Feedback controlled differential fiber interferometer

摘要

A differential fiber interferometer includes first and second optical fibers that pass through a coupler which has both input and output ends. A laser optically energizes a first one of the fibers and, via the coupler, the second fiber. A telescope lens system focuses optical beams from the first and second fibers onto an object and receives reflections therefrom for retrotransmission. The object is caused to oscillate at a first frequency so as to modulate the phase of the reflected optical beams. An optical sensor, positioned on the input side of the coupler, converts to electrical signals the reflected optical energy that appears on the second fiber. The reflected energy includes optical energies from both the first and second fibers. A first detector is responsive to the sensor's electrical outputs to produce a signal that is proportional to the differential phase between the reflected optical energies. A second feedback detector is coupled between the sensor and the second fiber and phase adjusts optical signals on the second fiber to compensate for environmental fluctuations of the second fiber.