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US 7,742,157 B2Granted
Method and apparatus for acoustic sensing using multiple optical pulses
AssigneeAT&T Intellectual Property II, L.P.
InventorsAndrew B. Lewis, Stuart Russell
Life of this patent
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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.
Claims26
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 characteristic of a beat signal between a given pair of pulse modulated electromagnetic waves that are scattered by the medium;
- and
- sampling said detected characteristic based on the common pulse width so as to examine said medium in sections having a width equal to the common pulse width.
2 more elements
A method comprising:
- 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 characteristic of a beat signal between a given pair of pulse modulated electromagnetic waves that are scattered by the medium;
- and
- sampling said detected characteristic based on the common pulse width so as to examine said medium in sections having a width equal to the common pulse width.
2 more elements
A method comprising:
- 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 pulse-modulated electromagnetic-wave 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, and a frequency separation between the pulse modulated electromagnetic waves in two pulse-modulated electromagnetic-waves within a first group being different from a frequency separation between the pulse modulated electromagnetic waves in two pulse-modulated electromagnetic-waves within a second group;
- detecting a characteristic of a beat signal between a given pair of pulse modulated electromagnetic waves that are scattered by the medium;
- and
- sampling said detected characteristic based on the common pulse width so as to examine said medium in sections having a width equal to the common pulse width.
1 more element
A method comprising
- launching into a medium a plurality of groups of pulse-modulated electromagnetic-waves, each pulse-modulated electromagnetic-wave having a common pulse width, the frequency separation between the pulse modulated electromagnetic waves in two pulses within a first group being different from the frequency separation between the pulse modulated electromagnetic waves in two pulses within a second group;
- detecting a characteristic of a beat signal between a given pair of pulse modulated electromagnetic waves that are scattered by the medium;
- and
- sampling said detected characteristic based on the common pulse width so as to examine said medium in sections having a width equal to the common pulse width.
1 more element
A apparatus comprising:
- 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 characteristic of a beat signal between a given pair of pulse modulated electromagnetic waves that are scattered by the medium;
- and
- means for sampling said detected characteristic based on the common pulse width so as to examine said medium in sections having a width equal to the common pulse width.
1 more element
Dependencies are inferred from the claim text.