Method to eliminate fiber interferometer reflections

Abstract

Improved performance in a fiber interferometer gyro results from eliminat signals attributed to unwanted reflections from the fiber ends and the coupling lenses. A coiled single-mode fiber bidirectionally transmits beams radiating from a continuous wave laser to a detector. A fixed frequency oscillator amplitude modulates the laser output and provides a reference signal at the same frequency to enable synchronous detection of the detector output signals. Shifting the reference signal .pi./2 radians from the modulating signal eliminates the detector output signals which are attributed to reflections from the fiber ends and coupling lenses. By properly selecting the modulating frequency and reference phase, the information validity of beam signals passing through the coiled single-mode fiber is enhanced.