Optical Fibre Cable Asymmetric Buffer Pressure Sensing
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Solution Overview
Problem
Existing optical fiber cables for detecting pressure in fluids face challenges such as high manufacturing costs, limited pressure range, and reduced sensitivity as the measurable pressure range increases, due to the use of side-hole fibers which are difficult and expensive to produce.
Innovation Solution
An optical fiber cable with a standard single mode fiber surrounded by an asymmetric buffer that deforms under isotropic pressure, inducing asymmetric strain and birefringence, allowing for the detection of pressure distribution along a fluid path using polarimetry on backscattered light, with varying buffer thickness and potentially multiple fibers for different sensitivity ranges.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If side-hole fibre is used to convert isotropic pressure to anisotropic deformation, then pressure measurement sensitivity is improved, but manufacturing cost and difficulty increase
Solution Approach 1:
The patent replaces expensive side-hole fibres with standard single-mode fibres that are inexpensive and readily available. The asymmetric buffer structure is simple to manufacture using conventional techniques, making the overall sensor cable cost-effective while maintaining pressure measurement functionality
Solution Approach 2:
The patent introduces asymmetry at the buffer level rather than requiring asymmetric fibre construction. The asymmetric buffer deforms under isotropic pressure to create asymmetric strain on the standard fibre, achieving the same effect as side-hole fibres but with simpler manufacturing
2Stress or pressure
If fibre construction is designed for large pressure range, then maximum measurable pressure increases, but absolute sensitivity to pressure changes decreases
Solution Approach 1:
The asymmetric buffer creates localized strain concentration in specific regions of the fibre where the buffer thickness varies. This local strain concentration maintains high sensitivity even when the overall pressure range is large, as the strain is focused in critical areas rather than distributed uniformly
Solution Approach 2:
The patent uses multiple fibres with different buffer asymmetricities or positions to create a set of sensors with different sensitivities. By selecting appropriate fibres for different pressure ranges, the system can maintain high absolute sensitivity across various maximum pressure ranges
3Ease of manufacture
If standard single mode fibre is used instead of side-hole fibre, then manufacturing cost decreases, but the ability to convert isotropic pressure to detectable anisotropic strain is lost
Solution Approach 1:
The asymmetric buffer acts as an intermediary that converts isotropic pressure into asymmetric strain on the standard fibre. The buffer mediates between the isotropic pressure field and the fibre, creating the necessary anisotropic deformation for detection without requiring modified fibre construction
Solution Approach 2:
The patent replaces the mechanical asymmetry built into side-hole fibres with a separate asymmetric buffer structure. This substitution allows standard fibres to be used while achieving the same strain conversion function through the buffer's asymmetric deformation under pressure
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 solution enables cost-effective, high-sensitivity measurement of pressure over large ranges by converting isotropic pressure into asymmetric strain in the fiber, allowing for precise spatial distribution mapping of fluid pressure along extended paths like pipelines or oil wells.
Implementation Method 1
asymmetric strain which changes the birefringence of the one or more optical fibres
Implementation Method 2
strain induced changes in birefringence of at least one of the optical fibres
Implementation Method 3
The related technique of optical time domain reflectometry (OTDR) is commonly used in telecommunications for verifying the performance of optical fibre
Implementation Method 4
detecting light reflected or backscattered from the fibre
Implementation Method 5
a buffer or casing surrounding the optical fibre and is adapted to deform asymmetrically under isotropic pressure
Data Source
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AI summary
An optical fibre cable for distributed fibre sensing of fluid pressure is disclosed. There are also disclosed a method and an apparatus for distributed fibre sensing of fluid pressure using the optical fibre cable. The optical fibre cable is adapted for distributed pressure sensing, and comprises: one or more optical fibres (120); and a buffer (130) surrounding the one or more optical fibres and adapted to deform asymmetrically under isotropic pressure (P) such that the fibre experiences asymmetric strain changing the birefringence of the one or more optical fibres. The optical fibres incorporated in the cable may be conventional single mode optical fibres. The optical fibre cable may be used to determine a pressure distribution along the length of the cable. The cable, apparatus or method may be used to detect pressures over long distances such as in pipes, pipelines, or wells.