Enabling gigabits-per-second underwater wireless optical communication with a Kramers-Kronig relation-based...

Area of Science:

• Optical Communications
• Signal Processing

Background:

• Underwater wireless optical communication (UWOC) systems face challenges in achieving high data rates over extended distances.
• Existing modulation schemes like Quadrature Amplitude Modulation (QAM) and Carrierless Amplitude and Phase (CAP) modulation have limitations in complexity and efficiency for UWOC.

Purpose of the Study:

• To propose and evaluate a novel modulation scheme for UWOC systems based on the Kramers-Kronig relation.
• To enable high-speed data transmission in UWOC links with reduced computational complexity.

Main Methods:

• Development of a modulation scheme leveraging the Kramers-Kronig relation to encode amplitude and phase information.
• Utilizing 8-coupled green laser diodes (LDs) for data transmission.
• Implementation of a transmitter requiring only a single Hilbert filter, avoiding the need for a mixer.
• Employing a two-stage equalizer, including a CAP equalizer and an Artificial Neural Network (ANN) equalizer, to enhance signal quality.

Main Results:

• Achieved a data transmission rate of 1 Gb/s over a 100-meter UWOC link.
• Demonstrated a bit error rate (BER) of 2 × 10⁻³, which is below the hard decision forward error correction (HD-FEC) threshold.
• Significantly reduced computational complexity compared to traditional QAM and CAP modulation schemes.

Conclusions:

• The proposed Kramers-Kronig relation-based modulation scheme offers an efficient and effective solution for high-speed UWOC.
• The scheme's reduced complexity and strong performance make it a promising technology for future UWOC applications.
• Future research will focus on extending the transmission distance for UWOC systems.