Optical Receiver Phase Polarization Control for Stable Coherent Detection
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Solution Overview
Problem
The existing digital coherent optical communication techniques, such as those described in PTL 1, face challenges in maintaining stable reception quality due to noise increase when gain is set high to compensate for signal components fixed on the in-phase or quadrature axes, leading to signal quality degradation.
Innovation Solution
An optical receiver is designed with local oscillation light output, phase adjustment, polarization control, multiplexing, photoelectric conversion, and control means to adjust the phase and polarization of the local oscillation light based on reception status, ensuring stable coherent detection and signal quality.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If gain is set high to compensate for signal components fixed on the in-phase or quadrature axes, then output amplitude increases, but noise increases and signal quality degrades
Solution Approach 1:
The patent applies dynamic gain control where the gain is adjusted based on the reception status of the optical signal. The control means monitors the signal quality and dynamically modifies the gain setting in the detection element, transitioning from a static high gain to an adaptive gain that prevents noise amplification while maintaining sufficient output amplitude for reliable detection.
Solution Approach 2:
The patent changes the gain parameter based on reception status information. By monitoring signal quality metrics and adjusting the gain parameter accordingly, the system optimizes the balance between output amplitude and noise level, preventing the degradation of signal quality that occurs with consistently high gain settings.
2Reliability
If phase and polarization of local oscillation light are not adjusted, then system complexity is reduced, but reception quality becomes unstable
Solution Approach 1:
The patent implements feedback control where the control means receives information about reception status and uses this feedback to adjust the phase and polarization of the local oscillation light. This closed-loop system maintains stable reception quality by continuously monitoring and correcting deviations, while the automatic nature of the feedback reduces the need for complex manual intervention.
Solution Approach 2:
The system performs self-adjustment of phase and polarization parameters through automatic control mechanisms. The control means autonomously monitors reception quality and modifies the local oscillation light parameters without requiring external intervention, enabling the system to maintain optimal performance while managing complexity through automation.
3Measurement precision
If frequency of local oscillation light is not set based on optical signal frequency, then device complexity is reduced, but coherent detection accuracy decreases
Solution Approach 1:
The patent applies preliminary frequency setting where the frequency of the local oscillation light is pre-configured based on the expected frequency of the optical signal. This preliminary action ensures that the coherent detection is performed at the correct frequency offset, improving detection accuracy while avoiding the need for complex real-time frequency adjustment mechanisms.
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 solution enables stable coherent detection and maintains reception signal quality by adjusting the phase and polarization of local oscillation light, reducing noise and improving bit error rate in optical communication systems.
Implementation Method 1
The photoelectric conversion means converts the optical signal multiplexed by the multiplexing means into an electric signal
Data Source
AI summary
A local oscillation light output unit; a phase adjustment unit; a polarization control unit; a multiplexing unit; a photoelectric conversion unit; a demodulation unit; and a control unit. The phase adjustment unit adjusts the phase of local oscillation light. The polarization control unit controls polarization rotation of an optical signal. The multiplexing unit multiplexes the local oscillation light output from the phase adjustment unit with the optical signal output from the polarization control unit. The demodulation unit performs a demodulation process based on an electric signal obtained through conversion performed by the photoelectric conversion unit. The control unit, on the basis of information about the reception status of the optical signal, controls the execution of at least one of the phase adjustment of the local oscillation light in the phase adjustment unit and the polarization rotation of the optical signal in the polarization control unit.