A theoretical and experimental investigation of the performance of an open-loop optical chaotic communication system for the isochronous synchronization solution is presented, under strong optical injection conditions. Various modulation techniques are considered and tested at multigigabit rates and for different levels of optical injection to the receiver. Theoretical and experimental results are presented for the back-to-back configuration, while in the experimental part a complete chaotic communication system including fiber transmission is demonstrated. Both theoretical and experimental tests prove the possibility of a robust chaotic communication system. Bir error rates (BER) values lower than 10-7 for 1Gb/s encrypted message bit rates are demonstrated for transmission distances of up to 100Km.