200-m/500-Mbps underwater wireless optical communication system utilizing a sparse nonlinear equalizer with a...

Area of Science:

• Optical Communications
• Signal Processing
• Underwater Technology

Background:

• Underwater wireless optical communication (UWOC) systems suffer from performance degradation due to linear and nonlinear impairments.
• Limited device bandwidth and inherent nonlinearity significantly impact signal quality and data rates.

Purpose of the Study:

• To propose and evaluate a sparse Volterra series model-based nonlinear post equalizer for mitigating impairments in UWOC systems.
• To enhance system performance and data rates by addressing nonlinear distortions and inter-symbol interference (ISI).

Main Methods:

• Development of a sparse Volterra series model for nonlinear equalization.
• Implementation of a Variable Step Size Generalized Orthogonal Matching Pursuit (VSgOMP) algorithm for efficient Volterra equalizer compression.
• Integration of VSgOMP with generalized orthogonal matching pursuit (gOMP) and adaptive step size methods.

Main Results:

• Achieved a maximum data rate of 500 Mbps over 7m and 200m underwater transmissions.
• Reduced the number of kernels in the sparse Volterra equalizer by 70% without significant Bit Error Rate (BER) degradation.
• The VSgOMP algorithm demonstrated significant reductions in running time compared to OMP and ROMP schemes (68.6% and 29.2% respectively).

Conclusions:

• The proposed sparse Volterra equalizer with the VSgOMP algorithm effectively mitigates nonlinear impairments and ISI in UWOC systems.
• This approach enables high-speed, long-distance underwater optical communication with improved efficiency.
• This represents the first application of a sparse Volterra equalizer combined with VSgOMP for nonlinear equalization in long-distance, high-speed UWOC systems.