Distributed backscattering
First Claim
1. A method of monitoring an optical waveguide to detect a dynamic physical disturbance of the optical waveguide, the method comprising:
- transmitting pairs of signal copies of a signal output from an optical source onto an optical waveguide including a sensing portion along which a transmitted signal senses a disturbance along the sensing portion, and a return portion, for returning said transmitted signal by a process of distributed backscattering towards the sensing portion;
receiving returned backscattered signals generated by the signal copies previously transmitted onto the optical waveguide;
for returned backscattered signal components of the signal copies, combining a backscattered component of one signal copy of a pair with the other signal copy of that pair, such that, from the combination of the two backscattered component signal copies of a pair, a combination signal is generated; and
generating a disturbance alert signal from the combination signal,wherein the backscattered component signal copies are returned from said return portion by a process of distributed backscattering along the optical waveguide.
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Accused Products
Abstract
The present invention relates to a method for detecting or inferring a physical disturbances on a communications link, in particular by using distributed backscattering. The method includes the steps of: transmitting test signals onto a link; receiving test signals returned from a remote portion of the link; performing a function on the returned test signals; and in dependence on at least one characteristic of the combination signal, inferring the presence of a disturbance. The test signal are returned by a process Rayleigh backscattering along the fibre, so existing fibre installations can be used without requiring a mirror to be specifically introduced.
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Citations
29 Claims
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1. A method of monitoring an optical waveguide to detect a dynamic physical disturbance of the optical waveguide, the method comprising:
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transmitting pairs of signal copies of a signal output from an optical source onto an optical waveguide including a sensing portion along which a transmitted signal senses a disturbance along the sensing portion, and a return portion, for returning said transmitted signal by a process of distributed backscattering towards the sensing portion; receiving returned backscattered signals generated by the signal copies previously transmitted onto the optical waveguide; for returned backscattered signal components of the signal copies, combining a backscattered component of one signal copy of a pair with the other signal copy of that pair, such that, from the combination of the two backscattered component signal copies of a pair, a combination signal is generated; and generating a disturbance alert signal from the combination signal, wherein the backscattered component signal copies are returned from said return portion by a process of distributed backscattering along the optical waveguide. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23)
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24. A method of using distributed backscattering in a waveguide to detect or infer the presence of a disturbance in the waveguide, wherein the disturbance is a dynamic disturbance, comprising:
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(a) transmitting outbound test signals along the fibre, which test signals are formed as pairs of signal copies of a signal from an optical source; (b) receiving inbound test signals, which inbound test signals are formed by a backscattered component of the outbound test signals arising from distributed backscattering of the outbound test signals along a remote portion of the fibre; and (c) combining the respective copies of each pair of received inbound test signals in order to detect or infer the presence of a disturbance, the disturbance being located such that at least some of the received inbound signals are affected by the disturbance. - View Dependent Claims (25, 26, 27)
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28. An optical waveguide sensor arranged to detect a dynamic physical disturbance, the sensor including:
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an optical waveguide comprising; a sensing portion along which a transmitted signal senses a disturbance along the sensing portion, and a return portion, for returning a said transmitted signal by a process of distributed backscattering towards the sensing portion, and at the near end of the optical waveguide; a signal transmitter for transmitting pairs of signal copies of a signal from an optical source onto the optical waveguide; an optical receiver for receiving returned backscattered components of signal copies previously transmitted onto the optical waveguide; and a signal processing system for processing returned backscattered components of signal copies by combining a backscattered component signal of one signal copy of a pair with a backscattered component signal of the other signal copy of that pair, such that, from the combination of the two backscattered component signals of the signal copies of a pair, a combination signal is generated; and
, from the combination signal, a disturbance alert signal is generated,wherein the signal copies are returned from said return portion by a process of distributed backscattering along the optical waveguide. - View Dependent Claims (29)
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Specification