Method and apparatus for acoustic sensing using multiple optical pulses
First Claim
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1. A method comprising:
- launching into a medium at least four pulse modulated electromagnetic waves,each of said pulse-modulated electromagnetic-waves having an associated electromagnetic-wave frequency and a common pulse width,a frequency separation between a first and second of said waves being different from a frequency separation between a third and fourth of said waves;
detecting a signal associated with the pulse modulated electromagnetic waves that are scattered by the medium; and
sampling said detected signal based on the common pulse width so as to examine said medium in sections having a width equal to the common pulse width.
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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, 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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Citations
27 Claims
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1. A method comprising:
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launching into a medium at least four pulse modulated electromagnetic waves, each of said pulse-modulated electromagnetic-waves having an associated electromagnetic-wave frequency and a common pulse width, a frequency separation between a first and second of said waves being different from a frequency separation between a third and fourth of said waves; detecting a signal associated with the pulse modulated electromagnetic waves that are scattered by the medium; and sampling said detected signal based on the common pulse width so as to examine said medium in sections having a width equal to the common pulse width. - View Dependent Claims (2)
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3. A method comprising:
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launching into a medium a plurality of pulse modulated electromagnetic waves, each of said pulse-modulated electromagnetic-waves having an associated electromagnetic-wave frequency and a common pulse width, a frequency separation between the pulse modulated electromagnetic waves in two pulse-modulated electromagnetic-waves being different from a frequency separation between the pulse modulated electromagnetic waves in two other pulse-modulated electromagnetic-waves; detecting a signal associated with the pulse modulated electromagnetic waves that are scattered by the medium; and sampling said detected signal based on the common pulse width so as to examine said medium in sections having a width equal to the common pulse width. - View Dependent Claims (4)
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5. A method comprising:
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launching into a medium a plurality of groups of pulse-modulated electromagnetic-waves, each of said groups comprising a plurality of pulse-modulated electromagnetic-waves, each of said pulse-modulated electromagnetic-waves within a group having an associated electromagnetic-wave frequency, each of said pulse-modulated electromagnetic waves having a common pulse width, the associated pulse modulated electromagnetic wave frequency of one of said pulse modulated electromagnetic-waves within a group being different from the associated electromagnetic-wave frequency of another of said pulse-modulated electromagnetic-waves within the same group, thereby resulting in a frequency separation between the pulse modulated electromagnetic waves in two pulse-modulated electromagnetic-waves within the group, a frequency separation between the electromagnetic waves in two pulse-modulated electromagnetic-waves within a first group being different from a frequency separation between the electromagnetic waves in two pulse-modulated electromagnetic-waves within a second group; detecting a signal associated with the pulse modulated electromagnetic waves that are scattered by the medium; and sampling said detected signal based on the common pulse width so as to examine said medium in sections having a width equal to the common pulse width. - View Dependent Claims (6)
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7. A method comprising:
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launching into a medium a plurality of groups of pulse-modulated electromagnetic-waves, each pulse-modulated electromagnetic-wave having a common pulse width, a frequency separation between the pulse modulated electromagnetic waves in two pulses within a first group being different from a frequency separation between the pulse modulated electromagnetic waves in two pulses within a second group; detecting a signal associated with the pulse modulated electromagnetic waves that are scattered by the medium; and sampling said detected signal based on the common pulse width so as to examine said medium in sections having a width equal to the common pulse width. - View Dependent Claims (8, 9, 10, 11, 12, 13, 14, 15, 16, 17)
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18. An apparatus comprising:
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means for launching into a medium a plurality of groups of pulse-modulated electromagnetic-waves, each pulse modulated electromagnetic-wave having a common pulse width, a frequency separation between the pulse modulated electromagnetic waves in two pulses within a first group being different from a frequency separation between the pulse modulated electromagnetic waves in two pulses within a second group; means for detecting a signal associated with the pulse modulated electromagnetic waves that are scattering by the medium; and means for sampling said detected signal based on the common pulse width so as to examine said medium in sections having a width equal to the common pulse width. - View Dependent Claims (19, 20, 21, 22, 23, 24, 25, 26, 27)
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Specification