Coherent Receiver ALC Histogram Control for Noisy Equalized Signals
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
In optical digital coherent receivers, existing methods struggle to accurately adjust signal levels from adaptive equalizers to optimize error correction, especially when input signals contain significant noise components, leading to variations in signal component levels due to noise inclusion.
Innovation Solution
An optical digital coherent receiver is designed with an Automatic Level Control (ALC) processing unit that generates a level adjustment coefficient by analyzing amplitude values from adaptive equalizer outputs, using a histogram to determine the most frequent amplitude value and adjusting signal levels to an optimum value for error correction, thereby isolating noise components.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If signal level adjustment is performed using conventional methods in optical digital coherent receivers, then the signal processing can proceed through the adaptive equalizer, but the signal level varies due to noise components affecting signal components, leading to insufficient precision in error correction processes
Solution Approach 1:
The patent extracts only the signal component from the composite signal (signal + noise) by detecting zero-crossing points and determining amplitude values at these points where noise influence is minimized. This separation allows precise measurement of signal level independent of noise components, directly resolving the contradiction between measurement precision and error correction reliability.
Solution Approach 2:
The patent introduces an Automatic Level Control (ALC) processing unit as an intermediary between the adaptive equalizer and frequency offset estimation unit. This ALC unit performs sophisticated signal level detection using zero-crossing point analysis and histogram generation to determine optimal amplitude values, acting as a mediator that ensures precise signal level control before error correction, thereby improving both measurement precision and correction reliability.
2Productivity
If noise components are present in the signal from adaptive equalizer, then the signal can be processed, but the amplitude values vary leading to variations in signal quality and precision
Solution Approach 1:
The patent implements feedback mechanisms where the ALC processing unit continuously monitors signal amplitude values, generates histograms to determine statistical characteristics, and adjusts signal levels accordingly. This feedback loop stabilizes the signal composition by compensating for amplitude variations caused by noise, maintaining stable signal quality while preserving processing efficiency.
Solution Approach 2:
The patent performs preliminary signal level stabilization in the ALC processing unit before the signal proceeds to frequency offset estimation and error correction stages. By detecting zero-crossing points and determining amplitude values in advance, the system prepares a stabilized signal with consistent amplitude characteristics, ensuring both processing efficiency and signal stability throughout subsequent operations.
Data Source
AI summary
An ALC processing unit to adjust the signal level of outputs from an adaptive equalizer to a target value is provided in a stage later than the adaptive equalizer and earlier than a frequency offset estimation/compensation unit in an optical digital coherent receiver. The ALC processing unit generates a histogram that counts the number of samples for discrete monitored values corresponding to amplitude values of outputs from the adaptive equalizer, and determines a level adjustment coefficient that is to be multiplied by an output from the adaptive equalizer so as to multiply the determined coefficient by the output from the adaptive equalizer so that the monitored value of the peak value of the histogram is the target value.