OPTICAL FIBER SENSOR

PROBLEM TO BE SOLVED: To eliminate the influence of an optical fiber oscillation and to improve measurement accuracy by separating a signal into a signal by a reflected light and a signal by a signal light beam, adjusting the gain of a separated signal and subtracting an addition value of each signal by a reflector light beam. SOLUTION: A reflected light beam emitted from a light emitted diode(LED) 2A, reflected from a total reflection mirror 19a and returned along an optical fiber 3a, is separated from a light beam going to a sensor part 5 from the LED 2a by an optical fiber coupler 18a, and received by a photodiode(PD) 11a. This signal is synchronized with a driving pulse Pa and the synchronized signal is detected by a sample-and-hold amplifier(S/H) 16a. The reflected light beam emitted from the LED 2b is synchronized with a driving pulse Pb and the synchronized signal is detected by an S/H 16b in similar manner. Then, the light emitted from the LED 2a, reflected from a polarizer 6 and received by a PD 11b, is synchronized with the driving pulse Pa and the synchronized signal is detected by the S/H 16c. Then, the gain of the separated signal is adjusted by an arithmetic circuit 17, and the addition value of each signal by the reflected light is subtracted from the signal by the signal light.