Evaluating the position of an optical fiber disturbance
First Claim
1. A method of interferometrically evaluating the position of a time varying disturbance on an optical waveguide, comprising:
- transmitting a plurality of outbound sensing signals from a continuous wave incoherent optical source onto the optical waveguide, which outbound sensing signals have imposed thereon a modulation by a modulation signal having a frequency which is dependent, at least in part, on the time of transmission of the outbound sensing signals, wherein the outbound sensing signals are guided along an outbound path along the optical waveguide;
receiving disturbance sensing signals, which are progressively returned from the outbound path by a process of distributed backscattering, wherein the disturbance sensing signals have been exposed to the disturbance, wherein the disturbance sensing signals are returned in a reverse direction along a waveguide portion of the optical waveguide, the waveguide portion comprising the same waveguide portion used to guide the outbound sensing signals in the outbound direction; and
using the previously imposed outbound modulation on the sensing signals, evaluating the position of the disturbance from the progressively returned disturbance sensing signals.
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Abstract
The present invention relates to a method of and apparatus for evaluating the position of a time-varying disturbance on an optical waveguide. The steps include: transmitting sensing signals onto the optical waveguide, which sensing signals have imposed thereon a modulation which is dependent, at least in part, on their time of transmission; receiving returned sensing signals, which signals have been exposed to the disturbance; and, from the previously imposed modulation on the returned sensing signals, evaluating the position of the disturbance. Because the sensing signals have a modulation that is dependent at least in part on their transmission time, the round-trip time for the signals to travel to and from a disturbance can be inferred. From this round trip time, or a value related thereto, it is possible to directly or indirectly evaluate the position of the disturbance.
162 Citations
14 Claims
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1. A method of interferometrically evaluating the position of a time varying disturbance on an optical waveguide, comprising:
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transmitting a plurality of outbound sensing signals from a continuous wave incoherent optical source onto the optical waveguide, which outbound sensing signals have imposed thereon a modulation by a modulation signal having a frequency which is dependent, at least in part, on the time of transmission of the outbound sensing signals, wherein the outbound sensing signals are guided along an outbound path along the optical waveguide; receiving disturbance sensing signals, which are progressively returned from the outbound path by a process of distributed backscattering, wherein the disturbance sensing signals have been exposed to the disturbance, wherein the disturbance sensing signals are returned in a reverse direction along a waveguide portion of the optical waveguide, the waveguide portion comprising the same waveguide portion used to guide the outbound sensing signals in the outbound direction; and using the previously imposed outbound modulation on the sensing signals, evaluating the position of the disturbance from the progressively returned disturbance sensing signals. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13)
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14. Apparatus for interferometrically evaluating the position of a time varying disturbance on an optical waveguide comprising:
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means for transmitting a plurality of outbound sensing signals from a continuous wave incoherent optical source on the optical waveguide, wherein the outbound sensing signals are guided along an outbound path along the optical waveguide; means for imposing on the outbound sensing signals a modulation by a modulation signal having a frequency which is dependent, at least in part, on the time of transmission of the outbound sensing signals, means for receiving disturbance sensing signals which are progressively returned from the outbound path by a process of distributed backscattering, wherein the disturbance sensing signals have been exposed to the disturbance, and wherein the disturbance sensing signals are returned in a reverse direction along a waveguide portion of the optical waveguide, the waveguide portion comprising the same waveguide portion used to guide the outbound sensing signals in the outbound direction; and means for evaluating from the returned signals the position of the disturbance using the previously imposed modulation on the outbound sensing signals.
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Specification