Opt. Express 23, 23302–23309 (2015)

A high-speed underwater optical communications link that operates at a data rate of 4.8 Gbits s−1 over a distance of 5.4 m has been demonstrated by scientists in Saudi Arabia and Taiwan. The link is the result of work by Hassan Oubei and co-workers from King Abdullah University of Science and Technology (KAUST), National Taiwan University and National Chiao Tung University. It makes use of a 15 mW blue laser diode with a wavelength of 450 nm to transmit light pulses in the blue-green low-absorption window of seawater, which are then detected by a silicon avalanche photodiode-based receiver. A 16-QAM-OFDM modulation and multiplexing format is used to optimize the link's signal-to-noise ratio (15.63 dB) and bit error rate (2.6 × 10−3). Such high-speed underwater communication links are expected to be useful for providing data connections to sensor networks and remotely operated vehicles.