11.2 Gbps 100-meter free-space visible light laser communication utilizing bidirectional reservoir computing...

Area of Science:

• Optical Communications
• Signal Processing
• Machine Learning

Background:

• Visible light communication (VLC) systems face challenges with signal distortion due to nonlinearities.
• Existing equalization techniques like Least Mean Square (LMS) and Neural Networks (NNs) have limitations in performance, training time, or parameter requirements.

Purpose of the Study:

• To introduce and evaluate a novel post-equalization technique for VLC systems.
• To demonstrate the effectiveness of bidirectional reservoir computing (BiRC) in mitigating nonlinearities and improving signal quality.

Main Methods:

• Implementation of a post-equalization strategy based on bidirectional reservoir computing (BiRC).
• Application of the BiRC technique to waveform-to-symbol level equalization in a visible light laser communication system.
• Experimental setup involving a 100-meter transmission using a 520 nm green laser and 32-amplitude phase shift keying (32APSK) modulation.

Main Results:

• Successful 100-meter transmission of a 32APSK signal at 11.2 Gbps.
• Achieved a bit error rate (BER) below the 7% hard decision forward error correction (HD-FEC) threshold of 3.8E-3.
• Demonstrated superior nonlinearity resistance compared to LMS equalizers and reduced training requirements over NN-based equalizers.

Conclusions:

• Bidirectional reservoir computing (BiRC) offers an effective and efficient post-equalization solution for visible light communication.
• The proposed BiRC technique enables high-speed, long-distance VLC with robust performance against signal impairments.
• This innovation paves the way for advanced VLC systems with enhanced data rates and reliability.