In general, chaos communications involve transmitters and receivers operating in synchronised chaotic regime located far one from another. One should therefore overcome the dispersion effects which considerably impede the synchronization, even for a transmission over few kilometers of fiber links. Using broadband chaotic carrier generated from electro-optic delayed system, I will report some managements techniques which are currently used to get around the dispersion in the realistic field experiments. In addition, I will show how the time delay can be detected by a potential eavesdropper and how dificult it becomes when high bit rate message is included.