Overcoming Capacity and Energy Limits in Optical Communications

The world's Internet infrastructure is of ever increasing importance to both the national and global economy, enabling ever more efficient international trade and a host of new business opportunities. As a result data traffic on the world's networks has steadily been growing at around 40% per year over the past decade and no respite in this trend is anticipated for the foreseeable future. However, it is becoming impractical to satisfy this increased demand through the obvious and traditional measures such as improving spectral efficiency and utilization, installing more optical fibres, and increasing the number or size of the data centres, since today's telecommunications infrastructure is already estimated to be responsible for about 2% of world carbon emission (more than the aviation industry!). Consequently further capacity scaling using the existing technology is likely to have a significant impact on the environment. Another key issue is that the heat dissipation in data centres has reached its limit per unit volume, which effectively means that if current technological platforms are used to upgrade capacity then this will require new strategies for thermal management, likely further increasing the power consumption, cost and complexity. Clearly such a situation is unsustainable in the longer term.

Current networks are mostly limited - both in terms of capacity and energy efficiency - by the architectures/technologies used. These in turn have traditionally been driven by the philosophy of designing the network so as to minimize the usage of expensive and relatively unreliable optical components and exploiting the maturity of electronics - with its potential for cost reduction when mass produced - to do the majority of the signal routing, processing and transmission impairment mitigation. However, this approach - given the previously discussed energy scaling constraints - will not be sustainable moving forward, dictating a change in this approach. Specifically it will be necessary to increase the amount of optics in the network to reduce the burden placed upon the electronics. I strongly believe that the transition to more optically empowered systems is simply unavoidable.

The aim of this proposal is to investigate the possibility of employing the array of new optical components and subsystems that I am currently researching (which includes Optical Comb generators, injection locked lasers and devices that amplify signals differently depending on their phase) into optical networks, in a manner that allows for scaling to larger data transmission capacities with a simultaneous reduction in power consumption and/or better thermal management characteristics. Today, there are several main concepts relevant to future optical communications, all of them relying on having higher quality optical signals (e.g., signal-to-noise ratio), or tight control of the coherence properties of optical signals carrying independent data streams (called 'superchannel' technologies). My current research deals with development of high purity (low noise) Optical Combs that allow for tight control of coherence - promising to give both the key parameters necessary. Within the Fellowship, I plan to implement this technology into the generation and reception part of optical links. Higher signal-to-noise ratio transmitters and lower-noise and higher speed demultiplexing of data at the detection side should allow for extended reach without the need for additional in-line amplification and allow the use of modulation formats carrying more information inside the same spectral bandwidth. Among other advantages, the energy-per-transmitted-bit can be reduced in both these cases. However, I will not limit my research to optical communications and will investigate other fields where the results might also be helpful - e.g., ultraprecise transfer of time and frequency. I will work in close collaboration with academic as well as non-academic partners.

Societal impact: Technologies associated with my research field (ICT) consume more energy than avionics (with about 40% annual growth) and it is widely held within our community that photonic based approaches could lead to significant power savings in many instances, which may help in terms of environmental sustainability and protection. I consider trying to identify applications leading to lower power consumption for next-generation technology an important aspect of my research.

Academic impact: The proposed research is expected to develop innovative methodologies, equipment and techniques. It is also expected to yield highly skilled researchers as I plan to hire and train several PhD students in the course of the Fellowship. I would also contribute to the training and career development of more established researchers by working with and supervising post-doctoral researchers throughout the project. By sustaining and improving the reputation of the ORC and the University of Southampton through the world-class research, I hope to help the university to achieve its objective of improving its ranking amongst the best universities in the world, which should bring larger number of high quallity students, further improving the quality of the university, as well as its sustainability.

I will also contribute to meeting of EPSRC research challenges:

Manufacturing the future EPSRC challenge theme: It is expected that the proposed research would help enable next-generation communication and related technologies (e.g., precise time transfer relevant to GPS, etc.) and thus is expected to support the delivery of new ICT products and services that require high Internet bandwidths both in the UK and on a global scale.

Energy EPSRC challenge theme: It is recognized that photonics-aided signal processing may reduce the power requirements of ICT, as the power requirements in photonics-aided circuits do not necessary scale with the processing speed/bandwidth. Lowering power consumption in the next-generation communication networks is a key focus of my proposal.

The Western economy requires a continuous stream of innovations in order to remain competitive. I am in contact with a range of major non-academic UK organizations (including e.g. Oclaro, National Physics Laboratory, Stingray Ltd and Phoenix Photonics Ltd) to help me identify which of my research results might be of interest to them in their business, and I am ready to use their feedback in shaping my research to best effect to help them exploit the results I achieve. I am also in contact with several EU-based companies (Eblana Photonics, Ireland; CESNET, Czech Republic; Kylia, France; etc.). I firmly believe that higher UK competitiveness can be further aided via strengthening EU-based collaboration and cooperation.