Optical Receiver Nonlinear Distortion Compensation
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Solution Overview
Problem
Conventional optical receivers face challenges in compensating for distortion caused by nonlinear responses, which deteriorate signal quality and cannot be adequately addressed by existing methods.
Innovation Solution
An optical transmission system that includes a receiver transfer function estimation section to estimate nonlinear response transfer functions and a compensation section using Volterra filters to correct nonlinear distortion, allowing for both linear and nonlinear distortion compensation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional linear response compensation methods are used in optical receivers, then linear distortion can be compensated, but nonlinear distortion caused by TIA or ADC cannot be compensated
Solution Approach 1:
The patent changes the mathematical model parameters from linear to nonlinear by introducing Volterra series expansion. This allows the compensation system to handle nonlinear responses by using higher-order kernel functions that capture nonlinear distortion characteristics, thereby expanding the compensation capability to include both linear and nonlinear distortions while maintaining signal quality
Solution Approach 2:
The patent introduces an intermediary nonlinear response compensation unit that acts as a mediator between the received signal and the final output. This unit specifically targets and compensates for nonlinear distortions introduced by TIA and ADC, allowing the system to maintain signal quality while gaining enhanced compensation capability for previously unaddressed nonlinear effects
2Quantity of substance
If the baud rate and modulation system are increased to enhance transmission capacity, then transmission capacity increases, but the requirement for favorable transmission characteristic in broad band becomes more stringent
Solution Approach 1:
The patent implements dynamic compensation by making the equalization filters adaptive. The filter coefficients are continuously adjusted based on the received signal characteristics, allowing the system to maintain precise transmission characteristics across broad bands even when operating at high baud rates and complex modulation schemes. This dynamic adaptation enables the system to handle the increased demands of high-capacity transmission
Solution Approach 2:
The patent segments the compensation function into multiple independent filter units, each handling specific frequency bands or distortion types. This segmentation allows precise control over different parts of the broad band spectrum, enabling the system to maintain high transmission characteristic precision across the entire bandwidth required for high-capacity transmission
3Reliability
If DSP is used to compensate transmission characteristic, then transmission characteristic can be improved, but the complexity of the optical receiver increases
Solution Approach 1:
The patent merges the nonlinear compensation function into the existing equalization filter structure. By combining multiple compensation functions (linear equalization, nonlinear compensation, and adaptive adjustment) into an integrated DSP unit, the system improves transmission characteristic while minimizing the increase in structural complexity. The merged architecture shares common computational resources and processing pipelines
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 accurate estimation and compensation of nonlinear responses within the optical receiver, thereby improving signal quality and transmission characteristics across a broad bandwidth.
Implementation Method 1
an optical receiver which performs coherent detection of a reception signal of the optical signal received from the optical transmission unit
Implementation Method 2
a balanced photo diode (BPD) and a trans-impedance amplifier (TIA). In the optical receiver, a signal obtained by photoelectric conversion is inputted to an analog to digital converter (ADC)
Data Source
AI summary
An optical transmission system according to an embodiment includes: an optical transmission unit which modulates an optical signal into which a known signal is inserted and transmits the optical signal; and an optical reception unit which receives the optical signal from the optical transmission unit, wherein the optical reception unit includes: an optical receiver which performs coherent detection of a reception signal of the optical signal received from the optical transmission unit; a receiver transfer function estimation section which estimates a nonlinear response transfer function of the optical receiver based on the known signal included in the reception signal after the detection by the optical receiver; and a receiver compensation section which compensates nonlinear distortion of the reception signal after the detection based on the nonlinear response transfer function which the receiver transfer function estimation section estimates.