48 Gbit/s 16-QAM-OFDM transmission based on compact 450-nm laser for underwater wireless optical communication

Abstract

We experimentally demonstrate an underwater wireless optical communications (UWOC) employing 450-nm TO-9 packaged and fiber-pigtailed laser diode (LD) directly encoded with an orthogonal frequency division multiplexed quadrature amplitude modulation (QAM-OFDM) data. A record data rate of up to 4.8 Gbit/s over 5.4-m transmission distance is achieved. By encoding the full 1.2-GHz bandwidth of the 450-nm LD with a 16-QAM-OFDM data, an error vector magnitude (EVM) of 16.5%, a signal-to-noise ratio (SNR) of 15.63 dB and a bit error rate (BER) of 2.6 × 10(-3), well pass the forward error correction (FEC) criterion, were obtained.

Performance evaluation of underwater wireless optical communications links in the presence of different air bubble populations

“…However, many relevant studies have mostly focused on the effects of absorption and scattering by particles on the optical channel [6][7][8][9], system level design and demonstrations [10][11][12][13], underwater turbulence [14][15][16], and there is little study on the effect of air bubbles in UWOC channels [17]. Air bubbles in the oceans are mainly produced by breaking surface waves and rain [18].…”

Blue Laser Diode Enables Underwater Communication at 12.4 Gbps

“…The reflector-induced loss could be excluded in a real case to the extent that the aforementioned transmission quality of the reflector-free UWOC link could be further improved. By comparison, our previous study employed a blue LD to demonstrate a tap water-based UWOC system for achieving a data rate of 4.8 Gbps over a 5.4-m distance33, which revealed a bit rate-distance product of 25.92 Gbps-m. A pair of plano-convex lenses with a 25.4-mm diameter and a 25.4-mm focal length was employed to collimate the laser beam for transmission and receiving. In contrast, the current study enabled the blue LD-based high-speed UWOC to be employed in tap-water for 1.7-m and 10.2-m transmissions at 12.4 and 5.6 Gbps, respectively.…”

“…More recently, Oubei et al . demonstrated a 450-nm LD-based UWOC system for carrying 4.8-Gbps 16-QAM OFDM data33, and Xu et al . proposed a 4.883-Gbps UWOC system for transmitting 32-QAM OFDM data over 6 m34.…”

6-m/10-Gbps underwater wireless red-light laser transmission system

“…[1][2][3][4][5] Compared with blue-laser light, the absorption rate of redlaser light in clear water is higher, resulting in a shorter transmission distance. However, red laser has a significantly wider frequency response at a much lower price and, thus, provides a considerably wider transmission bandwidth.…”

“…The system was employed to demonstrate a blue-light laser underwater transmission system. [15][16][17] The 16-QAM-OFDM has a very high-frequency effect because it can transmit nearly four times the amount of data at a low digital rate. To the best of the authors' knowledge, this study is the first attempt to adopt a 680-nm VCSEL transmitter in a 10-Gbps 16-QAM-OFDM UWRLLT system.…”