Optical Fiber Strain Sensing via Rayleigh Speckle Tracking

Resolve Bottlenecks,
Find Innovative SolutionsGenerate Solutions

Solution Overview

Problem

Standard φ-OTDR sensors are unable to make quantitative measurements of strain using Rayleigh backscattered light, and phase-measuring coherent sensors are expensive and susceptible to interference fading.

Innovation Solution

A system that generates a pulsed optical beam and records the evolution of a speckle pattern in the reflected beam to calculate strain in an optical fiber, using a controller to analyze data from a detector and calculate strain from the evolution of the speckle pattern.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If standard φ-OTDR sensors are used for strain measurement, then the system is simple and cost-effective, but quantitative measurement capability is lost

Engineering Contradiction:

Improvequantitative strain measurement capabilityVSAvoidsystem complexity

Core Design Contradiction:

Measurement precisionVSDevice complexity

Solution Approach 1:

The patent changes the measurement parameter from phase detection to amplitude detection of Rayleigh backscattered light. By monitoring amplitude variations of speckle patterns instead of phase information, the system achieves quantitative strain measurement without requiring complex coherent detection equipment, thus resolving the contradiction between measurement precision and device complexity

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent substitutes the mechanical/physical phase measurement system with an optical amplitude measurement system. Instead of using interferometric phase detection methods, the invention uses amplitude-based speckle pattern analysis to extract strain information, simplifying the overall system while maintaining quantitative measurement capability

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

2Measurement precision

If phase-measuring coherent φ-OTDR sensors are used, then quantitative measurement capability is achieved, but equipment cost and complexity increase

Engineering Contradiction:

Improvequantitative strain measurement capabilityVSAvoidequipment sophistication

Core Design Contradiction:

Measurement precisionVSDevice complexity

Solution Approach 1:

The patent employs a simpler, more cost-effective detection approach using amplitude-based speckle analysis instead of expensive coherent phase measurement equipment. This substitution provides quantitative strain measurement capability at a lower equipment sophistication level, directly addressing the contradiction between measurement precision and device complexity

Inventive Principle:

Principle #27Cheap short-living objects (Disposable)

3Measurement precision

If phase-measuring coherent φ-OTDR sensors are used, then quantitative measurements are possible, but susceptibility to interference fading increases

Engineering Contradiction:

Improvequantitative strain measurement capabilityVSAvoidsusceptibility to interference fading

Core Design Contradiction:

Measurement precisionVSReliability

Solution Approach 1:

The patent converts the traditionally problematic Rayleigh scattering phenomenon, which causes interference fading in coherent systems, into a useful resource. By using amplitude-based speckle pattern analysis, the system transforms the random scattering effects that cause fading into a measurable signal for quantitative strain detection, thereby improving reliability while maintaining measurement precision

Inventive Principle:

Principle #22Blessing in disguise (Convert harm into benefit)

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 quantitative measurement of strain in optical fibers without the need for expensive equipment, providing accurate strain data without requiring calibration and maintaining sensitivity over extended fiber lengths.

Implementation Method 1

In Rayleigh scattering, light elastically scatters off of naturally occurring fluctuations in a fiber density and refractive index

Methodology Applied

Scientific EffectRayleigh scattering: Rayleigh Scattering

Implementation Method 2

tracks an evolution of a speckle pattern carried by the reflected beam from the plurality of frames of data

Methodology Applied

Scientific EffectSpeckle pattern formation:

Data Source

PatentUS11788908B2Methods and apparatuses for quantitative sensing using Rayleigh scattering in optical fiber

Publication Date: 2023.10.17 THE GOVERNMENT OF THE UNITED STATES OF AMERICA AS REPRESENTED BY THE SECRETARY DEPARTMENT OF HEALTH & HUMAN SERVICES

AI summary

Methods and apparatuses for quantitatively measuring strain in an optical fiber. An optical source comprising an optical beam generator and a pulse generator receives instructions from a controller and generates a pulsed optical beam in response to those instructions. The pulsed optical beam is directed into an optical fiber to generate a reflected beam from scattering centers within the optical fiber. A detector records a plurality of frames of data generated by the reflected beam, and the controller tracks an evolution of a speckle pattern carried by the reflected beam from the plurality of frames and calculates a strain induced in a section of the optical fiber from the evolution of the speckle pattern.