Project dates: 1 Sept 2008 – 31 Oct 2011

The aim of this studentship was to help position NPL to play a key role in the development of all-optical remote comparison of optical clocks between NMIs using optical fibre networks.

Current satellite time and frequency transfer techniques are inadequate for the intercomparison of caesium primary frequency standards at the parts-in-10¹⁶ level. Development of better frequency transfer techniques is a prerequisite for a redefinition of the SI second based on optical frequency standards with accuracies into the parts-in-10¹⁷ or 10¹⁸ level. Optical frequency comparison has now been demonstrated to deliver the required level of frequency stability over timescales commensurate with the stability of the optical standards.

At the time of proposal of this project, preliminary work in this area had been led by LNE-SYRTE and PTB in Europe and by NIST in North America. A goal of this studentship was to assist in positioning NPL as a major participant with LNE-SYRTE and PTB in an EMRP project. An immediate benefit of the studentship lay in gaining access to the JANET Aurora Photonics Research Network, which to date has provided the only realistic testbed in the UK for optical frequency transfer. This network currently links the photonics networks research groups at the Universities of Essex and Cambridge, University College London (UCL), and the Opto-electronics Research Centre (ORC) at the University of Southampton.

In the long term, this work was envisaged as a step in the direction of fibre-based dissemination of time and optical frequency, which has potential applications in areas including ground segments of satellite systems for GNSS and earth observation, timing services for the financial sector, and remote calibration and synchronisation of communications networks and power grids.

NPL staff involved with the project

Stephen Lea
Giuseppe Marra
Patrick Gill

Collaborations

• JANET Aurora Consortium and JANET network.

Conferences and Presentations

• A poster presentation at QuAMP 2009 (won second prize in the student poster competition).