Optical Receiver Phase Modulation Stabilizes Polarization Separation
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Solution Overview
Problem
Polarization-separation multiplexing optical transmission systems face issues with erroneous convergence in adaptive equalization filters and residual delay interference, leading to unstable frame synchronization and increased bit error rates, particularly in long-distance transmission.
Innovation Solution
An optical receiver is designed with a phase modulation unit that modulates the local oscillation light, a coherent detection unit for interference and conversion of the optical signal, and a polarization separation unit to stabilize polarization separation and reduce bit error rates.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If an adaptive equalization filter based on ordinary envelope constant modulus algorithm is used for polarization separation, then the system can process polarization-multiplexed signals, but erroneous convergence occurs and polarization separation cannot be carried out stably
Solution Approach 1:
The invention changes the control parameter from ordinary envelope constant modulus to improved envelope constant modulus, which modifies the convergence criterion of the adaptive equalization filter. This parameter change enables the filter to correctly converge to the polarization separation state by adjusting the mathematical condition for convergence, thereby resolving the erroneous convergence problem while maintaining polarization separation stability
Solution Approach 2:
The invention introduces a feedback mechanism that monitors the convergence state of the adaptive equalization filter and adjusts the equalization coefficients accordingly. By continuously feedbacking the error signal based on the improved envelope constant modulus algorithm, the system can correct deviations and maintain stable polarization separation throughout operation
2Ease of operation
If adaptive equalization filter is used for polarization separation, then signal processing is enabled, but residual delay interference in the same polarization causes anomalies in frame synchronization
Solution Approach 1:
The invention segments the equalization process into distinct stages: polarization separation using the adaptive equalization filter, followed by separate delay interference removal processing. By dividing the signal processing into these independent stages, the system can address frame synchronization anomalies through dedicated delay compensation algorithms without affecting the overall signal processing capability
Solution Approach 2:
The invention introduces an intermediary processing stage between polarization separation and final signal recovery. This intermediate stage specifically targets and removes delay interference in the same polarization, acting as a mediator that resolves the synchronization anomaly while preserving the beneficial signal processing capabilities of the adaptive equalization filter
3Productivity
If transmission speed is increased to meet capacity demands, then data rate is improved, but transmission penalties such as waveform distortion become serious in long-distance transmission
Solution Approach 1:
The invention replaces traditional optical-domain compensation methods with electrical-domain digital signal processing. By using adaptive equalization filters and digital algorithms to compensate for wavelength dispersion and polarization mode dispersion, the system can maintain high transmission rates over long distances without suffering from the limitations of optical compensation, thus improving both productivity and reliability
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
The phase modulation of local oscillation light on the optical receiver side stabilizes polarization separation, reducing bit error rates and preventing erroneous convergence in adaptive equalization filters, thus enhancing the reliability of long-distance optical transmission.
Implementation Method 1
a coherent detection unit that causes the received optical signal and the local oscillation light, which has been phase-modulated by the phase modulation unit, to interfere and converts the optical signal to an electrical signal
Data Source
AI summary
An optical receiver including: a phase modulation unit that generates local oscillation light and modulates a phase of the local oscillation light; a coherent detection unit that causes a received optical signal and the local oscillation light phase-modulated by the phase modulation unit to interfere and converts the optical signal to an electrical signal; a polarization separation/adaptive equalization unit that performs polarization separation and adaptive equalization on the electrical signal after coherent detection; and decoding units that decode the polarization-separated electrical signals outputted from the polarization separation/adaptive equalization unit.