Backscattering Optical Amplification Device for Mode-Specific Raman Gain Control

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Solution Overview

Problem

In optical fiber testing using OTDR, amplifying a desired propagation mode of backscattered light with a desired gain through stimulated Raman scattering is unclear, especially in two-mode regions of Few-mode optical fibers and general single-mode fibers, due to varying amplification gains from interacting propagation modes.

Innovation Solution

A backscattered light amplification device and method that control the power, incident timing, and pulse width of pump pulses for each propagation mode, allowing for arbitrary Raman amplification gain to be applied to desired propagation modes of backscattered light, using a probe pulse and pump pulses with controlled power ratios, pulse lengths, and time differences to achieve specific Raman amplification gains.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Power

If stimulated Raman scattering is used to amplify backscattered light in two-mode region of Few-mode optical fiber or SMF, then amplification gain is obtained, but the amplification gain varies depending on propagation modes making mode-specific control difficult

Engineering Contradiction:

Improveamplification gainVSAvoidmode-specific control

Core Design Contradiction:

PowerVSEase of operation

Solution Approach 1:

The invention segments the pump light into multiple wavelengths corresponding to different Raman gain spectra. Each wavelength component selectively amplifies a specific propagation mode of backscattered light. This segmentation allows independent control of amplification gain for each mode, resolving the contradiction between obtaining amplification gain and achieving mode-specific control.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The invention changes the wavelength parameter of pump light to control which propagation mode is amplified. By adjusting the wavelength of pump light, different Raman gain spectra are excited, enabling selective amplification of fundamental mode or higher-order modes. This parameter change provides precise mode-specific control while maintaining amplification gain.

Inventive Principle:

Principle #35Parameter changes

2Length of stationary object

If pump light is used to amplify backscattered light, then measurement distance is extended, but control over which propagation mode is amplified becomes unclear

Engineering Contradiction:

Improvemeasurement distanceVSAvoidmode identification accuracy

Core Design Contradiction:

Length of stationary objectVSMeasurement precision

Solution Approach 1:

The invention segments pump light into multiple wavelength components, each corresponding to a specific propagation mode. This segmentation enables precise identification of which mode is being amplified at each distance point, improving measurement precision while extending measurement distance through Raman amplification.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The invention uses feedback by detecting the wavelength-dependent Raman gain spectrum and using this information to identify which propagation mode is present. The system adjusts pump light wavelength based on detected feedback signals, enabling accurate mode identification throughout the extended measurement distance.

Inventive Principle:

Principle #23Feedback

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

Enables the desired propagation mode of Rayleigh backscattered light to be amplified with a specific gain, effectively addressing the challenge of varying amplification gains in multi-mode optical fibers, allowing for precise OTDR measurements.

Implementation Method 1

amplifying distributedly in FUT backscattered light generated by a probe pulse propagating in FUT using pump light having a frequency (short wavelength) higher by the Raman frequency shift

Methodology Applied

Scientific EffectStimulated Raman scattering:

Implementation Method 2

pump light having a frequency (short wavelength) higher by the Raman frequency shift

Methodology Applied

Scientific EffectRaman frequency shift:

Implementation Method 3

acquires distribution data (OTDR waveform) based on intensity and round trip time of backscattered light of Rayleigh scattered light derived from a test light pulse

Methodology Applied

Scientific EffectRayleigh scattering: Rayleigh Scattering

Data Source

PatentUS11486791B2Backscattering optical amplification device, optical pulse testing device, backscattering optical amplification method and optical pulse testing method

Publication Date: 2022.11.01 NIPPON TELEGRAPH & TELEPHONE CORP

AI summary

The present invention is to provide a backscattered light amplification device, an optical pulse test apparatus, a backscattered light amplification method, and an optical pulse test method for amplifying a desired propagation mode of Rayleigh backscattered light with a desired gain by stimulated Raman scattering in a fiber under test having the plurality of propagation modes. The backscattered light amplification device according to the present invention is configured to control individually power, incident timing, and pulse width of a pump pulse for each propagation mode when the pump pulse is incident in a plurality of propagation modes after the probe pulse is input to the fiber under test in any propagation mode.