MULTICHANNEL TYPE OPTICAL-FIBER SENSOR SYSTEM

摘要

A time division multiplexing, fiber optic data gathering system, including two or more sensors formed on an optical fiber, and a phase sensitive detector. Each sensor includes two reflectors separated by a section of the fiber having length L. Each reflector may be activated so that when an interrogating light signal propagates in a first direction past the activated reflector, a portion of the interrogating light signal will be reflected back into a direction opposite the first direction. Each reflector may also be deactivated so that the interrogating signal may propagate unhindered past the deactivated reflector. Variations in the optical path length between the reflectors of a sensor, due to changes in an external parameter of interest, will cause phase modulations that are extracted in the phase sensitive detector by homodyne or heterodyne techniques. In a preferred embodiment, the activated reflectors produce a specific type of acoustic field resulting from superposition of two acoustic waves, which acoustic field will interact with the interrogating light signal so as to reflect a portion of the interrogating light signal by 180 DEG .