Method and apparatus for acoustic sensing using multiple optical pulses
First Claim
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1. A method comprising:
- launching into a medium a first pair of electromagnetic waves comprising a first electromagnetic wave and a second electromagnetic wave;
detecting a first beat signal resulting from a scattering of the first pair of electromagnetic waves by the medium;
determining, from the first beat signal, complex signals corresponding to a plurality of fixed locations along the medium; and
detecting a disturbance in the medium by extracting phase information from the complex signals.
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Abstract
An improved technique for acoustic sensing involves, in one embodiment, launching into a medium, a plurality of groups of pulse-modulated electromagnetic-waves. The frequency of electromagnetic waves in a pulse within a group differs from the frequency of the electromagnetic waves in another pulse within the group. The energy scattered by the medium is detected and, in one embodiment, the beat signal may be used to determine a characteristic of the environment of the medium. For example, if the medium is a buried optical fiber into which light pulses have been launched in accordance with the invention, the presence of acoustic waves within the region of the buried fiber can be detected.
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20 Claims
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1. A method comprising:
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launching into a medium a first pair of electromagnetic waves comprising a first electromagnetic wave and a second electromagnetic wave; detecting a first beat signal resulting from a scattering of the first pair of electromagnetic waves by the medium; determining, from the first beat signal, complex signals corresponding to a plurality of fixed locations along the medium; and detecting a disturbance in the medium by extracting phase information from the complex signals. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9)
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10. A system comprising:
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a plurality of sources launching into a medium a first pair of electromagnetic waves comprising a first electromagnetic wave and a second electromagnetic wave; a plurality of detectors detecting a first beat signal resulting from a scattering of the first pair of electromagnetic waves by the medium; a demodulator determining, from the first beat signal, complex signals corresponding to a plurality of fixed locations along the medium; a processor; and a memory to store computer program instructions, the computer program instructions when executed on the processor cause the processor to perform operations comprising; detecting a disturbance in the medium by extracting phase information from the complex signals. - View Dependent Claims (11, 12, 13, 14, 15)
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16. A non-transitory computer readable storage medium storing computer program instructions, the computer program instructions, when executed on a processor, cause the processor to perform operations comprising:
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detecting a first beat signal resulting from a scattering of a first pair of electromagnetic waves by a medium, the first pair of electromagnetic waves comprising a first electromagnetic wave and a second electromagnetic wave; determining, from the first beat signal, complex signals corresponding to a plurality of fixed locations along the medium; and detecting a disturbance in the medium by extracting phase information from the complex signals. - View Dependent Claims (17, 18, 19, 20)
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Specification