There is increasing worldwide dependency on global navigation satellite systems (GNSS) that deliver uninterrupted timing signals. This GNSS dependency is driving novel holdover clock development to flywheel over periods when the GNSS signal is unavailable. Enhanced GNSS with next-generation optical clock technologies could facilitate both significantly reduced positioning errors and improved holdover resilience. Both requirements will be addressed in this new project.

The UK National Physical Laboratory (NPL) is working with the Optoelectronics Research Centre (ORC; Southampton, UK) and Eblana Photonics (Dublin, Ireland) to develop a novel optical clock at ~1540 nm. On short timescales, this new clock will pre-stabilise an Eblana laser to an NPL-patented cubic cavity using the Pound-Drever-Hall technique. On longer timescales, the cavity drift will be corrected via reference to absorption lines in acetylene confined in hollow-core fibre provided by ORC. Cubic cavities are undergoing development for future space deployment within parallel-running ESA-funded activities and hollow-core fibre is also expected to be well-suited to future operation in space.  Although not targeting the accuracy and stability of cold ion or atom optical clocks, the overall physics package is more compact and will outperform existing microwave clocks.