JPS63107325A - Radiant ray resistance optical transmission system - Google Patents

Abstract

PURPOSE:To decrease the margin of transmission loss and to attain stable signal optical transmission by sending a signal light as well as a monitor light through an optical fiber so as to detect the increment of the loss of transmission loss at the coloring center and feeding back the result. CONSTITUTION:A light of different wavelength is respectively from a signal light source 2 and a monitor light source 3, a multiplexer 4 multiplexes two lights and leads the result through the optical fiber 5. The optical fiber 5 passes through a radiant ray environment 6 and the transmission loss of signal light and monitor light transmitted through the optical fiber 5 is increased. The signal light and monitor light transmitted through the optical fiber 5 are demultiplexed again into the original received light and monitor light again at a demultiplexer 7. The signal light is sent to a signal light detector 9, from which a system output is extracted. On the other hand, the monitor light is detected by a monitor light detector 8 and its output and a monitor light source 3 are compared by a comparator 10. As a result, the output of the monitor light detector 8, that is, the level of the light transmitted through the radiant ray environment 6 is smaller, then the signal light source is controlled by a control means 11 to increase the output of the signal light source.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a radiation-resistant optical transmission system, and more particularly to a radiation-resistant optical transmission system that receives monitor light and reduces optical power loss in a radiation environment.

[Technical Background of the Invention] In recent years, the use of optical fibers in radiation environments has been increasing. A sensor for detecting radiation exposure using optical fibers is the "leakage radiation detector"
159670), “Leakage Radiation Detector J (Unexamined Japanese Patent Publication No. 159670)
-15! ]671), ``Radiation exposure Ij! amount detector using optical fiber'' (Japanese Patent Application Laid-Open No. 161577).

Since the main component of an optical fiber is glass, when it is irradiated with radiation, a colored center, that is, the absorption band described above, is formed, leading to deterioration in transmission loss. Conventionally, a system was configured by taking a margin for the increase in transmission loss from this experimental value.

[Problems with the background technology] However, if there is not enough margin, there are restrictions on the installation environment. There were drawbacks such as things that could not be done.

[Purpose of the Invention] The present invention has been made to eliminate the drawbacks of the conventional ones as described above, and includes a monitor light in the optical fiber at the same time as the signal light, thereby reducing the increase in transmission loss caused by the Wakamura center. The purpose of the present invention is to provide a long-life trJ bk fiber optic transmission system that is capable of stable signal optical transmission by detecting and feeding back information, and is less susceptible to restrictions in the installation environment.

[Summary of the Invention] In order to achieve the above objects, a radiation-resistant optical transmission system according to the present invention includes a multiplexer connected to a signal light source and a monitor light source, an optical fiber connected to the multiplexer, and an optical fiber connected to the multiplexer. a duplexer connected to the other end; a signal photodetector and a monitor photodetector connected to the duplexer;
It consists of a comparator that compares the outputs of the monitor photodetector and the monitor light source, and a control means that manually inputs the results of the comparator to control the output of the signal light source.

[Embodiment of the invention] When an optical fiber is irradiated with radiation, a colored center ('#
: absorption band) occurs, and transmission loss increases.

However, this colored center disappears due to external light or heat, resulting in a phenomenon in which transmission loss is transferred. The effect caused by light is called a photobleaching effect, and the effect caused by heat is called a thermal bleaching effect. The present invention utilizes this photobleaching effect. A graph showing the photobleaching effect is shown in FIG. in particular,
By constantly inputting light that does not affect the signal transmission light, and comparing the input power and output power, the degree of deterioration can be ascertained, and the input power is increased to compensate for the decrease using the photobleaching effect. Provide feedback to encourage students to do the same.

First, in this embodiment, 12 step index type optical fibers are used, and a signal light having a wavelength of 0.857 zm is input. The monitor light uses a wavelength different from that of the signal light.

Next, to explain the connection relationship in this embodiment, as shown in FIG.
The multiplexer 4 is connected to one end of the optical fiber 5. The optical fiber 5 passes through a radiation environment 6 and passes through a demultiplexer 7.
and its output is connected to a monitor photodetector 8 and a signal photodetector 9. The outputs of the monitor light source 3 and the monitor photodetector 8 are input to the comparator 10 , and the results are sent to a controller 11 as a control means, which controls the output of the signal light source 2 .

Next, the operation of the system of this embodiment will be described. First, light of different wavelengths is emitted from the signal light source 2 and the monitor light source 3, and is sent to the multiplexer 4. The multiplexer 4 combines the two lights and guides them into the optical fiber 5. optical fiber 5
passes through the radiation environment 6 as shown in the figure. Therefore, the transmission loss of the signal light and monitor light transmitted through the optical fiber 5 increases. The signal light and monitor light that have passed through the optical fiber 5 are separated again into the original signal light and monitor light by a demultiplexer 7. The signal light is sent to a signal light detector and taken out as a system output. On the other hand, the monitor light is sent to the monitor light detector 8. Here, the intensity of the monitor light source 3, i.e., the original light, and the output of the monitor photodetector, i.e., the light after the transmission loss has changed due to radiation, are determined by the comparator I.
Humanized by O and compared. As a result, if the output of the monitor photodetector 8, that is, the level of the light passing through the radiation environment 6, is smaller, the control means 11 controls the signal light source to increase the output of the signal light source.

At this time, due to the photobleaching effect, an equilibrium state is reached at a position where the transmission loss is recovered.

[Effects of the Invention] As can be seen from the above embodiments, in the radiation-resistant optical transmission system according to the present invention, the monitor light is transmitted through the optical fiber at the same time as the signal light, and the increase in transmission loss due to the colored center is detected. Feedback reduces the transmission loss margin, which can be used for signal transmission, allowing a longer distance system with the same configuration to achieve +K rE, making it less susceptible to the constraints of the installation environment. Therefore, it can be applied to environments with higher dose rates (or has a longer service life under the same environment), and the degree of deterioration of the system due to radiation can be grasped in real time.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing an embodiment of the present invention, and FIG. 2 is a graph showing the photobleaching effect which is the principle of the present invention. 210. Signal light source 301. Monitor light source 4911 Multiplexer 503. Optical fiber 611. Radiation environment 71.9 Demultiplexer 800. Monitor photodetector 909. Signal photodetector 101. Comparator 113. Good luck means (controller) Agent Patent attorney Moritani -Yu Figure 1 □□□-m □□□-1 Figure 2? Irradiation time (h'') Procedure n 1 Official document December 26, 1986 1 Display of the case Patent application No. 254070 of 1988 2 Title of the invention Radiation-resistant optical transmission system 3 Relationship with the person making the amendment Patent application 2-1-1 Oda Sakae, Kawasaki-ku, Kawasaki-shi (225) Representative of Showa Electric Wire and Wire Co., Ltd. Sat 1) Yoshio 4 Representative Director 3-9-5 Nihonbashi Honmachi, Chuo-ku, Tokyo 6 Subject of amendment: 111 Hm. Column for detailed explanation of defense and drawings. 7 Contents of amendment (1) "Transmission loss" in Mei S, page 6, line 10 is corrected to "1 transmission loss increase." (2) Correct Figure 2 as shown in the attached sheet. that's all

Claims (1)

[Claims] A multiplexer connected to a signal light source and a monitor light source, an optical fiber connected to the multiplexer, a demultiplexer connected to the other end of the optical fiber, and a signal light detector connected to the demultiplexer. a comparator for comparing the outputs of the monitor photodetector and the monitor light source; and a control means for inputting the results of the comparator and controlling the output of the signal light source. Features a radiation-resistant optical transmission system.