DSP Circuit Segmentation for Optical Signal Phase Noise Compensation
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Solution Overview
Problem
The adaptive equalizer in existing digital signal processing systems for optical communication has limitations in accurately compensating for in-transmitter distortion due to the influence of phase noise from the light source.
Innovation Solution
A digital signal processing circuit and method that includes a chromatic dispersion compensation filter, an adaptive equalizer, and a filter coefficient updating unit, which multiplies and phase-rotates signals for carrier phase compensation, including frequency offset, and updates the complex impulse response to improve the accuracy of in-transmitter distortion compensation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If phase rotation for carrier phase compensation is applied in the adaptive equalizer, then carrier phase noise is compensated, but the accuracy of in-transmitter distortion equalization deteriorates due to phase noise influence
Solution Approach 1:
The patent divides the equalization process into two distinct stages: a first adaptive equalizer that performs in-transmitter distortion equalization without phase rotation, and a second adaptive equalizer that performs carrier phase compensation with phase rotation. This segmentation allows each equalizer to be optimized for its specific function, preventing phase noise from degrading the in-transmitter distortion equalization accuracy.
Solution Approach 2:
The patent introduces an intermediary processing stage where the output of the first adaptive equalizer is processed to generate training signals, which are then used by the second adaptive equalizer for carrier phase compensation. This intermediary mechanism allows the two equalization functions to work sequentially rather than simultaneously, eliminating the interference between phase rotation and in-transmitter distortion equalization.
2Device complexity
If a single adaptive equalizer performs both in-transmitter distortion equalization and carrier phase compensation, then device complexity is reduced, but equalization accuracy deteriorates due to mutual interference between functions
Solution Approach 1:
The patent segments the equalization functionality into two separate adaptive equalizers: the first adaptive equalizer dedicated to in-transmitter distortion equalization, and the second adaptive equalizer dedicated to carrier phase compensation. This functional segmentation eliminates mutual interference between the two processes while maintaining manageable system complexity through clear division of labor.
Solution Approach 2:
The patent merges the two separate equalization functions into a unified processing pipeline where the first adaptive equalizer processes the input signal and its output feeds into the second adaptive equalizer. This merging allows both functions to be implemented in a coordinated manner, with the training signal generation mechanism enabling the second equalizer to operate effectively without requiring completely independent hardware.
Data Source
AI summary
A chromatic dispersion compensation filter is configured to multiply each of a real component and an imaginary component of each of a first polarization and a second polarization of a polarization-multiplexed optical signal by a filter coefficient that compensates for chromatic dispersion. An adaptive equalizer is configured to multiply input signals and their phase conjugates by a complex impulse response and add the signals multiplied by the complex impulse response. The adaptive equalizer is configured to perform, for each polarization, phase rotation for carrier phase compensation including a frequency offset and rotation reverse to the phase rotation and add, for each polarization, the signals subjected to the phase rotation and the signals subjected to the rotation reverse to the phase rotation.