Apparatus and Method for Minimizing Polarization-Induced Signal Fading in an Interferometric Fiber-Optic Sensor Using Input-Polarization Control.
Patent Application, Filed 25 Jan 89,
DEPARTMENT OF THE NAVY WASHINGTON DC
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An apparatus and method for minimizing polarization-induced signal fading in an interferometric fiber-optic sensor is disclosed. In a preferred embodiment of the invention, the polarization state of an input light beam is changed by a polarization controller as a function of first and second control signals applied to the controller. The input light beam with the changed polarization state is applied to the input of an interferometric fiber-optic sensor, causing the interferometric fiber-optic sensor to form an interference pattern at its output. This interference pattern is photodetected to develop an electrical signal that has a peak-to-peak amplitude proportional to the visibility of the interference pattern. A control circuit is responsive of the interference pattern. A control circuit is responsive to the electrical signal for controllably developing the first and second control signals to change the polarization state of the input light beam to maximize the peak-to-peak amplitude of the electrical signal, thereby minimizing the polarization-induced signal fading in the interferometric fiber-optic sensor. The electrical signal is also demodulated to produce an output signal that is proportional to the field being sensed by the interferometric fiber-optic sensor. Patent applications. rh
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