Fibre-Optic Measurement System Using Mode Filtering for Multi-Mode Fibre Sensing

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Solution Overview

Problem

Current fibre-optic measurement systems face limitations in using multi-mode optical fibres due to signal detection challenges and non-linear phenomena, which restrict their application in distributed measurements for temperature, strain, and pressure sensing, especially in telecommunications networks.

Innovation Solution

A fibre-optic measurement system equipped with a selective mode device and processing unit that implements OFDR or COTDR techniques, allowing the use of multi-mode optical fibres by selectively filtering higher-order modes and separating optical distance changes caused by different variables, enabling simultaneous measurement of temperature and strain.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Adaptability or versatility

If multi-mode optical fibres are used for distributed measurements, then the application scope in telecommunications networks is expanded, but signal detection becomes impossible due to differences in light propagation speed between modes and spatial distribution

Engineering Contradiction:

Improveapplication scopeVSAvoidsignal detection

Core Design Contradiction:

Adaptability or versatilityVSDifficulty of detecting and measuring

Solution Approach 1:

The patent extracts and eliminates the problematic higher-order modes from the multi-mode optical fibre by introducing a mode filter that selectively removes modes other than the fundamental mode, thereby enabling signal detection while preserving the use of multi-mode fibres for expanded applications

Inventive Principle:

Principle #2Taking out (Extraction)

Solution Approach 2:

The patent introduces a mode filter as an intermediary device between the light source and the multi-mode optical fibre, and between the fibre and the detector. This intermediary selectively transmits only the fundamental mode while blocking higher-order modes, thus mediating the conflict between using multi-mode fibres and achieving signal detection

Inventive Principle:

Principle #24Intermediary (Mediator)

2Difficulty of detecting and measuring

If single-mode optical fibres are used for distributed measurements, then signal detection is enabled, but the maximum measurement distance is limited due to non-linear effects that increase with optical power magnitude

Engineering Contradiction:

Improvesignal detectionVSAvoidmaximum measurement distance

Core Design Contradiction:

Difficulty of detecting and measuringVSLength of stationary object

Solution Approach 1:

The patent changes the key parameter from using single-mode fibres with limited power to using multi-mode fibres with filtered higher-order modes, allowing higher optical power to be transmitted without non-linear effects, thereby extending the maximum measurement distance while maintaining signal detection capability

Inventive Principle:

Principle #35Parameter changes

3Power

If higher-order modes are transmitted in multi-mode optical fibres, then optical power transmission capacity is increased, but measurement accuracy deteriorates due to mode-dependent propagation characteristics

Engineering Contradiction:

Improveoptical power transmissionVSAvoidmeasurement accuracy

Core Design Contradiction:

PowerVSMeasurement precision

Solution Approach 1:

The patent removes higher-order modes that cause measurement inaccuracies while preserving the fundamental mode for precise measurements, thereby maintaining measurement accuracy while still allowing optimized power transmission through the fundamental mode

Inventive Principle:

Principle #2Taking out (Extraction)

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 system enhances measurement visibility and accuracy, increasing the maximum measurement distance while avoiding non-linear phenomena, allowing for effective distributed sensing in multi-mode optical fibre networks, particularly in indoor and inter-building telecommunications.

Implementation Method 1

a fibre-optic measurement system (100) equipped with a system for generating radiation (1) and a receiving system (2) connected via an optical path

Methodology Applied

Scientific EffectRayleigh scattering: Rayleigh Scattering

Implementation Method 2

The system uses a single spatial mode filtering system to select a single Rayleigh backscattering circle

Methodology Applied

Scientific EffectMode filtering: Filter (optical)

Data Source

PatentUS12068779B2Fibre-optic measurement system, method of adaptation of the communication optical fibre into a measurement system, and fibre-optic measurement and communication system

Publication Date: 2024.08.20 INPHOTECH

AI summary

A fibre-optic measurement system equipped with a controlled light generation system (1) and a receiving system (2) connected via an optical path which comprises a directional device (4) and which, in addition, has a processing unit (9) for controlling the light generation system (1) and for receiving and processing the signal from the receiving system (2), according to the invention, it is characterized by the fact that it has a selective mode device (5) and is adapted to be connected to a fibre-optic telecommunications network by a selective mode device (5) and the processing unit (9) is adapted to implement the OFDR and/or COTDR measurement technique for measuring changes in the optical distance and processing them into one or more parameters. Moreover, the object of the invention is also the method of adaptation of a telecommunications network into a sensor network and a fibre-optic measurement and communication system.