Optical Receiver Phase Error Compensation via Dual-Stage Exponentiation
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Solution Overview
Problem
Digital-coherent receiving devices in optical transmission systems face limitations in phase-error compensation, particularly with phase slip occurring when phase errors exceed 2π/2n, leading to burst errors in received signals due to the limited phase-estimation range of existing methods like exponentiation by n.
Innovation Solution
A receiving device that includes a synchronizing circuit to extract a pilot signal, estimate phase errors, and conduct phase rotation on constellation points, allowing for improved phase compensation by consolidating constellation points into a single area, thereby reducing phase noise and preventing phase slip.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If exponentiation by n is used to compensate phase errors, then phase noise is reduced and constellation points are consolidated, but phase slip occurs when phase errors exceed 2π/2n leading to burst errors
Solution Approach 1:
The patent segments the phase compensation process into two distinct stages: (1) gross phase error compensation using exponentiation by n to handle large phase deviations, and (2) fine phase error compensation using a second exponentiation by m (where m < n) to correct residual phase errors. This segmentation allows each stage to operate within its optimal phase error range, preventing phase slip while maintaining high phase estimation accuracy.
Solution Approach 2:
The patent dynamically adapts the exponentiation order based on the detected phase error magnitude. When phase errors are large, it uses exponentiation by n for gross compensation; when phase errors are small, it uses exponentiation by m for fine compensation. This dynamic adaptation ensures that the phase compensation method always operates within the valid phase estimation range, preventing phase slip while maintaining high accuracy.
2Device complexity
If a single exponentiation by n is used for phase compensation, then the process is simple, but the phase estimation range is limited to 2π/2n
Solution Approach 1:
The patent segments the phase compensation into two sequential processes with different exponentiation orders. The first process uses exponentiation by n for gross phase error compensation, and the second process uses exponentiation by m (m < n) for fine phase error compensation. This segmentation extends the overall phase estimation range beyond what a single exponentiation method can achieve, while keeping each individual process relatively simple.
Solution Approach 2:
The patent ensures continuous phase compensation by chaining two exponentiation processes together. The output of the first exponentiation by n feeds into the second exponentiation by m, creating an uninterrupted compensation chain that covers a wider phase error range. This continuous action ensures that no phase error magnitude is left uncorrected, enhancing adaptability while maintaining procedural simplicity.
Data Source
AI summary
A receiving device receives a received signal in which a data signal, modulated by using a phase modulation method, and a pilot signal are time-multiplexed. The receiving device includes a synchronizing circuit that synchronizes the phase of the received signal. The synchronizing circuit extracts a pilot signal from the received signal. The synchronizing circuit estimates a phase error by comparing the extracted pilot signal and a predetermined pattern. The synchronizing circuit conducts phase rotation on constellation points of the received signal in accordance with the reference phase, obtained from the phase error, and the phase in the modulation method related to the received signal. The synchronizing circuit estimates a phase estimate value of the received signal in accordance with the constellation points, on which phase rotation has been conducted. The synchronizing circuit compensates for a phase error of the received signal in accordance with the phase estimate value.