Digital Signal Conditioning for Optical Signal Deskew and Resampling
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Solution Overview
Problem
Current communication systems face challenges in aligning and processing dual-polarization quadrature optical signals, leading to signal skew and inefficiencies in data transmission due to varying input oversampling factors, which affect the consistency and quality of digital sample streams.
Innovation Solution
A digital signal conditioner (DSC) system is implemented in a DSP circuit, incorporating an overhang module, sample selector bank, filter bank, and tap weights selector bank to deskew and resample input digital sample blocks, ensuring output digital sample blocks are consistently formatted at a predetermined fixed output oversampling factor, regardless of input conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If digital sample blocks are processed with varying input oversampling factors, then the system can accommodate different input conditions, but the output consistency and signal alignment deteriorate due to signal skew
Solution Approach 1:
The overhang module performs preliminary action by appending additional samples to each input digital sample block before processing. This pre-processing step ensures that sufficient data is available for subsequent filtering and resampling operations, enabling the system to handle varying input oversampling factors while maintaining consistent output formatting.
Solution Approach 2:
The system dynamically changes the oversampling factor parameter through selective filtering and resampling. The filter bank and tap weights selector bank adjust filtering parameters based on the input conditions, transforming the variable input oversampling factor into a fixed predetermined output oversampling factor, thereby resolving the contradiction between adaptability and consistency.
2Measurement precision
If signal processing operations are performed to align dual-polarization quadrature optical signals, then signal quality improves, but processing complexity increases
Solution Approach 1:
The signal processing system is segmented into distinct functional modules: overhang module for preliminary processing, sample selector bank for selective sampling, filter bank for frequency domain processing, and tap weights selector bank for parameter adjustment. This segmentation allows each module to perform its specific function efficiently, achieving high signal alignment precision while managing overall system complexity through modular design.
Solution Approach 2:
The overhang module acts as an intermediary that prepares input digital sample blocks by appending additional samples before they enter the main processing pipeline. This intermediary step simplifies subsequent processing operations by ensuring uniform data structure, thereby reducing the complexity burden on downstream modules while maintaining signal alignment precision.
3Reliability
If filtering and resampling operations are applied to remove artifacts and distortions, then signal quality improves, but processing time increases
Solution Approach 1:
The filter bank applies partial filtering operations by selectively processing only the necessary frequency components of the signal. Rather than applying full-spectrum filtering to all data uniformly, the system identifies and processes only the relevant portions, achieving improved signal quality while minimizing unnecessary processing time consumption.
Solution Approach 2:
The overhang module performs preliminary processing by appending samples and preparing data structures before the main filtering and resampling operations. This pre-processing ensures that the subsequent filtering operations work with optimally prepared data, reducing the time required for artifact and distortion removal while maintaining signal quality.
Data Source
AI summary
One example includes a digital signal conditioner (DSC) system. A sample selector bank receives a digital sample block of an input signal that is provided at a supported input oversampling factor and selects a subset of samples from the digital sample block based on a selection signal. A tap weights selector bank generates a set of tap weights based on the selection signal. A filter bank receives the subset of the samples from each of the sample selectors and a respective set of tap weights. Each filter provides a weighted sample associated with the respective subset of samples and the respective set of tap weights. A reformattor receives the weighted sample from each of the filters and provides a filtered sample block including the weighted sample from a subset of the filters at an output oversampling factor for each supported input oversampling factor based on a selected supported resampling ratio.