Distributed Acoustic Sensor Lateral Offset Determination
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Solution Overview
Problem
Distributed acoustic fibre optic sensors cannot determine the lateral offset of the origin of an acoustic wave relative to the sensing fibre, only indicating whether an acoustic disturbance has occurred along the fibre but not providing information on its point of origin in relation to the fibre.
Innovation Solution
The use of time of arrival techniques to analyze signals from multiple longitudinal sensing portions of the fibre, determining the direction and distance of the acoustic wave source by calculating the difference in time of arrival at different fibre sections, and employing fibre geometry with offset sensing portions to resolve positional ambiguities, along with frequency analysis to determine range and attenuation patterns.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If distributed acoustic fibre optic sensors are used to detect acoustic disturbances along the fibre, then the sensing coverage along the fibre length is improved, but the ability to determine lateral offset and direction of the acoustic source is lost
Solution Approach 1:
The patent transitions from one-dimensional sensing (along the fibre length only) to two-dimensional or three-dimensional localization by incorporating transverse spatial coordinates. Multiple fibres arranged in a spatial configuration enable determination of lateral offset and direction by analyzing time differences of arrival and signal characteristics across multiple sensing elements positioned at different locations in space.
2Measurement precision
If time of arrival techniques are applied to determine acoustic source location, then lateral offset and direction information is obtained, but signal processing complexity increases
Solution Approach 1:
The patent replaces complex mechanical or geometric positioning systems with optical signal-based localization. By using time of arrival measurements and signal characteristic analysis from multiple fibres, the system achieves accurate source localization through computational methods rather than physical positioning mechanisms, reducing mechanical complexity while maintaining measurement precision.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
Enables the determination of the lateral offset and direction of an acoustic wave source from the fibre, providing accurate location information in two or three dimensions, enhancing the capability to detect and monitor acoustic events in various applications.
Implementation Method 1
The Rayleigh backscattering of light from intrinsic reflection sites within the fibre is sampled and demodulated at the frequency difference between the pulses in a group
Data Source
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AI summary
Techniques for determining lateral offset of the source of an acoustic disturbance in a distributed acoustic fibre optic sensor are described. The sensor comprises an optical source (112) for interrogating an optical fibre (104) and a detector (116) and processor (108) arranged to detect any backscattered radiation and determine a measurement signal for a plurality of discrete longitudinal sensing portions of the optical fibre. The processor is also arranged to analyse the measurement signals to identify signals corresponding to the same acoustic wave arriving at different parts of the fibre and determine from the time of arrival of said acoustic wave the direction and/or distance of the origin of said acoustic wave from the optical fibre. The geometry of the fibre may be arranged to ensure that any positional ambiguity can be resolved and the use of multiple fibres (501, 502) is disclosed.