Trellis-Based Processor for ISI and Phase Noise Mitigation
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Solution Overview
Problem
Optical communication systems face challenges in compensating for inter-symbol interference (ISI) and phase noise (PN) impairments, particularly in high-speed transmission systems, where existing methods are computationally intensive and difficult to implement effectively with limited hardware resources, and current ISI compensation methods are not easily adaptable for PN compensation.
Innovation Solution
A method and apparatus for digitally processing optical digital multi-band (DMB) signals, involving demultiplexing into separate frequency bands and using trellis-based processors (TBPs) to adaptively mitigate ISI and PN, with a mode selector configuring TBPs to process either ISI or PN based on the frequency band, enabling effective compensation of both types of impairments.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If existing ISI compensation methods are used, then inter-symbol interference is mitigated, but the methods are computationally intensive and difficult to implement with limited hardware resources
Solution Approach 1:
The patent segments the compensation task by separating ISI and PN compensation into distinct functional modules within the TBP architecture. Each module processes specific impairment types independently, allowing for targeted optimization and reducing overall computational complexity while maintaining effectiveness.
Solution Approach 2:
The TBP is designed as a universal processor that can handle both ISI and PN compensation through configurable modes. This multi-functionality eliminates the need for separate dedicated hardware for each compensation type, reducing hardware complexity while maintaining comprehensive impairment mitigation.
2Reliability
If dedicated compensation methods for ISI are used, then ISI is effectively mitigated, but the methods are not easily adaptable for PN compensation
Solution Approach 1:
The TBP implements a unified architecture with configurable modes that can adapt to handle both ISI and PN compensation. The processor switches between ISI compensation mode and PN compensation mode based on the impairment type, providing versatility without sacrificing effectiveness for either impairment type.
Solution Approach 2:
The compensation method dynamically adapts to the dominant impairment type through mode selection. The system can switch between ISI-focused and PN-focused compensation strategies based on channel conditions and signal characteristics, enhancing adaptability while maintaining effectiveness.
3Reliability
If multiple separate processors are used for ISI and PN compensation, then both impairments are mitigated, but the device complexity increases
Solution Approach 1:
The patent merges ISI and PN compensation functionalities into a single TBP unit. This unified processor integrates both compensation algorithms and shares common hardware resources, reducing the total number of processors needed while maintaining effective mitigation of both impairment types through coordinated operation.
Data Source
AI summary
Aspects of the present disclosure are directed in part to a receiver DSP unit including an equalization module. The equalization module includes a trellis-based equalization module that may utilize multiple trellis-based processors (TBP), which can each be individually adaptively configured for performing a trellis-based equalization. The design of the TBPs allows them to be configured for compensating a residual Inter-Symbol Interference (ISI) as well as compensating a residual Phase Noise (PN). ISI is an example of an additive impairment and PN is an example of a multiplicative impairment that communication systems, particularly high speed transmission systems such as coherent optical systems, can suffer from.