Colloquium: SuperGPS through optical networks



M1.29, W&N-building, VU University Amsterdam, De Boelelaan 1081, 1081 HV Amsterdam

Colloquium: Jeroen Koelemeij

Dr. Jeroen Koelemeij, LaserLaB, VU University Amsterdam, Amsterdam




SuperGPS through optical networks

Global navigation satellite systems such as GPS broadcast radio signals which are used to determine a receiver's position (x,y,z,ct) in space-time. As this is done through the measurement of propagation delays, accurate timing is essential to both navigation and network synchronization (e.g. for telecom and power grids) to GPS ‘atomic time’. However, the accuracy of GPS is insufficient to synchronize and compare super-accurate optical clocks, which are based on ultrastable lasers and laser-cooled atoms or ions. To solve this, several research groups have recently developed methods to transfer frequency through telecom optical fiber, which provide sufficient stability to compare even the most accurate optical clocks through links of hundreds of kilometers length.
In my talk I will present the status and first results of the 'SuperGPS' project which has recently started at LaserLaB VU. Apart from the development of an aluminum-ion optical clock, this project involves optical frequency transfer between LaserLaB and KVI Groningen through a 2x317 km fiber pair of the SURFnet optical network. I will also present a new method for simultaneous time and data (10 Gbps) transfer over 75 km distance with 10 ps accuracy –three orders of magnitude more accurate than GPS– obtained in collaboration with TU Eindhoven and SURFnet. The long-term objective of the SuperGPS project is an optically synchronized e-infrastructure, which delivers accurate time and frequency to users for a wide range of novel applications. Examples include the use of optical clocks as ‘Einstein sensors’ or for searches for time-varying fundamental constants, as well as the synchronization of wireless networks for high-capacity 4G/5G mobile telecommunication, and positioning with centimeter (and possibly millimeter) accuracy – hence the name ‘SuperGPS’.