Asymmetric Pulse-Shaping Filters for Optical ISI and Jitter
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Solution Overview
Problem
Optical communication systems face challenges with noise and distortions in subcarrier signals leading to intersymbol interference (ISI) and jitter, which affect data recovery and synchronization, particularly in digital subcarrier communication systems.
Innovation Solution
Implement asymmetric pulse-shaping filters at both the transmitter and receiver to minimize ISI and jitter, using asymmetric pulse-shaping to maintain time synchronization and improve frequency offset estimation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If symmetric pulse-shaping filters are used at transmitter and receiver, then ISI is reduced, but jitter performance and frequency offset detection are degraded
Solution Approach 1:
The patent applies asymmetric pulse-shaping filters where the transmitter uses a root-raised cosine filter with roll-off factor β1 and the receiver uses a root-raised cosine filter with roll-off factor β2, where β1 ≠ β2. This asymmetric configuration reduces ISI while preserving jitter performance and frequency offset detection capabilities, resolving the contradiction between ISI reduction and measurement precision.
2Reliability
If pulse-shaping filters are applied to minimize ISI, then data recovery is improved, but system complexity increases
Solution Approach 1:
The patent applies pulse-shaping filters at the transmitter before signal transmission to pre-condition the signal and minimize ISI at the receiver. This preliminary action improves data recovery accuracy while keeping the receiver simpler, as the bulk of the filtering is done in advance at the transmitter side.
Data Source
AI summary
Methods, systems, and apparatus, including computer programs encoded on computer storage media, for performing asymmetric pulse-shaping filtering. In some implementations, a receiver comprises a detector circuit operable to receive optical signal data from an optical link. The receiver comprises a filter circuit, coupled to the detector circuit, operable to (i) filter the optical signal data according to an asymmetric filtering scheme and (ii) output the filtered optical signal data, wherein the asymmetric filtering scheme comprises utilizing a shaping filter with first criteria, the first criteria including one or more values greater than one or more values of second criteria utilized by a shaping filter at a transmitter, the transmitter communicating with the receiver.