JPH035874Y2 - - Google Patents

Description

[Detailed Description of the Invention] [Background and Purpose of the Invention] The present invention relates to an optical fiber sensor. Fiber optic rotary angular velocity meters and acoustic sensors that utilize the Sagnatsk effect and photoelastic effect have been widely studied.

In the conventional method, the lens system at the coupling part between the optical fiber sensor part and the light transmitting/receiving element was complicated, and it was not suitable for mass production. In addition, optical fibers are often mounted by winding them around boppins, and the optical fibers are not sufficiently lightweight or compact. Further, due to the difference in linear expansion coefficient between the optical fiber and the bobbin, unnecessary lateral pressure and strain are applied to the optical fiber, which becomes a source of noise in the light receiving system.

This invention was created in view of the above points,
The object of the present invention is to provide an optical fiber sensor that allows for improved mounting performance, mass productivity, and temperature characteristics.

[Summary of the invention] In other words, the invention provides an optical fiber sensor using a coil in which polarization-preserving optical fibers provided with a reinforcing layer are wound in a cylindrical shape and fixed with plastic having a coefficient of linear expansion that is approximately the same as that of the reinforcing layer. A light source and a light receiver each having a light transmitting and receiving picktail optical fiber formed of the polarization maintaining optical fiber and a light transmitting and receiving picktail optical fiber formed of the polarization maintaining optical fiber, and a light transmitting and receiving picktail optical fiber and the coiled optical fiber of the light source and the light receiver. The optical fiber sensor is characterized in that it is constructed by fusion splicing with the inherent polarization axes of the two aligned or shifted by 90° or 45°, whereby the optical fiber sensor maintains the polarization plane. A light source and a light receiver, each of which combines a coiled optical fiber formed by winding an optical fiber into a coil, and a picktail optical fiber for transmitting and receiving light formed of a polarization preserving optical fiber, and a picktail light for transmitting and receiving light from these light sources and light receivers. It is composed of a fiber and a connecting portion in which a coiled optical fiber is fused and spliced.

[Example] The present invention will be described below based on the illustrated example. FIG. 1 shows an embodiment of the present invention. In this example, the optical fiber sensor is made by winding polarization-maintaining optical fibers with a reinforcing layer in a cylindrical shape.
A light source 4 and a light receiver 5 are each coupled with a coiled optical fiber 1 fixed with plastic having a coefficient of linear expansion substantially the same as that of the reinforcing layer, and picktail optical fibers 2 and 3 for transmitting and receiving light formed of polarization-maintaining optical fibers. , the picktail optical fibers 2 and 3 for light transmission and reception of the light source 4 and the light receiver 5 and the coiled optical fiber 1 are fusion-spliced with their characteristic polarized optical axes either aligned or shifted by 90°C or 45°C. It is composed of a connecting part 6. By doing this, the optical fiber sensor combines the coiled optical fiber 1, which is a polarization-maintaining optical fiber wound into a coil, and the picktail optical fibers 2 and 3 for transmitting and receiving light, each formed of a polarization-maintaining optical fiber. It is composed of a light source 4 and a light receiver 5, and a connecting part 6 in which the picktail optical fibers 2 and 3 for transmitting and receiving light of the light source 4 and the light receiver 5 and the coiled optical fiber 1 are fused and spliced. It is possible to obtain an optical fiber sensor that enables improvements in mounting performance, mass productivity, and temperature characteristics.

That is, as shown in FIG. 2, the polarization maintaining optical fiber used includes a core 7, a cladding 8 provided on the outer periphery of the core 7, and an anisotropic fiber provided on the outer periphery of the cladding 8. a sexual strain applying section 9;
It is comprised of a support 10 provided on the outer periphery of this anisotropic strain applying section 9. A coiled optical fiber 1 was made using the polarization preserving optical fiber 11 constructed as described above, and the coating was coated with ultraviolet curing, that is, UV curing. That is, the outer diameter
50μm on top of 125μm polarization maintaining optical fiber 11
The reinforcing layer was applied with a reinforcing layer of approximately 200 m in length on a vinyl bobbin (both not shown), and the surface was fixed by coating with epoxy resin. Next, the vinyl bobbin was shrunk, and the coiled optical fiber 1 and the bobbin were separated. Both ends of the coiled optical fiber 1 formed in this way are aligned with the picktail optical fibers 2 and 3 for transmitting and receiving light, each consisting of a polarization-maintaining optical fiber 11 coupled to a light source 4 and a light receiver 5, so that their inherent polarization axes coincide with each other. The fusion splice was made by holding the connection part 6 as shown in FIG. Note that depending on the detection direction, it may be effective to shift the intrinsic polarization axis by 45 degrees.

In the optical fiber sensor configured in this manner, when directly polarized light is input from the incident side (light source 4), the polarization preserving optical fiber 1 is used at the receiver 5 side.
It is possible to detect a stable amount of phase change with extremely high sensitivity to physical quantities corresponding to sound waves, pressure, etc. applied to the coiled optical fiber 1 made in 1 and the picktail optical fibers 2 and 3 for transmitting and receiving light. Further, since no lens system is used, the device can be made smaller and lighter, and reliability such as vibration characteristics can be improved. In addition, the optical fiber section (coiled optical fiber 1) and the light transmitting/receiving section (light source 4 and receiver 5, which combine picktail optical fibers 2 and 3 for transmitting and receiving light) can be produced separately, and can be combined by connection, so mass production is possible. Direction. In addition, since the coiled optical fiber 1 does not have a core bobbin and is made of a material with the same coefficient of linear expansion as a whole, it not only improves mounting efficiency and has stable temperature characteristics, but also has a coiled optical fiber. Since the optical fiber 1 has no core, it has particularly high sensitivity as a sound wave sensor.

Although the coiled optical fiber 1 is hardened with epoxy resin in this embodiment, it is not limited to this, and urethane, enamel, etc. can be used.

[Effects of the invention] As described above, the present invention improves the mountability, mass-productivity, and temperature characteristics of an optical fiber sensor, and provides an optical fiber sensor that enables improvements in mountability, mass-productivity, and temperature characteristics. can be obtained.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of an embodiment of the optical fiber sensor of the present invention, and FIG. 2 is a sectional view of a polarization-maintaining optical fiber according to the embodiment. DESCRIPTION OF SYMBOLS 1... Coiled optical fiber, 2... Picktail optical fiber for light transmission, 3... Picktail optical fiber for light reception, 4... Light source, 5... Light receiver, 6...
Connecting section, 7... Core, 8... Cladding, 9... Anisotropic strain applying section, 10... Support, 11... Polarization maintaining optical fiber.

Claims (1)

[Claims for Utility Model Registration] (1) A coiled optical fiber in which a polarization-maintaining optical fiber provided with a reinforcing layer is wound in a cylindrical shape and fixed with plastic having a coefficient of linear expansion approximately the same as that of the reinforcing layer. , a light source and a light receiver each having a picktail optical fiber for transmitting and receiving light formed of the polarization-maintaining optical fiber coupled to each other, and a picktail optical fiber for transmitting and receiving light and the coiled optical fiber of these light sources and light receivers; Match the unique polarization optical axes, or set them at 90° or
An optical fiber sensor characterized by consisting of a fusion spliced connection part shifted by 45 degrees. (2) The polarization-maintaining optical fiber includes a core, a cladding provided on the outer periphery of the core, an anisotropic strain applying section provided on the outer periphery of the cladding, and an outer periphery of the anisotropic strain applying section. The optical fiber sensor according to claim 1, which comprises a support provided in the utility model.