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Reflections on Opening New Telecommunication Windows


Fatima Gunning


Current trends suggest that bandwidth demands will continue to increase. Optical networks research is responding to satisfy this need on several fronts: a move to spatial division multiplexing or increasing the spectral efficiency of currently deployed single mode fibres with more efficient modulation formats, perhaps also with the potential for nonlinear mitigation.

Whatever method, or plurality of methods, significant digital signal processing at the transmitter and/or receiver will be required.  The latter is already appearing in the marketplace as commodity hardware building blocks, in particular with 200G/400G solutions for metropolitan interconnect between hyper-scale datacentres.

But what might the future hold? Although C+L bands have been researched for several decades, it is only recently that there has been a shift to offer such systems to the market. An alternative approach is perhaps to extend the available fibre bandwidth beyond C+L into a fourth telecommunications window. Is this new? Well, not really. Back in the 80s, before EDFAs transformed transmission networks, research efforts were not only focused on coherent detection, but also investigated low-loss fibre materials and geometries at wavelengths beyond the Rayleigh scattering edge and just before the infrared resonance in glass at mid-infrared.

We know how to exploit rare-earth doped glass for amplification, so now is the time to reconsider transmission around 2µm wavelength. There is a suite of emerging new fibres [designs, geometries] which can support greater bandwidths, and also new optical components that act as key enabling technologies to operate at this waveband. 

As we begin to explore further into the IR, we can appreciate that silicon’s increased transparency would enable very efficient silicon-based optical devices, which would complement silicon-based electronic processing devices that benefited from a half-century of Innovation exploiting Moore’s Law.

So in this webinar I will reflect on the potential of opening new wavelength windows for telecommunications, exposing the key enabling technologies that are emerging, bringing to a new journey in the decades to come.