecting means 54 are not installed, but the first temperature detecting means 54 is not installed. Only the temperature detecting means 53 is installed, and the first temperature detecting means 5 is installed.
3, the temperature at any one position is measured, and the temperature measurement value T1 is used to perform the first calculation in the first arithmetic processing unit.
The temperature may be corrected, and the second temperature correction may be performed in the second arithmetic processing unit.

In this embodiment, the first arithmetic processing unit 51 and the second arithmetic processing unit 52 are installed, but the first arithmetic processing unit is not installed and the first arithmetic processing unit 51 is installed. Only the processing unit 51 may be installed, and the first arithmetic processing unit 51 may perform the first temperature correction using the average value of the first temperature measurement value T1 and the second temperature measurement value T2.

In the present embodiment, the optical fiber gyro having the structure described in the first embodiment has been described with reference to FIG. 1, but the same applies even if the same temperature correction is performed for the optical fiber gyro having another structure. The effect of can be expected.

[0071]

As described above, the optical fiber gyroscope of the present invention firstly controls the output intensity of the light source by one of the first and second output signals and uses the other output signal. By calculating the rotational angular velocity with the use of a small number of parts, the cost can be significantly reduced, and the rotational angular velocity can be derived with high accuracy.

Secondly, by deriving the rotational angular velocity using the third output signal output from the third light receiving means, the number of parts is small and the cost is significantly reduced, and the rotational angular velocity is highly accurately determined. Can be derived.

Thirdly, in the light source output control means,
By deriving the rotational angular velocity using the value of the current injected into the light source, the number of parts is small, the cost is significantly reduced, and the rotational angular velocity can be derived with high accuracy.

Fourth, by arranging the depolarizing means in at least one position of the entire optical path, fluctuation of the output due to polarization fluctuation can be suppressed and the rotational angular velocity can be derived with high accuracy. .

Fifth, by correcting the output signal using a plurality of correction coefficients based on a plurality of temperature values output from a plurality of temperature detecting means, the temperature value of each optical component and the temperature It becomes possible to perform temperature correction corresponding to the characteristics, and the rotational angular velocity can be derived with high accuracy.

[Brief description of drawings]

FIG. 1 is a configuration diagram of an optical fiber gyro according to a first embodiment of the present invention.

FIG. 2 is a configuration diagram of an optical fiber gyro according to a second embodiment of the present invention.

FIG. 3 is a configuration diagram of an optical fiber gyro according to a third embodiment of the present invention.

FIG. 4 is a configuration diagram of an optical fiber gyro according to a fourth embodiment of the present invention.

FIG. 5 is a conceptual diagram showing a part of arithmetic processing means in an optical fiber gyro according to a fifth embodiment of the present invention.

FIG. 6 is a configuration diagram of an optical fiber gyro in a conventional example.

[Explanation of symbols]

 11 light source 12 optical branching / coupling means 13 sensing loop 14 first light receiving means 15 second light receiving means 16 light source output control means 17 arithmetic processing means 48 depolarizing means 51 first arithmetic processing section 53 first temperature detecting means P1 First output signal P2 Second output signal P3 Third output signal C1 Injection current value

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Hidehiko Negishi 3-10-1 Higashisanda, Tama-ku, Kawasaki-shi, Kanagawa Matsushita Giken Co., Ltd.

Claims (10)

[Claims] 1. A light source that emits light, a sensing loop that is formed by winding an optical fiber and that causes light to enter from both ends thereof to produce a Sagnac effect, and a first branch that splits the light emitted from the light source. From the second branch to the second branch and the third branch to be incident on both ends of the sensing loop, and two lights emitted from both ends after propagating through the sensing loop are divided into the second and third branches. Optical branching / coupling means that is incident from a branch, is coupled and branched, and is emitted from the fourth and fifth branches, and first and second light receiving means that receive the light emitted from the fourth and fifth branches, respectively. Using the light receiving means, the arithmetic processing means for deriving the rotational angular velocity using the first output signal output from the first light receiving means, and the second output signal output from the second light receiving means. Light source output for controlling light output intensity of the light source An optical fiber gyro equipped with a control means. 2. A light source which emits light, a sensing loop which is formed by winding an optical fiber, and which produces a Sagnac effect by injecting light from both ends thereof, and a first branch of the light emitted from the light source. From the both ends of the sensing loop after propagating through the sensing loop and branching into the second, third, and sixth branches from the second and third branches. Optical branching / coupling means for injecting the two emitted lights from the second and third branches, coupling and branching them, and emitting from the fourth and fifth branches, and the fourth, fifth, and sixth branches. First, second and third light receiving means for respectively receiving the light emitted from the branch, and a first output signal output from the first light receiving means and an output signal from the third light receiving means. The rotational angular velocity using at least one of the third output signals An optical fiber gyro including a calculation processing unit for deriving and a light source output control unit for controlling a light output intensity of the light source by using a second output signal output from the second light receiving unit. 3. A light source that emits light, a sensing loop that is formed by winding an optical fiber and that causes light to enter from both ends thereof to produce a Sagnac effect, and a first branch that splits the light emitted from the light source. From the second branch to the second branch and the third branch to be incident on both ends of the sensing loop, and two lights emitted from both ends after propagating through the sensing loop are divided into the second and third branches. Optical branching / coupling means that is incident from a branch, is coupled and branched, and is emitted from the fourth and fifth branches, and first and second light-receiving means that receive the light emitted from the fourth branch and the fifth branch, respectively. A light output intensity of the light source using a second light receiving unit and at least one of a first output signal output from the first light receiving unit and a second output signal output from the second light receiving unit. Light source output control means for controlling An optical fiber gyro including an arithmetic processing unit that derives a rotational angular velocity by using a current value injected into the light source by the output control unit. 4. The path from the light emitted from the light source and incident on the first branch is branched by the optical branching / coupling means to the light passing through the sensing loop to be coupled by the optical branching / coupling means. The optical fiber gyro according to any one of claims 1, 2, and 3, wherein depolarizing means is disposed at at least one of them. 5. The depolarizing means is arranged between the light source and the light splitting / coupling means, and
An optical fiber gyro according to any one of 1. 6. The optical fiber gyro according to claim 1, wherein the optical branching / coupling means is an optical fiber coupler. 7. The optical fiber gyro according to claim 1, wherein the optical branching / coupling means is an integrated optical waveguide. 8. An optical fiber gyro having a temperature detecting means and correcting an output signal using a plurality of correction coefficients based on a temperature value output from the temperature detecting means. 9. An optical fiber gyro, comprising a plurality of temperature detecting means, wherein an output signal is corrected using an average value of a plurality of temperature values output from the plurality of temperature detecting means. 10. A plurality of temperature detecting means are provided, and the output signal is corrected using a plurality of correction coefficients based on each of a plurality of temperature values output from the plurality of temperature detecting means. Fiber optic gyro.