Dual-Filter Phase Correction for Optical Transmission
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Solution Overview
Problem
Current carrier phase estimation methods in optical transmission systems face challenges in accurately mitigating both laser phase noise and non-linear induced phase noise, particularly at higher data rates where phase fluctuations become rapid and uncorrelated, leading to decreased filter performance and increased cycle slips.
Innovation Solution
A method that differentiates between slowly-varying and rapidly-varying noise phases, with separate filtering processes to correct each, using distinct averaging windows and algorithms to generate phase-corrected signal samples, thereby reducing cycle slips and improving phase estimation accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the filter length is increased to improve carrier phase estimation accuracy, then laser phase noise is better cancelled, but non-linear induced phase noise is not effectively mitigated and cycle slips increase
Solution Approach 1:
The patent segments the carrier phase estimation process into two distinct filters: a first filter with a longer tap-weight vector for tracking slow laser phase noise, and a second filter with a shorter tap-weight vector for tracking fast non-linear induced phase noise. This segmentation allows each filter to be optimized for its specific noise type, resolving the contradiction between reducing laser phase noise (requiring long filter) and avoiding cycle slips from non-linear noise (requiring short filter).
Solution Approach 2:
The patent implements dynamic adaptation by selectively applying different filters based on the characteristics of the observed phase noise. The system monitors phase variations and dynamically switches between the first filter (for slow variations) and the second filter (for fast variations), allowing the system to adapt to changing noise conditions and maintain both accuracy and reliability.
2Device complexity
If a single filter is used for carrier phase estimation, then the system is simple to implement, but it cannot optimally track both slow laser phase noise and fast non-linear phase noise
Solution Approach 1:
The patent divides the phase estimation function into two separate filters, each specialized for a specific time scale of phase noise. The first filter handles slow laser phase noise with a longer memory, while the second filter handles fast non-linear phase noise with a shorter memory. This segmentation improves tracking accuracy for both noise types without requiring an overly complex adaptive system.
Solution Approach 2:
The patent creates a multi-functional phase estimation system where two filters work together to handle different types of phase noise. The first filter provides long-term stability for laser phase noise, while the second filter provides short-term responsiveness for non-linear effects. Together, they create a universal solution that handles both slow and fast phase variations effectively.
Data Source
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AI summary
The invention provides a method for correcting the phase shift of a transmission channel, comprising: - providing a plurality of signal samples at succeeding time instances, comprising a data phase and a residual phase; for each successive signal sample: - determining a slowly-varying noise phase, and shifting the signal sample by the slowly-varying phase noise, - determining a rapidly varying noise phase and shifting the intermediate signal sample by the rapidly varying noise phase. The invention also provides a device.