JPH06265362A - Optical rotation-detection device - Google Patents

Abstract

PURPOSE:To reduce the drift of a zero point by suppressing a beam of returned light from the edge of an optical fiber in an optical-fiber gyro using the optical fiber as a sensing coil regarding an optical rotation-detection device wherein the rotation state of an object to be detected is detected by using a beam of light. CONSTITUTION:An angle-polishing treatment or an antireflection treatment or both the angle-polishing treatment and the antireflection treatment as edge treatments are executed to at least one edge out of a total of four edges of an optical fiber, i.e., one part each of the open end of an optical-fiber coupler 2 and the open end of an optical-fiber coupler 5, one part in a light-source module 1 and one part in a light-receiving means 3. When any one treatment out of them is executed, the drift of a zero point can be reduced.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical rotation detecting device used for a moving body or the like, and more particularly to an optical fiber gyro.

[0002]

2. Description of the Related Art Among devices used as an optical rotation detecting device is a gyroscope.

This gyroscope can obtain not only angular velocity but also azimuth data by time-integrating it.

Among these gyroscopes is an optical fiber gyro using an optical fiber as a sensing coil.

This optical fiber gyro has no moving parts and can be miniaturized, and further, in terms of minimum detectable angular velocity (sensitivity), zero point drift, measurable range (dynamic range), and stability of scale factor. ,
It is superior to the conventional mechanical gyroscope, and has been attracting attention in recent years and has been actively researched and developed.

A phase modulation method, a frequency modulation method, an optical heterodyne method, etc. have been proposed as a signal processing method for the output light of the optical fiber gyro, but here, a conventional optical fiber adopting the phase modulation method is proposed. A gyro will be described as an example with reference to FIG.

In FIG. 3, 11 is a light source and optical means for propagating light from the light source, for example, a light source module having a lens, 12 and 15 are optical fiber couplers for branching and recombining light, 13 is a light receiving means, and 14 is a light receiving means. Polarizer, 15 is an optical fiber coupler, 16 is an optical fiber coil, 17 is a phase modulator, 18 is an optical fiber coil 16 and a phase modulator 1.
Sensing loop part including 7 etc., 21 to 29 are optical paths,
Reference numerals 31 to 33 are end faces of the optical path.

The operation of the optical fiber gyro configured as above will be described. First, the light source module 1
The light excited and oscillated by the first light source enters the optical path 21 from the end face 31 via the lens in the light source module 11.

Next, the light incident on the optical path 21 is branched into two by the optical fiber coupler 12, and one of the two branched light is incident on the polarizer 14 via the optical path 23. At this time, the other light is emitted to the outside from the end face of the optical path 24 which is the open end.

The light emitted from the polarizer 14 is
It is incident on the optical fiber coupler 15 through the optical path 25, and
Branched.

At this time, one of the two branched light beams has an optical path 2
It is incident on the optical fiber coil 16 which is a sensing coil via 7. The other light enters the phase modulator 17 via the optical path 28, and then enters the optical fiber coil 16 via the optical path 29.

The phase modulator 17 has a structure in which an optical fiber is wound around a cylindrical piezoelectric vibrator or the like, and piezoelectric vibration is generated by applying a predetermined modulation signal, for example, a sine wave signal to the piezoelectric vibrator. The child is expanded and contracted, and the length, propagation constant, etc. of the optical fiber generated according to this expansion and contraction are changed, and phase modulation is caused when light propagates in the wound optical fiber.

As described above, the lights that are incident on the sensing loop portion 18 and propagate in opposite clockwise and counterclockwise directions are recombined by the optical fiber coupler 15, and one of the combined lights is passed through the optical path 25. It is incident on the polarizer 14 via. Further, the other of the combined lights is emitted to the outside from the end face 33, which is the open end, through the optical path 25.

The light emitted from the polarizer 14 is
It is incident on the optical fiber coupler 12 through the optical path 23,
It is branched into two by the optical fiber coupler 12.

One of the two light beams thus branched is incident on the light receiving means 13 such as a photoelectric detector through the end face 34 through the optical path 22, and the other through the end face 31 through the optical path 21 and the light source module 11. Is incident on.

The light received by the light receiving means 13 is
It is converted into an electric signal and then processed by a signal processing system (not shown).

The optical fiber gyro which operates as described above is provided with the optical fiber coil 16 of the sensing loop section 18.
However, when it is moved due to rotation, etc., Sagnac (Sagna)
Due to the effect c), a phase difference occurs in the lights propagating in opposite directions.

The light having the phase difference is coupled by the optical fiber coupler 15 to cause interference, the interference light is received and detected by the light receiving means 13, and then signal processing is performed to obtain the angular velocity of movement and the like.

In the optical fiber gyro, when all the optical paths are composed of optical fibers, it is considered that they are composed of single mode fibers and those of polarization maintaining fiber.

The single-mode optical fiber has the advantage of being less expensive than the polarization-maintaining fiber, but the plane of polarization fluctuates due to disturbance such as temperature change, and zero-point drift (rotational output fluctuation in a stationary state) occurs. It occurs greatly.

Therefore, in the sensing loop section 18,
It is necessary to insert a depolarizing means to cancel the fluctuation of the plane of polarization.

Therefore, in general, there are many examples in which a polarization maintaining fiber constitutes the entire optical path. When an optical fiber is used in the optical path, there are at least four end faces 31 to 34.

[0023]

As described above, in the optical fiber gyro, the signal used for detecting the angular velocity or the like corresponds to the interference output light, and in general, the intensity of the interference output light is high. It is a signal.

Therefore, when the propagation states of light and interference light propagating in opposite directions are different from each other due to disturbance or the like, or when a fluctuation component is added to the interference light or the like for some reason, interference occurs. There is a problem that an error component that is not a true detection component is generated in the output light, zero point drift increases, and the S / N ratio decreases.

The inventors of the present application have made various studies on the cause of the error component, and as a result, unnecessary return light is generated due to the reflection of light at the end face of the optical fiber, which is an error component. I found that.

More specifically, in at least one of the four end faces 31 to 34 in FIG. 3, most of the light transmitted through the optical fiber passes through the end faces and is emitted to the outside. , Part of it is reflected by the end face.

At this time, the reflected light has an angle smaller than the total reflection angle defined by the relative refractive index between the core and the clad of the optical fiber, and the reflected light reflects the boundary surfaces 31 to 34 of the core and the clad.
When it is incident on, the reflected light propagates as it is in the direction opposite to the original optical path.

When the return light thus generated is incident on the sensing loop portion 18, it causes different propagation states of light propagating in opposite directions.

Further, when the return light enters the optical fiber such as the optical path 22 toward the light receiving means 13, it causes a variation component to be added to the interference light or the like.

The above-mentioned problems such as an increase in zero-point drift due to the generation of return light are practically negligible when used in the consumer field when the optical path is composed of a polarization-maintaining fiber. However, especially when the optical path is composed of a single mode fiber, the influence on the fluctuation of the output signal is extremely large, and it is an important issue to be overcome in order to improve the detection accuracy even for consumer use. .

The present invention has solved the above-mentioned problems and has a sufficiently low zero-point drift property and a high S / N ratio not only when the optical path is formed by a single mode fiber but also when it is formed by a polarization-maintaining fiber. It is an object of the present invention to realize an optical rotation detection device that can realize the above.

[0032]

In order to solve the above-mentioned problems, an optical rotation detecting device of the present invention comprises: an end face of an optical fiber which allows light emitted from a light emitting element in a light source module to enter the optical fiber; An end face of an optical fiber not coupled to any one branch of the first optical fiber coupler, an end face of an optical fiber not coupled to any branch of the second optical fiber coupler, and a light receiving means Among the end faces of the optical fiber that emits light to the light receiving element, at least one end face of the optical fiber is configured to perform processing that does not generate return light.

The processing for preventing the return light from being generated is one in which either or both of the angle forming processing and the non-reflection processing are performed.

This angle forming process is performed on the end surface of the optical fiber so that the return light reflected from the end surface of the optical fiber is not substantially reflected at the boundary portion between the core portion and the clad portion of the optical fiber. To give an angle to
An angle polishing process is preferable.

On the other hand, the antireflection treatment is to form the antireflection treatment material layer adjacent to the end face of the fiber.

The thickness of the antireflection treatment substance layer is preferably set so that the reflected light from the end face of the antireflection treatment substance layer opposite to the optical fiber does not enter the core portion of the optical fiber. Has been done.

[0037]

By using the above-described structure, the optical rotation detecting device of the present invention is arranged such that the light reaching the end face of the optical fiber is reflected by the end face and returns to the sensing loop portion in the opposite direction to turn counterclockwise. Changes in light or clockwise light, light returned to the light emitting element destabilizes the oscillation state of the light emitting element, or propagates to the optical fiber to the light receiving means and changes to the interference light itself. Will not be given.
This makes it possible to completely eliminate the adverse effect of the returning light, so that the zero-point drift can be further reduced and the S / N ratio of the optical rotation detection device can be improved.

[0038]

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

FIG. 1 is a schematic diagram showing the structure of an optical rotation detecting device according to an embodiment of the present invention. In FIG. 1, reference numeral 1 denotes a light source module using a super luminescent diode as a light emitting element, which has a lens into which light emitted from the light emitting element is incident and an optical fiber as an optical path.

Next, 2 is an optical fiber coupler for splitting the light from the light source module 1 into two, 3 is a light receiving means for receiving the light propagating in the optical fiber and converting it into an electric signal, and 4 is A polarizer (for example, a laminated type or a fiber type polarizer can be used) for defining a polarization direction of one of the lights branched into two by the optical fiber coupler 2 and linearly polarizing the light, Reference numeral 5 denotes an optical fiber coupler for splitting the light linearly polarized by the polarizer 4 into two.

Here, the optical fiber couplers 2 and 5 are optical fiber type couplers using inexpensive and highly reliable single mode optical fibers, and the branching ratios thereof are adjusted to 1: 1.

Next, 6 is an optical fiber coil constructed by winding a single mode optical fiber around a bobbin, and is for obtaining a phase difference between the counterclockwise light and the clockwise light by the Sagnac effect. Reference numeral 7 is a phase modulator formed by winding a single mode optical fiber around a cylindrical piezoelectric vibrator, and gives a predetermined phase difference at a predetermined timing between the counterclockwise light and the clockwise light passing through this portion. It is a thing.

Next, a depolarizing means 8 is provided adjacent to the optical fiber coil 6 for the purpose of forcibly depolarizing the propagating light and removing an unnecessary interference noise component due to the change of the polarization state. Has been inserted.

However, in addition to the position shown in FIG. 1, the depolarizing means 8 is inserted between the optical fiber coupler 5 and the phase modulator 7 or between the optical fiber coil 6 and the phase modulator 7. Any of the above positions is possible, and the positions may be inserted at a plurality of positions.

Further, in the present embodiment, the depolarizing means is arranged in the sensing loop section 9. However, the depolarizing means may not be provided.

As the depolarizing means, LY in which the principal axis angle of the polarization-maintaining optical fiber is inclined by about 45 degrees and fused is used.
A fiber type depolarizer of OT type is suitable.

As the depolarizing means, a bulk type depolarizer in which crystal plates having optical anisotropy are combined so that their principal axes are displaced by about 45 degrees may be used.

In this embodiment, 51 to 60 are optical paths, and the optical paths 51 to 60, the optical path of the optical fiber coil 6 and the optical path of the phase modulator 7 are all single mode optical fibers. It is composed of.

A structure in which some or all of these optical fibers are replaced with polarization-maintaining optical fibers may be used.

Reference numerals 61 to 64 are end faces of the optical fiber.
Specifically, reference numeral 61 is an end face when the light excited by the light emitting element is incident on the optical path 51 from the optical fiber inside the light source module, and 62 and 63 are the light transmitted through the optical paths 54 and 56, respectively. It is the end face that goes out, and 6
Reference numeral 4 denotes an end face for emitting the light propagating through the optical path 52 to the light receiving means 3.

FIG. 2 is a diagram showing the concept of light propagation in the vicinity of the end face of the optical fiber in the embodiment of the present invention.

In FIG. 2, 100 is an axis of the optical fiber, 101 is an end face of the optical fiber, 102 is a clad having a refractive index m, 103 is a core having a refractive index n, 111 Is light that has propagated in the optical fiber, 112 is light that has passed through the end face 101 of light 111, 113 is light that is reflected by the end face 101 of light 111, and 114 is light 113 that is the core 103 and the cladding. The light is transmitted through the boundary surface of 102.

Further, i is the incident angle of the light 111 with respect to the end face 101, j is the outgoing angle of the light 112 with respect to the end face 101, and k is the core 103 and the clad 102 of the light 113.
Is the angle of incidence with respect to the boundary surface of
03 and the clad 102.

Next, the operation of the present optical rotation detector will be described in detail with reference to FIGS. 1 and 2. The light output from the light source module 1 passes through the optical path 51 and is input to the optical fiber coupler 2.

The light split into two by the optical fiber coupler 2 sequentially passes through the optical path 53, the polarizer 4 which defines the polarization state in only one direction, and the optical path 55, and then the optical fiber coupler 5
Is incident on.

The light input to the optical fiber coupler 5 is equally split into two optical paths 57 and 58.

The input light to the optical path 57 is depolarized by the depolarizing means 8, travels clockwise through the optical fiber coil 6 via the optical path 60, then passes through the optical path 59, and has a preset optical phase. The optical path 508 passes through the phase modulator 7 to be added.
After passing through, the light is input to the optical fiber coupler 5 in the opposite direction.

Here, the phase modulator 7 adds a preset optical phase in order to enhance the detection sensitivity of the Sagnac phase difference generated in the optical fiber coil 6.

On the other hand, the light split into two in the optical fiber coupler 5 and input to the optical path 58 travels in the direction completely opposite to the above-described light wave.

That is, the optical path 58, the phase modulator 7, the optical path 5
The light that has passed through 9 in this order propagates counterclockwise in the optical fiber coil 6, then passes through the optical path 60, the depolarizer 8 and the optical path 57 in this order, and is input to the optical fiber coupler 5.

The light thus split into two in the opposite directions by the optical fiber coupler 5 is sent to the optical fiber coil 6
After propagating, the optical fiber coupler 5 couples them again.

After the combined light passes through the optical path 55, it propagates in the reverse direction through the polarizer 4, the optical path 53 and the optical fiber coupler 2, and is input into the light receiving means 3 by the optical path 52 and converted into an electric signal.

The optical fiber gyro having the above structure has four end faces of the optical fiber.

That is, one each of the optical fiber coupler 2 and the optical fiber coupler 5, and the light source module 1
4 places, one in the inside and one in the light receiving means 3.
There are end faces 61 to 64 of the optical fiber at the location.

Conventionally, these end faces have not been subjected to any special treatment, and they have been cut or polished so that the end faces are perpendicular to the axis of the optical fiber, as in the case of cutting an optical fiber.

However, when the light propagating through the optical fiber reaches these end faces, most of the light passes through the end faces and goes out of the optical fiber, but some of them are reflected by the end faces. .

When the direction of such reflected light forms an angle smaller than the critical angle for causing total internal reflection with the boundary surface between the core and the clad of the optical fiber, the reflected light passes through the inside of the optical fiber. , But it travels in the direction opposite to the direction in which it propagates.

Here, when the critical angle is θ, θ is expressed by the following equation.

[0069]

[Equation 1]

That is, as shown in FIG. 2, when the incident angle k of the reflected light 113 with respect to the boundary surface between the core 103 and the clad 102 is larger than (90 degrees-θ), the return light is returned to the optical fiber again. Will propagate through.

If such return light propagates through the sensing loop section 11, unnecessary interference may occur, or the return light may reach the light source and cause variations in the light emitting state of the light emitting element. Will have a bad effect.

For this reason, the return light from the end face of the optical fiber must be reduced as much as possible.

In this embodiment, in order to reduce the return light from the end faces of the optical fibers as much as possible, the end faces 61 to 64 of the four optical fibers existing in the optical fiber gyro are end face treated.

As shown in FIG. 2, even if the light 111 is reflected by the end surface 101, the reflected light 113 is reflected by the end surface treatment.
The incident angle k with respect to the boundary surface between the core 103 and the clad 102 is smaller than (90 ° −θ), and the end face 101 of the optical fiber 101 is emitted so as to be emitted to the clad without being totally reflected.
Is formed diagonally.

Specifically, there is also a method of cutting into an oblique shape, but it is technically difficult and there are many failures, so it is more preferable to perform angle polishing that is reliable and has almost no failures. .

When the end face 61 of the optical fiber in the light source module 1 is subjected to this angle polishing, the light emitted from the light emitting element and reflected by the end face 61 does not return to the light emitting element again. It was confirmed that the light emitting state was stable.

When the angle polishing is applied to the end face 64 of the optical fiber in the light receiving means 3, the light propagating through the optical fiber is reflected by the end face 64 and propagates to the sensing loop portion 11 again. The right-handed light and the left-handed light for sensing are not adversely affected, and the output bias irrelevant to sensing is reduced in the light output output to the light receiving means 3.

Further, when the end face 62 at the open end of the optical fiber coupler 2 is angle-polished, the output bias irrelevant to sensing, which is generated when the return light from the end face 62 reaches the light receiving means 3, is greatly reduced. .

Furthermore, when the end face 63 at the open end of the optical fiber coupler 5 is angle-polished, the return light from the end face 63 is branched by the optical fiber coupler 5 and propagates in the sensing loop portion 11, and the optical fiber coupler Since it will not combine again at 5 and cause unnecessary interference,
It was confirmed that the noise was significantly reduced, and the output fluctuation of the optical rotation detection device in a stationary state, that is, the zero point drift was significantly reduced.

Note that these treatments may be applied to all four open ends or may be applied in an appropriate combination.

(Second Embodiment) Next, a second embodiment of the present invention will be described in detail with reference to FIGS.

FIG. 3 is a diagram showing the concept of light propagation in the vicinity of the end face of the optical fiber in the embodiment of the present invention.

In FIG. 3, 200 is an axis of the optical fiber, 201 is an end face of the optical fiber, 202 is a clad, 203 is a core, and 204 is a material layer applied for antireflection treatment. Yes, 205 is the end face of the antireflection treatment material layer 204, 211 is the light that has propagated through the optical fiber, 212 is the light that has passed through the end face 201 of the optical fiber, and 213 is the light 211. Is the light transmitted through the end surface 205 of the non-reflection treated material,
Reference numeral 4 denotes light that has passed through the end surface 205 of the antireflection treatment material layer.

As the non-reflective material layer 204, the core 2 is used.
Of the light 211 propagating through 03
As long as the substance has a refractive index almost the same as that of the core 203 so as to transmit 01, it can be used regardless of whether it is an inorganic substance or an organic substance.

Next, the operation of this embodiment will be described with reference to FIG. As shown in FIG. 3, the core 203
The light 211 propagating in the light is transmitted into the antireflection treatment material layer 204 without being substantially reflected by the end face 201.

The transmitted light 212 is partially transmitted by the end surface 205 of the antireflection treatment material layer 204 and becomes transmitted light 213, and the other is reflected and becomes reflected light 214.

In the structure of FIG. 3, since the light 211 is not reflected by the end face 201 but is transmitted to the non-reflection processed material layer 204 side by the non-reflection processed material layer 204, the return light is not generated in this portion. Absent.

Furthermore, the end surface 2 of the antireflection treatment material layer 204
In 05, the reflected light 214 is certainly generated, but the length L of the non-reflection treated material layer 204 is equal to the reflected light 214.
By setting the length so that the light does not enter the optical fiber 03, it is possible to prevent generation of return light into the optical fiber.

When this anti-reflection treated material layer was applied to the open end face 62 of the optical fiber coupler 2 of FIG. 1, the end face 6 was obtained.
The output bias irrelevant to sensing, which is caused by the return light from 2 reaching the light receiving means 3, was significantly reduced.

When an antireflection treatment material layer is applied to the open end face 63 of the optical fiber coupler 5 shown in FIG.
The return light from the optical fiber 3 is branched by the optical fiber coupler 5 and propagates in the sensing loop unit 11, and unnecessary interference noise generated when the optical fiber coupler 5 recombines is significantly reduced, resulting in zero-point drift. Significantly reduced.

Further, when the antireflection treatment material layer of this embodiment is formed on the other end face, the same effect as that of the first embodiment can be obtained.

These treatments may be applied to all four open ends, or may be applied in an appropriate combination.

(Third Embodiment) Next, a third embodiment of the present invention will be described in detail with reference to FIG.

The present embodiment has a construction in which the end face processing of both the first embodiment and the second embodiment is performed.

FIG. 4 is a drawing showing the concept of light propagation in the vicinity of the end face of an optical fiber in an embodiment of the present invention.

In FIG. 4, 300 is an axis of the optical fiber, 301 is an end face of the optical fiber, 302 is a clad, 303 is a core, 304 is a non-reflective treatment material layer, and 305 is nothing. It is an end surface of the reflection treatment material layer.

Further, 311 is light propagating in the optical fiber, 312 is light that the light 311 transmits through the end face 301, 313 is light that the light 311 reflects at the end face 301, and 314 is light. 313 is the core 303 and the clad 3
The light is transmitted through the boundary surface of No. 02, and the reference numeral 315 is an antireflection treatment material layer.

Further, i is the incident angle of the light 311 with respect to the end face 301, j is the outgoing angle of the light 312 with respect to the end face 301, and k is the core 303 and the clad 302 of the light 313.
Is the angle of incidence with respect to the boundary surface of, and l is the core 3 of the light 314.
03 and the clad 302.

In this embodiment, in order to reduce the returned light from the end faces of the optical fibers as much as possible, the end faces 61 to 64 of the four optical fibers existing in the optical fiber gyro are end face treated.

As shown in FIG. 4, one of the end face treatments is such that, even if the light 311 is reflected by the end face 301, the incident angle k of the reflected light 313 with respect to the interface between the core 303 and the clad 302 is small. , And their critical angle is θ, (90
The end face 101 of the optical fiber is obliquely formed by angle polishing or the like so as to be emitted to the clad without being totally reflected.

Further, one end surface treatment is to form the non-reflection treated material layer 304 similar to that of the second embodiment on the end surface 301 side of the optical fiber.

The length M of the antireflection treatment material layer 304 is
The length is set to be sufficient as in the second embodiment so that the reflected light 316 from the end face 305 does not enter the core 303.

When both of these end face treatments are applied to the end face 61 of the optical fiber in the light source module 1 in FIG. 1, the light emitted from the light emitting element and reflected by the end face 61 can return to the light emitting element again. It was confirmed that the light emission state of the light emitting element became stable.

When these processings are applied to the end face 64, the light propagating through the optical fiber is reflected by the end face 64 and propagates again to the sensing loop portion 11, and the clockwise light and the left light for sensing. The adverse effect on the ambient light is eliminated, and the output bias irrelevant to sensing is reduced in the optical output output to the light receiving means 3.

Further, when these processes are applied to the end face 62, the output bias unrelated to sensing, which is generated when the return light from the end face 62 reaches the light receiving means 3, is greatly reduced.

When the end face 63 at the open end of the optical fiber coupler 5 is subjected to these treatments, the return light from the end face 63 is branched by the optical fiber coupler 5 and propagates in the sensing loop portion 11, Since the optical fiber coupler 5 does not couple again to cause unnecessary interference, noise is greatly reduced, and output fluctuation of the optical rotation detection device in a stationary state, that is, zero-point drift is significantly reduced. Was confirmed.

Further, both the open end face 62 of the optical fiber coupler 2 and the open end face 63 of the optical fiber coupler 5 are subjected to these end face treatments, and the end face 61 of the optical fiber in the light source module 1 and the light receiving means. When the end face 64 of the optical fiber in 3 is formed into an optical fiber gyro that has been subjected to an angle polishing treatment, and the output voltage value converted into an electric signal by the light receiving means 3 is measured, it is found that the above treatment is not performed. The voltage bias value was reduced by about 20% as compared with.

Further, as a result of measuring the zero point drift, the zero point drift in the conventional configuration was within 0.05 (degrees / second).
It was 0.005 (degrees / second), and the experimental result that the reflection noise component generated by the returning light from each end face was extremely reduced was obtained.

Therefore, by appropriately combining the two end face treatments of this embodiment, the return light due to reflection is
It was found that the light was suppressed sufficiently so as not to propagate to the light receiving means 3.

Note that these end face treatments have the effect that one or both of them are applied to at least one end face, and the effect is obtained not only by the pattern shown above but also by different patterns. You may perform the process of.

[0111]

As described above, according to the present invention, the end light of the optical fiber existing in the optical fiber gyro is subjected to the angle polishing treatment and / or the anti-reflection treatment so that the return light due to the end face reflection is prevented. Since the light does not propagate through the optical fiber again, unnecessary fluctuations are not given to the light propagating through the sensing loop portion and the interference signal light serving as the output signal.

Therefore, the zero point drift is reduced and S /
It is possible to provide a highly accurate optical rotation detection device having a high N ratio.

[Brief description of drawings]

FIG. 1 is a schematic diagram of an optical rotation detection device according to an embodiment of the present invention.

FIG. 2 is a conceptual diagram of light propagation near the end face of the optical fiber described in the first embodiment of the present invention.

FIG. 3 is a conceptual diagram of light propagation in the vicinity of the end face of the optical fiber described in the second embodiment of the present invention.

FIG. 4 is a conceptual diagram of light propagation in the vicinity of the end face of the optical fiber described in the third embodiment of the present invention.

FIG. 5 is a schematic diagram of an optical rotation detection device in a conventional example.

[Explanation of symbols]

 1 Light source module 2 Optical fiber coupler 3 Light receiving means 4 Polarizer 5 Optical fiber coupler 6 Optical fiber coil 7 Phase modulator 8 Depolarization means 9 Sensing loop unit 11 Light source module 12 Optical fiber coupler 13 Light receiving means 14 Polarizer 15 Optical fiber coupler 16 optical fiber coil 17 phase modulator 18 depolarizing means 19 sensing loop part 21 optical path 22 optical path 23 optical path 24 optical path 25 optical path 26 optical path 27 optical path 28 optical path 29 optical path 31 end face 32 end face 33 end face 34 end face 51 optical path 52 optical path 53 optical path 54 optical path 55 optical path 56 optical path 57 optical path 58 optical path 59 optical path 61 end surface 62 end surface 63 end surface 64 end surface 100 center axis 101 end surface 102 clad 103 core 200 center axis 201 end surface 202 clad 203 core 204 non-reflecting Processing material layer 300 central axis 301 end face 302 clad 303 core 304-reflective treatment material layer

 ─────────────────────────────────────────────────── ─── Continued Front Page (72) Inventor Susumu Tsubosaka 3-10-1 Higashisanda, Tama-ku, Kawasaki City, Kanagawa Prefecture Matsushita Giken Co., Ltd. 3-3-1 Matsushita Communication Industry Co., Ltd. (72) Inventor Hidehiko Negishi 3-10-1 Higashisanda, Tama-ku, Kawasaki City, Kanagawa Prefecture Matsushita Giken Co., Ltd.

Claims (8)

[Claims] 1. A light source module including a light emitting element, a first optical fiber coupler that splits the light emitted from the light source module into two, and one of the light split by the first optical fiber coupler. The second light having an incident polarizer, a second optical fiber coupler for injecting the light emitted from the polarizer and bifurcating the light, an optical fiber coil for producing a Sagnac effect, and a phase modulation means are provided. A sensing loop unit coupled to a fiber coupler, emitted from the sensing loop unit, passed through the second optical fiber coupler and the polarizer, branched into two by the first optical fiber coupler, and emitted from an optical fiber. An optical rotation detection device comprising a light receiving means for receiving light, the light source module, a first optical fiber coupler, a polarizer, a second optical fiber coupler, and a senshin. An optical rotation detecting device in which at least one of all the end faces of the optical fiber existing in at least one of the inside of the group part and the light receiving means or the part connecting them is subjected to an end face treatment that does not generate return light. . 2. An end face of an optical fiber which receives light from a light emitting element in a light source module and emits the light to the next optical element,
An end face of the optical fiber that is not coupled to any of the branches of the first optical fiber coupler, an end face of the optical fiber that is not coupled to any of the branches of the second optical fiber coupler, and the light receiving means. 2. The optical rotation detecting device according to claim 1, wherein at least one end face of the end faces of the optical fiber that emits light to the light receiving element is subjected to an angle forming process. 3. An end face of an optical fiber which receives light from a light emitting element in a light source module and emits the light to the next optical element,
An end face of the optical fiber that is not coupled to any of the branches of the first optical fiber coupler, an end face of the optical fiber that is not coupled to any of the branches of the second optical fiber coupler, and the light receiving means. The optical rotation detecting device according to claim 1, wherein at least one end face of the end faces of the optical fiber that emits light to the light receiving element is subjected to antireflection treatment. 4. An end face of an optical fiber which receives light from a light emitting element in a light source module and emits the light to the next optical element,
An end face of the optical fiber that is not coupled to any of the branches of the first optical fiber coupler, an end face of the optical fiber that is not coupled to any of the branches of the second optical fiber coupler, and the light receiving means. The optical rotation detecting device according to claim 1, wherein at least one of the end faces of the optical fiber that emits light to the light receiving element is subjected to at least one of an angle forming process and a non-reflection process. 5. The angle forming treatment is performed on the end surface of the optical fiber so that the return light reflected from the end surface of the optical fiber is not substantially reflected at the boundary portion between the core portion and the cladding portion of the optical fiber. The optical rotation detection device according to claim 2, wherein an angle is provided with respect to the optical axis. 6. The optical rotation detection device according to claim 2, 4 or 5, wherein the angle forming process is an angle polishing process. 7. The optical rotation detector according to claim 3, wherein the antireflection treatment forms a nonreflection treatment material layer adjacent to the end face of the optical fiber. 8. The thickness of the antireflection treatment material layer is set so that the reflected light from the end face of the antireflection treatment material layer opposite to the optical fiber does not enter the core portion of the optical fiber. The optical rotation detection device according to claim 7.