Fiber Segment Interferometry for Bend-Resistant Temperature Sensing

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Solution Overview

Problem

Existing optical fiber sensors for temperature measurement, such as Fiber Bragg Grating and Fiber Segment Interferometry, face challenges in localized temperature measurement due to strain induced by fiber bending and weak measurement signals, especially in environments requiring multiple bends, leading to measurement errors and inefficiencies.

Innovation Solution

An optical sensing method using optical fiber segments with a dedicated sensing element having a higher thermo-optic coefficient than the fiber, featuring reflective surfaces with broadband reflection, allowing temperature measurement by modulating light wavelength and analyzing interference patterns to determine temperature changes.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If Fiber Bragg Grating sensors are used for temperature measurement, then temperature can be measured, but fiber bending induces strain that results in measurement errors

Engineering Contradiction:
Improvetemperature measurement accuracyVSAvoidstrain-induced measurement errors
Core Design Contradiction:
Measurement precisionVSObject-affected harmful factors

Solution Approach 1:

The invention divides the fiber optic sensor into multiple discrete segments, each containing a sensing element and reference reflector. This segmentation allows independent measurement zones that are not affected by strain in other segments, eliminating the propagation of strain-induced errors along the fiber length.

Inventive Principle:
Principle #1Segmentation

Solution Approach 2:

The invention introduces a reference reflector as an intermediary element within each fiber segment. By comparing the optical path length changes of the sensing element against this stable reference, the system can differentiate between temperature-induced changes and strain-induced changes, thereby compensating for bending effects.

Inventive Principle:
Principle #24Intermediary (Mediator)

2Adaptability or versatility

If multiple fiber bends are required to route sensors around battery cells, then sensor coverage is improved, but strain on the fiber increases causing measurement errors

Engineering Contradiction:
Improvesensor routing flexibilityVSAvoidtemperature measurement accuracy
Core Design Contradiction:
Adaptability or versatilityVSMeasurement precision

Solution Approach 1:

By segmenting the sensor into discrete units with local reference reflectors, the invention enables flexible routing around battery cells while maintaining measurement accuracy in each segment. Each segment operates independently, so bending in one segment does not affect measurements in other segments.

Inventive Principle:
Principle #1Segmentation

Solution Approach 2:

The invention applies local quality by providing each fiber segment with its own reference reflector and sensing element configured for optimal local performance. This allows each segment to be optimized for its specific installation location, maintaining high measurement precision even when routed around complex battery pack geometries.

Inventive Principle:
Principle #3Local quality

3Measurement precision

If Fiber Segment Interferometry is used for localized temperature measurement, then localization is improved, but measurement signal strength remains weak

Engineering Contradiction:
Improvelocalized temperature measurement capabilityVSAvoidmeasurement signal strength
Core Design Contradiction:
Measurement precisionVSUse of energy by moving object

Solution Approach 1:

The invention merges the advantages of Fiber Segment Interferometry with enhanced reflector designs and optical cavity configurations. By combining multiple reflective interfaces and optimizing the optical path within each segment, the system amplifies the measurement signal while maintaining localized temperature measurement capability.

Inventive Principle:
Principle #5Merging (Combining)

Solution Approach 2:

The invention utilizes parameter changes by varying the optical cavity lengths, reflector positions, and sensing element characteristics within each fiber segment. These parameter optimizations enhance the interferometric signal strength and improve the sensitivity of localized temperature measurements without requiring increased system complexity.

Inventive Principle:
Principle #35Parameter changes

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 method enables accurate temperature measurement without fiber curvature, enhancing measurement accuracy and sensitivity by leveraging the thermo-optic coefficient of the sensing element, reducing strain-induced errors and improving signal strength.

Implementation Method 1

the sensing element has a thermo-optic coefficient larger than the thermo-optic coefficient of the fiber

Methodology Applied
Scientific EffectThermo-optic coefficient: Electro-Optic Effects

Implementation Method 2

The first reflective surface is parallel to the second reflective surface

Methodology Applied
Scientific EffectReflection: Reflection

Implementation Method 3

analyzing interference patterns to determine temperature changes

Methodology Applied
Scientific EffectInterference: Interference

Data Source

PatentEP4686924A1Optical sensing method and optical sensor system for an optical sensing method
Publication Date: 2026.02.04 KISTLER HLDG AG
  • EP4686924A1 patent drawingFigure 1~3
  • EP4686924A1 patent drawingFigure 4~6
  • EP4686924A1 patent drawingFigure 7~9

AI summary

The invention relates to an optical sensor system (100) adapted for a sensing method using fiber segment interferometry, wherein a sensing element 1.i with a thermo-optic coefficient larger than the thermo-optic coefficient of an optical fiber 73.i is arranged at a distal end of the fiber 73.