Research Fellows Directory
Dr Andrew Ellis
Broadband communication now underpins much of modern society, with strong influence on social interaction, education, entertainment, government and commence to name a few. However, in order to meet these demands the number of wavelengths, or colours, used has steadily increased allowing operators to avoid installing new cables at significant cost. However, as a consequence the light intensity at the core of an optical fibre in the core of the network now exceeds that of the sun at the upper surface of the Earth’s atmosphere. Unsurprisingly, the properties of the optical fibre become influenced by such high intensities, distorting the communication signals. We have included these nonlinear distortions in Shannon’s analysis, predicting a Nonlinear Shannon limit. Current networks operate close to this limit, and unless resolved network operators will be forced to pass on the cost of new cables with obvious implications.Recently, we demonstrated that it is possible to transmit information beyond this limit using a simple device called an “optical phase conjugator”, which can be thought of as a spectral mirror , translating the blue wavelengths into red ones, and vice versa. We used this device to reduce the nonlinear signal distortion without any other changes to the system. .
Our studies of optical networks and outreach activities led to OFCOMs announcement of targets towards Pure Fibre services in the access network, and we beleive that they contributed to the governments announcement of a substantial subsidy for pure fibre networks in the 2016 autumn statement.