SLED Light Source Noise Reduction in Single Mode Fiber DTS

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Solution Overview

Problem

Single mode distributed temperature sensing systems suffer from temperature noise originating from their light sources, which existing mitigation techniques such as averaging and denoising have proven ineffective in eliminating, especially due to source coherence.

Innovation Solution

Employing lowly polarized superluminescent emitting diodes (SLEDs) and/or unpolarized amplified spontaneous emission (ASE) light sources in Raman-based distributed temperature sensing systems to reduce noise characteristics, with configurations involving CW SLED or ASE sources, CW EDFA, and DWDM filters, and direct pulsing or elimination of CW EDFA and SOA.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If conventional light sources (DFB lasers, SLDs) are used in single mode DTS systems, then the system can operate with single mode fiber, but temperature noise increases due to source coherence

Engineering Contradiction:

Improvesingle mode fiber operationVSAvoidtemperature noise

Core Design Contradiction:

ReliabilityVSMeasurement precision

Solution Approach 1:

The patent changes the coherence parameter of the light source by using SLEDs with extended cavity designs that reduce spatial coherence while maintaining temporal coherence properties necessary for Raman scattering. This parameter modification allows single mode fiber operation while reducing coherence-induced temperature noise in the measurements

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent introduces polarization maintaining components and wavelength division multiplexing filters as intermediary elements between the SLED source and the single mode fiber. These intermediaries help manage the coherence properties of the light while enabling reliable single mode fiber operation and reducing noise in the temperature measurements

Inventive Principle:

Principle #24Intermediary (Mediator)

2Measurement precision

If averaging and denoising techniques are applied to mitigate noise, then some noise reduction is achieved, but the fundamental coherence-related noise remains ineffective

Engineering Contradiction:

Improvenoise reductionVSAvoidnoise mitigation effectiveness

Core Design Contradiction:

Measurement precisionVSReliability

Solution Approach 1:

The patent applies preliminary action by modifying the light source coherence properties before the light enters the fiber and interacts with the Raman scattering process. By using SLEDs with reduced spatial coherence from the outset, the system prevents coherence-related noise from being generated in the first place, making post-processing denoising techniques unnecessary for the fundamental coherence noise

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

Significantly reduces temperature noise in single mode fiber DTS systems, achieving noise levels of ±1°C to ±0.5°C over initial 20 km of fiber length, improving signal quality and reducing noise interference.

Implementation Method 1

employing lowly polarized superluminescent emitting diodes (SLEDs) and/or unpolarized amplified spontaneous emission (ASE) light sources

Methodology Applied

Scientific EffectSuperluminescent emission: Luminescence

Implementation Method 2

Raman-based systems, methods, and structures for distributed temperature sensing

Methodology Applied

Scientific EffectRaman scattering: Scattering

Implementation Method 3

single mode fiber distributed temperature sensing

Methodology Applied

Scientific EffectOptical fiber propagation: Optical Fibre

Data Source

PatentUS11204286B2Single mode fiber distributed temperature sensing with improved noise characteristics

Publication Date: 2021.12.21 NEC CORP

AI summary

Aspects of the present disclosure describe single mode fiber distributed temperature sensing (DTS) with improved noise characteristics employing superluminescent emitting diodes (SLEDs) and/or amplified spontaneous emission (ASE) light sources.