PURPOSE: To prevent the influence by reflection and to know not only qualitatively but also quantitatively the temp. change in sensor parts by forming light absorptive layers to the free ends of fiber type couplers.
CONSTITUTION: The temp. change in the sensor parts is detected by coupling the fiber type couplers 2, 3, 4 at every prescribed interval to a long-sized optical fiber 1 in the longitudinal direction, providing the sensor parts A, B, C having temp. dependency at one end of the couplers 2, 3, 4 and detecting the levels of the light pulses which are made incident to the fiber 1 from one end thereof and are reflected from the sensor parts A, B, C. The light absorptive layers (a), (b), (c) are formed to the free ends of the couplers 2, 3, 4 to prevent the influence of reflection. SiO2 doped with, for example, an absorptive material such as Ti, Fe, Cr, V or Cu is usable for the layers (a), (b), (c).
FUKUDA TAKERU
SHIODA TAKAO
