Nonlinear Distortion Detection Circuit for Optical Receivers
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Solution Overview
Problem
Current optical transmission systems face limitations in accurately detecting and compensating for nonlinear distortion in optical fibers, which restricts the transmission distance and capacity due to the lack of effective nonlinear distortion detection methods.
Innovation Solution
A nonlinear distortion detecting module that includes a first estimator for signal quality based on error correction, a second estimator to remove nonlinear effects, and a calculator to quantify nonlinear effects by identifying differences between signal qualities, allowing for precise compensation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If digital coherent technique and equalizing technique are used to compensate for linear distortion, then transmission distance and capacity are improved, but nonlinear distortion remains undetected and limits further improvement
Solution Approach 1:
The patent introduces an intermediary measurement approach by injecting a test signal and using a correlation calculator to measure nonlinear distortion. The correlation calculator acts as an intermediary device that processes the test signal and original signal to extract nonlinear distortion characteristics, enabling indirect measurement of what would otherwise be difficult to detect directly.
Solution Approach 2:
The patent replaces direct physical measurement of nonlinear distortion with a signal processing-based measurement system. Instead of attempting direct detection, the system uses mathematical operations (correlation calculation) on electrical signals to quantify nonlinear effects, substituting physical measurement with computational analysis.
2Productivity
If transmission distance is increased to boost capacity, then information streaming capability is improved, but optical waveform distortions including nonlinear distortion worsen
Solution Approach 1:
The patent implements a feedback mechanism where the measured nonlinear distortion is fed back to control the equalizer. The correlation calculator continuously monitors distortion levels and provides feedback signals that adjust the equalizer parameters in real-time, enabling dynamic compensation as transmission distance increases.
Solution Approach 2:
The patent applies preliminary action by measuring nonlinear distortion using a test signal before it fully affects the transmission. The correlation calculator proactively identifies distortion characteristics early in the transmission process, allowing the equalizer to be pre-adjusted or continuously adjusted to compensate for upcoming distortion effects.
3Reliability
If existing compensation techniques are used, then some nonlinear distortion can be compensated, but detection accuracy is insufficient for optimal compensation
Solution Approach 1:
The patent changes the measurement parameter by using correlation coefficients between test signals and original signals to quantify nonlinear distortion. Instead of relying on indirect or approximate measurement methods, the system uses correlation analysis to directly measure distortion parameters, providing precise quantification for optimal compensation.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
Enables high-accuracy detection and compensation of nonlinear distortion, thereby enhancing the transmission capacity and distance of optical transmission systems by effectively monitoring and mitigating signal quality degradation.
Implementation Method 1
a first estimator that estimates a signal quality based on an error correction number of an electrical signal obtained by photoelectrically converting a received optical signal
Data Source
AI summary
An apparatus includes a first estimator that estimates a signal quality based on an error correction number of an electrical signal obtained by photoelectrically converting a received optical signal; a second estimator that estimates a signal quality from which the influence of nonlinear effects is removed based on signals upstream and downstream of an identification calculator identifying the electrical signal; and a calculator that calculates the difference between the signal qualities estimated by the first and second estimators to calculate the amount of nonlinear effects.