Optics: measuring and testing – By particle light scattering – With photocell detection
Patent
1991-12-13
1994-03-01
McGraw, Vincent P.
Optics: measuring and testing
By particle light scattering
With photocell detection
356351, G01B 902, G02B 530
Patent
active
052912663
ABSTRACT:
An apparatus comprised of a depolarized light source for fiber optic sensors is disclosed. In a preferred embodiment, the depolarized light source of the apparatus comprises: a first laser for generating a first beam at a first frequency, the first beam having a linear polarization state; a second laser for generating a second beam at a second frequency, the second beam having a linear polarization state; a means for rotating the polarization state of the second beam so that the first and second beams have orthogonal linear polarization states with respect to each other; and a means for combining the first beam with the polarization-rotated second beam to obtain a composite beam which is depolarized. In a system operation, the apparatus comprises: a source of depolarized light; an integrated optic modulator means for receiving a modulator drive signal; a first low-birefringence fiber for conveying the depolarized light beam from the depolarized light source to the integrated optic modulator means, the integrated optic modulator means modulating only one linear polarization state in the depolarized light beam as a function of the modulator drive signal to produce a modulated beam; a photodetector; and a second low-birefringence fiber for conveying the modulated light beam to the photodetector, the photodetector being responsive to the modulated light beam for developing an electrical signal proportional to the modulator drive signal.
REFERENCES:
patent: 4266850 (1981-05-01), Burns
patent: 4529312 (1985-07-01), Pavlath et al.
patent: 4897543 (1990-01-01), Kersey
patent: 4932783 (1990-06-01), Kersey et al.
patent: 5104222 (1992-04-01), Kersey et al.
Application, S/N 07/584,221, Filed Sep. 18, 1990, Inventors: A. D. Kersey al., "System and Method for Minimizing Input Polarization-Induced Phase Noise in an Interferometric Fiber-Optic Sensor Using Depolarized Input Light".
Publication, "New Polarization-Insensitive Detection Technique for Coherent Optical Fibre Heterodyne Communications" Electronics Letters, vol. 23, No. 18, Aug. 27, 1987, pp. 924-926.
Publication, "Dependence of Visibility on Input Polarization in Interferometric Fiber-Optic Sensors", by A. D. Kersey et al., Optics Letters, vol. 13, Apr. 1988, pp. 288-290.
Publication, "Observation of Input-Polarization-Induced Phase Noise in Interferometric Fiber-Optic Sensor", by A. D. Kersey et al., Optics Letters, vol. 13, No. 10, Oct. 1988, pp. 847-849.
Publication, "Demonstration of Lead Sensitivity of a Fiber Interferometer Due to Magneto-Optically Induced Input Polarization Fluctuation", by A. D. Kersey et al., Optical Fiber Sensors, Springer Proceedings in Physics, vol. 44, 1989 pp. 166-171.
Publication, "Monomode Fibre Polarisation Scrambler", by A. D. Kersey et al., Electronics Letters, vol. 23, No. 12, Jun. 4, 1987, pp. 634-636.
Publication, "Analysis of Input-Polarization-Induced Phase Noise in Interferometric Fiber-Optic Sensors and Its Reduction Using Polarization Scrambling", by A. D. Kersey et al., Journal of Lightwave Technology, vol. 8, No. 6. Jun. 1990, pp. 838-845.
Burns William K.
Howerton Marta M.
Moeller Robert P.
Jameson George
McDonnell Thomas E.
McGraw Vincent P.
The United States of America as represented by the Secretary of
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