Optical sensor and method of use
First Claim
1. An apparatus, comprising:
- a pulsed light source;
an optical fibre deployed in an environment to be monitored and arranged to receive pulses of light from the pulsed light source;
an interferometer arranged to receive light backscattered and/or reflected from along the length of the optical fibre as the pulses of light travel along the fibre and to generate an interference signal in dependence thereon, the light being backscattered and/or reflected in dependence on acoustic perturbations incident along the length of the optical fibre, and the interference signal comprising first, second, and third interference signal components having phase shifts therebetween;
a first photodetector arranged to measure an intensity of the first interference signal component to provide first intensity data;
a second photodetector arranged to measure an intensity of the second interference signal component to provide second intensity data;
a third photodetector arrange to measure an intensity of the third interference signal component to provide third intensity data; and
a processor time synchronised with the pulsed light source and arranged to;
i) receive the first, second and third intensity data and to determine therefrom any optical phase modulation in the received light, and thereby obtain optical phase modulation data from along the length of the optical fibre; and
ii) identify acoustic perturbations incident along the optical fibre in dependence on the determined optical phase modulation, wherein the optical phase modulation data obtained from along, the length of the optical fibre is synchronised to enhance signal sensitivity.
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Abstract
An interferometer apparatus for an optical fiber system and method of use is described. The interferometer comprises an optical coupler and optical fibers which define first and second optical paths. Light propagating in the first and second optical paths is reflected back to the optical coupler to generate an interference signal. First, second and third interference signal components are directed towards respective first, second and third photodetectors. The third photodetector is connected to the coupler via a non-reciprocal optical device and is configured to measure the intensity of the third interference signal component directed back towards the input fiber. Methods of use in applications to monitoring acoustic perturbations and a calibration method are described.
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Citations
11 Claims
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1. An apparatus, comprising:
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a pulsed light source; an optical fibre deployed in an environment to be monitored and arranged to receive pulses of light from the pulsed light source; an interferometer arranged to receive light backscattered and/or reflected from along the length of the optical fibre as the pulses of light travel along the fibre and to generate an interference signal in dependence thereon, the light being backscattered and/or reflected in dependence on acoustic perturbations incident along the length of the optical fibre, and the interference signal comprising first, second, and third interference signal components having phase shifts therebetween; a first photodetector arranged to measure an intensity of the first interference signal component to provide first intensity data; a second photodetector arranged to measure an intensity of the second interference signal component to provide second intensity data; a third photodetector arrange to measure an intensity of the third interference signal component to provide third intensity data; and a processor time synchronised with the pulsed light source and arranged to; i) receive the first, second and third intensity data and to determine therefrom any optical phase modulation in the received light, and thereby obtain optical phase modulation data from along the length of the optical fibre; and ii) identify acoustic perturbations incident along the optical fibre in dependence on the determined optical phase modulation, wherein the optical phase modulation data obtained from along, the length of the optical fibre is synchronised to enhance signal sensitivity. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11)
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Specification