Systems and Methods for Spread Spectrum Distributed Acoustic Sensor Monitoring
First Claim
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1. A system for monitoring regions of interest for occurrences that generate acoustic perturbations, comprising:
- a. an optical fiber span positioned into a region of interest;
b. a light source for generating a continuous coherent signal of a pre-determined wavelength into the optical fiber;
c. a binary code sequence generator driven by a master clock;
d. an optical modulator having first and second ports for receiving the primary coherent light signal from the light source and a generated binary code from the binary code sequence generator to produce a modulated light signal;
e. an optical circulator/coupler to receive the modulated light signal from the optical modulator and pass it into the optical fiber span positioned into the region of interest;
f. a detector system driven by the master clock for de-modulating, correlating, and de-multiplexing returned backscattered Rayleigh signals from the optical fiber span positioned into the region of interest, wherein the detector system has a processor to detect coherent Rayleigh noise generated by the optical fiber span positioned in the region of interest to identify acoustic events in the regions of interest; and
g. wherein the returned backscattered Rayleigh signals from the optical fiber span positioned into the region of interest are directed to the detector system by the optical circulator/coupler.
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Abstract
A method and device for monitoring oil field operations with a fiber optic distributed acoustic sensor (DAS) that uses a continuous wave laser light source and modulates the continuous wave output of the laser light source with pseudo-random binary sequence codes.
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Citations
24 Claims
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1. A system for monitoring regions of interest for occurrences that generate acoustic perturbations, comprising:
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a. an optical fiber span positioned into a region of interest; b. a light source for generating a continuous coherent signal of a pre-determined wavelength into the optical fiber; c. a binary code sequence generator driven by a master clock; d. an optical modulator having first and second ports for receiving the primary coherent light signal from the light source and a generated binary code from the binary code sequence generator to produce a modulated light signal; e. an optical circulator/coupler to receive the modulated light signal from the optical modulator and pass it into the optical fiber span positioned into the region of interest; f. a detector system driven by the master clock for de-modulating, correlating, and de-multiplexing returned backscattered Rayleigh signals from the optical fiber span positioned into the region of interest, wherein the detector system has a processor to detect coherent Rayleigh noise generated by the optical fiber span positioned in the region of interest to identify acoustic events in the regions of interest; and g. wherein the returned backscattered Rayleigh signals from the optical fiber span positioned into the region of interest are directed to the detector system by the optical circulator/coupler. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10)
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11. A method for monitoring regions of interest for occurrences that generate acoustic perturbations, comprising:
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a. deploying a fiber optic cable into a region of interest; b. transmitting a continuous wave laser light source through the fiber optic cable; c. modulating the continuous wave output of the laser light source with pseudo-random binary sequence codes; d. detecting backscattered Rayleigh signals from the deployed fiber optic cable; and e. using the detected backscattered Rayleigh signals to identify and measure the acoustic perturbations from locations in the region of interest. - View Dependent Claims (12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24)
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Specification