Optical Receiver Chromatic Dispersion Compensation
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Solution Overview
Problem
Existing digital coherent optical receivers face challenges in accurately estimating and compensating for chromatic dispersion in a short time, leading to delays in system recovery during optical path switching or failures.
Innovation Solution
An optical receiver configuration that includes a coherent receiver, A/D converter, waveform distortion compensator, phase detector, phase adjuster, demodulator, phase controller, peak detector, and compensation controller, which adjusts the sampling phase to detect peak values in phase information, enabling precise chromatic dispersion compensation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If chromatic dispersion is estimated based on transmission path distance and optical fiber characteristics, then the estimation process is simple, but the estimation accuracy is low due to large margin of error
Solution Approach 1:
The patent replaces the mechanical/mathematical calculation method (based on distance and fiber characteristics) with an electrical signal processing method. By injecting test signals and measuring the actual phase response of the optical fiber through electrical signal analysis, the system achieves accurate chromatic dispersion measurement without relying on theoretical calculations, thus resolving the contradiction between estimation simplicity and accuracy.
2Reliability
If chromatic dispersion compensation amount is determined during error correction procedure, then all demodulated signals can be corrected, but the estimation time becomes longer delaying system recovery
Solution Approach 1:
The patent performs chromatic dispersion estimation using test signal injection and phase response measurement before the main signal demodulation and error correction processes. By obtaining the chromatic dispersion compensation amount in advance through this preliminary electrical signal analysis, the system can immediately apply the correct compensation settings when switching optical paths, avoiding the time-consuming iterative error correction approach and enabling rapid system recovery while maintaining correction accuracy.
3Ease of operation
If analog clock recovery circuit is used to estimate chromatic dispersion, then clock signals are available for estimation, but residual dispersion is greater making accurate estimation difficult
Solution Approach 1:
The patent replaces the analog clock recovery method with a digital signal processing approach. Instead of using analog phase-locked loops that suffer from residual dispersion, the system injects known test signals, converts them to electrical signals, and performs digital correlation and phase analysis to accurately measure chromatic dispersion. This substitution of analog mechanical recovery with digital signal processing eliminates the residual dispersion problem while maintaining operational simplicity.
Data Source
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Figure 3A~3B
AI summary
An optical receiver includes: a waveform distortion compensator (41) to perform an operation on digital signal representing an optical signal generated by an A/D converter to compensate for waveform distortion of the optical signal; a phase detector (42) to generate phase information representing sampling phase of the A/D converter; a phase adjuster (43) to generate digital signal representing an optical signal in which the sampling phase of the A/D converter is adjusted from an output signal of the waveform distortion compensator using the phase information; a demodulator (44) to generate a demodulated signal from the output signal of the phase adjuster; a phase controller (45) to control the sampling phase of the A/D converter; a peak detector (48) to detect a peak value of the phase information while the sampling phase of the A/D converter is controlled by the phase controller; and a compensation controller (49) to control the waveform distortion compensator using the peak value.