Fibre Parametric amplifiers for Real Applications in Optical Communication Systems (FPA-ROCS)

The Fibre Optical Parametric Amplifier (FOPA) has been investigated by many research groups over the preceding thirty-five years as a potential "holy grail" of optical amplification, but has yet to evolve outside of the laboratory. The tantalising prospect of significantly increasing fibre capacity within optical systems by simply and directly employing FOPAs, each with gain bandwidth far exceeding that of the ubiquitous EDFA, has always been historically somewhat offset by a range of challenging physical barriers. Chief amongst these is the innate polarisation sensitivity of the parametric amplification process. This demands that close alignment must be maintained between the polarisation state of an incoming signal and an optical parametric pump which supplies energy to the signal via a nonlinear medium. In a DWDM system, this requirement scales extremely problematically - multiple signals of differing wavelength and in random states of polarisation (often with data carried on both orthogonal modes), must each correlate polarisation-wise with the pump or pumps to receive gain. We believe we have uncovered a ground-breaking new architecture for the FOPA which will ultimately effectively eradicate this significant hurdle, and forms the basis for this proposal's research direction. Other FOPA performance issues must also be overcome. For example, the transfer of intensity noise from the pump to the signals, and the unwanted generation of nonlinear crosstalk within the FOPA via signal-signal interactions are certainly drags on the performance ultimately achievable and will require significant investigation to minimise their effects. However, we do not consider these latter challenges to be such a considerable brick-wall against real-world operation as 'the polarisation question'.
FPA-ROCS, is a focused research programme which will provide the required breakthrough to transition the FOPA from problematic laboratory experiment to an amplifier with real potential to impact across the optical communications world. This key advance will be based on our recent first experiments of an innovative FOPA design based on what we are calling the Half Pass Nonlinear Optical Loop or HPL NOL as shown in. We have recently demonstrated the world's first amplification of polarisation-multiplexed DWDM signals using this architecture , and believe it solves several of the large issues highlighted above, most notably offering polarisation independent black-box gain together with exceptional potential for significantly expanded bandwidth beyond the 20nm so far demonstrated. This potential has been outlined by separate characterisation studies undertaken by our team which demonstrated a single polarisation gain bandwidth of >110nm (i.e. 3x greater than that of the EDFA) with a gain variation across the band of only 1dB . We envisage using the HPL NOL to supply gain in regions of the fibre transmission spectrum which are currently untapped, such as at 1300nm (O-band) or 1500nm (S-band). By exploiting new bands in this way, together with considerably wider gain bandwidth per band, the capacity increase offered by FPA-ROCS will be extremely large (>500% current capability) and thus industry and, perhaps, world changing. The technology will be able to operate in parallel with existing optical communications infrastructure due to the transparency of the HPL-NOL outside its gain region (a feature not present in doped fibre amplifiers), enabling co-deployment with field-deployed EDFAs. This will enable a low-cost future upgrade path for network operators without the expensive and environmentally-unfriendly need to lay new fibre as capacity limits are approached. We envisage massively increased data throughputs from our radical redesign of the optical amplifier, allowing fibre systems to be future proofed to some degree at a UK-wide level and beyond.

The main impact of FPA-ROCS will be as a result of the primary technical objective to massively extend the available bandwidth of installed optical fibre and thus increase the capacity of optical transmission systems significantly. We are confident that our approach to amplification will ultimately lead to benefits for both network operators such as BT, who will be able to keep capital and operating expenditure down by expanding services without laying new fibre, as well as satisfying the demand of the end-user - the general public and businesses who will be able to access this additional capacity with ever more data-hungry apps and services. There is potential therefore for realising significant positive economic gain from the outputs of the programme which we believe will spread to a global reach.

FPA-ROCS will help reinforce the position of Aston University as an international academic centre of excellence for nonlinear signal processing. We will endeavour to promote the worldwide understanding of the developed techniques and processes applicable to optical communications systems as well as much needed progress made for parametric amplifier control and eye safety due to the use of high power pump lasers within operator sites. The project outputs will not just influence optical amplifier designs, but will cross-pollinate to other related disciplines such as all-optical nonlinear transmission compensation and optical wavelength translation amongst others.

In addition to the specific technical objectives outlined in the proposal, and the usual high impact journals and high profile conference publications which will be produced continually throughout the programme, ROCS will:

1. Maintain a high quality core science programme and share outputs with existing UK based photonic industries including, for example, Oclaro, II-VI (project partner), Xtera, and BT. These companies both either develop or directly use optical amplifiers and will certainly benefit from strides forward in the field.
2. Integrate applied research within the programme to create industry-relevant technologies and products. ROCS will continue to generate valuable IP with an expected rate of one invention disclosure per research fellow per year, one patent application per year, one significant know-how transfer or patent license over the course of the project. This process will be managed by the Aston Business Partnership Unit, and will ensure that IP is protected in the major international photonic manufacturing locations worldwide. Use of associated technologies will be managed through appropriate international standardisation and appropriate IP protection will be deployed for the duration of any standardisation process.
3. Foster public awareness through education and outreach programmes. We will encourage all self and Aston University-funded PhD students associated with the ROCS project activities to participate in Aston University's outreach programme, and the applicants will participate personally in appropriate events with a wider public audience. Press-releases to non-specialist journals and professional magazines will also be used to publicise breakthroughs of particular importance to the wider public.
4. Provide a focus for international research. We anticipate that a successful execution of this proposal will lead to significant international interest in associated technologies. We will welcome the participation of other international research groups in advancing the knowledge base, as additional improvements can only speed up the advent of this technology, thereby hastening the adoption pace, and consequently leveraging our own work. To foster this interaction, at appropriate times we will organise international workshops to facilitate direct scientific exchange and future collaborative