Optical Receiver Phase Cycle Slip Reduction
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Solution Overview
Problem
In optical transmission systems using coherent detection, phase cycle slips occur due to noise and non-linear optical effects, leading to incorrect carrier phase estimation and increased bit error rates, with existing solutions like differential coding and pilot-based correction either increasing bit error rates or reducing transmission efficiency.
Innovation Solution
A phase cycle slip reduction system that includes a gain adjustment circuit to improve carrier phase estimation accuracy and a phase cycle slip determination/compensation unit to detect and compensate phase cycle slips, reducing their occurrence without increasing bit error rates or degrading transmission efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If differential coding is used to counter phase cycle slip, then phase cycle slip effects are restricted, but bit error rate increases
Solution Approach 1:
The patent introduces a phase cycle slip detection unit as an intermediary component that monitors the carrier phase estimation output and detects cycle slips. When a cycle slip is detected, a phase cycle slip compensation unit acts as a mediator to correct the phase error by adjusting the phase estimation. This intermediary detection and compensation mechanism resolves the contradiction by providing phase cycle slip protection without requiring differential coding, thus avoiding the bit error rate penalty.
2Reliability
If pilot-based correction is used to detect and correct phase cycle slips, then phase synchronization is restored, but transmission efficiency decreases
Solution Approach 1:
The patent implements a self-service mechanism where the phase cycle slip detection unit continuously monitors the carrier phase estimation output and automatically detects and triggers compensation when cycle slips occur. The system serves itself by using its own estimation output for detection and correction, eliminating the need for external pilot symbols. This self-service approach maintains transmission efficiency while restoring phase synchronization accuracy.
3Measurement precision
If carrier phase estimation is performed continuously for each symbol, then phase tracking is improved, but phase cycle slips occur due to noise and non-linear optical effects
Solution Approach 1:
The patent implements a feedback mechanism where the carrier phase estimation output is fed back to a detection unit that monitors for cycle slips. When a cycle slip is detected in the feedback loop, a compensation unit adjusts the phase estimation and feeds the corrected value back into the system. This feedback control stabilizes the phase estimation by continuously correcting errors caused by noise and non-linear optical effects, resolving the contradiction between tracking accuracy and estimation stability.
Data Source
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AI summary
An optical receiving device receives an optical signal that has been modulated by means of phase modulation or quadrature amplitude modulation, converts the received optical signal into an electrical signal using coherent detection, and performs phase compensation on the converted received signal, and includes: a carrier phase estimation unit that estimates carrier phase errors in a received symbol string obtained from the received signal; a gain adjustment unit that performs gain adjustment on symbols input into the carrier phase adjustment unit; a phase cycle slip reduction unit that, by performing statistical processing on an output from the carrier phase estimation unit, detects general noise that causes a phase cycle slip, and reduces the phase cycle slip; and a phase compensation circuit that compensates carrier phase errors contained in the received signal using an output from the carrier phase estimation unit.