Underwater Video Achieves Quality by Improving Bandwidth

Researchers have demonstrated high-quality real-time video streaming over an underwater wireless optical communication (UWOC) link, up to a five-meter distance, using phase-shift keying modulation and quadrature amplitude modulation to improve the accuracy of the detected signal. UWOC systems, such as the one developed by researchers from King Abdullah University of Science & Technology (KAUST), could provide flexible and cost-effective means for streaming high-quality underwater video images.

Existing technologies like acoustic communications and low-frequency radio waves are limited by narrow bandwidths and the need for large antennae and high-transmission powers, making them unsuitable for streaming good-quality, real-time video. UWOC systems could consume significantly less power and offer the higher bandwidths required for streaming live video.

Abdullah Al-Halafi checks the received optical signal power through the underwater channels. Courtesy of KAUST.

The KAUST team’s communication system uses software defined platforms connected to a commercial TO-9 packaged pigtailed 520 nanometer, directly modulated laser diode (LD) with 1.2 gigahertz bandwidth as the optical transmitter, and an avalanche photodiode (APD) module as the receiver.

“We first built the real-time video transmission system and then integrated it into an UWOC setup,” said researcher Abdullah Al-Halafi. “Although the design and development of the system were very challenging, its ability to be programed enabled us to reconfigure the system into several different arrangements.”

To simulate various underwater channels, researchers performed experiments on clear, coastal and harbor I and harbor II ocean water types, measuring the bit error rates (the errors that occurred during transmission of the video streams). They further evaluated the quality of the received live video images using structural similarity. According to researchers, the system achieved values of about 0.9 for the first three water types, and about 0.7 for harbor II.

“Our system produced the highest-quality video streaming so far achieved in UWOC systems and provides a reconfigurable and cost-effective communications system for underwater live video streaming,” said Al-Halafi. “It could lead to advances in underwater research and the discovery of new resources.”

Wireless technologies capable of producing real-time video underwater could be useful for inspecting and maintaining underwater pipelines and offshore oil and gas fields.

The research was published in the Journal of Optical Communications and Networking, a publication of OSA, the Optical Society (doi: 10.1364/JOCN.9.000826).