Characterization of a 450-km-baseline GPS carrier-phase link using an optical fiber link

Intercontinental frequency comparisons require satellite based techniques. We characterize a GPS carrier phase link with a baseline of 450 km using a long-distance phase-stabilized optical fiber link. Active hydrogen masers at both ends are compared via the GPS link and, via optical frequency combs at both ends, through the 920 km fiber link simultaneously. This technique allows us to independently assess the instability and accuracy of the GPS link with sub 1 μ 10
^-15
resolution.