| 摘要 |
<p>PURPOSE:To detect a fire free of the effect of the electric and magnetic induction of an electric wire cable, by projecting light from one end of the optical fiber arranged along a long sized article in a loop form to receive the same at the other end thereof and detecting the increase in the attenuation quantity of luminous intensity. CONSTITUTION:An optical fiber 2 consisting of a core comprising quartz glass and a clad comprising plastic is arranged in a loop form along the longitudinal direction of a laid electric wire cable 1 being a long-sized article. Further, a light emitting part 3 is provided to one end of the optical fiber 2 and a light receiving part 4 is provided to the other end thereof and a light receiving quantity change amount detection circuit 5 and an alarm circuit 6 are successively connected to the light receiving part 4 on the output side thereof. When the light transmitting attenuation quantity of the optical fiber increases by the rising in temp. due to the generation of a fire and light receiving quantity is reduced with respect to light emitting quantity, this state is detected by the change amount detection circuit 5 to input a signal to an alarm circuit 6 and an alarm is emitted to inform the generation of the fire.</p> |
