| 摘要 |
PROBLEM TO BE SOLVED: To sensitively detect physical signals of shock, vibration, etc., applied to an optical fiber by using a sensor of simple constitution which uses a laser and a loop type optical fiber. SOLUTION: On the basis of a signal outputted from a photoreceptor 12, physical change applied to a loop type optical fiber 3 is detected as the phase change generated between a light A propagating clockwise in the fiber 3 and a light B propagating counterclockwise. A pilot signal of a given frequency is imparted to the fiber by a pilot signal imparting means 14. From a signal outputted through an optical branch coupling element 13, the pilot signal is extracted and the signal level is observed. When the level of the pilot signal is low, the planes of polarization of the clockwise propagation light and the counterclockwise propagation light are operated by a plane of polarization operating means 15. Thereby the level of the pilot signal is maintained to be higher than a predetermined value. |
