JPS6166935A - Optical fiber temperature sensor - Google Patents

Abstract

PURPOSE:To improve the heat resistance of a temperature sensor and to reduce in size by removing the core at the end part of an optical fiber to specific depth, charging a temperature sensor material in the hollow part, and providing a reflecting film thereupon. CONSTITUTION:The optical fiber 11 consists of the core 11a and a clad 11b. The end part of the core 11a is hollowed to specific depth. Then, the temperature sensor material 12 which varies in light absorption characteristics with temperature is charged in the hollow part. This material 12 uses, for example, GaAs or CdTe. Then, a material having a small refractive index, e.g. SiO2 is used to form the reflecting film 13 on the material 12. Thus, the temperature sensor material is charged by an epitaxial method, so the optical coupling between the core and sensor member is increased and no adhesive is used, so the heat resistance of the sensor is improved.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to an optical fiber temperature sensor, and particularly to an optical fiber temperature sensor in the form of a sensor transmission line with good heat resistance.

[Conventional technology]

Optical fiber warm sensors are broadly divided into sensor element types in which the optical fiber itself functions as a temperature sensor, and sensor transmission line types in which another temperature sensor is attached to the optical fiber (Basic; Applied Physics, 49.1020° (1980)). Furthermore, there are two types of sensor transmission line-type optical fiber temperature sensors: one is a reflective type in which a temperature-to-light reflection converter is installed at the end of the optical fiber as a temperature sensor, and the other is a reflective type in which a temperature-to-light reflection converter is installed as a temperature sensor at the end of the optical fiber. There is a transmission type that has a permeability converter inside the membrane.

As this reflection type sensor transmission line type optical fiber temperature sensor, there is one having a structure as shown in FIG. 6, for example. This optical fiber sensor IFi has one end surface KGaAa of the optical fiber 2 serving as an optical transmission line.

A sensor part 5 formed by forming a reflective film 4 such as a 0° thin film on the -+ni of a semiconductor crystal wafer 3 such as CdTe is integrally attached and fixed using an adhesive 6. That is, after precisely polishing the joint end surface of the optical fiber 2 and the joint end surface of the sensor member 5 (the end surface without the reflective film 4), these ? It is made by fixing with a heat-resistant adhesive 6 such as epoxy, silicone, or polyimide, while keeping the +111 and 111 abutted against each other exactly.

[Problems that the invention attempts to solve]

However, in such an optical fiber temperature sensor 1, since the organic adhesive 6 is used to fix the optical fiber 2 and the sensor member 3, the heat resistance as a temperature sensor is low, and at most 30° There was a problem that it could only be used up to level C. In addition, since the semiconductor crystal Ueno-3 is used for the sensor member 5, the sensor member 5 inevitably becomes large, and there is a problem that it is difficult to miniaturize the sensor member 5. This process is troublesome and has drawbacks such as variations in the optical coupling efficiency between the original fiber 2 and the sensor member 5.

[Means for solving problems]

Therefore, in the original fiber +&1 degree sensor of this invention, the core at the end of the original fiber, which is the optical transmission line, is removed by a depth of 1'9T, and the space thus formed is filled with GaA
A material (hereinafter referred to as a temperature sensor material) whose light absorption characteristics change with temperature changes, such as semiconductor crystals such as S and CdTe, is grown and filled by a method such as molecular beam epitaxy, and then a reflective film is formed. K was designed to solve the above-mentioned problems by forming the following.

[lol example]

FIG. 1 shows an example of a reflection type optical fiber temperature sensor having a sensor transmission line according to the present invention, and reference numeral 11 in the figure indicates an optical fiber serving as an optical transmission line. 1 liter of this optical fiber
Although there are no particular limitations, a surplus corded optical fiber with good heat resistance is suitable, and in this example, an aluminum coated optical fiber consisting of a core 11a, a cladding 11b, and an aluminum coat 11o is used. This optical fiber 1
1, the core nose at the end that becomes the detection end is removed from the end surface by a predetermined depth ζ, usually about 50 to 100 μm,
The space formed therein is filled with a temperature sensor material 12. Examples of the temperature sensor material 12 include materials whose light absorption coefficient changes, whose light absorption spectrum changes to Kf, or whose fluorescence occurs as the temperature changes, such as GaAs.

Compound semiconductor crystals such as CdTe, InAg, CaTe, and CaP are suitable. Then, the remaining space filled with the temperature sensor material 12 is filled with! [A reflective film 13 made of a material with a lower refractive index than the sensor material 12 is filled in the area ζ. As this reflective film 13, S'Of +
A etOs + T i Ol or the like is used, and its thickness is usually about 11 to 2 μm. The upper dL temperature sensor material 12 and this reflective film 13 form a sensor member 14.
is configured. A protective film 15 is provided that roughly covers the reflective film 13, extends to the aluminum coat 11c, and covers the entire end portion. This circulation membrane 15 has
SiQ.

A u T T i etc. are used, and the thickness is usually (
It is exposed by about 11 to 2 μm. Note that the molar retaining film 15 and the reflective film 1
It is also possible to use both ζ and omit one of them.

Next, regarding the manufacturing method of a sensor with such a structure,
This will be explained with reference to FIGS. 2 to 5.

First, a protective mask 16 is provided to cover the clad llb and aluminum coat 11c on the end face of the optical fiber 11. This is done by forming a silicon group by sputtering using ordinary photolithography. Next, the end face of the optical fiber 11 on which the first protective mask 16 has been formed is subjected to a reactive ion etching method or a reactive ion beam etching method, as shown in FIG. 3, to remove the core 11& to a predetermined depth. A space 17 is formed. Next, the space 17 thus formed is filled with the temperature sensor material 12 as shown in FIG. When using semiconductor crystals, Ktj: Molecular beam epitaxy (MB
E method), the internal pressure of the space 17 is made to generate these crystals.

At this time, a shield mask is provided so that the growth occurs only in the space 17. Next, as shown in FIG.
The remaining space 17 is filled with a reflective film 13 made of O, etc. by K, such as sputtering. Then, the protective mask 16 is removed and 810. By providing the protective film 15 made of the following, the desired optical fiber temperature sensor shown in FIG. 1 can be obtained.

Next, how to use such a temperature sensor will be explained. For example, G a A s in mud IW sensor material 12 .

When compound semiconductor crystals such as CaTa are used, the absorption edge of these semiconductor crystals changes as the temperature increases, as shown in FIG.
With the increase in f, the high wavelength side also moves to the lower wavelength side by [7 degrees]. Therefore, a light emitting diode (T, ET
)) By measuring the light intensity change at α85pm and α90μm of reflection-reflection using α85μm light, the temperature change can be known. In addition, temperature sensor material 1
2KX If a material whose absorption coefficient at a specific wavelength changes with temperature change is used, temperature changes can be known from K by measuring the intensity of reflected light at the specific wavelength. Furthermore, if light of a wavelength whose absorption coefficient does not change due to temperature change is simultaneously used as a reference at this time, disturbances applied to the optical fiber 11 and the sensor member 14 can be removed, and highly accurate temperature measurement is possible.

[For production]

In a temperature sensor with such a structure, the optical fiber 1
1 in the space 17 of the core 11a at the end.

Since the sensor member 14 made of the temperature sensor material 12 and the reflective film 13 is enclosed, there is no need to use adhesive to attach or fix the sensor member 14 to the optical fiber 11, which is the optical transmission path. The heat resistance temperature of the adhesive becomes sufficiently high regardless of the heat resistance temperature of the adhesive, and the heat resistance temperature of 500'
It becomes possible to measure temperatures up to about C. Further, since the sensor member 14 is enclosed in the space 17, the size of the detection end is approximately the same as the diameter of the fiber 11, making it possible to make it extremely compact. In contrast, if molecular beam epitaxy is used to fill the temperature sensor material 12, the core 11
A coupling between & and the sensor member 14 with little optical loss is achieved, resulting in high optical coupling efficiency and no variation.

[Experiment example]

An aluminum-coated quartz optical fiber with a core diameter of 80 μm, an outer diameter of 150 μm, and an aluminum coated quartz fiber with a diameter of 210 μm was cut vertically. A protective mask made of metal silicon covering the aluminum coating and cladding on the cut end face was formed by sputtering. Next, the core was etched 70 μm from the end surface by reactive ion etching.
The depth was removed to form a space. FiCC14 was used as the ion gas in the reactive ion etching method, and the pressure was 10
-'Torr was used. Then, using a molecular beam epitaxy device, GILAs crystals were grown and filled in this space. At this time, a shield mask was provided so that the GaAa crystal grew only within the space. Next, the protective mask was removed, and an 810° film with a diameter of 11 mm and 2 μm was formed by sputtering on the entire end face of the optical fiber as a reflective film and a protective film, thereby obtaining an optical fiber sensor.

The thus obtained temperature sensor showed a change in reflected light with respect to temperature change in a line Ii manner, and was capable of measuring temperatures up to 500''C.

〔Effect of the invention〕

As explained above, the optical fiber temperature sensor of the present invention is of a reflective type sensor transmission line type in which a temperature sensor material is filled in the space from which the core is removed at the end of the optical fiber and a reflective film is provided. , it is no longer necessary to use glue to attach the optical fiber, which is the optical transmission line, and the sensor member, which consists of the temperature sensor material and the reflective film, and the heat resistance of the sensor is improved, allowing it to withstand temperatures up to 500℃. Can be measured. Furthermore, since the dimensions of the sensor are the same as the diameter of the optical fiber, it can be extremely miniaturized. Furthermore, when a semiconductor crystal is used as the two-temperature sensor material and filled by molecular beam epitaxy, highly efficient optical coupling between the optical fiber and the sensor member is possible, and improvements in detection sensitivity and the like can be achieved.

[Brief explanation of drawings]

FIG. 1 is a schematic cross-sectional view showing an example of the optical fiber temperature sensor of the present invention, FIGS. 2 to 5 are schematic cross-sectional views showing the manufacturing method of the optical fiber temperature sensor of the present invention in order of steps, and FIG. 7 is a schematic cross-sectional view showing an example of a conventional reflective sensor transmission line type optical fiber temperature sensor, and FIG. 7 is a spectrum showing the relationship between the movement of the light absorption edge of a semiconductor crystal due to temperature change and the emission spectrum of a light emitting diode. It is. 11...Bifai/<, 1111...
Core, 12...Temperature sensor material, 13...
...Reflection film, 14...Sensor member, 17...
···space. Also, Fig. 1 11c ',' Fig. 2 11c 1, 1 1c ■ U)
Kano, oo and

Claims (2)

[Claims] (1) An optical fiber temperature sensor characterized in that the space at the end of the optical fiber from which the core has been removed is filled with a material whose light absorption characteristics change with temperature changes, and a reflective film is formed on this end. . (2) The optical fiber temperature sensor according to claim 1, wherein the material filled in the space is formed by a molecular beam epitaxy method.