Acoustically Coupled Dual-Path Optical Disturbance Sensing
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Solution Overview
Problem
Existing interferometric techniques for sensing disturbances along optical links, such as acoustic waves, are unsuitable for long haul links due to the need for backscattering or reflection, which is blocked by repeater amplifiers with optical isolators.
Innovation Solution
A sensing system with two acoustically coupled optical paths, where one path has a delay stage upstream and the other downstream of the sensing region, allowing for interferometric signal combination to detect disturbances without requiring backscattering or reflection, using optical fibres in a common jacket or separate cables with spaced apart clips.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If backscattering or reflection is used for sensing disturbances, then sensing capability is achieved, but the technique becomes unsuitable for long haul links with repeater amplifiers
Solution Approach 1:
Instead of using backscattering or reflection to sense disturbances, the patent uses forward-propagating light in a dual-path interferometric configuration. The sensing is achieved by comparing phase differences between two forward-propagating paths rather than analyzing backscattered light, thereby eliminating the conflict with optical isolators in repeater amplifiers.
Solution Approach 2:
The patent introduces an acoustic coupling medium that mechanically couples the two optical paths without requiring optical backscattering. This intermediary mechanism allows disturbance sensing through acoustic wave coupling between paths while maintaining forward-only light propagation, resolving the contradiction between sensing capability and compatibility with repeater amplifiers.
2Measurement precision
If delay stages are introduced to realign signal copies, then system sensitivity is maintained, but dispersion may increase
Solution Approach 1:
The patent carefully controls the delay parameter to be within the coherence time of the light source, optimizing the balance between maintaining system sensitivity through proper signal realignment and minimizing dispersion effects. By adjusting the delay parameter within specific bounds, both sensitivity and dispersion control are achieved.
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 effective detection of disturbances along long haul optical links, including seismic events, by maintaining system sensitivity and reducing dispersion, while avoiding the need for backscattered light, making it suitable for applications like underwater sensing.
Implementation Method 1
interferometrically combining light from the first path with light from the second path so as to provide an interferometric signal from which the presence of a disturbance can be inferred
Implementation Method 2
the first and second paths are acoustically coupled in the sensing region, such that, in use, a disturbance experienced at one of the first and second paths is experienced at the other of the first and second paths
Implementation Method 3
A delay stage is provided in each of the first and second paths. The delay stages are arranged such that a temporal offset is imposed between signal copies of a given pair
Data Source
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AI summary
The present invention relates to a system for sensing a disturbance in a sensing region along an optical path. The sensing system includes: a source of optical radiation; an upstream junction for channelling light along a first path and along a second path, the first and second paths each extending through the sensing region in an acoustically coupled relationship, such that, in use, a disturbance experienced at one of the first and second paths is experienced at the other of the first and second paths; and, a downstream junction for combining light from the first path with light from the second path so as to provide an interferometric signal from which the presence of a disturbance can be inferred.