JPH0933264A - Optical fiber gyro - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent the generation of noises in gyro signals by passing the light from a light source through a beam splitter, propagating the light through the waveguide of an optical integrated circuit, changing the optical path of the light propagated through the waveguide in the reverse direction through the beam slitter and combining the first mode generated at the first Y branch at the second Y branch again. SOLUTION: The light from a light source 11 reaches a beam splitter 22, is condensed with a condenser lens 22B, and reaches a half mirror 22A. The half of the light is reflected from the mirror 22A and detected by a light receiving device 13A. The other half is transmitted through the mirror 22A, guided to the waveguide 23, and reaches a Y branch 26. One light is propagated clockwise through an optical fiber loop 19 through a Y branch 26A and a connecting device 35, and the other light is propagated counterclockwise through the loop 19 through a Y branch 26B and the device 35. The light beams propagated clockwise and counterclockwise through the loop 19 and phase-modulated by phase modulators 27 and 28 arranged along the branches 26A and 26B of the Y branch 26, and combined by the Y branch 26.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fiber optic gyro for measuring angular velocity.

[0002]

2. Description of the Related Art An optical fiber gyro is configured to measure an angular velocity by utilizing the Sagnac effect of light (Sagnac effect), and has an advantage that it has high reliability and can miniaturize an apparatus.

FIG. 5 shows an example of a phase difference modulation type optical fiber gyro among conventional interferometric optical fiber gyros.
This optical fiber gyro includes a light source 101 such as a semiconductor laser and a light emitting diode, and a light receiver 1 for converting incident light into an electric current.
02 and an optical fiber loop 103 formed by winding one optical fiber a plurality of times, a polarizer 104, and couplers 105 and 106 that combine or branch light propagating through the optical fiber.

The light output from the light source 101 passes through the first coupler 105 and the polarizer 104,
It is led to 6. The light is split by the second coupler 106, and the two split lights thus propagate in the optical fiber loop 103 in opposite directions. That is, one propagates clockwise through the optical fiber loop 103 and the other propagates counterclockwise.

When an angular velocity Ω is applied to the optical fiber loop 103, the optical fiber loop 10
A phase difference Δφ occurs in the lights propagating in 3 in opposite directions. The phase difference Δφ is proportional to the angular velocity Ω and is represented by the following equation.

[0006]

## EQU1 ## Δφ = (2πLD / λC) Ω

Where Ω is the angular velocity around the central axis of the optical fiber loop 103, D is the loop diameter of the optical fiber loop 103, L is the length of the optical fiber loop 103, and λ is the wavelength of the light output from the light source 101. , C represent the speed of light.

This optical fiber gyro is further provided with an electric current
Voltage converter 107, phase modulator 108, and signal generator 10
9 and a synchronous detector 110. The current output from the light receiver 102 is converted into a voltage by the current / voltage converter 107 and output as a voltage. The phase modulator 108 is arranged at one end of the optical fiber loop 103, and is operated by the reference signal supplied from the signal generator 109. The optical fiber loop 103 by the phase modulator 108
Light propagating in the opposite directions to each other is phase-modulated. When the angular frequency of the signal supplied from the signal generator 109 is ω _P , the output voltage V of the current / voltage converter 107 is represented by the following equation.

[0009]

## EQU2 ## I = K [1 + cos Δφ · {J ₀ (z) -2J
₂ (z) cos2ω _P t + ··｝ −sinΔφ · ｛2J
₁ (z) cosω _P t -...}]

Where z is the degree of phase modulation, J ₀ , J ₁ , J
_2, ... are Bessel functions, K is a proportionality constant, t is time.

Is there a signal generator 109 for the synchronous detector 110?
Angular frequency ω_PSignal is supplied by the reference signal
Is the angular frequency nω of the output voltage V_PAngular frequency component
Min ω _PIs synchronously detected and output 2K proportional to sin Δφ
J₁(Z) sin Δφ is output. Thus Δφ
Then, the angular velocity Ω can be obtained from the equation (1).

A serrodyne optical fiber gyro is known as an improved version of the phase difference modulation optical fiber gyro. In such a serrodyne system, a serrodyne phase modulator 108 'is further provided in addition to the phase modulator 108. For details of the cellodyne type optical fiber gyro, refer to Japanese Patent Application No. 4-306975 filed by the same applicant as the present applicant.

FIG. 6 shows another example of the conventional optical fiber gyro. In this example, the optical integrated circuit 115 is used. In the optical fiber gyro shown in FIG. 6A, the two Y branches 118, 118, the polarizer 104, the phase modulator 108, and the serrodyne phase modulator 108 ′ are combined into a single optical integrated circuit 1.
It is incorporated in 15. In the fiber optic gyro shown in FIG. 6B, the polarizer 104, one Y-branch 118, the phase modulator 108 and the serrodyne phase modulator 108 ′ are integrated in a single optical integrated circuit 115.

A connecting device 11 is provided at both ends of the optical integrated circuit 115.
6 is attached, and the end of the waveguide of the optical integrated circuit 115 is connected to the optical fiber 131 depending on the connection device 116.

The optical integrated circuit 115 uses the photolithography technique to form the Y branch 118 and the phase modulator 1 on the upper surface of the substrate.
It is manufactured by forming 08, 108 '. As the substrate, for example, lithium niobate (LiNbO ₃ ) or lithium tantalate (LiTaO ₃ ) is used. Y
The branches 118, 118 are constituted by waveguides.
As a method of forming the waveguide, there are a thermal diffusion method, a proton exchange method and the like.

The light output from the light source 101 has two polarization planes TE and TM having the same polarization and having orthogonal polarization planes.
Including polarized light. In a fiber optic gyro, polarized light with a single plane of polarization is used to obtain high measurement accuracy.
Therefore, the optical fiber gyro is usually provided with a polarization separation function for obtaining polarized light from light from the light source 101. In the optical fiber gyro shown in FIG. 5, a polarizer 104 is provided in the optical path. In the optical fiber gyro shown in FIG. 6, the optical integrated circuit 115 has a polarization separation function.

In the proton exchange type optical integrated circuit, since the waveguide functions as a polarizer, it is not necessary to provide the polarizer 104. However, the titanium diffusion type optical integrated circuit 1
Since the waveguide does not function as a polarizer in 15, the polarizer 104 needs to be formed in the optical integrated circuit 115. The polarizer 104 may be formed as a metal loaded type.

Another example of the conventional optical fiber gyro will be described with reference to FIGS. This example is described in Japanese Patent Application No. 5-327971 filed on Dec. 24, 1993 by the same applicant as the present applicant. Please refer to the same application for details.

This optical fiber gyro has a light source 11, a light receiver 13, an optical integrated circuit 21, and a connection device 35. The optical fiber loop 19 is attached to the connection device 35. The light source 11 is supported by a sub carrier 15, and the sub carrier 15 is mounted on the upper surface of the first supporting member 17.

The light receiver 13 is mounted on the inner end surface of the second supporting member 31, and the optical integrated circuit 21 is mounted on the upper surface of the second supporting member 31. The second support member 31 is attached to the first support member 17 by a pair of bolts 33, but the first support member 17 and the second support member 31 may be integrally formed.

The optical integrated circuit 21 is in the form of a trapezoidal plate as shown in the figure, and the front end face facing the light source 11 is perpendicular to the longitudinal direction, but the rear end face on the opposite side is inclined with respect to the longitudinal direction.

A waveguide 23 is formed on the upper surface of the optical integrated circuit 21, and the waveguide 23 includes two Y branches 25 and 26. The tip of one branch 25A of the first Y branch 25 is directed toward the light source 11, and the other branch 2A of the first branch 25 is
5B is directed to the light receiver 13. Phase modulators 27, 28 are provided on both sides of each branch 26A, 26B of the second Y branch 26.
Is arranged. The second phase modulator 28 may be a serrodyne phase modulator.

The light from the light source 11 enters one branch 25A of the first Y branch 25 and is guided to the second Y branch 26 via the first Y branch 25. The light is split into two in the second Y-branch 26, one light propagates clockwise through the optical fiber loop 19 via the one branch 26A and the connection device 35, and the other light branches in the other. The optical fiber loop 19 is propagated counterclockwise through 26B and the connection device 35.

Both the light propagating clockwise and the light propagating counterclockwise in the optical fiber loop 19 are arranged along the respective branches 26A and 26B of the second Y-branch 26, and the phase modulator 2 is provided.
7 and 28 are phase modulated.

In this way, the right-handed propagating light and the left-handing propagating light which have been phase-modulated are combined by the second Y-branch 26, and the interference light is received by the photodetector 13 via the first Y-branch 25. To be done. The light receiver 13 outputs a current signal indicating the intensity and phase of the interference light. As shown, the second support member 31 is provided with a pair of termination resistors 47, 47 and a current-voltage converter 49, each of the termination resistors 47, 47 being connected to a phase modulator 27, 28. The current-voltage converter 49 is connected to the light receiver 13.

As described above, when the optical integrated circuit 21 is a titanium diffusion type, the waveguides 23, 25 and 26 do not serve as a polarizer, so that it is necessary to form the polarizer 29 in the optical integrated circuit 21. is there.

FIG. 8 shows a sectional structure of an optical fiber gyro. As shown, the optical fiber gyro is provided with a temperature control device. Such a temperature adjusting device has a temperature sensor 41 mounted on the first supporting member 17 and a heating / cooling device 43 arranged on the lower surface of the first supporting member 17. The heating / cooling device 43 may include, for example, a Peltier element. The heating / cooling device 43 is arranged on the base 39.

The temperature sensing portion of the temperature sensor 41 is preferably arranged near the light source 11. The temperature sensor 41 detects the light source temperature, and a signal indicating the light source temperature is supplied to the heating / cooling device 43. In this way, the heating / cooling device 43 is adjusted so that the temperature near the light source 11 is always constant.

[0029]

Although the optical integrated circuit 115 is used in the example shown in FIG. 6, the optical fiber loop 103 is used.
Since the optical fiber is used in other portions, it is necessary to align the optical axis at the connection portion, and the task of accurately aligning the optical axis is complicated.

In the example shown in FIG. 7, an optical fiber gyro module that does not use an optical fiber is constructed except for the optical fiber loop 19 of the optical fiber gyro. Therefore, the step of connecting the optical fibers is not required. However, it has the following disadvantages.

Half of the 0th-order mode (single mode) light propagating through the waveguide 25A is 1 at the first Y branch 25.
It becomes the next mode (multi-mode) light. The first mode light is
Since the light intensity distribution is asymmetric with respect to the optical axis, the waveguide 2
3 is emitted into the substrate of the optical integrated circuit 21 outside of 3, and a part of such emitted light propagates to the second Y branch 26. Therefore, in the second Y branch 26, the light passing through the waveguide 23 and the light passing through the outside of the waveguide 23 are recombined. As a result, a phase difference is generated between the lights branched into the two waveguides 26A and 26B, which causes a noise of the gyro signal.

In view of the above point, the present invention has an object to provide an optical fiber gyro which does not require alignment of the optical axes and therefore has no error caused by the mismatch of the optical axes.

In view of the above point, the present invention, in an optical integrated circuit having two Y branches, recombines the first-order mode light generated in the first Y branch 25 in the second Y branch 26. It is an object of the present invention to provide an optical fiber gyro that does not cause noise in a gyro signal due to the above.

[0034]

According to the present invention, an optical integrated circuit having a light source, a waveguide arranged in alignment with the optical path of light from the light source, and an optical fiber loop connected to the waveguide are provided. In the optical fiber gyro having, a beam splitter is provided in an optical path between the light source and the waveguide, light from the light source passes through the beam splitter, propagates in the waveguide of the optical integrated circuit, and The light propagating in the opposite direction is configured to change the optical path by the beam splitter.

According to the present invention, in the optical fiber gyro, the light source, the beam splitter, and the optical integrated circuit are formed as an integral component which is supported by one supporting member and does not include an optical fiber. Characterize.

According to the present invention, in the optical fiber gyro, the beam splitter is configured to include a half mirror inclined by 45 ° with respect to the optical path. The beam splitter includes a condenser lens. Alternatively, the condenser lens is provided in one or both of the optical path between the light source and the beam splitter and the optical path between the beam splitter and the optical integrated circuit. The beam splitter includes a right angle prism having a half mirror surface inclined at 45 ° with respect to the optical path.

According to the present invention, in the optical fiber gyro, a light receiver is provided in the modified optical path for detecting light propagating in the opposite direction of the waveguide and modified by the beam splitter. Is characterized by.

According to the present invention, in the optical fiber gyro, the optical integrated circuit has a Y branch connected to the waveguide and a phase modulator provided along the Y branch.

According to the present invention, in the optical fiber gyro, a temperature adjusting device is provided in the vicinity of the light source so that the light source is always maintained at a constant temperature. .

According to the present invention, since the optical fiber is not included except for the optical fiber loop 19, the work of connecting the light source 11 and the optical fiber is not required in the manufacture of the optical fiber gyro, and the light source 11 and the optical fiber are not required. It does not require the work of aligning the optical axes of.

According to the present invention, the beam splitter is connected to the end face of the waveguide 23A on the front end face of the optical integrated circuit 21, and the Y on the light source side of the two Y branches of the optical integrated circuit 21 is connected.
Since no branching is required, no error occurs in the gyro signal due to the light of the primary mode generated in the Y branch.

[0042]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A first embodiment of the optical fiber gyro according to the present invention will be described with reference to FIG. The optical fiber gyro of this example has a light source 11, an optical integrated circuit 21, and an optical fiber loop 19 (only both ends are shown). The light source 11 is supported by the sub-carrier 15, and such sub-carrier 15
Is attached to the upper surface of the first support member 17.
A temperature sensor 41 is provided below the sub carrier 15, which will be described later.

The optical integrated circuit 21 is attached to the upper surface of the second supporting member 31. The second support member 31 is attached to the first support member 17 by a pair of bolts (only one is shown), but the first support member 17 and the second support member 31 are integrally formed. Good.

On the upper surface of the optical integrated circuit 21, a waveguide 23 and a Y branch 26 composed of a waveguide are formed. The tip of the waveguide 23 may be configured to have an enlarged cross sectional area. Phase modulators 27 and 28 are arranged on both sides of each branch 26A and 26B of the Y branch 26.

According to this example, the light source 11 and the optical integrated circuit 21
The beam splitter 22 is attached to the optical path between the front end faces 21A of the. The beam splitter 22 of this example has a half mirror 22A that is inclined by 45 ° with respect to the optical path, and has condenser lenses 22B and 22C on the front side and the rear side along the optical path. The half mirror 22A may be formed by a right angle prism.

The distance between the light source 11 and the first condenser lens 22B and the distance between the first condenser lens 22B and the optical integrated circuit 21.
The distance between the front end faces 21A of the
It may be a few mm.

The light receiver 1 is provided on both sides of the beam splitter 22.
3A and 13B are provided. One light receiver 13A is used to monitor the light emission state of the light source 11, and the other light receiver 13B is provided to detect the light propagating in the waveguide 23 in the opposite direction.

A connecting device 35 is provided on the rear end surface of the optical integrated circuit 21.
Is attached, and both ends of the optical fiber loop 19 are connected to the connecting device 35. Thus, both ends of the optical fiber loop 19 are connected to the Y branch 2 via the connection device 35.
6 branches are connected to each of the branches 26A and 26B.

The light from the light source 11 is emitted from the beam splitter 22.
And reaches the half mirror 22A by being condensed by the first condenser lens 22B. Half of the light is half mirror 2
2A is reflected and detected by the first light receiver 13A, and the other half of the light is transmitted through the half mirror 22A, guided to the waveguide 23, and reaches the Y branch 26. The propagating light is split into two at the Y branch 26. One light propagates clockwise through the optical fiber loop 19 via the one branch 26A and the connecting device 35, and the other light propagates to the other branch 26B and the connecting device 35.
Propagates in the left-hand direction through the optical fiber loop 19 via.

Both the light propagating clockwise and the light propagating counterclockwise in the optical fiber loop 19 are arranged in phase modulators 27, 2 arranged along the respective branches 26A, 26B of the Y branch 26.
It is phase-modulated by 8. The second phase modulator 28 may be a serrodyne phase modulator.

In this way, the phase-modulated right-handed propagating light and left-handed propagating light are combined by the Y branch 26, and the interference light reaches the beam splitter 22 via the waveguide 23.
The interference light reaching the beam splitter 22 is condensed by the second condenser lens 22C and reaches the half mirror 22A. Half of the interference light is reflected by the half mirror 22A and detected by the second light receiver 13B, and the other half of the interference light is transmitted by the half mirror 22A.

The first light receiver 13A monitors the light emitting state of the light source 11. Although not shown in the figure, the first light receiver 13A
A control loop may be provided for adjusting the current signal supplied to the light source 11 by inputting the output signal of the light source 11 of FIG. The second light receiver 13B outputs a current signal indicating the intensity and phase of the interference light. As shown, the second support member 31 has 1
A pair of termination resistors 47, 47 and a current-voltage converter 49 are provided, and each of the termination resistors 47, 47 is a phase modulator 2.
7 and 28, the current-voltage converter 49 is connected to the light receiver 13
B.

As described above, when the optical integrated circuit 21 is a titanium diffusion type, the waveguide 23 and the Y branch 26 do not serve as a polarizer, so that it is necessary to form the polarizer 29 in the optical integrated circuit 21. is there.

FIG. 2 shows a sectional structure of the optical fiber gyro shown in FIG. As shown in the figure, the optical fiber gyro is provided with a temperature adjusting device, and the temperature adjusting device may have the same configuration as that described with reference to FIG. Mounted temperature sensor 41
And a heating / cooling device 43 arranged on the lower surface of the first supporting member 17. The heating / cooling device 43 may include, for example, a Peltier element. The heating / cooling device 43 is the base 3
It is placed on top of 9.

The temperature sensing portion of the temperature sensor 41 is preferably arranged near the light source 11. The temperature sensor 41 detects the light source temperature, and a signal indicating the light source temperature is supplied to the heating / cooling device 43. In this way, the heating / cooling device 43 is adjusted so that the temperature near the light source 11 is always constant.

A second example of the optical fiber gyro according to the present invention will be described with reference to FIG. The optical fiber gyro of this example is different from the example shown in FIG.
2 may be the same as the example of FIG. 1 except for the configuration and arrangement state.

According to this example, the beam splitter 22 has a half mirror 22A and a condenser lens 22B, and the condenser lens 22B is arranged on the light source 11 side. The beam splitter 22 is a front end face 2 of the light source 11 and the optical integrated circuit 21.
It is arranged in contact with the front end face 21A of the optical integrated circuit 21 between 1A. The distance between the light source 11 and the condenser lens 22B may be about several tens of μm to several mm.

The light from the light source 11 is reflected by the beam splitter 22.
Is condensed by the condenser lens 22B of the half mirror 2
Reach 2A. Half of the light is transmitted through the half mirror 22A and guided to the waveguide 23 of the optical integrated circuit 21, and the other half of the light is reflected by the half mirror 22A and reaches the first light receiver 13A.

The interference light propagating in the waveguide 23 of the optical integrated circuit 21 in the opposite direction reaches the half mirror 22A of the beam splitter 22. Half of the interference light is reflected by the half mirror 22A and reaches the second light receiver 13B.

FIG. 4 shows the front structure of the second example of the optical fiber gyro of the present invention shown in FIG. Also in this example, a temperature adjusting device is provided, and the temperature adjusting device may have the same configuration as that described with reference to FIG.
The temperature sensor 41 mounted on the supporting member 17 and the heating / cooling device 43 arranged on the lower surface of the first supporting member 17. The heating / cooling device 43 may include, for example, a Peltier element. The heating / cooling device 43 is arranged on the base 39.

In this example, as shown in the drawing, the front end of the optical integrated circuit 21 is mounted so as to project forward from the support member 31, whereby the front end face 21A of the optical integrated circuit 21 is favorably attached to the beam splitter 22. Can be contacted.

Although the embodiments of the present invention have been described in detail above, those skilled in the art will understand that the present invention is not limited to the above-mentioned embodiments and various other configurations can be adopted without departing from the gist of the present invention. Easy to understand.

In the above example, the condenser lenses 22B and 22C are used.
Although it has been described as a component of the beam splitter 22, it may be provided as a component separate from the beam splitter 22. In such a case, the condenser lenses 22B and 22C are
It is provided on one or both of the optical path between the light source 11 and the beam splitter 22, and the optical path between the beam splitter 22 and the optical integrated circuit 21.

[0064]

According to the present invention, the optical fiber loop 19
Since there is no optical fiber other than the part, there is an advantage that the optical fiber gyro can be manufactured without the work of connecting the light source 11 and the optical fiber.

According to the present invention, since the optical fiber is not included except for the optical fiber loop 19, there is an advantage that the optical fiber gyro can be manufactured without the work of aligning the optical axes of the light source 11 and the optical fiber.

According to the present invention, the light source 11 and the optical integrated circuit 2
Since the beam splitter 22 is provided between 1,
Among the two Y branches of the optical integrated circuit 21, there is an advantage that the Y branch on the light source side is not required.

According to the present invention, of the two Y-branches of the optical integrated circuit 21, the Y-branch on the light source side is not required, so that there is an advantage that the first-order mode light is not generated in the Y-branch. There is an advantage that the error of the gyro signal caused by the light of the next mode does not occur.

[Brief description of drawings]

FIG. 1 is a diagram showing a planar configuration of a first example of an optical fiber gyro of the present invention.

FIG. 2 is a diagram showing a front configuration of a first example of an optical fiber gyro of the present invention.

FIG. 3 is a diagram showing a planar configuration of a second example of the optical fiber gyro of the present invention.

FIG. 4 is a diagram showing a front configuration of a second example of the optical fiber gyro of the present invention.

FIG. 5 is a diagram showing an example of a conventional optical fiber gyro.

FIG. 6 is a diagram showing another example of a conventional optical fiber gyro.

FIG. 7 is a diagram showing still another example of a conventional optical fiber gyro.

8 is a diagram showing a cross-sectional configuration of the optical integrated circuit of FIG.

[Explanation of symbols]

 11 light source 13, 13A, 13B light receiver 15 subcarrier 17 support member 19 optical fiber loop 21 optical integrated circuit 22 beam splitter 23 waveguide 25, 26 Y branch 27, 28 phase modulator 29 polarizer 31 support member 33 bolt 35 connection Device 39 Base 41 Temperature sensor 43 Heating / cooling device 47 Termination resistor 49 Current-voltage converter 101 Light source 102 Light-receiver 103 Optical fiber loop 104 Polarizer 105, 106 Coupler 107 Current-voltage converter 108, 108 'Phase modulator 109 Signal Generator 110 Synchronous detector 115 Optical integrated circuit 116 Connection device 117 Connection part 118 Y branch 131 Optical fiber

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Sadaomi Sakuma 2-16-46 Minami Kamata, Ota-ku, Tokyo Within Tokimec Co., Ltd.

Claims (9)

[Claims] 1. An optical fiber gyro having a light source, an optical integrated circuit having a waveguide arranged in alignment with an optical path of light from the light source, and an optical fiber loop connected to the waveguide. A beam splitter is provided in an optical path between the waveguides, light from the light source passes through the beam splitter and propagates in the waveguide of the optical integrated circuit, and light propagated in the opposite direction in the waveguide is An optical fiber gyro characterized by being configured to change an optical path with a beam splitter. 2. The optical fiber gyro according to claim 1, wherein the light source, the beam splitter, and the optical integrated circuit are supported by one support member and are formed as an integral component that does not include an optical fiber. An optical fiber gyro characterized by the above. 3. The optical fiber gyro according to claim 1 or 2, wherein the beam splitter is configured to include a half mirror inclined by 45 ° with respect to an optical path. 4. The optical fiber gyro according to claim 1, 2 or 3, wherein the beam splitter includes a condenser lens. 5. The optical fiber gyro according to claim 1, 2 or 3, wherein a condensing lens is provided on one or both of an optical path between the light source and the beam splitter and an optical path between the beam splitter and the optical integrated circuit. An optical fiber gyro which is provided with. 6. The optical fiber gyro according to claim 1, 2, 3, 4 or 5, wherein the beam splitter includes a right-angled prism having a half mirror surface inclined by 45 ° with respect to an optical path. Fiber gyro. 7. The optical fiber gyro according to claim 1, 2, 3, 4, 5 or 6, wherein the light propagates in the opposite direction of the waveguide and is detected by the beam splitter to change the optical path. An optical fiber gyro, wherein a light receiver is provided in the changed optical path. 8. The optical fiber gyro according to claim 1, 2, 3, 4, 5, 6 or 7, wherein the optical integrated circuit comprises a Y branch connected to the waveguide and the Y branch.
An optical fiber gyro having a phase modulator provided along a branch of the branch. 9. The optical fiber gyro according to claim 1, 2, 3, 4, 5, 6, 7 or 8, wherein a temperature adjusting device is provided close to the light source, whereby the light source is always constant. An optical fiber gyro characterized by being configured to be maintained at a temperature of.