Giuseppe Marra is a Principal Scientist in the Time and Frequency department. His specialist area of research expertise is optical frequency metrology, with a focus on dissemination of ultra-stable optical frequencies over optical fibre links, including for comparison of distantly located optical atomic clocks. His team has led seminal work to demonstrate how interferometric approaches can permit monitoring of earthquakes, storms and other processes on in-service, repeatered cable systems across 1000s of km.