Fractional Sampling Digital Dispersion Compensation
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Solution Overview
Problem
High-speed optical communication systems face challenges in efficiently processing signals at line rates above 10 Gbaud due to aliasing issues and increased power consumption, which limits the reliability and practicality of digital signal processing.
Innovation Solution
The technique involves sampling digital signals at a fractional multiple of the symbol rate (N < 2) and using low-pass filters with a cut-off frequency of 1/2T to suppress aliasing, allowing for digital compensation of phase distortions and enabling reliable operation at higher line rates.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If digital signals are sampled at a higher rate to satisfy the Nyquist criterion, then aliasing is suppressed, but power consumption increases significantly
Solution Approach 1:
The patent applies partial sampling by using a sampling rate that is a fractional multiple (N < 2) of the symbol rate rather than fully satisfying the Nyquist criterion (N ≥ 2). This partial action approach suppresses aliasing to an acceptable level while significantly reducing power consumption compared to full Nyquist-rate sampling
Solution Approach 2:
The patent changes the sampling rate parameter from the conventional Nyquist rate (≥2× symbol rate) to a fractional multiple (N < 2) of the symbol rate. This parameter change enables the system to operate at lower power consumption while maintaining acceptable signal processing reliability through the use of low-pass filtering and digital compensation techniques
2Speed
If digital signals are processed at higher line rates, then communication speed increases, but aliasing effects worsen
Solution Approach 1:
The patent introduces low-pass filters as intermediary components in the signal processing path. These filters act as mediators between the fractional-rate sampling process and the digital signal processing stages, suppressing aliasing effects generated by the reduced sampling rate while allowing the system to operate at higher line rates
Solution Approach 2:
The patent extracts and removes aliasing components from the signal by using low-pass filtering before digital processing. This extraction of harmful frequency components enables the system to process signals at higher line rates without the detrimental effects of aliasing
3Productivity
If digital signal processing is performed at higher line rates, then data transmission rate increases, but thermal barriers increase
Solution Approach 1:
The patent applies partial sampling at a fractional multiple (N < 2) of the symbol rate, which reduces the processing burden and power consumption compared to full Nyquist-rate processing. This partial action approach enables higher data transmission rates while generating less heat and avoiding thermal barriers
Data Source
AI summary
A method of suppressing effects of aliasing in a system for digitally processing a high speed signal having a symbol rate of 1/T. The high speed signal is sampled at a fractional multiple (N) of the symbol rate, wherein 1<N<2, to generate a corresponding sample stream, and filtered using a low-pass filter characteristic having a cut-off frequency corresponding to 1/2T. Phase distortions due to the filtering are compensated by digitally processing the sample stream.