Strain Isolated Fiber Bragg Grating Sensor Design

Solution Overview

Problem

Existing methods for isolating strain from fiber Bragg grating sensors in optical fibers within metal tubes are time-consuming and expensive, making it difficult to achieve precise excess fiber length for accurate temperature measurements.

Innovation Solution

A support member is coupled to the ends of the optical fiber section containing the fiber Bragg grating sensor, allowing a length greater than the support member itself, thereby isolating the sensor from strain through rigid or flexible supports, which can be coupled using techniques like bonding with epoxy, to minimize strain during temperature fluctuations.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If controlled operations are used to place the optical fiber within the metal tube to achieve specific excess fiber length, then strain isolation and measurement precision are improved, but manufacturing time and cost increase significantly

Engineering Contradiction:

Improvetemperature measurement accuracyVSAvoidmanufacturing time

Core Design Contradiction:

Measurement precisionVSLoss of time

Solution Approach 1:

The optical fiber is divided into three distinct sections: a first section with FBG sensors that needs strain isolation, a second intermediate section that provides the excess length, and a third section for connection. This segmentation allows the intermediate section to absorb strain while keeping the sensor section isolated, eliminating the need for time-consuming controlled placement operations.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The intermediate section of the optical fiber acts as a mediator between the sensor section and the connection section. It provides the necessary excess length that isolates the FBG sensors from strain applied to the fiber during installation and operation, thereby enabling accurate temperature measurements without requiring precise controlled placement.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Measurement precision

If controlled operations are used to place the optical fiber within the metal tube to achieve specific excess fiber length, then strain isolation and measurement precision are improved, but manufacturing complexity and cost increase

Engineering Contradiction:

Improvetemperature measurement accuracyVSAvoidmanufacturing process complexity

Core Design Contradiction:

Measurement precisionVSDevice complexity

Solution Approach 1:

The optical fiber is divided into three distinct sections: a first section with FBG sensors that needs strain isolation, a second intermediate section that provides the excess length, and a third section for connection. This segmentation allows the intermediate section to absorb strain while keeping the sensor section isolated, eliminating the need for time-consuming controlled placement operations.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The invention changes the structural parameter of the optical fiber by incorporating an intermediate section with specific length characteristics. This parameter change (adding the intermediate section) simplifies the manufacturing process by eliminating the need for precise controlled placement operations while maintaining the necessary strain isolation for accurate measurements.

Inventive Principle:

Principle #35Parameter changes

3Measurement precision

If excess fiber length is increased to isolate FBG sensors from strain, then measurement accuracy is improved, but fiber installation efficiency decreases

Engineering Contradiction:

Improvesensor measurement accuracyVSAvoidfiber installation efficiency

Core Design Contradiction:

Measurement precisionVSProductivity

Solution Approach 1:

The optical fiber is divided into three distinct sections: a first section with FBG sensors that needs strain isolation, a second intermediate section that provides the excess length, and a third section for connection. This segmentation allows the intermediate section to absorb strain while keeping the sensor section isolated, eliminating the need for time-consuming controlled placement operations.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The intermediate section is pre-configured with the appropriate excess length during fiber manufacturing. This preliminary action ensures that when the fiber is installed in the metal tube, the strain isolation is already in place, eliminating the need for time-consuming post-installation adjustments and improving installation efficiency.

Inventive Principle:

Principle #10Preliminary action

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 solution effectively reduces strain on the fiber Bragg grating sensors, enhancing measurement accuracy and allowing for efficient installation of optical fibers with excess length into tubes, suitable for harsh environments.

Implementation Method 1

The optical fiber may have a section containing a fiber Bragg grating (FBG) sensor

Methodology Applied

Scientific EffectFiber Bragg grating: Bragg Diffraction

Data Source

PatentUS10451807B2Strain isolated fiber Bragg grating sensors

Publication Date: 2019.10.22 WEATHERFORD TECHNOLOGY HOLDINGS LLC

AI summary

A sensing device is used for measuring physical characteristics. The sensing device may include an optical fiber disposed in a tube. The optical fiber may have a section containing a fiber Bragg grating (FBG) sensor. A support member may be coupled to the ends of the section, such that the section includes a length greater than a length of the portion of the support member disposed between the ends of the section. The support member is configured to isolate the FBG sensor from strain in the optical fiber.