 A GPS carrier phase frequency transfer link with a 450 km baseline has been established and characterized by comparing it to an optical fiber link of 920 km length, using two active hydrogen mazes as local oscillators. The characterization resulted in a frequency instability of backslash times 10-13 $ in 30s and backslash times 10-16 $ for long averaging times, with no deviation larger than the statistical uncertainty of backslash times 10-16 $. This successful cross-check confirms the measurement uncertainty of a truly remote end fiber link. This article was authored by Stefan Drosti, Christian Griebing, Julia Lute, and others.