JPH0258677B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an optical fiber sensor, and in particular provides an optical fiber sensor that operates stably against environmental changes such as temperature changes.

Optical fiber sensors are temperature sensors, current sensors,
It is known that it can be used for many applications such as vibration sensors. In the optical fiber sensor, as shown in FIG. 1, light emitted from a light emitting section 1 passes through an optical fiber 2 and an optical connector 6 and enters an optical sensor 3. For example, this light undergoes a change in intensity due to the movement of a mirror bonded to a bimetal due to a temperature change and a change in coupling loss, and is then photoelectrically converted in the light receiving section 4. get information.

In this way, in the method of measuring the target physical quantity from the change in the intensity of the optical output at the light receiving part, measurement errors may occur if the transmission loss in the optical fiber 2 changes due to temperature changes, or if the coupling loss changes due to the connection or removal of the connector 1. arise.

Therefore, as another conventional example, an optical fiber sensor as shown in FIG. 2 has been considered. In this optical fiber sensor, two lights with different wavelengths are multiplexed and transmitted, and the two lights are separated by a demultiplexer 7 just before the sensor part 3 that senses temperature etc., and one light with a wavelength of λ ₁ is sent to the sensor part 3. 3, and other light having a wavelength of λ ₂ is passed through a demultiplexer 7, and then directly enters a multiplexer 8 for multiplex transmission. Next, if the light receiving section 4 detects the light of each wavelength λ ₁ and λ ₂ separately and compares the output, this comparison output will remain constant even if the loss of the optical fiber fluctuates, so there will be no measurement error and the target physical quantities can be detected.

However, the installation of the conventional optical fiber sensor demultiplexer 7 and multiplexer 8 having such a configuration is essential as a component, and there is a drawback that the number of parts increases.
For example, FIG. 2 shows a configuration example in which a reflection type multiplexer is used, and three sets of a multiplexer 8 using a rod lens 9 having a similar structure, a demultiplexer, and an optical sensor 3 are required. This optical fiber sensor also has a demultiplexer and
There was a drawback that measurement errors occurred due to fluctuations in insertion loss due to temperature changes in the multiplexer.

The present invention was made in order to eliminate the above-mentioned drawbacks of the conventional technology, and by integrating a demultiplexer, a multiplexer, and an optical sensor, and by comparing two types of light, temperature, current, etc. can be measured in the external environment. To provide an optical fiber sensor that realizes a configuration with one rod lens that is not affected by

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

FIG. 3 shows an example of a temperature sensor according to an embodiment of the present invention, and the same parts as in the conventional row are given the same numbers. In the figure, a filter 10 that reflects light with a wavelength λ ₁ and transmits light with a wavelength λ ₂ is configured on the end face of a converging rod lens 9 with a 1/4 period length, and an incident fiber is formed on the focal plane of the other end. 12 and an output fiber 13 are bonded together.

The reflecting mirror 11 is supported by a bimetal 11', and its inclination angle with respect to the lens end surface changes according to temperature changes. Wavelengths λ ₁ and λ ₂ incident from the fiber 12
After passing through the lens 9, the light becomes parallel light, and the light with wavelength λ ₁ is reflected by the filter 10, passes through the lens 9 again, and enters the fiber 13. On the other hand, light of wavelength λ ₂ passes through the filter 10, is reflected by the mirror 11, passes through the filter 10 and the lens 9, and enters the fiber 13, but is combined due to the inclination angle of the mirror 11, that is, the temperature change. Efficiency changes.

Since the sensor using the optical device of the above embodiment has only one lens, which also serves as the optical demultiplexer ₇ and ₈ in FIG. By comparing the output intensities, stable measurements can be made without being affected by loss fluctuations due to the influence of the external environment in the transmission line or loss changes due to the attachment and detachment of connectors.

FIG. 4 shows another embodiment of the optical fiber sensor of the present invention. In the figure, fibers 14-16 bonded to lens 9 are arranged at equal intervals, and fibers 14 and 14' are symmetrical about the lens axis. A reflecting mirror 17 is formed in the lower half of the other end surface of the lens 9. Among the light incident from the fiber 14, the light reflected by the mirror 17 enters the fiber 15. The remaining light that is not reflected by the mirror 17 is reflected by the mirror 11 and enters the fiber 14', and the coupling efficiency at this time depends on the tilt angle of the mirror by the bimetal 11', that is, the temperature. On the other hand, the light that is incident on the fiber 15 and reflected again by the mirror 17 is incident on the fiber 14'.

How to use this temperature sensor will be explained with reference to FIG. Fiber numbers 14 to 16 in the diagram
is the same as the configuration shown in Figure 3, and the fiber 1
8 is a delay fiber. When a pulse-like input is applied from the light emitting section, the light that does not pass through the sensor section has a time delay compared to the light that passes through the sensor section. Therefore, the output of the light receiving element has a waveform as shown in FIG. In the figure, 19 is the sensor output, 20 is the comparison output,
t is the time delay. If a comparison value of the peak values of these pulses is obtained, it is easy to see that the target physical quantity can be measured stably even if there is a loss variation due to the influence of the external environment of the transmission line or a loss change of the connector. Although the embodiments related to temperature sensors have been described above, similar measurements can be performed with current sensors and the like.

As explained above, according to the optical fiber sensor of the present invention, it is possible to obtain the desired physical quantity without using a plurality of independent optical components such as a demultiplexer/combiner, and without being affected by fluctuations in transmission path loss. can be measured. Furthermore, since the optical fiber sensor also serves as a demultiplexer and multiplexer, the number of parts is reduced, so reliability is improved and the system can be configured at low cost.

[Brief explanation of drawings]

1 and 2 are diagrams each showing the configuration of a conventional optical fiber sensor, FIG. 3 is a configuration diagram of an optical fiber sensor according to an embodiment of the present invention, and FIG. 4 is a diagram showing the configuration of an optical fiber sensor according to another embodiment of the present invention. FIG. 5 is a diagram showing the main parts of the optical fiber sensor, FIG. 5 is a diagram showing the overall configuration of the optical fiber sensor, and FIG. 6 is a diagram for explaining the operation of the optical fiber sensor. 2, 12, 13, 14, 15, 16... Optical fiber, 3... Sensor section, 9... Rod lens, 1
0...Filter, 11...Mirror, 11'...Bimetal, 17...Reflector, 18...Delay fiber.

Claims (1)

[Scope of Claims] 1. A light source, an optical fiber sensor, a light receiving section that receives light from the optical fiber sensor, and a signal processing section that obtains a physical quantity to be measured based on a signal from the light receiving section. In the measuring device, the light source is a light source that emits light of two different wavelengths, and the optical fiber sensor includes a lens having an optical fiber disposed on one end surface of the optical fiber for receiving light from the light source. , a filter that reflects light of one of the two wavelengths and transmits the other wavelength on the opposite end surface of the lens; and a reflecting member that causes the light that has passed through the filter to enter the lens again. An optical fiber sensor, wherein the reflecting member changes the amount of light incident on the light receiving section according to a change in a physical quantity to be measured. 2. A measuring device comprising a light source, an optical fiber sensor, a light receiving section that receives light from the optical fiber sensor, and a signal processing section that obtains a physical quantity to be measured based on a signal from the light receiving section, The optical fiber sensor includes: a lens having an optical fiber arranged on one end surface thereof for receiving light from the light source; and a first reflecting member provided on the opposite end surface of the lens to reflect a part of the light. , provided on the one end surface of the lens, and provided on the first end surface of the lens.
a delay member that delays the light reflected by the reflective member; and a second reflective member that causes the light emitted from the opposite end surface of the lens to re-enter the lens, the second reflective member . An optical fiber sensor, characterized in that an amount of light incident on the light receiving section is changed in accordance with a change in a physical quantity to be measured.