Polarimetric Fabry-Perot sensor
First Claim
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1. A fiber optic interferometer for detecting an external field, comprising:
- an optical fiber waveguide capable of supporting two independent radiation modes, the two ends of the waveguide being highly reflecting, the input end of which is partially transmitting,means for launching coherent radiation of said two modes in fixed relation to each other into said input end of the waveguide,means for tuning said waveguide to near the resonances of said modes,means for sensing the external field to be detected that differentially affects said two modes simultaneously so that the differential mode signal of said two modes varies with said external field signal,and means for measuring said differential mode signal.
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Abstract
A polarimetric Fabry-Perot sensor comprising a source of coherent polarized light, an optical cavity, preferably an optical fiber, capable of supporting two independent modes of that light and coated with partially reflecting material on both ends, a sensing element for detecting the external field that differentially affects the two modes, and means for measuring interference between the two modes.
21 Citations
13 Claims
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1. A fiber optic interferometer for detecting an external field, comprising:
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an optical fiber waveguide capable of supporting two independent radiation modes, the two ends of the waveguide being highly reflecting, the input end of which is partially transmitting, means for launching coherent radiation of said two modes in fixed relation to each other into said input end of the waveguide, means for tuning said waveguide to near the resonances of said modes, means for sensing the external field to be detected that differentially affects said two modes simultaneously so that the differential mode signal of said two modes varies with said external field signal, and means for measuring said differential mode signal.
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2. A fiber optic interferometer for detecting an external field signal, comprising:
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a fiber optic waveguide capable of supporting two independent orthogonally polarized light modes of substantially equal frequency, the two ends of said waveguide being highly reflecting, the input and output ends of which are partially transmitting; a coherent light source that launches said two modes of equal amplitudes into said input end of said waveguide; at least one phase shifter for tuning said waveguide to near the resonances of both said modes; at least one sensing element that senses the external field to be detected that differentially shifts the phase of said two modes whereby the differential mode phase signal varies with said external field signal; and means for detecting the differential phase shifts of the resonances of said two modes. - View Dependent Claims (3, 4, 5)
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6. A fiber optic interferometer for detecting an external field signal, comprising:
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an optical fiber waveguide capable of supporting two independent orthogonally polarized light modes of substantially equal frequency, the two ends of said waveguide being highly reflecting, the input end and output end of which are partially transmitting; a coherent light source that launches said two modes of equal amplitudes into said input end of said waveguide; phase shifters for tuning said waveguide to near the resonances of said modes; at least one sensing element that senses the external field to be detected that differentially shifts the phase of said two modes whereby the differential mode phase signal varies with said external field signal; means for dividing the beam transmitted through said output end of said waveguide into two beams composed of unequal contributions of two said light modes; two detectors that measure the intensities of said two divided beams; and feedback circuitry from the outputs of said two detectors to said phase shifters that tune said waveguide to fixed points on the resonances of said two modes, whereby the amount of differential phase shift applied to said two modes is a measure of said external field signal. - View Dependent Claims (7, 8, 9, 10, 11, 12, 13)
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Specification