Equalization Signal Processing Circuit for Optical Fiber Non-Linear Distortion Compensation
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Solution Overview
Problem
Existing optical fiber communication systems face limitations in compensating for non-linear distortion in transmitters and receivers, which affects the accuracy of signal processing and spectral utilization efficiency, especially when high-order multi-level modulation is used.
Innovation Solution
A communication system with an equalization signal processing circuit that includes a series of filters, including non-linear and linear distortion compensation filters, where filter coefficients are adaptively controlled using an error back propagation method to minimize the difference between output and desired signals, effectively addressing both intra-receiver and intra-transmitter distortions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If high-order multi-level modulation is adopted to achieve high spectral utilization efficiency, then spectral efficiency is improved, but signal susceptibility to distortion increases
Solution Approach 1:
The equalization signal processing circuit is divided into multiple functional blocks: wavelength dispersion compensation block, polarization separation block, carrier phase compensation block, and IQ distortion compensation block. Each block independently processes specific types of distortion, allowing high-order modulation to be used while maintaining signal integrity through targeted compensation for each distortion source.
2Reliability
If reception side equalization digital signal processing is performed to compensate for wavelength dispersion and polarization effects, then signal quality is improved, but IQ distortion compensation becomes difficult
Solution Approach 1:
The equalization circuit is segmented into distinct functional blocks, with the IQ distortion compensation block specifically designed to handle IQ mismatches independently. This segmentation allows the system to address IQ distortion without interfering with other compensation functions, simplifying the overall design despite the multiple distortion sources.
Solution Approach 2:
The IQ distortion compensation block is positioned to perform compensation at an appropriate stage in the signal processing chain. By addressing IQ mismatches at the reception side after coherent detection but before final signal recovery, the system preliminarily corrects these distortions, making subsequent processing easier and more effective.
3Measurement precision
If adaptive coefficient control is implemented to follow polarization state variation, then compensation accuracy is improved, but system complexity increases
Solution Approach 1:
The coefficient updating unit implements adaptive control by continuously monitoring the signal characteristics and adjusting filter coefficients in real-time. This feedback mechanism allows the system to track polarization state variations and maintain high compensation accuracy without requiring manual intervention or complex external control systems.
Solution Approach 2:
The equalization signal processing circuit performs self-adjustment through adaptive coefficient control. The system automatically updates its own filter coefficients based on the received signal characteristics, eliminating the need for external calibration or manual tuning, thereby improving accuracy while keeping the control mechanism relatively simple.
Data Source
AI summary
A detector coherent-receives a signal being transmitted from a transmitter. A filter group includes a plurality of filters connected in series along a signal path of a reception signal. The plurality of filters include a plurality of non-linear distortion compensation filters and one or more linear distortion compensation filters. A coefficient updating unit controls a filter coefficient of the plurality of non-linear distortion compensation filters and a filter coefficient of at least some of the linear distortion compensation filters. The coefficient updating unit adaptively controls the filter coefficient, by using an error back propagation method, based on a difference between an output signal being output from the filter group and a predetermined value of the output signal.