  We study the way that chromatic dispersion affects the visibility and the
synchronization on Quantum Key Distribution (QKD) protocols in a widely-used
setup based on the use of two fiber-based Mach-Zehnder (MZ) interferometers at
transmitter/receiver stations. We identify the necessary conditions for the
path length difference between the two arms of the interferometers for
achieving the desired visibility given the transmission distance -- where the
form of the detector's window can be considered. We also associate the above
limitations with the maximum detection rate that can be recorded in our setup,
including the quantum non-linearity phenomenon, and to the maximum time window
of the detector's gate. Exploiting our results we provide two methods,
depending on the clock rate of the setup, to perform chromatic dispersion
compensation techniques to the signal for keeping the correct order of the
transmitted symbols. At the end, we apply our theoretical outcomes in a more
realistic QKD deployment, considering the case of phase-encoding BB84 QKD
protocol, which is widely used. Our proposed methods, depending on the
transmission distance and on the photon emission rate at transmitter station,
can be easily generalized to every fiber-optic QKD protocol, for which the
discrimination of each symbol is crucial.
