| 摘要 |
PURPOSE:To detect an unusual temp. with high reliability by providing a thermally distorting member, which is expanding or shrinking in accordance with temp. change and causes to change the transmitting characteristics of an optical fiber, at a desired point in the longitudinal direction of the optical fiber. CONSTITUTION:A heat thermally distorting member 2 such as polyamide is fixed to a desired point 1a at the longitudinal direction of an optical fiber or at the spirally winding position 1a'. The fiber 1 is laid along, for example, a transporting pipe 7 for low-temp. liquefied gas and is so laid in which the member 12 is adjacent to e.g. a jointing part of the pipe 7. The signal light from the light source 3 is projected to one end 1b of the fiber with a half mirror 4 and the reflected light is monitored by a photoreceptor 5 which is set at another end 1c. And, the thermally distorting member in shrinked by the liquefied gas which leaks from a jointed part A of the pipe, then the output of the signal light is changed by distoring of the fiber. Therefore, an unusual temp. is detected with high reliability. |
