JPS59122902A - Light applied sensor - Google Patents

Abstract

PURPOSE:To make it possible to receive light signals having a stable output pattern, even when lightguides are bent or connecting parts of the transmission paths of the light signals are attached or detached, by bending the lightguides at the connecting parts of a detecting part and the lightguides at a specified radius of curvature. CONSTITUTION:Emitted pattern stabilizing means 20, wherein lightguides 2 and 4 at the parts close to a detecting part 3 are wound by several turns -several tens of turns at a specified radius, are provided. Even though, the sending and receiving lightguides 2 and 4 are bent and light signals at a higher order mode are emitted or the mode is changed, the signals at the higher order mode are emitted at the emission pattern stabilizing means 20 to the outside of the sending and receiving lightguides 2 and 4. The emitted pattern, especially the emitted pattern at a reflecting plate 3a, is made to be the stable pattern comprising a lower order mode which has fewer effect of bending. Therefore, even though the signals are emitted to the outsides of the higher order mode lightguides 2 and 4, physical quantities can be measured without the effect of the high order mode.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to improvements in optical sensor devices that measure physical quantities using optical signals.

[Technical background of the invention and its problems]

FIG. 1 and FIG. 2 are configuration diagrams of a conventional optical sensor device. First, the optical sensor device shown in FIG. 1 will be explained. Reference numeral 1 denotes an optical signal transmitting section, and an optical signal is transmitted through the sending optical waveguide 2 and sent to the detecting section 3 by light emission from the light emitting element 1&. In this detection unit 3, the optical signal is reflected by a reflecting plate 3a that is displaced in the A direction according to the physical quantity to be measured (for example, pressure), and is converted into a light intensity corresponding to the physical quantity.
A portion of the light is incident on the side optical waveguide 4. Here, the optical signal incident on the receiving and receiving side optical waveguides 4 is a light amount that is a function of the distance between the transmitting side and the receiving side optical waveguides 2 and 4 and the reflecting plate 3a in the detection section 3. The optical signal incident on the side optical waveguide 4 is sent to the optical signal receiving section 5, which converts it into an electric signal by the light receiving element 5a and measures the light intensity of the optical signal. Since it is a function of the displacement (a) of
The optical sensor device shown in the figure will be explained. In this optical application sensor device, the detection unit 6 depends on the physical quantity to be measured ←)
The first optical lens 6b applies the optical signal from the transmitting side optical waveguide 7 to the blocking plate 6a, and the receiving side receives the optical signal sent via the blocking plate 6a. It is composed of a second optical lens 6c that enters the optical waveguide 8, and measures a physical quantity by the amount of light of the optical signal, similar to the sensor device shown in FIG. Stabilization of the light emission and 9W from the transmitting section 1, and the transmitting and receiving side optical waveguides 2, 4, 7.8
The optical signal is stabilized by compensating for changes in loss. However, it may not always be possible to obtain a stable optical signal simply by stabilizing the light emitting power and compensating for changes in loss.In particular, it may not be possible to obtain a stable optical signal due to the curvature of the optical waveguide or the attachment or detachment of the connector that connects the light source and the optical waveguide. Big changes will occur.

Therefore, the causes of fluctuations in optical signals due to curvature and attachment/detachment of the optical waveguide will be explained. FIGS. 3(a) and 3(b) are diagrams showing the structure of an optical waveguide and the emission pattern from this optical waveguide. Here, 9 is the cladding of the optical waveguide, 10 is the core, and its refractive index distribution is step-like, and the refractive index of the core 10 is set slightly larger than that of the cladding 9. When the signal goes from the core 10 to the cladding 9, it is totally reflected, and a waveguide mode exists within the core 10.

When such an optical signal is emitted from the optical waveguide 27, the third
This results in nine turns S of exit as shown in Figure (b). This emission pattern S is obtained when a plurality of waveguide modes in the optical waveguides 2 and 7 are uniformly excited.

The i4 turn (Afield pattern) at the output end face of the optical waveguide has the same step-like distribution as the refractive index distribution, but the output pattern S at a position r slightly away from the end face is as shown in Figure 3(b). is approximated by a trapezoid.

Here, the output angle θ of the optical signal at the end face of the optical waveguide increases as the mode changes from a low-order mode to a high-order mode. Further, this emission pattern S is composed of a plurality of waveguide modes of the optical waveguide and is greatly influenced by the state of the waveguide modes and the power ratio between the modes. As is well known, when an optical waveguide is bent beyond a predetermined radius of curvature, the higher-order waveguide mode becomes a radiation mode and leaks, or mode conversion occurs.・Gutan S
will change. FIG. 4 shows a diagram of changes in the output pattern when the optical waveguide is bent.

As shown in Fig. 4, when the higher-order mode leaks, the emission A?
The meta-S changes from the emission pattern S1 to the emission pattern S2. In this way, the amount of light of the optical signal changes depending on the degree of bending of the optical waveguide 2゜4s7t8, and in particular, the amount of light incident on the side optical waveguides 4 and 8 decreases, so the reflection plate 3
Even if the a and the base plate 6a are not displaced, the displacement is measured as an apparent displacement.

Further, the influence of the curves of the optical waveguides 2, 4, 7, and 8 not only reduces the amount of light but also affects the output characteristics of the optical signal. 5(a) and 5(b) show the output characteristics of the optical signal, (&) is an output characteristic diagram in a normal case, and (b) is a characteristic diagram in a case where a leak occurs. Figure 5(a)(b)
), when a leak occurs in the optical waveguide, the rise position and maximum peak position of the signal in its output characteristics change. For this reason, especially when measuring a physical quantity using the initial rise characteristic, sensitivity changes or zero point drift occurs. Therefore, accurate measured values cannot be obtained when measuring physical quantities. This also applies to graded index optical waveguides in which the optical waveguides 2, 4, 7.8 are not step index, but have a parabolic refractive index distribution, for example.

Furthermore, changes in sensitivity and zero point drift occur also in the optical sensor device shown in FIG.

[Purpose of the invention]

The present invention has been made in view of the above-mentioned circumstances, and it is possible to obtain an optical signal with a stable output pattern even by bending the optical waveguide or attaching/detaching the connection part on the optical signal transmission path, and eliminates sensitivity changes and zero point drift. The purpose is to provide a light-applied sensor device.

[Summary of the invention]

In an optical sensor device that measures physical quantities using optical communication, the present invention provides an optical waveguide that transmits an optical signal between a signal transmitter, an optical signal receiver, and a detector in the optical sensor device. This is an optical sensor device which attempts to achieve the above object by providing an output pattern/stabilizing means such as (1) bending the optical waveguide with a predetermined radius of curvature and (2) alternately providing a plurality of optical waveguides having different refractive indexes.

[Embodiments of the invention]

A first embodiment of the present invention will be described below with reference to FIG. Note that the same parts as in FIG. 1 are denoted by the same reference numerals and detailed explanations will be omitted.

FIG. 1 is a block diagram of an optical sensor device according to the present invention. This optical sensor device has an optical waveguide 2, which is close to the connecting portion between the transmitting side and receiving side optical waveguides 2, 4 and the detection section 3.
Output/Zo-turn stabilizing means 2, which is made by winding the four parts seven turns at a predetermined radius (for example, about 3 cm or less) from several turns to several tens of turns.
0 is set.

Next, the operation of the apparatus configured as described above will be explained. The light emitting element 1a of the optical signal transmitter 1 emits light, and the optical signal enters the transmitting side optical waveguide 2. As a result, an optical signal is transmitted to the transmitting side optical waveguide 2. When the optical signal reaches the output/zoom stabilizing means 20, it is transmitted as follows.

In other words, since the higher-order mode in the optical signal undergoes mode conversion in the radiated mode by the curve i of the optical waveguide as described above,
cm or less) and is transmitted through the output pattern stabilizing means 20, it is radiated to the outside of the optical waveguide. As a result, the optical signal emitted to the reflection plate 3a in the detection unit 3 becomes a low-order mode that is less affected by bending.

Further, the optical signal that enters and is transmitted from the reflection plate 3a to the sending optical waveguide 4 is converted into an optical signal consisting of a lower order mode by the output/mother turn stabilizing means 20 and sent to the optical signal receiving section 5, in the same manner as described above. incident. Then, the optical signal is subjected to electro-optical conversion by the light receiving element 5a of the optical signal receiving section 5, and the amount of light of the optical signal is measured, and the physical quantity measured by the detecting section 3 is determined from this amount of light.

In this way, according to the present device, the output stabilizing means 20 is provided in which the optical waveguide 2.4 in the vicinity of the detection part 3 is wound several turns from seven to several turns at a predetermined radius. Even if the side optical waveguides 2 and 4 are bent and the higher-order modes in the optical signal are radiated or mode converted, in any case, in the output pattern stabilizing means 20, the higher-order modes are transferred to the sending and receiving side optical waveguides, .

4 is emitted to the outside, and its emission pattern is reflected by the reflection plate 3.
It is assumed that the exit nodal turn at a is stable and consists of low-order modes that are less affected by bending. Therefore, even if the higher-order mode is radiated to the outside of the optical waveguide 2.4, physical quantities can be measured without being affected by this.

Here, the emission no-turn stabilizing means 20 may radiate the higher-order mode using the following means. For example, it is a means for sandwiching the optical waveguide 2.41 between the stabilizing member 21 provided with a large number of uneven parts. Group 7 shows a block diagram of this means. With such a single stage, the optical waveguides 2 and 4 are formed with a predetermined radius of curvature 1.
By bending the optical signal, the higher-order mode in the optical signal is radiated to the outside, and a stable output pattern consisting of the lower-order mode is created, as in the first embodiment.

Next, a second embodiment of the present invention will be described with reference to FIGS. 8 and 9. Among them, as in the first embodiment, the first
Components that are the same as those in the figures are given the same reference numerals and detailed explanations will be omitted. FIG. 8 is a block diagram of the second embodiment. 8th
The optical sensor device shown in the figure emits light A? A turn stabilizing means 3o is provided. The output pattern stabilizing means 3o includes a graded index optical waveguide 31.32 having a parabolic refractive index distribution and a step index optical waveguide 33.34 having a step refractive index distribution.
They are connected alternately, for example, by fusion bonding.

Next, the operation of the apparatus configured as described above will be explained. FIG. 9 is a diagram showing the transmission of optical signals in the emission pattern stabilizing means 30. In FIG. 9, 33 is the core of the step index optical waveguide 33, and 31 is the core of the graded index optical waveguide 31. Here, the waveguide mode of the optical signal is determined by whether the optical signal undergoes repeated total reflection at a given angle in the step index optical waveguide 33, and
1 is determined by the position and angle at which the light is incident. For this reason, in the step index optical waveguide 334, the optical signal CI.

C2 becomes parallel as shown in FIG. The tabs have the same waveguide mode. On the other hand, in the graded index optical waveguide 31, since the incident positions of the optical signals C1 and C2 are different, the optical signal C1 is transmitted in a high-order mode and the optical signal C2 is transmitted in a low-order mode. That is, in the graded index optical waveguide 31, the optical signal CI.

Even if the incident angle of C2 is the same, since the incident position is different, each waveguide mode becomes different and is transmitted. Therefore, in the step index optical waveguide 33, the optical signals CI and C2 in one waveguide mode that have been reflected and transmitted at the same angle enter the graded index optical waveguide 31 and are dispersed into a plurality of waveguide modes. This kind of output <? The optical signal from the optical signal transmitting section 1 transmitted through the turn stabilizing means 30 is outputted to the reflecting plate 3 & in the detecting section 3 in a uniform output pattern.

Therefore, according to the device as shown in FIG.
Since graded index optical waveguides 31, 32 and step index optical waveguides 33, 34 having different refractive index distributions are provided at the connecting portions between the optical waveguides 2 and 4, the transmission 9
The side optical waveguide 2 and the receiver have a stabilized output pattern because each waveguide mode is dispersed and made uniform even if the waveguide mode is converted or shifted due to bending of the side optical waveguide 4. can be obtained.

〔Effect of the invention〕

According to the present invention, the optical waveguide at the connection portion between the detection unit and the optical waveguide is bent with a predetermined radius of curvature, or optical waveguides with different refractive index distributions are provided alternately. It is possible to obtain an optical signal with a stable emission pattern even by attaching and detaching the connecting portion, and to provide an optical sensor device that does not cause sensitivity changes or zero point drift.

[Brief explanation of the drawing]

Figures 1 and 2 are configuration diagrams of conventional optical sensor devices, and Figures 3 (a) and 3 (b) show the configuration of the optical waveguide and its Q.
FIG. 4 is a diagram showing changes in the output pattern, FIG. 5 (a) and (b) are output characteristic diagrams of a conventional optical sensor device, and FIG. 6 is an optical sensor according to the present invention. A configuration diagram showing the first embodiment of the device, FIG.
A configuration diagram of another emission pattern stabilizing means in the embodiment of
FIG. 8 is a block diagram showing a second embodiment of the present device, and FIG. 9 is a diagram for explaining the operation of the second embodiment. DESCRIPTION OF SYMBOLS 1... Optical signal transmitter, 2... Transmission side optical waveguide, 3...
- Detection unit, 4... Receiving side optical waveguide, 5... Optical signal receiving unit, 20.30... Output pattern stabilizing means, 21.
... Stabilizing member, 31.32... Brake 4 index optical waveguide, 33.34... Step index optical waveguide. Applicant's Representative Patent Attorney Takehiko Suzue Figure 6 Figure 7 Figure 8 Figure 9

Claims (3)

[Claims] (1) In an optical sensor device that measures a physical quantity using optical communication, an optical signal generating means for generating an optical signal in the optical communication, and a plurality of optical waveguides for transmitting the optical signal from the optical signal generating means. a detection means for converting the optical signal transmitted through the optical waveguide into a light intensity corresponding to a change in the physical quantity and detecting the physical quantity; Transmit to the wave path,
an optical signal receiving means for measuring the amount of light of the transmitted optical signal and detecting the physical quantity; and the optical signal emitted from the optical waveguide to the optical waveguide at a connecting portion between the optical waveguide and the detecting means. An optical sensor device characterized in that it is equipped with an output four-turn stabilizing means for stabilizing and fixing the output and the turn. (2) The optical sensor device according to claim (1), wherein the output/arm turn stabilizing means is formed by bending the optical waveguide with a predetermined radius of curvature. (3) The output pattern stabilizing means is a sensor device that applies different light with refractive index distribution.