Optical Signal Nonlinear Compensation via Dispersion-Based Coefficient Setting
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Solution Overview
Problem
Existing methods for demodulating optical signals that are polarization multiplexed and multilevel modulated, especially those requiring nonlinear compensation, struggle when the received signal quality is low, as they cannot set the necessary coefficients for effective nonlinear compensation.
Innovation Solution
A signal processing device and method that generate an electric signal from the optical signal, perform dispersion compensation using a first filter coefficient, determine a second filter coefficient based on the amount of dispersion for nonlinear effect compensation, and apply this coefficient to compensate for nonlinear effects in the signal processing unit.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If backpropagation is used for nonlinear compensation with combined dispersion and nonlinear compensation functions, then waveform distortion is compensated, but the number of FFT/IFFT circuits increases leading to larger mounting area and higher power consumption
Solution Approach 1:
The patent divides the compensation process into separate stages: dispersion compensation is performed first using FFT/IFFT circuits, then nonlinear compensation is performed separately using backpropagation. This segmentation allows each function to be optimized independently, reducing the need for multiple combined FFT/IFFT circuits while maintaining effective waveform distortion compensation.
Solution Approach 2:
The patent performs dispersion compensation as a preliminary step before nonlinear compensation. By removing dispersion effects first, the subsequent nonlinear compensation using backpropagation becomes more effective and requires fewer circuit stages, thereby reducing the overall number of FFT/IFFT circuits needed.
2Reliability
If existing nonlinear compensation methods are used, then compensation is effective for high-quality signals, but coefficient setting becomes impossible for low-quality signals that require nonlinear compensation for demodulation
Solution Approach 1:
The patent implements a feedback mechanism where the system monitors the quality of the received signal and automatically adjusts the nonlinear compensation coefficients accordingly. This feedback loop enables the system to adapt to different signal quality conditions, allowing coefficient setting to work effectively for both high-quality and low-quality signals that require nonlinear compensation for demodulation.
Solution Approach 2:
The patent makes the nonlinear compensation coefficients dynamic rather than fixed. The system can adjust coefficients in real-time based on signal conditions, enabling it to handle varying signal qualities including low-quality signals that require nonlinear compensation for successful demodulation.
Data Source
AI summary
An optical reception device 20 includes an electric signal generation unit 200, a linear compensation unit 301, a nonlinear compensation unit 300, and a second coefficient setting unit 400. The electric signal generation unit 200 generates an electric signal based on an optical signal received over a transmission path 30. The linear compensation unit 301 performs processing for compensating for dispersion that occurs on optical signal in the transmission path 30 to the electric signal, using a first filter coefficient. The second coefficient setting unit 400 determines a second filter coefficient for compensating for a nonlinear effect that occurs on the optical signal in the transmission path 30, using an amount of dispersion that occurs in the transmission path 30. The nonlinear compensation unit 300 performs processing for compensating the electric signal for the nonlinear effect, using the second filter coefficient that is determined by the second coefficient setting unit 400.