Dual-Frequency Comb Optical Fiber Interrogation

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Solution Overview

Problem

Conventional phase-sensitive OTDR systems for interrogating optical fibers face challenges in achieving high-resolution measurements due to the need for high-frequency electronics, which degrades noise performance and increases data acquisition and processing requirements, leading to significant costs and complexity.

Innovation Solution

The use of dual-frequency comb technology, where two coherent optical frequency combs with slightly different repetition rates are used to down-convert the backscattering signal to the RF domain, allowing for high-resolution spectroscopy with low-bandwidth electronics and reducing the need for high-frequency detection.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If high-frequency electronics with high bandwidth are used to achieve high-resolution measurements, then spatial resolution is improved, but noise performance degrades and data acquisition requirements increase

Engineering Contradiction:

Improvespatial resolutionVSAvoidnoise performance

Core Design Contradiction:

Measurement precisionVSReliability

Solution Approach 1:

The patent changes the detection parameter from high-frequency electrical signals to optical frequency domain measurements. By using optical frequency comb spectroscopy and analyzing the spectrum in the optical domain rather than converting to electrical domain, the system achieves high resolution without requiring high-frequency electronics, thus maintaining noise performance while improving spatial resolution.

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent replaces the electrical detection mechanism with an optical detection mechanism. Instead of using high-frequency electrical electronics to detect signals, the system uses optical spectroscopy techniques to analyze the backscattered light spectrum, substituting the mechanical/electrical detection system with an optical one that operates at different frequency scales.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

2Measurement precision

If high-frequency electronics with high bandwidth are used to achieve high-resolution measurements, then spatial resolution is improved, but data acquisition and processing requirements increase

Engineering Contradiction:

Improvespatial resolutionVSAvoiddata acquisition and processing requirements

Core Design Contradiction:

Measurement precisionVSDevice complexity

Solution Approach 1:

The patent replaces complex high-frequency electrical data acquisition systems with optical spectroscopy measurements. By performing measurements in the optical frequency domain and using spectral analysis techniques, the system reduces the complexity of electrical data acquisition and processing while maintaining high spatial resolution through optical means.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

3Measurement precision

If more energy is injected into the optical fiber to improve signal strength, then measurement accuracy is improved, but nonlinearities are induced

Engineering Contradiction:

Improvemeasurement accuracyVSAvoidnonlinearities

Core Design Contradiction:

Measurement precisionVSObject-generated harmful factors

Solution Approach 1:

The patent uses optical frequency comb spectroscopy to create a replicated spectrum that contains multiple frequency components. By analyzing the spectral copies of the input signal through the fiber, the system can achieve high measurement accuracy without requiring high peak power, as the comb structure distributes energy across multiple frequency bins rather than concentrating it in a single high-power pulse.

Inventive Principle:

Principle #26Copying

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 approach enables high-sensitivity, broadband spectroscopy with reduced detection and acquisition requirements, improving signal-to-noise ratio and allowing for more energy to be injected into the optical fiber without inducing nonlinearities, thereby enhancing the spatial resolution and measurement accuracy.

Implementation Method 1

all of these interrogation methods require sending optical energy into the optical fiber to produce a backscattered light signal which is analysed to extract spatially-resolved measurements

Methodology Applied

Scientific EffectBackscattering: Scattering

Implementation Method 2

The use of dual-frequency comb technology, where two coherent optical frequency combs with slightly different repetition rates are used to down-convert the backscattering signal to the RF domain

Methodology Applied

Scientific EffectFrequency mixing: Heterodyne

Data Source

PatentUS11549860B2Method and system for interrogating optical fibers

Publication Date: 2023.01.10 ARAGON PHOTONICS LABS S L U

AI summary

A method and a system for interrogating an optical fiber includes a probe signal that has a first frequency comb at a first repetition rate (Δf) injected into the optical fiber. A backscattering signal that includes the probe signal convolved with an impulse response of the optical fiber in reflection which is sensitive to at least one parameter being measured from the optical fiber is gathered. The backscattering signal is beaten with a local oscillator signal to generate a beating signal, the local oscillator signal including a second frequency comb at a second repetition rate that is offset from the first repetition rate (Δf+δf) and being mutually coherent with the first frequency comb. The resulting beating signal is analysed to thereby determine the at least one parameter being measured from the optical fiber.