Optical Receiver Frequency Domain Equalization for Polarization Multiplexed Signals
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Solution Overview
Problem
Current optical receivers for ultra-high speed optical communication systems face challenges in demodulating polarization multiplexed signals efficiently due to high power consumption and cost, particularly in compensating for polarization mode dispersion and noise, which requires complex filter coefficients that demand significant circuit resources.
Innovation Solution
An optical receiver with a polarization diversity unit and a frequency domain equalization unit that uses filters with simplified filter coefficients, calculated using Minimum Mean Square Error (MMSE) or other algorithms, to compensate for transmission degradation without the need for extensive circuit resources, allowing for correct demodulation of original transmission data from polarization multiplexed signals.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If complex filter coefficients are used to compensate for polarization mode dispersion and noise in polarization multiplexed signals, then demodulation accuracy is improved, but power consumption and circuit resource requirements increase
Solution Approach 1:
The patent divides the complex equalization task into separate processing paths for different polarization components (X-polarization and Y-polarization). By segmenting the signal processing into distinct channels that can be handled independently with simpler filters, the system achieves accurate demodulation without requiring a single complex filter that would consume excessive power and circuit resources.
2Measurement precision
If complex filter coefficients are used to compensate for polarization mode dispersion and noise, then demodulation accuracy is improved, but device complexity increases
Solution Approach 1:
The patent segments the polarization multiplexed signal into separate X and Y polarization components that can be processed independently. This segmentation allows each processing path to use simpler filters rather than requiring a single complex filter, thereby reducing device complexity and circuit resource requirements while maintaining demodulation accuracy.
Solution Approach 2:
The patent employs universal filter structures that can be applied to both X and Y polarization components. By using the same filter architecture for multiple polarization channels, the system avoids duplicating complex circuitry and reduces overall device complexity while achieving accurate compensation for polarization mode dispersion and noise across all channels.
3Reliability
If dynamic control of transfer matrix is implemented to approximate reverse transfer matrix of fiber, then compensation for polarization rotation and dispersion is improved, but ease of operation and control complexity worsen
Solution Approach 1:
The patent applies inverse filtering by designing filters whose coefficients are derived from the inverse of the channel response. Instead of dynamically controlling a transfer matrix to approximate the reverse transfer matrix, the system uses fixed inverse filters that inherently compensate for polarization rotation and dispersion, simplifying the control mechanism while maintaining high compensation accuracy.
Data Source
AI summary
An optical receiver according to the invention includes a polarization diversity unit receiving a polarization multiplexed optical signal obtained by multiplexing two optical signals having a same frequency band of carrier waves and polarization states orthogonal to each other, and a frequency domain equalization unit receiving signal components parallel to mutually orthogonal polarization axes from the polarization diversity unit, wherein the frequency domain equalization unit includes filters for which filter coefficients thereof are set for compensating degradation of transmission characteristics in one optical signal without polarization multiplexing by means of the frequency domain equalization.