Asymmetric Optical Cable Neutral Plane Shift for Bending Sensitivity
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Solution Overview
Problem
Current optical cables used in distributed acoustic monitoring for wells lack sufficient sensitivity, particularly in applications like vertical seismic profiling, where increased fiber sensitivity is needed.
Innovation Solution
The optical cable design includes an outer tubing with an asymmetric stiffness configuration and a stiffening member that shifts the neutral plane away from the optical fiber, positioning the fiber closer to the outer periphery, thereby increasing the strain and sensitivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the optical fiber is placed at the center of the cable, then the cable structure is simple and symmetric, but the bending sensitivity is insufficient
Solution Approach 1:
The patent applies asymmetry by positioning the optical fiber off-center within the cable, specifically at a location where the distance to the neutral plane is greater than the distance to the cable center. This asymmetric placement increases the fiber's exposure to strain during cable bending, thereby enhancing bending sensitivity while maintaining a relatively simple overall cable structure.
Solution Approach 2:
The patent implements local quality by creating a specific structural configuration where the distance from the optical fiber to the neutral plane is optimized. This local structural modification at the fiber placement location increases strain concentration without requiring complex modifications to the entire cable structure, thus improving sensitivity with minimal added complexity.
2Measurement precision
If the optical fiber is placed nearer to the outside of the cable, then the bending sensitivity increases, but the distance from the neutral plane increases which may reduce signal stability
Solution Approach 1:
The patent applies parameter changes by precisely controlling the fiber's radial position within the cable. The fiber is placed at an optimized distance from the cable center that maximizes the distance to the neutral plane for enhanced sensitivity, while still maintaining adequate signal stability. This optimal parameter selection balances both sensitivity and reliability requirements.
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
This design enhances the bending sensitivity of the optical fiber, leading to a stronger optical signal and improved detection capabilities in downhole monitoring applications.
Implementation Method 1
recording the light that is reflected back via Rayleigh backscatter
Implementation Method 2
a stiffening member configured to bend with bending of the outer tubing; wherein the stiffening member shifts a neutral plane of the cable away from the at least one optical fiber
Implementation Method 3
an outer tubing having a central axis, a stiffness of the outer tubing asymmetric with respect to the central axis
Data Source
AI summary
An optical cable includes an outer tubing. At least one optical fiber disposed within the outer tubing. A stiffening member configured to bend with bending of the outer tubing; wherein the stiffening member shifts a neutral plane of the cable away from the at least one optical fiber. Also included is a method of increasing a bending sensitivity in an optical cable.