Optical fibres underpin the development of the global data communication infrastructure and have to a large extend enabled the internet which has transform our modern society. Currently, 99% of all data is carried around the world via optical fibres, in multiple different formats, from computers or CPUs on a chip to data centres or mobile networks. The transmission distances cover many orders of magnitude – from sub-meters to thousands of kilometres. However, it is recognised that global communication systems are rapidly approaching the fundamental information capacity of current transmission technologies.

The UNLOC project funded by the EPSRC is a 5 year research programme set out to understand the achievable information capacity limits of optical communication systems. In contrast to wireless communication channel or optical channels in free space, the optical channel in fibre is nonlinear. A main research theme within UNLOC is quantifying the fundamental capacity limits for the nonlinear channels carried over optical fibres, and developing techniques to approach those limits so as to maximise the achievable channel capacity for the optical network. The challenge is to understand to what degree optical nonlinearity can also be compensated or, indeed, used, to unlock the fibre capacity, maximise both the information transmission rate and the total bandwidth. Our dedicated team of researchers at UCL, our partner institution Aston University and multiple industry partners conduct collaborative theoretical and experimental research to develop, through theory and experiment, disruptive approaches to unlocking the capacity of future optical communication systems that go beyond the limits of what is possible today. In particular, we work on new digital signal processing techniques, advanced modulation formats for information encoding and new approaches to optimised detection schemes, tailored to the nonlinear optical channel. The development of optical coherent detection techniques, able to manipulate the properties of the signal amplitude and phase in the electronic domain, both at the optical transmitter and receiver, offer the tantalising possibility to be able to mitigate detrimental nonlinearities. They potentially allow to optimally tailor both the transmission and detection to the properties of the nonlinear channel.

The research will combine techniques from information theory, coding, study of advanced modulation formats, digital signal processing and advanced photonic concepts to shape the next generations of high speed optical communications which will support the growth of the world’s communication infrastructure.

The project will follow the path of:

  • understanding the properties and the existing theory for the nonlinear optical channel in different fibre types
  • investigation of different modulation formats and DSP for tailored to the nonlinear optical channel, using the analytical and numerical simulation techniques, by extending the existing and proposing new channel model
  • implementation of the proposed DSP algorithms and study of its effectiveness using the multiwavelength terabit/s recirculating optical fibre loop test-bed through a range of optical transmission experiments.


Project lead institutions: UCL and Aston University

Project industry partners: BT, Arden Photonics, Ciena, Deutsche Telekom, Google, Huawei, Orange Labs, Oclaro, Xtera, EnSillica, Gennum, Vodaphone Group

Official website: http://www.unloc.net/

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