JPH0835843A - Optical fiber sensor - Google Patents

Abstract

PURPOSE:To reduce output errors of an optical fiber sensor attributed to changes in environment by housing a part including an optical directive coupler and a sensing coil into a shielding structure. CONSTITUTION:A sensing coil 6 is wound on a winding frame 62 through a coil cover member 63 and two outgoing ends or incoming ends 61 are pulled out of the winding frame 62 to be connected to an optical directive coupler 4 comprising an optical IC having phase modulation and optical coupling/ branching functions. A flat plate part 69 of a winding frame is set at half the height of the winding frame 62 vertical to a rotating shaft of the coil 6 over the entire internal surface of the winding frame 62 from the inner diameter thereof. The outgoing ends or the incoming ends 61 between the coil 6 and the coupler 4 also contact an elastic cover 64 and is mounted on the flat plate part 69 therethrough. Then, a shielding structure is built being closed with a single layer or a plurality of layers of a laminated layer having both of a high heat conduction layer 65 and a heat insulating layer 66 laminated. This enables the obtaining of adiabatic effect, thermal uniformity effect, heat stress removing effect, vibration absorbing effect and the like.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical fiber sensor, and more particularly to an optical fiber sensor that is appropriately protected by a protective member and is not affected by temperature, vibration and other external environment.

[0002]

2. Description of the Related Art First, an optical fiber sensor will be described with reference to FIG. The light emitted from the light source 1 is sent as right-handed light and left-handed light into the sensing coil 6 via the optical directional coupler 2, the polarizer 3, and the optical directional coupler 4. The clockwise light in the sensing coil 6 is first phase-modulated in the phase modulator 5, and the phase-modulated clockwise light is sequentially arranged in the optical directional coupler 4, the polarizer 3, and the optical directional coupler 2. To reach the light receiver 7. Similarly, the counterclockwise light is first phase-modulated in the phase modulator 5, and the phase-modulated counterclockwise light is sequentially received via the optical directional coupler 4, the polarizer 3, and the optical directional coupler 2. Reach vessel 7. The phase-modulated light that has reached the light receiver 7 is photoelectrically converted into an electric signal here. The electric signal photoelectrically converted by the light receiver 7 is input to the synchronous detector 8. In the synchronous detector 8, the signal supplied from the oscillator 9 is used as a reference signal to obtain the fundamental wave component 13 that is the angular velocity output.

[0003]

The optical fiber sensor as described above generally has a risk of generating an output error or damaging a component due to heat or vibration applied from the outside or inside of the optical fiber sensor. It has the envy of being large. On the other hand, conventionally, a heat insulating member and / or a vibration isolating member has been applied to the entire optical fiber sensor as a protection member for protecting the optical fiber sensor from heat or vibration. That is, the light source 1, the optical directional coupler 2, the polarizer 3, the optical directional coupler 4, the phase modulator 5, the sensing coil 6, and the light receiver 7 which constitute the optical fiber sensor are all a heat insulating member and / or a protective member. It is performed to cover with a protection member composed of a vibration member. When the entire optical fiber sensor is covered with a heat insulating member in this way, all other electric components such as the light source 1 are also housed in the heat insulating coating, and the heat generated by these electric components is radiated internally. To be hindered. The heat accumulated inside in this way causes malfunction of the electric parts having temperature characteristics that constitute the optical fiber sensor, or causes damage to these electric parts. In particular, inhibiting the heat radiation of the light source 1 may cause fatal damage to the optical fiber sensor.

Further, referring also to FIG. 4, a coil covering member 63 made of a heat insulating member is applied only to the winding frame 62 holding the sensing coil 6. By doing so, although the heat insulating effect extends to the sensing coil 6 wound around the winding frame 62, the winding frame 62 positioned between the sensing coil 6 and the optical directional coupler 4 is provided.
Since the two output ends or the input ends 61 drawn out from are not covered with the coil covering member 63, they are in a state where the heat insulating effect is not exerted.

Optical directional coupler 4 to sensing coil 6
The exit end or the entrance end 61 located between the two branches.
Is greatly affected by environmental changes such as temperature, and output errors occur due to environmental changes.
Although the influence of the environmental change in the vicinity of the midpoint of the sensing coil 6 is relatively small, the influence of the environmental change becomes large as the distance from the midpoint approaches the optical directional coupler 4 and a large output error occurs. Connect Therefore, it is assumed that the above-mentioned two emitting ends or the incident ends 61, which are the parts farthest from the middle point of the sensing coil 6, are the most sensitive parts to the environmental changes and are the parts where the output error is likely to occur. You can

The present invention provides an optical fiber sensor which solves the above problems.

[0007]

A light source 1, an optical directional coupler 4, a sensing coil 6 and a light receiver 7 are provided, and the light emitted from the light source 1 is branched by the optical directional coupler 4 to form a sensing coil. 6 from both ends as both left and right light, and these two lights are made to interfere again in the optical directional coupler 4 after being transmitted to the sensing coil 6, and the interference light is detected by the light receiver 7 to rotate around the center of the sensing coil 6. In an optical fiber sensor that detects the angular velocity applied to
An optical fiber sensor was constructed in which a portion including the optical directional coupler 4 and the sensing coil 6 was housed in the shielding structure immediately before the optical directional coupler 4 when viewed from the light source 1 side.

The shielding structure constitutes an optical fiber sensor composed of a single layer or a plurality of laminated layers in which a high thermal conductive material layer and a heat insulating material layer are laminated in this order from the inside to the outside. In addition, a part or all of a portion including the optical directional coupler 4 and the sensing coil 6 from immediately before the optical directional coupler 4 in contact with the high thermal conductive material layer of the innermost laminated layer constituting the shielding structure and this maximum. An optical fiber sensor was constructed in which an elastic body was installed between the inner layer and the high thermal conductive material layer.

Further, the reel around which the sensing coil 6 is wound is made of a high heat conductive material, and the reel flat plate portion 69 perpendicular to the rotation input shaft of the sensing coil 6 is wound at a position half the height of the reel. An optical fiber sensor is formed which is formed entirely inside the inner diameter of the frame, and this portion is attached to the shielding structure via a pillar 67 made of a heat insulating material. Here, further, a part or all of the portion including the optical directional coupler 4 and the sensing coil 6 from immediately before the optical directional coupler 4 in contact with the high thermal conductive material layer of the innermost laminated layer forming the shielding structure. An optical fiber sensor was also constructed in which an elastic body was also installed between the innermost laminated layer and the high thermal conductive material layer.

Also, an optical fiber sensor was constructed in which the entire portion including the optical directional coupler 4 and the sensing coil 6 was covered with a magnetic shield material immediately before the optical directional coupler 4.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT An embodiment of the present invention will be described with reference to FIGS. FIG. 3 is a diagram showing an optical fiber sensor which is a precondition to which the present invention is applied. The optical fiber sensor includes a light source 1, an optical directional coupler 4, a sensing coil 6 and a photodetector 7, and the light emitted from the light source 1 is shown. Is branched by the optical directional coupler 4 and is incident on the sensing coil 6 from both ends thereof as left and right bidirectional light, and these two lights are interfered again in the optical directional coupler 4 after the sensing coil 6 is transmitted. An optical fiber sensor for detecting the angular velocity detected by the light receiver 7 and applied around the center of the sensing coil 6 is shown. Here, according to the present invention, a shield structure is applied to the optical directional coupler 4 and the sensing coil 6 which are sensitive to environmental changes in these optical fiber sensor components, and the optical fiber sensor caused by environmental changes. It is intended to reduce the output error of.

In FIG. 1, 61 is a sensing coil 6.
An emitting end or an incident end is drawn out from the device, 62 is a winding frame of the sensing coil 6, and 63 is a coil covering member made of an elastic body interposed between the sensing coil 6 and the winding frame 6.
The sensing coil 6 is wound around the winding frame 62 via the coil covering member 63, and the two emitting ends or the incident ends 61 are wound around the winding frame 6.
It is connected to an optical directional coupler 4 which is an optical IC having a phase modulation function and an optical coupling / branching function, which is extracted from 2. 69
Is a reel flat plate portion, and is placed at a position half the height of the reel 62 perpendicular to the rotation input shaft of the sensing coil 6.
It is installed over the entire inner side of the inner diameter of. The two emitting ends or the incident ends 61 located between the sensing coil 6 and the optical directional coupler 4 also come into contact with the coating 64 made of an elastic body formed on a part of the winding frame 62, and the elastic body It is in a state of being attached to the winding frame flat plate portion 69 of the winding frame 62 via the coating 64 (in FIG. 1, for convenience of explanation, two emission ends or incidence ends 61 are shown floating from this coating. Originally, the plate-shaped optical directional coupler 4 is also
It is also shown floating from the elastic coating 64). 65
Is a high thermal conductive material layer, and 66 is a heat insulating material layer, which constitutes a shielding structure closed by a single layer or a plurality of laminated layers. This laminated layer is formed by laminating a high thermal conductive material layer 65 and a heat insulating material layer 66 in this order from the inside to the outside of the closed shielding structure. 67 is a pillar made of a heat insulating material. The winding frame 62 is fixed to the shielding structure via the support column 67. Reference numeral 68 denotes an optical fiber immediately before the optical directional coupler 4 when viewed from the light source 1 side. High thermal conductive material layer 6
A coating made of a magnetic shield material may be further provided on the outer side of the shield structure constituted by the laminated layer composed of 5 and the heat insulating material layer 66.

The order of forming the sensing coil 6 will be described with reference to FIG. First, the coil covering member 63 made of an elastic material is attached to the inside of the winding frame 62, and the optical fiber is wound thereon. Next, an elastic body is attached to the outer peripheral surface of the sensing coil 6 formed by winding, and eventually the coil covering member 63 made of the elastic body is formed. A member made of the same material as the former winding frame 62 is fitted on the surface of the coil covering member 63, and this member is joined to the former winding frame 62 to complete the winding frame 62. Since the two exit ends or entrance ends 61 extracted from this are sensitive to environmental changes, the coil covering member 63 and the elastic body covering 64 as shown in FIG. It is securely attached to the winding frame flat plate portion 69 of the winding frame 62 via.

By the way, in the optical directional coupler 4 and the sensing coil 6, the high thermal conductive material layer 65 and the heat insulating material layer 66 are provided.
Since the optical directional coupler 4 and the sensing coil 6 are accommodated in the shield structure composed of the laminated layers, the directional coupler 4 and the sensing coil 6 must use some kind of attachment member for the shield structure. Because it is attached by
It is inevitably in contact with the high thermal conductive material layer of the innermost laminated layer constituting the shielding structure. In this case, when heat enters the shield structure, the shield structure itself expands and contracts, and
The components extending from immediately before the optical directional coupler 4 to the optical directional coupler 4 and the sensing coil 6 also thermally expand and contract. Furthermore, it goes without saying that the above-mentioned mounting members, such as screws and adhesives, also thermally expand and contract. There is a difference in the thermal expansion and contraction rates between those that bond to each other, so it is necessary to absorb them. Here, a part or all of a portion including the optical directional coupler 4 and the sensing coil 6 from immediately before the optical directional coupler 4 which is in contact with the high thermal conductive material layer of the innermost laminated layer forming the shield structure. An elastic body is installed between the innermost laminated layer and the high thermal conductive material layer. By doing this, the elastic body absorbs the stress generated by the difference in the thermal expansion and contraction rates, and the output error due to the generated stress can be minimized. By installing the elastic body, it is possible to absorb the vibration applied to the shield structure from the outside.

Firstly, focusing on the closed shielding structure composed of a single layer or a plurality of laminated layers composed of the high thermal conductive material layer 65 and the heat insulating material layer 66, the closed shielding structure includes: All the parts including the optical directional coupler 4 and the sensing coil 6 are housed immediately before the optical directional coupler 4 when viewed from the light source 1 side in the optical fiber sensor. By doing so, all the parts of the optical fiber sensor that are most sensitive to environmental changes are contained in the shielding structure, so these are hardly affected by the environmental changes, and therefore the optical The output error of the fiber sensor can be minimized.

Further, paying attention to the fact that the shielding structure to be closed is composed of a single layer or a plurality of laminated layers in which the high thermal conductive material layer 65 and the heat insulating material layer 66 are laminated in this order from the inside to the outside. When the environmental temperature outside the optical fiber sensor fluctuates, the heat insulating material layer 66 located at the outermost side can block heat from entering the inside of the shield structure.
However, although this interruption is not made completely, the insulation layer 6
The heat entering through 6 is the high thermal conductive material layer 6 existing inside.
5 quickly conducts and makes uniform. As a result, the homogenized heat is conducted to a portion of the optical fiber sensor which is sensitive to environmental changes, and the output error of the optical fiber sensor due to the uneven thermal fluctuation is reduced. By using a plurality of laminated layers forming this shielding structure, the heat insulating effect and the uniformity of heat are further improved, and the output error is further reduced.

Further, the winding frame 62 around which the sensing coil 6 is wound is made of a high heat conductive material, and the sensing coil 6
The winding plate flat plate portion 69 perpendicular to the rotation input shaft is installed over the entire inside from the inner diameter of the winding frame 62 at a position half the height of the winding frame 62, and a part of this is shielded via the support column 67 made of a heat insulating material. Focusing on the fact that the structure is fixed, the heat that has entered from the outside is uniformly conducted to the sensing coil 6. Therefore, the portion including the optical directional coupler 4 and the sensing coil 6 immediately before the optical directional coupler 4 in the optical fiber sensor, which is sensitive to environmental changes, has a structure in which homogenization with respect to heat is further promoted. Therefore, the output error of the optical fiber sensor can be suppressed.

Here, a part of the portion including the optical directional coupler 4 and the sensing coil 6 from immediately before the optical directional coupler 4 in contact with the high thermal conductive material layer of the innermost laminated layer forming the shielding structure. Paying attention to the fact that an elastic body is installed between the whole and the high thermal conductive material layer 65 of the innermost laminated layer, thereby providing the combined effect of heat insulation, heat homogenization, and thermal stress removal as described above. Therefore, it is more effective in suppressing the output error of the optical fiber sensor.

Further, by providing a coating made of a magnetic shield material on the entire portion including the optical directional coupler 4 and the sensing coil 6 immediately before the optical directional coupler 4, a shielding effect against the earth magnetic field and other magnetism is provided. Therefore, the output error caused by various environmental changes including temperature and vibration can be suppressed to a minimum.

[0020]

As described above, the present invention includes the optical directional coupler 4 and the sensing coil 6 from immediately before the optical directional coupler 4 which is sensitive to environmental changes in the optical fiber sensor. Since the part to be accommodated is completely housed in the shielding structure, it is possible to exert the heat insulating effect, the heat uniform effect, the thermal stress removing effect, the vibration absorbing effect, and the magnetic shielding effect. The output error can be made extremely small.

[Brief description of drawings]

FIG. 1 is a diagram illustrating an example.

FIG. 2 is a diagram illustrating a sensing coil.

FIG. 3 is a diagram illustrating an optical fiber sensor.

FIG. 4 is a diagram illustrating a conventional example.

[Explanation of symbols]

 1 Light source 4 Optical directional coupler 6 Sensing coil 7 Light receiver

Claims (6)

[Claims] 1. A light source, an optical directional coupler, a sensing coil and a light receiver. The light emitted from the light source is branched by the optical directional coupler and is incident on the sensing coil as left and right bidirectional light from both ends thereof. In the optical fiber sensor that detects the angular velocity applied around the center of the sensing coil by detecting the interfering light with the optical directional coupler after transmitting both of these lights in the optical directional coupler again, the light source side An optical fiber sensor characterized in that a portion including an optical directional coupler and a sensing coil is housed in a shielding structure immediately before the optical directional coupler. 2. The optical fiber sensor according to claim 1, wherein the shielding structure is composed of a single layer or a plurality of layers in which a high thermal conductive material layer and a heat insulating material layer are laminated in this order from inside to outside. An optical fiber sensor characterized by being formed. 3. The optical fiber sensor according to claim 2, wherein the optical directional coupler and the sensing coil are provided immediately before the optical directional coupler in contact with the high thermal conductive material layer of the innermost laminated layer forming the shielding structure. An optical fiber sensor, characterized in that an elastic body is provided between a part or all of the included portion and the high thermal conductive material layer of the innermost laminated layer. 4. The optical fiber sensor according to claim 2, wherein the winding frame around which the sensing coil is wound is made of a high thermal conductive material, and the winding plate flat plate portion perpendicular to the rotation input shaft of the sensing coil is the winding frame. An optical fiber sensor, which is formed entirely inside the inner diameter of the bobbin at a position half the height of, and is attached to the shielding structure via a pillar made of a heat insulating material. 5. The optical fiber sensor according to claim 4, wherein the optical directional coupler and the sensing coil are provided immediately before the optical directional coupler in contact with the high thermal conductive material layer of the innermost laminated layer forming the shielding structure. An optical fiber sensor, characterized in that an elastic body is provided between a part or all of the included portion and the high thermal conductive material layer of the innermost laminated layer. 6. The optical fiber sensor according to claim 2, wherein the entire portion including the optical directional coupler and the sensing coil is magnetically shielded immediately before the optical directional coupler. An optical fiber sensor characterized by being coated.