Fast-Adaptive Multi-Tap Filter for Optical Impairment Mitigation
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
High-speed coherent optical transmission systems face challenges in mitigating fiber nonlinear effects and laser phase noise, particularly in long-reach terrestrial networks, due to the complexity and inefficiency of existing digital compensation methods and the conversion of phase noise into amplitude noise by long-memory filters.
Innovation Solution
A fast-adaptive multi-tap digital filter is used to simultaneously mitigate optical impairment from equalizer-phase noise interaction and fiber nonlinear effects, performing phase recovery and reducing signal distortion, which is implemented in a DSP-enabled coherent optical communication system.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If digital backward-propagation or Volterra-based nonlinear equalization methods are used to mitigate fiber nonlinear effects, then transmission reach is improved, but implementation complexity becomes prohibitively high
Solution Approach 1:
The patent replaces complex digital signal processing algorithms (DBP, Volterra) with a simpler, more computationally efficient digital filter that achieves comparable nonlinear compensation performance. This reduces implementation complexity while maintaining transmission reach, making the solution practical for real-world systems.
Solution Approach 2:
The patent changes the approach parameters by using a digital filter with optimized coefficients that directly compensate for nonlinear effects, rather than using iterative backward-propagation or high-order Volterra series. This parameter change simplifies the computational complexity while achieving the desired transmission reach.
2Reliability
If long-memory filter/equalizer is used to compensate for accumulated dispersion, then dispersion compensation is improved, but phase noise is enhanced and converted into amplitude noise causing additional signal distortion
Solution Approach 1:
The patent extracts and separately compensates for phase noise using a dedicated phase recovery algorithm before applying dispersion compensation. This separation prevents the long-memory filter from enhancing phase noise and converting it to amplitude noise, while still achieving effective dispersion compensation.
Solution Approach 2:
The patent performs phase recovery and phase noise compensation before dispersion compensation. This preliminary action removes the harmful phase noise enhancement effect that would otherwise occur during the subsequent long-memory filter operation, preventing conversion of phase noise to amplitude noise.
3Object-affected harmful factors
If hardware-based laser phase noise compensation method is used, then phase noise mitigation is improved, but system complexity and cost increase due to additional coherent receiver
Solution Approach 1:
The patent replaces the hardware-based (coherent receiver) phase noise compensation approach with a purely digital signal processing method. This substitution achieves comparable phase noise mitigation performance while avoiding the additional hardware complexity and cost of an extra coherent receiver.
Solution Approach 2:
The patent creates a digital replica of the phase noise characteristics and compensates for it in the digital domain, rather than using additional physical hardware to measure and compensate phase noise. This digital copying approach reduces system complexity while maintaining phase noise mitigation effectiveness.
Data Source
AI summary
A method and system for simultaneous mitigation of optical impairment from both equalizer-phase noise interaction (EPNI) and fiber nonlinear effects (FNE) is disclosed. In one embodiment, the method is directed to simultaneous mitigation of optical impairment from both equalizer-phase noise interaction (EPNI) and fiber nonlinear effects (FNE) using a fast-adaptive multi-tap digital filter.