Efficient sensors for underwater communications

The world has become accustomed to reliable, high-speed and ubiquitous communication. Whether through physical connections or radio-based systems (e.g. WiFi and Bluetooth) we take for granted the ability for people and, increasingly, autonomous devices to communicate.

However, ranged communication in the ocean is much more challenging, especially at high data transfer rates. But this capability is beneficial for an increasing range of ocean-based activities including defence and security capabilities, waste management, safety, environmental and pollution monitoring, and commercial work including remote maintenance of pipelines, decommissioning of oil and gas infrastructure, and aquaculture.

Sub-sea communication is very challenging, with ordinary radio solutions not feasible (power consumption, range and data transfer rate are unfavourable). Sonar systems - transmitting sound waves through water - have excellent range but only support slow data rates. So, for example, it is not possible to transmit enough data for a video feed using sonar.

By contrast, optical communication - transmitting light through water - can achieve extremely high data rates. For example, the world's first live stream of multiple cameras from a submersible to a global audience was achieved in 2019 using Sonardyne Ltd.'s BlueComm technology. https://www.sonardyne.com/worlds-first-live-video-broadcast-from-underwater-uses-sonardynes-bluecomm/

However, the range of sub-sea optical communication is very limited. A major problem is stray light, which can interfere with optical communications at the optimum wavelengths (colours) for transmission through sea water. At longer ranges the communication signal is swamped by the stray light, and so the effective range of the communications system can vary drastically depending on lighting conditions (depth, time of day, artificial light sources).

Our proposal aims to further develop a new type of light sensor, originally inspired by particle physics detector technology and developed as a collaboration between particle physics and surface science research groups in Warwick. A unique property of the sensor is that it can be made totally insensitive to the stray light found in typical sub-sea environments (submersible vehicles' and divers' lights and, near the surface, sunlight or even moonlight) without needing inefficient optical filters.

This sensor could form a vital part of the next generation of an advanced optical sub-sea communications system. The system will enable more efficient and longer-range high-speed communications between remote undersea vehicles, ocean sensor stations and other sub-sea infrastructure.