Subsea ultraviolet solar-blind broadband free-space optics communication

We examine the potential of subsea free-space optics (FSO) for sensor network applications leveraging the emerging technologies of highly sensitive photon-counting detectors and semi-conductor LED and laser light sources in the UV solar blind. Monitoring oil and gas production installations is the niche application discussed. The merits of FSO include the capacity for broadband communication that would enable the transmission of video data in real time, which is not possible with other technologies at present. However, subsea FSO is challenged by high extinction and the immense variability of background illumination in shallow waters. This has stimulated us to investigate the potential of underwater FSO in the UV solar-blind spectral range, where background illumination is nearly nonexistent and considerable scattering occurs. The achievable performance is compared to transmission at 520nm, where, in Clear Ocean, data rates of 100Mbps can be transmitted over distances of ∼170m, falling to under 15m in harbor waters. It is anticipated that ranges of 12m can also be obtained with UV solar-blind wavelengths, although experimental corroboration is not yet available.