Ground temperature impacts accuracy of network timing
Research at FOM, the VU University Amsterdam and the University of Groningen into the accuracy of new virtual connections to atomic clocks has revealed that ground temperature affects fibre-optic cables, and therefore also the accuracy of signals travelling through them. Working in cooperation with the Royal Netherlands Meteorological Institute (KNMI), the researchers developed a mathematical model to describe this effect. Their findings have been published in the specialist journal Applied Optics.
Virtual atomic clocks are used to keep time, as well as for highly accurate positioning, for instance as in GPS. In this study, scientists used SURFnet's fibre-optic network to transmit signals from highly stable atomic clocks in Amsterdam to Groningen for the purposes of fundamental research.
Rising ground temperature delays signal
Among the factors the study investigated was the effect of variation in ground temperature on the operation of the virtual atomic clock. When the temperature rises, fibre-optic cables stretch slightly due to thermal expansion, which causes a small delay in the time it takes a signal to travel from the atomic clock through the cable. By developing a model to describe this effect, the researchers have made it possible to make a remote prediction of the stability of the atomic clock when ground temperatures rise.
New applications
The existing fibre-optic connection makes it possible to take highly precise measurements of atoms and molecules in Groningen using atomic clocks located in Amsterdam. Such measurements can aid researchers in their fundamental research, and have practical applications as well. For example: in the future, virtual atomic clocks connected to the fibre-optic network could speed up mobile Internet as multiple synchronised transmission masts will be able to more efficiently exchange data with smartphones. Remote atomic clocks could potentially also be used for highly accurate positioning and navigation – crucial for self-driving cars.
Jeroen Koelemeij, who is a researcher at VU and the project coordinator, is excited about the network-connected clock: 'For researchers, it opens up a wonderful opportunity to do innovative fundamental research while at the same time developing a new technology that will soon be improving all sorts of applications we use every day. This is a great example of how everyone will ultimately be able to benefit from research financed to a significant extent by public funds.'
'Using the SURFnet network made it relatively easy for us to link the atomic clocks in Amsterdam to the experimental set-up in Groningen', adds Rob Smets, network expert at SURFnet. 'Now, the network is making a direct contribution to new fundamental research.'
The research was funded in part by the FOM, STW and SURFnet foundations
Contact
Nanja Nouwen, SURFnet, +31 (0)30 23 05 344
Tessa Weber / Paul Maris, Whizpr, +31 (0)31 74 10 483