JPH02116727A - Optical fiber temperature sensor - Google Patents

Abstract

PURPOSE:To obtain an optical fiber temperature sensor which is easy to make with a smaller size and a heat resistance by using a thin film made of an amorphous Si based material as thermosensitive substance of the optical fiber temperature sensor. CONSTITUTION:A thin film made of an amorphous silicon based material hydrogenated or fluorinated as thermosensitive substance 2 is formed at an end of an optical fiber 1 by CVD, evaporation or the like with a thickness of about 0.05-0.3mum. Moreover, a reflection filter 3 made of Al, Cu, Au or the like is formed on the thermosensitive substance 12. As the thermosensitive substance 2 of the amorphous Si based material is large in absorption on the short wavelength side, even a thin film with a thickness of about 0.1mum can have a larger inclination at an absorption end to allow a greater sensitivity with a limited effect of interference. With the control or the like of the degree of hydrogenation and the thin film, the area of change in reflection factor can match a light source and an element thereby facilitating the designing and building of a measuring system.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an optical fiber temperature sensor that measures temperature using an optical fiber.

[Prior art] Conventionally, as a temperature sensor using an optical fiber, a semiconductor crystal plate of GaAs or CdTeW is bonded to the end face of the optical fiber, and this semiconductor crystal plate is used as a @lag material to transmit and receive light. Some devices measure temperature from changes in reflectance or transmittance.

Problems to be Solved by Invention C] However, when a semiconductor crystal plate is used, it is difficult to bond it to the end face of an optical fiber, requires manufacturing technology, and there are also problems in heat resistance. In addition, in order to sharpen the rise of the absorption edge that causes changes in reflectance and transmittance, and to eliminate the influence of interference caused by thin films, semiconductor crystals such as Qa AS have a thickness of several tens of μm.
A film with good crystallinity as described above is required, and there is a problem in that it is difficult to manufacture.

SUMMARY OF THE INVENTION An object of the present invention is to address the above points and provide an optical fiber thirst sensor that is easy to manufacture, compact, and heat resistant.

[Means for Solving the Problems 1] The present invention provides an optical fiber temperature sensor that uses an optical fiber to emit and receive light onto a temperature-sensitive substance and measure temperature from changes in its reflectance or transmittance, in which hydrogen is used as the temperature-sensitive substance. This method uses a thin film of an amorphous Si-based material that has been fluorinated or fluorinated.

[Function] Easy to manufacture, thin films with various characteristics can be obtained depending on the manufacturing conditions, and concentration measurement is possible.

[Embodiment 1] FIG. 1 is a configuration explanatory diagram showing an embodiment of the present invention.

In the figure, a hydrogenated or fluorinated amorphous silicon material (a -8i :H, a -8i N:H, a
-8i C:H, a -8i Ge:H, etc.) 0.05-0.3am 8111. , CVD, sputtering, ion blating, vapor deposition, etc., and furthermore, an anti(M
l! Form I3. In addition, the entirety of the thin film temperature-sensitive material 2 and the anti-fJ4 film 3 at the end of the optical fiber 1 is coated with an appropriate insulation material.
! 1114 is preferably formed.

Light is emitted from a light source (not shown) through the thin film temperature-sensitive substance 2 and the optical fiber 1, and the reflected or transmitted light is measured by a detector (not shown).

This temperature-sensitive thing! As shown in Figure 3, the optical characteristics due to the temperature T in 2 change by moving the slope part at the absorption edge depending on the temperature T, and by measuring the appropriate wavelength of this slope part as the measurement wavelength, the temperature can be determined. The reflectance change for is determined,
From this, the temperature can be measured. Note that the temperature may be measured by using a wavelength with little temperature dependence as a reference wavelength and comparing it with the measurement wavelength.

This temperature-sensitive material t22 made of amorphous Si-based material has large absorption on the short wavelength side, so it has an nlI of about 0.1 μm.
Even at g, the slope of the absorption edge can be made large, and the influence of interference is small.
The sensitivity can be increased. In addition, by controlling the degree of hydrogenation, the thin film, etc., the region of change in reflectance can be matched to the light source and element, making it easy to design and construct the measurement system.

FIG. 2 shows another embodiment, in which Si02 m 5 was formed as a buffer layer between the temperature-sensitive material 2 and the reflective film 3 in the embodiment of FIG. By doing so, it is possible to prevent characteristic changes due to mutual diffusion between the temperature-sensitive substance 2 and the reflective film 3 during use at high humidity, and it is possible to improve the heat resistance characteristics of the temperature sensor.

[Effects of the Invention] As described above, the present invention uses an amorphous Si-based material as the temperature-sensitive substance of an optical fiber temperature sensor, and even a 7S film has good absorption edge rise characteristics and high sensitivity. In addition, the reflection and absorption characteristics can be controlled by controlling the material, degree of hydrogenation, film thickness, etc., and the measurement waveform can be adjusted to suit the light source, etc., making it possible to realize products suitable for various uses. In addition, thin film technology makes it easy to manufacture, suitable for childbirth, and small and inexpensive.

[Brief explanation of drawings]

1 and 2 are configuration explanatory diagrams showing one embodiment of the present invention, and FIG. 3 is a characteristic diagram. DESCRIPTION OF SYMBOLS 1... Optical fiber, 2...@diaphragm substance, 3... Reflective film, 4... Protective layer, 5... Si 021! Figure 31

Claims (1)

[Claims] 1. An optical fiber temperature sensor that uses an optical fiber to project and receive light onto a temperature-sensitive substance and measures temperature from changes in its reflectance or transmittance, in which hydrogenated or fluorinated material is used as the temperature-sensitive substance. Amorphous Si-based material with film thickness of 0.05~
Optical fiber temperature sensor using a 0.3μm thin film. 2. The optical fiber temperature sensor according to claim 1, wherein a temperature-sensitive substance is formed on the end face of the optical fiber, and a reflective film is formed thereon. 3. The optical fiber temperature sensor according to claim 2, wherein an SiO_2 film is provided between the temperature sensitive substance and the reflective film.