DISTURBANCE ELIMINATION TYPE HETERODYNE INTERFERENCE METHOD OPTICAL FIBER SENSOR

摘要

PURPOSE:To cancel and eliminate the influence of a disturbance caused by a heterodyne interference method optical fiber sensor by measuring a phase in an optical path of an optical fiber by a differential method without using a reference optical path. CONSTITUTION:A beam of an optical fiber F1 passes through a directional coupler C1 and reaches an optical fiber emitting end face. The beam is reflected partially by this end and returns through the optical fiber. A transmission light in the end face of the optical fiber F1 is emitted from the fiber, and thereafter, becomes parallel through a refractive index distribution type lens 1G, and irradiates a measuring object (ob). A reflected light beam is made incident in reverse on an optical fiber F2 through the lens 1G. In a photodetector PM1, a beat of an end face reflected light electric vector E1 and E2 of the optical fiber F1 is observed. In a photodetector PM2, an optical beat which has been reflected is observed. Subsequently, a phase difference of both the beats is detected by a phase indicator p.d. so that a disturbance can be eliminated.