Dual-Polarization Optical Interleaving for PDL and PMD Mitigation
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Solution Overview
Problem
Polarization-dependent effects, such as Polarization Dependent Loss (PDL) and Polarization Mode Dispersion (PMD), cause significant performance variations in dual-polarization optical communication systems, limiting the exploitation of performance advantages and requiring increased transmission power, which is bounded by system limits.
Innovation Solution
The method involves interleaving data symbols from multiple incoming data streams onto outgoing data streams, either in parallel or staggered times, to generate orthogonally polarized signals, which are then multiplexed for transmission, effectively averaging the effects of polarization distortions across multiple streams.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If polarization multiplexing is used to increase capacity, then bandwidth is effectively increased, but polarization-dependent effects (PDL, PMD) cause significant performance variations between polarizations
Solution Approach 1:
The patent segments the data streams into multiple polarization channels (first and second polarization channels) and applies different forward error correction codes to each channel. This segmentation allows independent optimization of error correction for each polarization, mitigating the performance variations caused by PDL and PMD while maintaining the capacity benefits of polarization multiplexing.
Solution Approach 2:
The patent applies different forward error correction codes with different error correction capabilities to different polarization channels based on their specific performance characteristics. This local quality approach allows each polarization channel to receive tailored error correction treatment, improving overall system reliability while preserving the high capacity enabled by polarization multiplexing.
2Reliability
If transmission power is increased to improve bit error rate, then BER performance improves, but transmission power is bounded by system limits
Solution Approach 1:
The patent changes the error correction parameters by selecting and applying different forward error correction codes with different error correction capabilities to different polarization channels. This parameter change allows the system to achieve better BER performance without increasing transmission power, as the error correction capability is enhanced through code selection rather than power increase.
3Productivity
If dual-polarization system transmits four 10 Gbps channels, then data capacity is maximized, but polarization distortions cause performance degradation
Solution Approach 1:
The patent converts the harmful effect of polarization distortions into a beneficial approach by using the distortion characteristics to guide the selection of error correction codes. The system analyzes the performance of each polarization channel and applies appropriate error correction, effectively turning the polarization distortion problem into a mechanism for optimizing overall system performance while maintaining maximum data capacity.
Data Source
AI summary
A method and system for averaging the effects of polarization distortions across a multitude of transmitted data streams in a dual polarization multiplexed optical communications system. Data streams are interleaved amongst each other in accordance with a predetermined pattern. The interleaved data streams are symbol mapped and modulated to provide a pair of optical signals. The pair of optical signals are orthogonally polarized, and multiplexed for transmission across an optical fiber. A receiver circuit receives the transmitted signal and extracts the interleaved data streams. The interleaved data streams are de-interleaved to generate the original data streams. While the data streams can be interleaved and transmitted via a single wavelength optical signal, the data streams can be interleaved and transmitted over two or more different wavelength optical signals to further mitigate the effects of polarization distortions.