Detection of moving objects
First Claim
1. A distributed acoustic sensor apparatus comprising:
- an interrogator unit for, in use, interrogating an optical fibre with optical radiation and producing a measurement signal indicative of incident acoustic signals from each of a plurality of sensing portions of said optical fibre; and
a processor configured to analyse said measurement signals to identify a signal characteristic of a Doppler shift so as to detect a moving object wherein the characteristic of a Doppler shift comprises a change in frequency over time of an acoustic signal detected at a particular sensing portion of the optical fiber and wherein the processor is configured to analyze the measurement signals from a plurality of sensing portions to determine a rate of change of frequency of a detected acoustic signal and to determine the time at which the maximum rate of change of frequency occurs for each sensing portion wherein in response to identifying the signal characteristic of the Doppler shift to detect the moving object, providing an alert that the moving object has been detected.
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Accused Products
Abstract
A system for moving object (402) detection is provided, the system comprising a fiber optic interrogator (106) adapted to provide distributed acoustic sensing on a optic fiber (104), for example arranged along a border. The measurement signals from each of a plurality of sensing portions (404, 406, 408, 410, 412) of said fiber are analyzed to determined a characteristic of a Doppler shift. The characteristic of a Doppler shift may be a generally continuous decrease in detected frequency. By detecting the time at which the rate of change of frequency is at a maximum for each of the sensing portions the time of closest approach (ti, t2, t3, t4, t5) of the object to those sensing portions can be determined with the sensing portion the object approaches closest to showing the greatest value of maximum rate of change of frequency. The distance of closest approach and velocity can be determined.
14 Citations
24 Claims
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1. A distributed acoustic sensor apparatus comprising:
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an interrogator unit for, in use, interrogating an optical fibre with optical radiation and producing a measurement signal indicative of incident acoustic signals from each of a plurality of sensing portions of said optical fibre; and a processor configured to analyse said measurement signals to identify a signal characteristic of a Doppler shift so as to detect a moving object wherein the characteristic of a Doppler shift comprises a change in frequency over time of an acoustic signal detected at a particular sensing portion of the optical fiber and wherein the processor is configured to analyze the measurement signals from a plurality of sensing portions to determine a rate of change of frequency of a detected acoustic signal and to determine the time at which the maximum rate of change of frequency occurs for each sensing portion wherein in response to identifying the signal characteristic of the Doppler shift to detect the moving object, providing an alert that the moving object has been detected. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18)
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19. A method of distributed acoustic sensing comprising:
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interrogating an optical fibre with optical radiation and producing a measurement signal indicative of incident acoustic signals from each of a plurality of sensing portions of said optical fibre; analysing said measurement signals to identify a signal characteristic of a Doppler shift so as to detect a moving object wherein the characteristic of a Doppler shift comprises a change in frequency over time of an acoustic signal detected at a particular sensing portion of the optical fiber; and
wherein the processor is configured to analyze the measurement signals from a plurality of sensing portions to determine a rate of change of frequency of a detected acoustic signal and to determine the time at which the maximum rate of change of frequency occurs for each sensing portion; andproviding an output of an indication of the heading and/or distance of the moving object with respect to the optical fibre. - View Dependent Claims (20, 21, 22)
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23. A distributed acoustic sensor apparatus comprising:
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a length of optical fibre having a plurality of sensing portions; an interrogator unit attached to an end of the optical fibre, the interrogator unit interrogating an the optical fibre with optical radiation and producing a measurement signal indicative of incident acoustic signals from each of a plurality of sensing portions of said optical fibre; a processor configured to analyse said measurement signals to identify a signal characteristic of a Doppler shift to thereby detect a moving object wherein the characteristic of a Doppler shift comprises a change in frequency over time of an acoustic signal detected at a particular sensing portion of the optical fiber and wherein the processor is configured to analyze the measurement signals from the plurality of sensing portions to determine a rate of change of frequency of a detected acoustic signal and to determine the time at which the maximum rate of change of frequency occurs for each sensing portion; and an output triggered by the processor upon detection of the moving object. - View Dependent Claims (24)
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Specification