JPS63144226A - Optical waveguide type pressure transducer - Google Patents

Abstract

PURPOSE:To obtain a high-accuracy pressure transducer which is not affected by pressure by making coherent light on an optical waveguide, straining one branching optical waveguide, and making the light interfere with light passed through the other optical waveguide. CONSTITUTION:Optical waveguides 1-3 made of SiO2 layers nearby the surface of an Si substrate 30 branch to 1a and 1b, 2a and 2b, and 3a and 3b in the middles and come together again to reach the other substrate and part. Holes 5a-5c are formed in the reverse surface on the opposite side from the optical waveguides and are positioned on the sides of one branching waveguide respectively, and diaphragms 6a-6c are formed of their bottom parts and the surface of the substrate. Light from a laser light source 10 which oscillates the coherent light is made incident from end parts of the waveguides 1-3 through an optical coupler 11 and an optical fiber 12. When pressure is applied to the substrate 30 while the light is incident on the waveguides 1-3, the diaphragms 6a-6c are strained by the pressure, but they differ in thickness, so when the same pressure is applied, optical path differences are generated between the holes 5a and 5b, diaphragms 6a and 6b, etc., and interference light is obtained at the confluence points of the optical waveguides.

Description

[Detailed description of the invention] <Industrial application field> The present invention relates to a pressure transducer using an optical waveguide.

<Prior art> Conventionally, a pressure sensor using an optical waveguide is shown in Fig. 3 (a).
) to (C) are known, based on the V principle. In the figure, <a) shows that the light propagating through the optical waveguide 40 formed on the substrate 30 leaks out of the waveguide, and is moved near the optical waveguide 40 by pressure. An evanescent wave absorption type in which a part of the guided light is absorbed by bringing the optical absorber 41 close to
A thin Si plate with a hole is used as a diaphragm, and a part of the guided light becomes leak light due to distortion of the waveguide due to pressure. Wave path distortion type, also (C)
This is a waveguide light 'a' cross-section in which the amount of guided light is changed by inserting a light shield 49 into the Si substrate 30 that moves by force.

<Problems to be Solved by the Invention> However, in the above-mentioned conventional technology, since the amount of attenuation of the output light with respect to the input light is measured, the degree of clarity is low, and the optical propagation characteristics of the waveguide change depending on the temperature. A possible problem is poor temperature characteristics.

The present invention has been made in view of the problems of the prior art described above, and involves making coherent light enter an optical waveguide.

By applying strain to one of the branched optical waveguides, we aim to create a highly accurate F converter that is not affected by temperature by interfering with the light that has passed through the other optical waveguide, which does not apply pressure. do.

〈Means for solving problems〉 The structure of the present invention for solving the above problems is as follows.

A plurality of optical waveguides with two branches are formed near the surface of one side of the pressure receiving plate, and the back side of one side of each branched optical waveguide is hollowed out to form diaphragms with different distortion resistance against pressure. death.

This device is characterized in that the pressure applied to the diaphragm is measured by comparing the interference light of the light that has passed through the front 22 optical waveguides.

・〈Example〉 Fig. 1 is a plan view (a) showing an example of a pressure transducer using an optical waveguide according to the present invention, and a sectional view taken along line XX in (a) (
b). In these figures, 30 is a Si 14 board with a predetermined thickness, and 5t is placed near the surface of this board.
An optical waveguide 1°2.3 made of an O2 layer is formed.

In these optical waveguides, light entering from one end of the substrate branches into 1a, 1b, 2a, 2b, 3a, and 3b, and then joins again to reach the other end of the substrate. 5a, 5b, 5
A diaphragm 5a c is located on one side of the eight-branched optical waveguide with holes formed by electric field machining or the like on the back surface of the side on which the optical waveguide is formed, and a diaphragm 5a is formed between the bottom and the surface of the substrate.

6b and 6c are formed. Diaphragms have different thicknesses by adjusting the depth of the holes. 10
is, for example, a laser light source that oscillates coherent light, and the light from this light source is made to enter from the end of the optical waveguide via an optical coupler 11 and an optical fiber 12. Although not shown in the drawings, it is assumed that the Sil plate 30 is fixed so that the side on which the holes are formed faces the object to be measured, and pressure is evenly applied to the diaphragm.

In the above configuration, if pressure is applied to the substrate with light starting to enter the optical waveguide, each diaphragm will be distorted by the pressure, but each diaphragm has a different thickness, so if the same pressure is applied (5a and 5b ), (6a and 6
An optical path difference occurs between the beams b) and (7a and 7b), and interference light is generated at the confluence of the optical waveguides.

Figure 2 shows the change in output light (interference light) with respect to pressure, and the curves 1', 2', and 3'' represent the output corresponding to optical waveguide 1.2.3 shown in Figure 1. According to the figure, each curve has a different period.As a result, when a certain pressure is applied, the output from waveguide 1 is hl, the output from waveguide 2 is h2, and waveguide 3 If the output from the waveguide is h3, the pressure at that time is specified as Pl, and if the output from the waveguides 1 and 3 is h5, respectively, and the output from the waveguide 2 is h4, the applied pressure at that time is is specified as P2.

Note that the characteristics shown in such a diagram are recorded in advance while gradually applying a known pressure.

In the above configuration, highly accurate pressure measurement is possible by providing an appropriate number of optical waveguides and diaphragms for the input span. In addition, since the waveguides on the side affected by pressure (diaphragm side) and the side not affected by pressure are placed in the same environment, the influence of ambient temperature, for example, can be canceled by manufacturing the optical waveguide with good symmetry. I can do it.

A. In addition, in this embodiment, the thickness of the diaphragm was changed in order to change the strain resistance against pressure, but the diameter of the diaphragm may also be changed. Alternatively, three laser light sources with similar performance may be prepared and the laser light sources may be directed into the respective optical waveguides. Further, although an example in which three waveguides are formed is shown, the number of waveguides is not limited to this example.

<Effect of the invention> .

By comparing it with a predetermined value, the applied pressure can be determined, increasing measurement accuracy.In addition, since each optical waveguide is placed in the same environment, it is an optical waveguide type with no output fluctuation due to temperature. A pressure transducer can be realized.

[Brief explanation of the drawing]

FIG. 1 is a plan view (a) showing an embodiment of the present invention and <
a) X-x sectional view (b) in the figure, Figure 2 is an explanatory diagram showing changes in output light with respect to pressure, Figure 3 (a), (b), (c)
1 is a diagram showing a conventional example. 1 to 3... Optical waveguide, -5a to 5C... Hole, 5a to
6C...diaphragm, 30...81 baseboard. Figure 1C゛α) (b) Decoy-゛guwork, f]L 5;1! e.

Claims (1)

[Claims] A plurality of optical waveguides with two branches in the middle are formed near the surface of one side of the pressure receiving plate, and the back side of one side of each branched optical waveguide is hollowed out to create a plurality of optical waveguides with different amounts of strain in response to pressure. An optical waveguide type pressure transducer characterized in that a diaphragm is formed and the pressure applied to the diaphragm is measured by comparing the interference light of the light that has passed through the two optical waveguides.