  In this work, we analyze the performance of the solution adopted for the
compensation of the phase drift of a 3 km optical fiber link used for the AWAKE
experiment at CERN. The link is devoted to transmit the reference signals used
to synchronize the SPS beam with the experiment to have a fixed phase relation,
regardless of the external conditions of the electronics and the link itself.
The system has been operating for more than a year without observed drift in
the beam phases. Specific measurements have proven that the jitter introduced
by the system is lower than 0.6 ps and the maximum phase drift of the link is
at the picosecond level.
