100 m/500 Mbps underwater optical wireless communication using an NRZ-OOK modulated 520 nm laser diode

TLDR

Tap water used in the experiments has an attenuation coefficient comparable to pure seawater. The study proposes and experimentally demonstrates a long‑distance, high‑speed underwater optical wireless communication system using a low‑cost green laser diode and NRZ‑OOK modulation. The system employs a pigtailed single‑mode 520 nm green laser diode with NRZ‑OOK modulation, operates over tap water with seawater‑like attenuation, and can extend distance by reducing received power to the minimum required for the target data rate. The system achieved 500 Mbps over 100 m of tap water with a BER of 2.5 × 10⁻³, below the FEC limit, and predicts 146 m at 500 Mbps and 174 m at 100 Mbps.

Abstract

In this paper, we proposed and experimentally demonstrated a long-distance high-speed underwater optical wireless communication (UOWC) system in a laboratory environment by using a low-cost green laser diode (LD) and power-efficient non-return-to-zero on-off keying (NRZ-OOK) modulation. The system successfully achieved a data rate of 500 Mbps through a 100 m tap-water channel by using a pigtailed single-mode fiber 520 nm green LD. The tap water was measured to have an attenuation coefficient comparable to pure seawater. The measured system bit error rate (BER) value of 2.5 × 10-3 was below the forward error correction (FEC) limit of 3.8 × 10-3 with 7% overhead. The distance can be extended if the received optical power is allowed to reduce to the minimum power to meet the data rate requirement. Based on the measured minimum required power and the power decay model in the water channel, the transmission performance was predicted to be 146 m/500 Mbps and 174 m/100 Mbps.