Current amplification techniques employed in transfer of optical frequencies over long distances exhibit a significant degree of complexity and impose specific constraints on the optical fibre link. The work of SIB02-REG3 project is mainly to study, characterise and experimentally demonstrate the benefits of distributed fibre Raman amplification in long-distance transfer of optical frequencies for time-frequency metrology, finally aiming at frequency comparisons at a level better than 10-18, and to exploit synergies with other amplification methods (i.e. Brillouin amplification) for a boosted performance.
The Research Excellence Grant (REG) SIB02-REG3 will develop research activity on distributed Raman amplification with a 12 month duration within the parent joint research project (JRP) NEAT-FT aiming at investigating new techniques for phase-coherent comparison of remotely located optical clocks, separated by distances of up to 1500 km. The REG and the parent JRP are funded by the European Commission under the European Metrology Research Programme (EMRP).
In detail, the REG is studying the use of distributed Raman amplification (DRA) for the phase coherent transfer of optical frequencies over long-range optical fibre links, providing high-gain, bi-directional coherent amplification of optical signal. In particular the objectives of REG are:
- to evaluate theoretically the behaviour of DRA with bi-directional pumping in terms of common figures of merit (on-off gain, signal-to-noise ratio, added phase noise and so forth), providing an optimised DRA design for subsequent stages.
- to experimentally characterise the performance of co-propagating, counter-propagating and bidirectional DRA on a laboratory link test-bed at a given JRP-partner location.
- to optimise systems employing Brillouin amplification and DRA together for boosted performance.
- to demonstrate the benefits of counter-propagating and bi-directional DRA through implementation of DRA in a suitable JRP fibre link.
- to enable, through multiple fibre amplification stages along JRP fibre links, frequency comparisons at a level better than 10-18 at one day.
Principal REG Investigator: Gabriele Bolognini – CNR