The mid-frequency Square Kilometre Array phase synchronisation system

This paper describes the technical details and practical implementation of the phase synchronisation system selected for use by the Mid-Frequency Square Kilometre Array. Over a four-year period, the system has been tested on metropolitan fibre-optic networks, on long-haul overhead fibre at the South African Square Kilometre Array site, and on existing telescopes in Australia to verify its functional performance. The tests have shown that the system exceeds the 1-s Square Kilometre Array coherence loss requirement by a factor of 2 560, the 60-s coherence loss requirement by a factor of 239, and the 10-min phase drift requirement by almost five orders-of-magnitude. The paper also reports on tests showing that the system can operate within specification over all the required operating conditions, including maximum fibre link distance, temperature range, temperature gradient, relative humidity, wind speed, seismic resilience, electromagnetic compliance, frequency offset, and other operational requirements.