Optics: measuring and testing – By dispersed light spectroscopy – Utilizing a spectrometer
Patent
1984-02-17
1988-03-01
Willis, Davis L.
Optics: measuring and testing
By dispersed light spectroscopy
Utilizing a spectrometer
G01C 1964
Patent
active
047281928
ABSTRACT:
A fiber optic rotation sensor, employing the Sagnac effect comprising all fiber optic components positioned along a continuous, uninterrupted strand of fiber optic material. The rotation sensor includes a detection system utilizing a modulator or modulators for phase modulating at first and second frequencies light waves which counter-propagate through a loop formed in the fiber optic strand. The second modulation frequency is much lower than the first frequency. An output signal from the sensor is gated synchronously with respect to the phase modulation at the second frequency so that the detected optical output signal is provided only during selected intervals of the phase modulation at the second frequency.
A phase sensitive detector generates a feedback error signal proportional to the magnitude of the optical output signal at the first phase modulation frequency. The feedback error signal controls a modulator which controls the amplitude of the second frequency driving signal for the phase modulator such that the signal at the first phase modulation frequency in the output signal from the rotation sensor is substantially cancelled by the phase difference modulation produced at the second modulation frequency during the interval when the optical output signal is present.
REFERENCES:
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patent: 4410275 (1983-10-01), Shaw et al.
patent: 4556321 (1985-12-01), Schiffner
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Kim Byoung Y.
Shaw Herbert J.
Stanford University
Turner S. A.
Willis Davis L.
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