Apparatus and method for phase modulating optical signals in a fiber optic rotation sensor
AssigneeLitton Systems, Inc.
InventorGeorge A. Pavlath
Life of this patent
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Abstract
The operating point of a fiber optic rotation sensor is to obtain an increased sensitivity in the measurement of the Sagnac phase shift between counterpropagating beams in a sensing loop. The two counterpropagating optical waves are mixed for detecting interference of the waves to indicate the phase difference between them. The phase of the waves is modulated in accordance with a periodic function having a frequency equal to f.sub.s =(2n+1)/2.tau. where .tau. is the transit time for an optical wave in the sensing loop. The interference pattern of the two waves is periodically sampled at a frequency equal to the modulation frequency.
Claims4
Apparatus for processing signals output from a fiber optic rotation sensor that guides a pair of counterpropagating light waves in a sensing loop of optical fiber and combines the waves to produce an interference pattern indicative of the phase difference between the waves, comprising:
- means for modulating the phase of light waves in the sensing loop with a periodic function having a frequency equal to (2n+1)/2.tau. where n is an integer greater than zero and t is the transit time of a light wave in the sensing loop;
- and
- detector means for detecting signals output from the sensing loop at a frequency producing a detector signal indicative of the phase difference of the waves.
A method for processing signals output from a fiber optic rotation sensor that guides a pair of counterpropagating light waves in a sensing loop of optical fiber and combines the waves to produce an interference pattern indicative of the phase difference between the waves, comprising the steps of:
- modulating the phase of light waves in the sensing loop with a periodic function having a frequency equal to (2n+1)/2.tau. where n is an integer greater than zero and t is the transit time of a light wave in the sensing loop;
- and
- detecting signals output from the sensing loop at a frequency producing a detector signal indicative of the phase difference of the waves.
Dependencies are inferred from the claim text.