Broadband Optical Source for Distributed Sensing Noise Rejection
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Solution Overview
Problem
Current distributed acoustic sensing systems face limitations in noise rejection, disturbance location accuracy, immunity to vibration, robustness, stability, and reliability due to high coherence length requirements, which increase system cost and complexity, and are prone to phase noise and non-linear effects that limit sensitivity and measurement range.
Innovation Solution
A distributed optical sensing system utilizing a broadband optical source with reduced coherence length and a phase and amplitude receiver for accurate measurement of optical path length changes, enabling improved noise rejection and increased accuracy with minimal system complexity and cost.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If high coherence length optical sources are used, then measurement sensitivity is improved, but system cost and complexity increase
Solution Approach 1:
The patent changes the coherence length parameter from high (conventional) to low (invention), using broadband optical sources with coherence lengths of 1mm to 100mm instead of conventional high coherence sources. This parameter change resolves the contradiction by achieving adequate measurement sensitivity through alternative mechanisms (phase and amplitude detection of backscattered light) while dramatically reducing system cost and complexity by eliminating the need for highly coherent, expensive laser sources
2Measurement precision
If high coherence length optical sources are used, then measurement sensitivity is improved, but phase noise and non-linear effects increase
Solution Approach 1:
The patent changes the coherence length parameter to reduce phase noise and non-linear effects. By using broadband sources with shorter coherence lengths, the system avoids the phase noise and non-linear optical effects that plague high coherence systems, while maintaining measurement sensitivity through distributed backscatter detection of both phase and amplitude
Solution Approach 2:
The patent converts the typically harmful effect of low coherence (which limits interference range) into a benefit by using it to reduce phase noise and non-linear effects. The shorter coherence length naturally filters out unwanted phase noise and prevents non-linear optical effects, turning what is usually a limitation into an advantage for stable, long-term sensing
3Reliability
If intensity variation detection is used, then disturbance detection is achieved, but quantitative measurement accuracy deteriorates
Solution Approach 1:
The patent transitions from one-dimensional intensity detection to two-dimensional detection by measuring both phase and amplitude dimensions of the backscattered light. This dimensional expansion allows the system to maintain reliable disturbance detection while achieving accurate quantitative measurements, as the phase information provides precise optical path length change data and amplitude provides complementary intensity information
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
The system achieves enhanced sensitivity and accuracy in measuring optical path length changes with improved noise rejection and robustness, allowing for quantitative and distributed measurement of multiple disturbances along an optical fiber, overcoming the limitations of existing systems.
Implementation Method 1
A distributed optical sensing system utilising a broadband optical source with reduced coherence length
Implementation Method 2
a phase and amplitude receiver for accurate measurement of optical path length changes, enabling improved noise rejection and increased accuracy with minimal system complexity and cost
Implementation Method 3
The system achieves enhanced sensitivity and accuracy in measuring optical path length changes with improved noise rejection and robustness
Data Source
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AI summary
A distributed optical detection system comprising: a broadband optical source; and a phase and amplitude receiver for measuring phases and amplitudes of distributed backscattered signals from a sensing medium. Methods of quantitatively sensing optical path length changes along a sensing medium in a distributed manner are also disclosed.