Dissemination of ultra-stable optical frequencies over commercial fiber networks

Precision Experiments

The aim of the PhD work to investigate the performance of “dark fibers” which is used in commercial telecommunication for the transmission of ultra-stable optical frequencies. The optical fiber is sensitive to acoustic and temperature fluctuations, which in turn effects the stability of frequencies propagating in the fiber. Therefore, we developed a scheme to compensate the phase and frequency fluctuations in the fiber. A laser at 1542 nm is used to avoid high attenuation at other wavelengths.

We made remote frequency measurements on Mg frequency standard in the University of Hanover using the frequency standards at PTB, Braunschweig. A fiber link of about 73 km is used. Two optical frequency combs are used to transfer the stability of the frequency standards to the transfer laser.

We showed that the frequency of a frequency-stabilized fiber laser can be transmitted over a total fiber length of 146 km with a relative frequency uncertainty below 1• 10-19, and short term frequency instability given by the fractional Allan deviation of σy(τ) = 3.3•10-15/(τ /s) when we used another similar links connecting Hanover university and PTB to return light to us.

We are in steps to make fiber link between PTB and MPQ in Munich over a total distance of 900 km.

Universität Hannover
Ph.D. student: