Non-linear Propagation Impairment Equalization Using Frequency Resolved Log Perturbation
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Solution Overview
Problem
Current methods for non-linear propagation impairment equalization in optical communications face challenges due to computational complexity and inefficiency, particularly in describing the input-output relationship of nonlinear fibre links, which limits effective compensation of transmission impairments.
Innovation Solution
A method using a frequency resolved log perturbation (FRLP) analytical approximation of the nonlinear Schrödinger equation to generate a discrete-time representation of the nonlinear time-variant impulse response, reducing computational effort by modeling nonlinear distortion as a multiplicative complex phase term and selecting a subset of frequencies to represent the signal bandwidth.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If Volterra Series Transfer Function (VSTF) is used to model nonlinear distortion, then measurement precision is improved, but device complexity increases due to triple integral computational complexity
Solution Approach 1:
The patent extracts the dominant nonlinear distortion characteristics from the complex VSTF triple integral model, isolating the essential frequency-dependent phase modulation effects. By taking out only the critical components (frequency resolved log perturbation terms) rather than processing the complete triple integral, the method achieves acceptable nonlinear distortion modeling with significantly reduced computational complexity.
Solution Approach 2:
Instead of applying the complete VSTF triple integral solution, the patent uses a partial action approach by implementing frequency resolved log perturbation that captures the most significant nonlinear effects. This partial modeling approach provides sufficient accuracy for practical equalization while avoiding the excessive computational burden of the full triple integral calculation.
2Device complexity
If Logarithmic Perturbation (LP) method is used with first-order solution, then device complexity is reduced, but measurement precision deteriorates at higher input power levels
Solution Approach 1:
The patent changes the modeling parameters from simple first-order log perturbation to frequency resolved log perturbation. By introducing frequency resolution as an additional parameter dimension, the method maintains computational efficiency while significantly improving accuracy at higher input power levels where conventional first-order solutions break down.
3Reliability
If digital back-propagation based on split-step Fourier method is used, then reliability of nonlinear compensation is improved, but productivity decreases due to high computational effort
Solution Approach 1:
The patent segments the nonlinear compensation process into frequency-resolved components, allowing independent processing of different frequency bands. This segmentation enables parallel computation and reduces the overall computational burden while maintaining the reliability of nonlinear compensation through comprehensive frequency coverage.
Data Source
AI summary
A method (10) of non-linear propagation impairment equalization, the method comprising the steps of: a. receiving (12) communications traffic carried by an optical communications signal transmitted over an optical communications link; b. generating (14) a time dependent filter representation of a nonlinear time-variant impulse response of the inverse of the optical communications link; and c. applying (16) the time dependent filter representation to the received communications traffic to form non-linear propagation impairment equalized communications traffic. An optical communications link nonlinear propagation impairment equalizer and optical communications signal receiver apparatus are also provided.