Optical sensor system
First Claim
1. An optical sensor system which comprises an optical waveguide, first and second means each for detecting light which is propagated along different paths in said waveguide to reach said detection means, means for deforming said waveguide to provide a bias deformation which, on the average, approximately equally partitions the light energy which propagates to said detecting means along said different paths, and to modulate the partitioning of light energy between said paths in response to the parameter to be sensed, and means for providing an electrical output corresponding to the difference between light energies detected by said first and second detection means.
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Abstract
An optical transducer with an optical waveguide having two paths for the propagation of light is deformed in response to acoustical pressure variations or other parameters to be sensed to modulate the amplitude of the light propagated along the two paths in opposite polarities. The light outputs of the two paths are sensed by photodetectors and applied to an electrical differencing circuit. The mean values of the photodetector outputs are balanced as by mechanically providing a predetermined bias deformation of the fiber, or by electrically matching outputs of the detectors such that, on the average, the output of the differencing circuit is zero. Dynamic deformation of the fiber in the transducer results in unbalanced outputs of the photodetectors which unbalance is sensed by the differencing circuit. This differential detection method minimizes optical and mechanical sources of noise in the light source and waveguide and leads to increased signal-to-noise and enhanced dynamic range of the transducer.
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Citations
29 Claims
- 1. An optical sensor system which comprises an optical waveguide, first and second means each for detecting light which is propagated along different paths in said waveguide to reach said detection means, means for deforming said waveguide to provide a bias deformation which, on the average, approximately equally partitions the light energy which propagates to said detecting means along said different paths, and to modulate the partitioning of light energy between said paths in response to the parameter to be sensed, and means for providing an electrical output corresponding to the difference between light energies detected by said first and second detection means.
- 11. An optical transducer system which comprises an optical waveguide having juxtaposed portions of material of different indexes of refraction which extend longitudinally, means for deforming said waveguide in response to the parameter to be transduced whereby to modulate the amplitude of the light propagated through said portions of said waveguide, and means for separately removing the light propagating through each of said portions and providing an electrical output corresponding to the difference in amplitudes therebetween.
- 26. An optical transducer system which comprises an optical waveguide having juxtaposed portions of material of different indices of refraction which extend longitudinally, means for introducing light energy into at least one of said portions, means for deforming said waveguide to provide a bias deformation which, on the average, partitions the light energy between said portions such that the light energy propagating away from said one portion is substantially reduced in magnitude, and the light energy propagating away from another of said portions is substantially increased in magnitude relative to the magnitudes present in the absence of said bias, and to modulate the partitioning of light energy between said portions around said average partitioning in response to the parameter to be sensed, and means for separately removing the light propagating through each of said portions and providing an electrical output corresponding to the difference in amplitudes therebetween such that in the absence of the parameter to be sensed the electrical output tends to zero.
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29. An optical transducer system which comprises an optical waveguide having juxtaposed portions of material of different indices of refraction which extend longitudinally in at least one of which light propagates in different modes, means for introducing light energy into at least one portion, means for deforming said waveguide to provide a bias deformation which, on the average, partitions the light energy between said different modes such that the light energy propagating in one of said different modes is substantially reduced in magnitude, and the light energy propagating in another of said different modes is substantially increased in magnitude relative to the magnitudes present in the absence of said bias, and to modulate the partitioning of light energy between said modes around said average partitioning in response to the parameter to be sensed, and means for detecting light separately propagating in said one and said other of said different modes and providing an electrical output corresponding to the difference in amplitudes therebetween such that in the absence of the parameter to be sensed the electrical output tends to zero.
Specification