Signal bandwidth enhancement in Parametric amplifiErs by Exploiting multi-moDe nonlinear effects in fibres (SPEED)

The development of energy-efficient, ultra-high capacity communication networks capable of connecting people and businesses seamlessly everywhere is one of the most important challenges facing modern society. The traffic on the global communications infrastructure keeps rapidly increasing, typically at a rate of 40% per annum, driven by the communication services applications that are drastically increasing in number ( e.g. Twitter, YouTube, Facebook, etc.) and demand on bandwidth (e.g. HDTV, 3D,...).

This continuously increase of available bandwidth/ capacity in a single optical fibre has been ensured by the enormous progress in optical communication systems over the years (e. g. employing many wavelengths or new types of complex modulated signals). When transmitting these new types of signals, current networks need to change their corresponding hardware (e. g. implementing new transmitters and receivers). However, the ideal network should handle them at no extra hardware cost.

The project SPEED proposes to investigate all-optical solutions that are compatible with the existing fibre technology and functionalities to guarantee that the network can handle signals that may be developed and used in coming years. This will guarantee that the consumer can continue enjoying new bandwidth-hungry services that have being offered at no extra cost.

So far, the proposed all-optical solutions are mainly based on coherent mixing in single mode nonlinear media. SPEED aims to develop a new nonlinear platform technology, the multi-mode one, with the vision to propose novel low-cost and energy-efficient solutions for the future-proof upgradable transmission systems discussed above. A detailed study will be conducted to demonstrate the advantages and the enhanced functionality offered by multi-mode nonlinear platform as compared to the widely developed single-mode one in a variety of disruptive applications in many key areas. The added degree of freedom given by the spatial dimension of few-mode waveguides will improve the system performance, mainly in terms of broadband operation and noise by a factor that is proportional to the number of modes.

The development of energy-efficient, ultra-high capacity communication networks capable of connecting people and businesses seamlessly everywhere is one of the most important challenges facing modern society. In 2012 alone, 4 billion hours of video were viewed via YouTube, each month and 7 petabytes of photo content was added to Facebook every single month, with the growth traffic on the global communications infrastructure typically running at 40% per annum.

The enormous progress in optical communication systems over the years (e. g. employing many wavelengths or new types of modulation) has ensured a continuous upgrade of the capacity on all parts of the network. Current networks respond to the signal upgrade changing the corresponding hardware (e. g. implementing new transmitters and receivers) to accommodate their processing. However, ideal networks should process new modulations and wavelengths without having to upgrade their corresponding hardware.

The optical parametric solutions proposed within SPEED guarantee their format and bit-rate transparency, allowing the processing of any type of modulated signals that may be developed and used in coming years, and, thus, representing low-cost and energy-efficient solutions for the continuously growing networks discussed above.

Similarly, the currently deployed erbium doped fibre amplifiers to optically boost the signal power, have a fixed bandwidth of the order of 5 THz, which has rapidly being exhausted. Therefore, there is a need to introduce novel optical amplifiers covering substantially broader bandwidths and again parametric processes represent a perfect remedy to the problem.

The capability of transmitting huge amounts of information (close to the fibre limit) is not only about being able to stream movies or games in a blink of an eye. The internet is transforming and globalizing society, bringing people and nations closer together and becoming the universal source of information for billions of people. Tele-conferencing, tele-education, tele-care, tele-medicine and many other applications, where vast amount of data needs to be transferred, will benefit from this work. Thus, it is believed that the societal impact of the proposed research could be profound, with all the connected society being the potential beneficiaries.

The complete multi-mode nonlinear understanding proposed within SPEED will have a clear and substantial impact on the spatial division multiplexing (SDM) technology, which is another solution proposed to tackle the capacity crunch problem.

However, telecommunications is not the only potential application area of SPEED. Cheap, fully spliced, robust and reliable tunable optical sources at the telecom wavelength can be wavelength converted using the proposed parametric process to any desired spectral range for many different applications, which use optical sources as their main building block, with significant commercial and scientific relevance. For example, the development of laser sources in the mid-infrared (MIR) region, spanning the wavelength range of 2-20 micrometres, is crucial for various important applications, such as sensing systems, medical diagnosis and chemical analysis, remote explosive detection, countermeasures against heat-seeking missiles and covert communication systems.

Finally, the impact of this research will be evident in the training of new people (new PhD students and post-docs) within the UK. This work will also drastically contribute to the development of future fibres and new nonlinear material platforms, in terms of design, fabrication as well as their corresponding applications, both in academia and industry. Potentially end users, such as Nokia Bell Lab, Oclaro and Huawei, will benefit from the findings of this research and some of them have already showed some interest.