PURPOSE: To enable detection of γ ray irradiation dose for a range of an optical fiber length and also accurate temperature detection by inputting a laser beam from a light source continuously into a reference optical fiber and discontinuously into a measuring optical fiber by using an optical switch.
CONSTITUTION: A laser beam generated at a laser beam source 2 by a pulse driving circuit 1 through control of a measuring time control circuit 13, is input both into a reference and a measuring optical fibers 4 and 5, by an optical switch 3 via an optical multiplexer/demultiplexer 6. A switch 3 is set so that the laser beam is always input into the optical fiber 4 and therewith generation of loss is suppressed by optical pleach effect by the laser beam, and the optical fiber 5 is set forth to be input discontinuously and therewith γ ray inducing loss is generated corresponding to γ ray irradiation. A back-scattering beam of those fibers 4 and 5 reaches a light receiving circuit via a wave division device 6 and thereafter the γ dose is detected from the difference between both the losses. And also, by selecting the fiber 4 by the circuit 13 and by detecting temperature, very accurate temperature detection can be performed even under a γ ray environment.
KAWAKAMI HIROSHI
TSUTSUI TERUAKI
