FIBER-OPTIC GYRO

PROBLEM TO BE SOLVED: To suppress the deterioration of the scale factor of a fiber-optic gyro caused by the sufficiency of the driving current of a semiconductor laser even if the temperature range becomes higher than that is considered when the gyro is designed and the control of the driving current of a semiconductor laser reaches another device. SOLUTION: In a system which detects an angular velocity signal by giving periodic phase modulation on both counterclockwise and clockwise light by means of a phase modulating means 17 provided between one end of a wave branching/detecting means 14 and a sensing coil 15 and converting the interference light between the light passed through the coil 15 into electric signals at the wave branching/detecting means 14 by means of a photoelectric converting means 16, and then, synchronously detecting the electric signals by means of a detecting means 18 by using a phase modulated signal, a light quantity detecting means 21 detects a light intensity signal arriving at the converting means 16 from a light source 11 and controls the driving current of the light source 11 so that the intensity signal may become constant. In addition, an arithmetic means 31 divides the detected output of the detecting means 18 by the detected light intensity signal of the detecting means 21 and outputs the quotient as an angular velocity signal.