JPS586431A - Temperature measuring method using optical fiber - Google Patents

Abstract

PURPOSE:To perform the measurement of temperature without receiving any disturbance of induction, by using an optical fiber having the light transmission factor varying by the temperature. CONSTITUTION:The light emitted from a laser diode 3 is reflected by a reflecting mirror 5 after passing through an optical signal transmitting optical fiber 1 and an optical fiber 2 of chalcogen compound and then detected by an optical detector 4 after passing through the optical fibers 1 and 2 again. In this case, the optical signal receives from the optical fiber 2 attenuation prescribed by the length and the temperature of the fiber 2. Accordingly the optical intensity detected by the detector 4 is proportional to the temperature.

Description

DETAILED DESCRIPTION OF THE INVENTION This invention describes a temperature measurement method using an optical fiber that easily measures and monitors the temperature at a remote point with high precision.

Conventionally, temperature remote measurement has been carried out by converting the temperature into an electrical signal and transmitting it via copper wire or wirelessly. This has the drawback of causing induction disturbances caused by lightning or current. Normally, the temperature detection section and the signal transmission section are made up of separate parts and have a disadvantage of having a complicated configuration. In order to eliminate these disadvantages, the present invention is made up of only optical fibers and uses only optical signals. In particular, the present invention will be described in detail with reference to the drawings, which allow temperature monitoring to be performed with high precision and with ease.

FIG. 1 shows the basic configuration of the present invention, (a) is a diagram showing an example where an optical fiber for a temperature sensor is provided in the middle of the optical fiber for optical signal transmission, and (b) is a diagram showing the optical fiber for optical signal transmission. This is a diagram showing an example in which an optical fiber for a temperature sensor is installed at one end of , where 1 is a core diameter of 10 μm, 1 an outer diameter/2! This is a graded type silica-based optical fiber (optical fiber for optical signal transmission) with a plastic coating on the μ door.
It is a chalcogen compound clad or graded optical fiber made of batted cotton with an outer diameter of 0 μm and a core of 2s and a cladding of A8!55865. 3 is GaI
The nAsP laser diode emits infrared light with a wavelength of /jμm. Hiro is a photodetector of G@Abara, Nshie photodiode, and! is a reflective mirror or a reflective part with a multilayer coating applied to the end face of the optical fiber. Figure 2 shows the above-mentioned chalcogen compound optical fiber (length L).
The light transmission characteristics of W J gl ) at -0°C and 60°C are shown. Based on 20℃ fcJj! In this case, as the temperature rises, the light transmittance of the main part of relatively short wavelengths decreases, and at a wavelength of 4μ, the light transmission height decreases by about 4I at 60℃ compared to 10℃. The light propagates through the silica-based optical fiber and passes through the chalcogen compound optical fiber,
It is reflected at its terminal end and returns to the original optical fiber, or it travels through a silica-based optical fiber connected to the other end to reach the photodetector.

At this time, the optical signal undergoes attenuation in the chalcogen compound optical fiber determined by its length and temperature - the light intensity at this time is equal to that of the other optical fiber for optical signal transmission, and the reflected light returns to the original optical fiber. is measured by a photodetector.

At this time, it is possible to detect the temperature from the absolute intensity change by using only the wavelength of the wavelength for measurement, or there is a method for detecting the temperature from the relative cost of the light intensity of the wavelength of the wavelength or more. It is a matter of course that the temperature change in the optical transmittance of the optical fiber for transmitting optical signals is a sufficiently small value that does not cause measurement errors. length/
A wavelength λ is connected to an optical fiber of length L = J a length L = J a km in the middle of a fiber of λ
This is a plot of the amount of change in light transmission due to temperature when a light beam of = 1.6 μm passes through the graph.

The accuracy of temperature measurement in this example was 1/D°C. As explained above, the temperature sensor using an optical fiber of the present invention is composed only of an optical fiber object, and there is no signal conversion. Therefore, the temperature measurement method using the optical fiber of the present invention uses only optical signals.
It has a simple configuration, is not subject to guidance interference, and has a high precision.
Furthermore, by using an optical fiber with sufficiently low loss for signal transmission, there is an advantage that temperature sensing at a sufficiently remote point can be performed without repeating.

[Brief explanation of the drawing]

Figure 1 shows the configuration of a temperature measurement system using the optical fiber of the present invention, Figure 2 shows the light transmission characteristics of the chalcogen compound optical fiber, and Figure 3 shows the chalcogen compound optical fiber of the present invention. FIG. 4 is a diagram showing the relationship between the temperature W and the change in light transmittance in the case of wavelength/4 μm in an optical fiber system in which a quartz glass optical fiber TLR is integrated. l... Optical fiber for optical signal transmission, Co... Optical fiber of chalcogen compound, 3... Light source section, Reference... light, detection section, j... Reflection mirror. Patent applicant Nippon Telegraph and Telephone Corporation

Claims (1)

[Claims] 1. An optical signal is transmitted through a first optical fiber in which the amount of change in optical transmission loss due to my is negligible, and the light transmittance connected to this optical fiber is controlled by temperature changes. Temperature measurement method using an optical fiber 02, characterized in that the temperature is measured by detecting the amount of change in the light transmittance of the optical fiber 2 of the optical fiber shown in FIG. In the temperature measurement method using an optical fiber, the first optical fiber is a cladded or graded type silica-based optical fiber mainly composed of 7 quartz, or a multi-component glass optical fiber whose main component is oxide. The first optical fiber is a clad type or Temperature measurement method using an optical fiber, characterized in that it is a graded optical fiber, and the second optical fiber is connected to the end or the middle of the seventh optical fiber.