Wavelength Dispersion Compensation for Phase Sensitive Amplifiers

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Solution Overview

Problem

Phase sensitive amplifiers (PSAs) face degradation in amplification characteristics due to wavelength dispersion, which is challenging to compensate for, especially in wide-band signals, and existing methods struggle to accurately measure and manage residual wavelength dispersion affecting gain characteristics.

Innovation Solution

A wavelength dispersion compensating apparatus and method that generates signal light with phase correlation centered on a degenerate frequency, uses a dispersion compensation transmission path and filter to compensate for wavelength dispersion, calculates residual dispersion, and adjusts the filter to cancel out calculated residual dispersion, ensuring accurate compensation.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Adaptability or versatility

If a wide amplification band is used in PSA, then the amplification coverage is improved, but the allowable wavelength dispersion amount decreases causing gain characteristic degradation

Engineering Contradiction:

Improveamplification bandVSAvoidgain characteristic

Core Design Contradiction:

Adaptability or versatilityVSReliability

Solution Approach 1:

The patent applies preliminary action by compensating for wavelength dispersion before the signal enters the PSA. The dispersion compensation transmission path pre-corrects the wavelength dispersion of the signal light, ensuring that when the wide-band signal passes through the PSA, the relative phase relationship among signal light, idler light, and excitation light remains optimal, thus preventing gain characteristic degradation while maintaining wide amplification band

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The patent implements feedback by measuring the actual wavelength dispersion amount affecting the PSA gain characteristics using an optical spectrum analyzer, comparing it with the target value, and adjusting the dispersion compensation transmission path to minimize the difference. This closed-loop feedback ensures accurate compensation and maintains optimal gain characteristics across the wide amplification band

Inventive Principle:

Principle #23Feedback

2Device complexity

If conventional dispersion compensation methods are used, then the dispersion compensation is simplified, but the residual wavelength dispersion cannot be accurately measured and compensated

Engineering Contradiction:

Improvecompensation methodVSAvoidresidual wavelength dispersion

Core Design Contradiction:

Device complexityVSMeasurement precision

Solution Approach 1:

The patent replaces conventional mechanical dispersion compensation methods with an optical measurement and compensation system. Instead of using complex mechanical adjustment mechanisms, the system uses optical spectrum analysis to precisely measure wavelength dispersion and applies compensation through a dispersion compensation transmission path, achieving high measurement precision without excessive device complexity

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

The patent introduces an intermediary measurement system consisting of an optical spectrum analyzer and control unit that acts as a mediator between the signal light and the dispersion compensation transmission path. This intermediary measures the wavelength dispersion characteristics and translates them into compensation parameters, enabling accurate residual wavelength dispersion compensation while keeping the overall system manageable

Inventive Principle:

Principle #24Intermediary (Mediator)

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 precise calculation and compensation of wavelength dispersion affecting PSA gain characteristics, leading to wide-band flat gain characteristics and improved transmission performance.

Implementation Method 1

a phase sensitive amplification operation is obtained by interaction among three lightwaves of which a frequency of the signal light, a frequency of the idler light, and a frequency of excitation light differ from each other

Methodology Applied

Scientific EffectNon-linear optical interaction:

Implementation Method 2

a shift occurs in a phase between the signal light and the idler light due to wavelength dispersion during fiber transmission

Methodology Applied

Scientific EffectWavelength dispersion: Dispersion (of waves)

Data Source

PatentUS11929784B2Wavelength dispersion compensation apparatus and wavelength dispersion compensation method

Publication Date: 2024.03.12 NIPPON TELEGRAPH & TELEPHONE CORP

AI summary

A wavelength dispersion compensating apparatus, including: a signal light generating unit which generates, from predetermined signal light, signal light having a phase correlation centered on a degenerate frequency of a phase sensitive amplifier; a dispersion compensation transmission path which compensates for a wavelength dispersion of the predetermined signal light included in the signal light; a filter which compensates for a residual wavelength dispersion after compensation by the dispersion compensation transmission path of the predetermined signal light included in the signal light; a phase sensitive amplifier which amplifies the signal light input via the dispersion compensation transmission path and the filter; a residual wavelength dispersion calculating unit which calculates a residual wavelength dispersion amount based on a measurement result of output light amplified by the phase sensitive amplifier; and a filter control unit which controls the filter so as to add a wavelength dispersion that cancels out the calculated residual wavelength dispersion amount to the predetermined signal light.