Underwater wireless transmission of high-speed QAM-OFDM signals using a compact red-light laser

Abstract

We first study the transmission property of red light in water in terms of extinction coefficient and channel bandwidth via Monte Carlo simulation, with an interesting finding that red light outperforms blue-green light in highly turbid water. We further propose and experimentally demonstrate a broadband underwater wireless optical communication system based on a simple and cost-effective TO56 red-light laser diode. We demonstrate a 1.324-Gb/s transmission at a bit error rate (BER) of 2.02 × 10^-3 over a 6-m underwater channel, by using 128-QAM OFDM signals and a low-cost 150-MHz positive-intrinsic-negative photodetector, with a record spectral efficiency higher than 7.32 bits/Hz. By using an avalanche photodetector and 32-QAM OFDM signals, we have achieved a record bit rate of 4.883 Gb/s at a BER of 3.20 × 10^-3 over a 6-m underwater channel.

Underwater optical wireless communications, networking, and localization: A survey

“…Subsequently, the authors in [33] demonstrated a UOWC system with the data rate of 4.8 Gbps using 16 quadrature amplitude modulationorthogonal frequency division multiplexing (QAM-OFDM). A UOWC system with the data rate of 4.88 Gbps was proposed in [34] by using 32 QAM-OFDM to get the transmission distance of 6 m. Recently, a 7.2 Gbps UOWC system has been proposed in [35] for 450 nm blue laser with the transmission distance of 6 m. Table I summarizes the comparison between three different kinds of underwater wireless communication systems.…”

375-nm ultraviolet-laser based non-line-of-sight underwater optical communication

“…Moreover, in the industry, the underwater transmission distance has been extended over 150 m with a data rate of 12.5 Mbps, as demonstrated by Sonardyne's BlueComm 200 system. Furthermore, the advancements of low-cost and energy-efficient light sources such as LEDs [11] and diode lasers [12] enable the construction of compact miniaturized optical transceivers for data, image, and video transmission [13].…”

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

“…A study on underwater transmission characteristics, attenuation coefficient, and channel bandwidth regarding blue, green, and red lights had been proposed, [7][8] from which an interesting finding was obtained-red light has a better transmission performance compared with blue and green lights in high turbidity water. [9][10][11][12][13][14] Therefore, an underwater wireless red-light laser transmission (UWRLLT) system is expected to provide a short-distance underwater highspeed link, similar to Wi-Fi-on-air in terms of function. In the situation of increasing popularity of oceanic exploration and oceanic leisure activities, the sense of distance experienced underwater or in the ocean is more obvious than that on the land.…”