Underwater wireless optical communication system using a 16-QAM modulated 450-nm laser diode based on an FPGA

Area of Science:

• Optical Engineering
• Wireless Communication
• Oceanography

Background:

• Underwater wireless optical communication (UWOC) is crucial for high-bandwidth data transfer in aquatic environments.
• Existing UWOC systems face challenges with data rates and transmission distances due to water's optical properties.

Purpose of the Study:

• To develop and evaluate a high-data-rate UWOC system for short to moderate underwater links.
• To demonstrate the feasibility of using 16-ary quadrature amplitude modulation (QAM) for efficient underwater data transmission.

Main Methods:

• A UWOC system was designed using a 450-nm laser diode and a 150-MHz PIN photodiode.
• 16-ary QAM modulation was implemented on a field-programmable gate array (FPGA) for high data throughput.
• Experiments were conducted in artificial seawater (35‰ salinity) to measure performance.

Main Results:

• The system achieved a data rate of 50 Mbps over a 3-meter distance.
• A bit error rate (BER) of 7.11×10^-4 was recorded, which is below the forward error correction target of 3.8×10^-3.
• The attenuation coefficient of the seawater was measured at 0.481.

Conclusions:

• The developed UWOC system provides reliable high-speed communication capabilities.
• The system is suitable for point-to-point UWOC links over short to moderate underwater distances.
• FPGA-based 16-ary QAM is an effective modulation scheme for enhancing UWOC performance.