JPH0676913B2 - Acoustic sensor manufacturing method - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of manufacturing an acoustic sensor that utilizes an optical phenomenon to replace an acoustic signal with a change in light intensity for detection.

2. Description of the Related Art In recent years, semiconductor lasers and optical fibers have come into practical use, and various acoustic sensors utilizing optical phenomena are being developed.

Hereinafter, an example of the conventional acoustic sensor as described above will be described with reference to the drawings.

FIG. 4 shows a sectional view of a conventional acoustic sensor.
In FIG. 4, 1 is a vibrating membrane, 1r is an end face of the vibrating membrane 1 having a partial reflection coating, 2 is a vibrating membrane ring that adheres and fixes the vibrating membrane 1, 3 is vibration that holds the vibrating membrane 1 flat and gives tension It is a membrane push-up ring. 4 is a rod lens, 4r is an end face of the rod lens 4 having a partial reflection coating, 5 is a lens holder, 6 is a single mode optical fiber, 7 is a resin coating of the single mode optical fiber 6, 8 is a ferrule, 9 is a casing, and 10 is a vibration. It is a static pressure adjusting hole for equalizing the static pressure on both sides of the membrane 1. The Fabry-Perot interferometer is formed by the partial reflection coating end surface 1r of the vibrating membrane 1 and the partial reflection coating end surface 4r of the rod lens 4.

The operation of the conventional acoustic sensor configured as described above will be described below.

FIG. 5 is a plan view showing the basic configuration of the conventional acoustic sensor shown in FIG. In FIG. 5, 6a and 6b are the core and the clad of the single mode optical fiber 6, respectively. Further, a is a core 6a of the single mode optical fiber 6.
In the optical fiber propagating toward the Fabry-Perot interferometer, b is the core 6a of the single-mode optical fiber 6.
Optical fiber inter-lens detection light emitted from the end surface of the fiber toward the rod lens 4, c is repeated reflection interference light in the Fabry-Perot interferometer, and d is emitted from the Fabry-Perot interferometer through the vibrating membrane 1 to the outside. Externally emitted light, e is the rod lens-optical fiber signal light from the Fabry-Perot interferometer returned from the end face of the rod lens 4 to the core 6a of the single mode optical fiber 6, and f is the single mode optical fiber 6 It is signal light in the optical fiber that propagates in the direction opposite to the detection light a in the optical fiber through the core 6a.

First, the in-optical fiber detection light a propagating from the semiconductor laser through the core 6a of the single mode optical fiber 6 is emitted from the emission end face thereof and becomes the detection light b between the optical fiber rod lenses. The detection light b between the optical fiber rod lenses is shaped into parallel light by the rod lens 4 and enters the Fabry-Perot interferometer. The light incident on the Fabry-Perot interferometer becomes the repeatedly reflected interference light c. Every time reflection is repeated, a part of the repeated reflection interference light c is transmitted through the partial reflection coat end faces 1r and 4r. The light transmitted through the end face 1r of the partial reflection coating of the vibrating film 1 becomes the external emission light d. On the other hand, the light transmitted through the end face 4r of the partial reflection coating of the rod lens 4 is condensed by the rod lens 4 and becomes the signal light e between the rod lens and the optical fiber. The signal light e between the rod lens and the optical fiber is shaped into parallel rays by the single mode optical fiber, and at the same time, the reflected light from the end face 4r of the partially reflective coat of the rod lens 4 is incident on the core 6a of the single mode optical fiber 6 again. To do. By the way, the diameter of the core 6a of the single-mode optical fiber 6 has a wavelength of 0.83 μm.
When using the semiconductor laser of about 6 μm, the wavelength is 1.
When using a 3 μm semiconductor laser, it is about 10 μm,
The optical axis alignment is not easy. After the optical axis alignment between the partial reflection coat end surface 1r of the vibrating film 1 and the partial reflection coat end surface 4r of the rod lens 4, the optical axis alignment is performed, and then the casing 9 is interposed and fixed by adhesion. This optical axis alignment is performed while paying attention to the parallelism between the facing surfaces of the vibrating membrane 1 and the rod lens 4 so that a Fabry-Perot interferometer is formed.

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention However, in the above configuration, optical coupling between the single mode optical fiber and the rod lens,
Not only is it easy to form the Perot interferometer, but it has a complicated structure and is not easy to assemble.

Further, in forming the air gap between the exit end surface of the rod lens forming the etalon portion and the vibrating film surface, it was extremely difficult to form a narrow air gap while maintaining parallelism.

In view of the above problems, the present invention is easy to assemble, has a simple structure, improves the surface accuracy of the fiber exit end, and facilitates the formation of an air gap while maintaining parallelism and a narrow air gap. A method of manufacturing an acoustic sensor that can be formed is provided.

Means for Solving the Problems In order to solve the above problems, the acoustic sensor of the present invention has a single mode fiber and its resin film adhered and fixed to a ferrule, and holds the outer periphery of the ferrule to polish the end face of the optical fiber. After flattening, insert the vibrating film push-up ring into the ferrule insertion part while holding the outer peripheral part of the ferrule and fix it with a YAG laser, and polish the end face of the vibrating film push-up ring to make it flat. The end face of the vibrating membrane push-up ring is made parallel, the distance between the fiber end face and the end face of the vibrating membrane push-up ring is adjusted, and further, the fiber end face is subjected to partial reflection coating with a dielectric multilayer film, while the incident end face is half-finished. A vibrating membrane ring with a partially reflective coating in the form of a transmissive film and a non-reflective coated vibrating film bonded to the emitting end face A method of manufacturing an acoustic sensor, which is fixed to a vibrating film push-up ring and is provided with an air gap with a vibrating film which is closely opposed to an optical fiber emission end face and whose incident end face is partially reflection-coated and the emission end face is anti-reflection coated. It is configured to provide an air gap.

Operation The present invention facilitates the formation of the Fabry-Perot interferometer and the optical engagement between the Fabry-Perot interferometer and the single-mode optical fiber by the method described above, which facilitates the assembly and the surface accuracy of the fiber output end. It is possible to provide a highly sensitive and highly stable acoustic sensor that can easily form a narrow air gap while maintaining parallelism.

Embodiment An embodiment of the present invention will be described below with reference to the drawings.

FIG. 2 shows a sectional view of an acoustic sensor in one embodiment of the present invention. In Fig. 2, reference numeral 11 denotes a polyimide film as a base material, and the incident end face is partially reflection-coated with the dielectric multilayer film, and the emission end face is non-reflectively coated with the dielectric multilayer film. , 12 is the diaphragm ring, 13 is the diaphragm thrust ring, 16
Is a single-mode optical fiber, 16r is an end face of the partially reflective coating, 17 is a resin coating of the single-mode optical fiber 16,
Reference numeral 18 is a ferrule, and 20 is a static pressure adjusting hole provided in the ferrule 18. L is the distance between the partial reflection coat end faces 11r and 16r. The Fabry-Perot interferometer is formed by partially reflecting coat end faces 11r and 16r.

The operation of the acoustic sensor configured as above will be described.

FIG. 3 shows the basic structure of the acoustic sensor of this embodiment shown in FIG. In FIG. 3, 16a and 16b are the core and the clad of the single mode optical fiber 16, respectively. Further, i is the core 16a of the single mode optical fiber 16.
In the optical fiber propagating toward the Fabry-Perot interferometer, k is the repeatedly reflected interference light in the Fabry-Perot interferometer, and t is emitted from the Fabry-Perot interferometer through the vibrating membrane 11 to the outside. External emission light, o is signal light in the optical fiber that propagates through the core 16a of the single mode optical fiber 16 in the opposite direction to the detection light i in the optical fiber.

First, the detection light i in the optical fiber propagating through the core 16a of the single mode optical fiber 16 from the semiconductor laser is incident on the Fabry-Perot interferometer and becomes the repeatedly reflected interference light k. A part of the repetitive reflection interference light k is transmitted and becomes the external emission light t, and the rest is returned to be the signal light o in the optical fiber.
Becomes The repeated reflection interference light k is not shaped into parallel rays, but the performance of the Fabry-Perot interferometer is not deteriorated when the distance between the partial reflection coat end faces 11r and 16r is about several tens of μm. Now, when an acoustic signal is applied to this system, the vibrating membrane 11 is displaced, and signal light subjected to intensity modulation corresponding thereto is obtained.

A method of manufacturing the acoustic sensor configured as above will be described.

FIG. 1 shows a method of manufacturing the acoustic sensor shown in FIG. In FIG. 1A, a single mode optical fiber (hereinafter referred to as fiber) 16 and its resin film 17 are adhesively fixed to phenol 18. Next, the maximum outer diameter part a of the ferrule outer diameter is held by a ring-shaped jig, and the end face of the optical fiber is polished by a parallel polishing machine.

Next, after the fiber end faces 16 are made parallel to each other and polished, the vibrating film push-up ring 13 is inserted into the ferrule and fixed by the YAG laser while being held at the maximum outer diameter part a of the outer peripheral part of the ferrule (FIG. 1B).

After that, the end face of the vibrating film push-up ring 13 is polished to be flat, and the end face of the fiber 16 and the vibrating film push-up ring 13 are also polished.
13 is made parallel, and the distance between the end face of the fiber 16 and the vibrating membrane push-up ring 13 is adjusted. The end face of the fiber configured as described above is partially reflected by a dielectric multilayer film to form a light semi-transmissive film. On the other hand, a vibrating membrane 11 whose entrance end face is partially reflective coated in a semi-transmissive film shape and whose exit end face is non-reflective coated is adhered to the vibrating film push-up ring 13 and fixed ( 1
In FIG. C), a predetermined air gap (air gap) is provided between the vibrating membrane 11 and the optical fiber exit end face in close proximity.

In the acoustic sensor configured as described above, the return light from the Fabry-Perot interferometer formed by the fiber 16 and the vibrating membrane 11 is returned to the single mode optical fiber again, and the return light is detected.

As described above, according to the present invention, not only the assembly is easy and the number of parts is small, but also the surface accuracy of the fiber exit end vibrating membrane surface can be increased, and the parallelism between the fiber exit end surface and the vibrating membrane surface is improved. It is possible to provide an acoustic sensor having high sensitivity and high stability because a stable etalon portion can be easily configured by maintaining the above.

[Brief description of drawings]

FIG. 1 is a sectional view showing a method of manufacturing an acoustic sensor according to an embodiment of the present invention, FIG. 2 is a sectional view showing an acoustic sensor of this embodiment, and FIG. 3 is a main part showing a basic configuration of the acoustic sensor. A plan view, FIG. 4 is a cross-sectional view of a conventional acoustic sensor, and FIG. 5 is a plan view showing a basic configuration of the conventional acoustic sensor shown in FIG. 11 …… Vibration membrane, 12 …… Vibration membrane ring, 13 …… Vibration membrane push-up ring, 16 …… Single-mode optical fiber, 17 ……
Resin cover, 18 …… ferrule, 20 …… static pressure adjustment hole, 11r,
16r …… The end face of the partially reflective coat.

Claims (1)

[Claims] 1. A single mode fiber and its resin coating are bonded and fixed to a ferrule, the outer periphery of the ferrule is held and the end face of the optical fiber is polished to be flat, and then the vibrating film push-up ring is held while holding the outer periphery of the ferrule. Inserted in the ferrule insertion part and fixed with a YAG laser, while polishing the end face of the vibrating film push-up ring to make it flat,
The fiber end face and the vibrating membrane pushing-up ring end face are made parallel, the distance between the fiber end face and the vibrating membrane pushing-up ring end face is adjusted, and further, the fiber end face is subjected to partial reflection coating with a dielectric multilayer film, while, The incident end face is partially reflective coated in a semi-transmissive film shape, and the emitting end face is adhered and fixed to the above vibrating film push-up ring with the non-reflective coated vibrating film adhered to the optical fiber exit end face. A method of manufacturing an acoustic sensor in which an air gap is provided between a vibrating film facing the entrance end face with partial reflection coating and the exit end face with non-reflection coating.