Fiber Bragg Grating Fluid Leak Detection via Strain-Induced Optical Shift
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Solution Overview
Problem
Current fiber optic leak detection systems for pipelines face limitations in detecting small leaks with high spatial resolution due to low signal-to-noise ratios and the need for large numbers of measurements, leading to false positives and costly, unstable chemical sensors, while fiber Bragg grating sensors are limited by the number of sensing elements and fiber length they can effectively monitor.
Innovation Solution
A system utilizing fiber Bragg grating sensors encapsulated in packages that apply strain when exposed to fluids, allowing for detection of changes in optical properties through laser interrogation, with the option of tensile or compressive strain and athermal packaging to minimize false positives and extend monitoring capabilities.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If distributed temperature sensing (DTS) or distributed acoustic sensing (DAS) techniques are used to detect leaks, then the ability to detect small leakages with high spatial resolution is improved, but the signal-to-noise ratio is low requiring large numbers of measurements which generates large amounts of data and false positives
Solution Approach 1:
The patent introduces a chemical intermediary substance that reacts with hydrocarbons to produce a detectable signal. This intermediary approach converts the weak thermal or acoustic signals into stronger optical signals through chemical reaction, thereby improving the signal-to-noise ratio while maintaining spatial resolution and reducing false positives.
Solution Approach 2:
The patent replaces the thermal/acoustic sensing mechanism with a chemical-optical sensing mechanism. Instead of detecting temperature changes or acoustic waves directly, the system uses chemical reactions that produce optical signals, which are easier to detect with higher signal-to-noise ratios and can be localized more precisely along the fiber optic cable.
2Measurement precision
If fiber Bragg grating sensors are used to detect fluid presence, then the detection sensitivity is improved, but the number of sensing elements and fiber length that can be effectively monitored is limited
Solution Approach 1:
The patent divides the sensing system into multiple discrete fiber Bragg grating sensor elements distributed along the fiber optic cable. Each grating acts as an independent sensing point, allowing the system to cover long distances while maintaining high detection sensitivity at each location. The segmented approach enables monitoring of extended pipeline lengths without signal degradation.
3Reliability
If chemical sensors are used to detect hydrocarbons, then the detection effectiveness is improved, but the cost increases and the stability of the chemically sensitive coating decreases over time
Solution Approach 1:
The patent uses fiber Bragg grating sensors that detect physical changes (strain, temperature) caused by chemical reactions rather than requiring direct contact between the sensing element and the chemical substance. This indirect detection method copies the chemical interaction effect into a physical measurement, eliminating the need for unstable chemical coatings while maintaining detection effectiveness.
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
Enhances the detection of fluid leaks by improving signal-to-noise ratios and reducing false positives, enabling more accurate and efficient monitoring of longer pipeline lengths with increased sensitivity and reduced mechanical fiber degradation.
Implementation Method 1
mounting a sensor array proximate a conduit for said fluid, said sensor array comprising a plurality of Bragg grating sensing elements within an optical waveguide, each Bragg grating sensing element being encapsulated in a package for subjecting the Bragg grating sensing element to a change in strain when contacted by said fluid
Implementation Method 2
interrogating said sensor array with laser light to detect any change in the optical properties of the Bragg grating sensing elements due to the change in strain
Data Source
AI summary
An apparatus, method and system are set forth for detection of fluids using Bragg grating sensors, wherein the Bragg grating sensing element comprises an optical fiber having a Bragg grating inscribed therein characterized by optical properties that are dependent upon the periodicity and effective refractive index of the grating, and a package for subjecting the Bragg grating to a change in strain when contacted by a fluid such that periodicity and effective refractive index of the grating changes, whereby when interrogated with laser light any such change in periodicity and effective refractive index may be detected.