PURPOSE: To make an optical transmission line for detecting water permeation applicable to places which are liable to receive electromagnetic induction, by constituting the optical transmission line of an optical transmission line composed of an optical fiber and contractive thread and detecting water permeation by means of the optical fiber by utilizing the contracting action of the contractive thread when absorbing water.
CONSTITUTION: The optical transmission line for detecting water permeation of this invention is composed of an optical transmission line 1 and contractive thread 2 and the thread 2 is tightly wound round the transmission line 1. When this transmission line contacts with water, the thread 2 contracts and the transmission line 1 bends, resulting in increase in transmission loss. In other words, the transmission loss increases by the section contacting with water and, when the back scattering method is used, the distance to the section contacting with water can be measured. A thread which is formed by intertwisting plural strands coated with a hygroscopic material can be used as the contractive thread 2. When the contractive thread 2 formed in such a way absorbs water, the hygroscopic material coating the surface of the strands swells and the contractive strands themselves increase in thickness against each other. As a result, the intertwisted radius of the contractive thread 2 increases and the total length of the thread 2 shrinks. Since this optical transmission line for detecting water permeation is constituted of a nonmetallic material, this can be applied to the places which are liable to receive electromagnetic induction.
KAWASE MASAAKI
TAKADO HIROSHI
| JPS57128304A | 1982-08-09 |
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