Optics: measuring and testing – By particle light scattering – With photocell detection
Patent
1991-04-24
1993-07-13
Turner, Samuel A.
Optics: measuring and testing
By particle light scattering
With photocell detection
25022727, G01B 902
Patent
active
052278573
ABSTRACT:
A fiber optic sensor system for cancelling phase noise while it senses a measurand field is disclosed. The system includes circuitry for developing a light beam that is frequency modulated at a fundamental frequency. First and second unbalanced interferometers, having equal path imbalances, are responsive to the frequency modulated light beam for producing respective first and second optical outputs. Detection circuitry is responsive to the fundamental frequency, the second harmonic of the fundamental frequency, and the first and second optical outputs for producing a plurality of sine and cosine signals containing phase difference and phase noise components. A signal processor is responsive to the plurality of sine and cosine signals for cancelling the phase noise components and only producing output sine and cosine components of the difference in the phase shift between the first and second unbalanced interferometers. The system can further include a demodulator for demodulating the sine and cosine components to produce an output signal proportional to the phase shift difference between the first and second unbalanced interferometers.
REFERENCES:
patent: 4609290 (1986-09-01), Cahill
patent: 4830486 (1989-05-01), Goodwin
patent: 5001337 (1991-03-01), Homuth
Publication. "Analysis of Input-Polarization-Induced Phase Noise in Interometric Fiber-Optic Sensors and Its Reduction Using Polarization Scrambling", by Alan D. Kersey et al., Journal of Lightwave Technology, vol. 8, No. 6, Jun. 1990. pp. 838-845.
Publication, Novel Passive Phase Noise Cancelling Technique for Interferometric Fiber Optic Sensors, by A. D. Kersey and T. A. Berkoff, Electronics Letters, vol. 26, No. 10 (10 May 1990).
Jameson George
McDonnell Thomas E.
The United States of America as represented by the Secretary of
Turner Samuel A.
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