FIBER-OPTIC INTERFERENCE-TYPE SENSOR AND METHOD FOR DETECTING FIBER-OPTIC INTERFERENCE-TYPE SIGNAL

摘要

PROBLEM TO BE SOLVED: To detect a physical signal, such as the impact, vibration signal, etc., applied to an optical signal with high sensitivity by using a sensor having a simple constitution and using a laser and a loop-like optical fiber. ;SOLUTION: The phase change caused between a clockwise propagated light ray and a counterclockwise propagated light ray in a loop-like optical fiber 3 by a physical change applied to the fiber 3 is detected, based on the signal outputted from a photoreceptor 224. Then part of the light rays propagated through the fiber 3 is taken out by means of an optical branching element 227 and the signal level of the taken-out light is detected by means of a signal level detecting means 228. In accordance with the signal level, the output level of the photoreceptor 224 is maintained at a prescribed value or higher by means of a light receiving level control means 230. Thus the phase change caused between the clockwise propagated light ray A and counterclockwise propagated light ray B in the fiber 3 by the physical change applied to the fiber 3 is always accurately detected by compensating the line loss of the propagated light rays.;COPYRIGHT: (C)2001,JPO