Optical Signal Timing Alignment for Burst Frame Convergence
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Solution Overview
Problem
In TDM-PON systems, the optimal tap coefficients for adaptive equalization filtering differ for each burst frame, leading to prolonged convergence times and reduced transmission efficiency due to the need for repeated feedback calculations and longer preambles.
Innovation Solution
A signal processing device with a symbol timing detecting unit, adaptive equalization filter unit, and timing matching unit that adjusts the input timing to align sample signals with the tap having the maximum coefficient, allowing for faster convergence of tap coefficients by matching symbol timing with peak tap coefficients.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If adaptive equalization filtering is performed with optimal tap coefficients for each burst frame, then signal quality is improved, but convergence time is prolonged and transmission efficiency is reduced
Solution Approach 1:
The patent performs preliminary action by calculating and storing optimal tap coefficients for each subscriber-side communication apparatus in advance, before actual burst frame transmission. When a burst frame arrives, the system quickly retrieves the pre-calculated coefficients matching the transmission source ID, avoiding the need for time-consuming feedback calculations during transmission. This preliminary preparation resolves the contradiction by enabling high signal quality through optimal coefficients while maintaining high transmission efficiency through rapid coefficient retrieval.
2Measurement precision
If feedback calculations are repeated for each burst frame to obtain optimal tap coefficients, then equalization accuracy is improved, but the number of feedback calculations increases and processing time is extended
Solution Approach 1:
The patent applies the copying principle by creating and storing copies of optimal tap coefficients for each subscriber-side communication apparatus in advance. Instead of performing repeated feedback calculations for each burst frame, the system copies the pre-calculated coefficients from storage based on the transmission source ID. This copying approach maintains high equalization accuracy by using optimal coefficients while dramatically reducing processing time by eliminating repeated calculations.
3Reliability
If the preamble length is increased to allow for convergence of tap coefficients, then equalization performance is improved, but the overall transmission efficiency is reduced
Solution Approach 1:
The patent performs preliminary action by pre-calculating and storing optimal tap coefficients before burst frame transmission. This allows the system to start equalization processing immediately upon receiving a burst frame without requiring a long preamble for coefficient convergence. The equalization performance is maintained through use of optimal pre-calculated coefficients, while transmission efficiency is improved by significantly reducing the required preamble length.
Data Source
AI summary
A signal processing device included in an optical reception device configured to receive a burst optical signal transmitted by one of a plurality of optical transmission devices, includes a symbol timing detecting unit configured to detect a symbol timing based on sample signals obtained by oversampling the burst optical signal converted into an electric signal with a sampling rate higher than a symbol rate, an adaptive equalization filter unit configured to perform an equalization process on the sample signals, and a timing matching unit configured to match timing such that, when the adaptive equalization filter unit takes in the sample signals, one of the taken-in sample signals corresponding to the symbol timing is given to a tap of which a tap coefficient has a maximum value among taps included in the adaptive equalization filter unit.