Comparative study between multi level modulations in chaotic optical communications

Performances of spectrally efficient multi level modulation schemes in chaotic optical communication systems are demonstrated numerically. In this paper we report usage of multi level modulation schemes in the form of QDPASK (quadrature differential phase amplitude shift keying) and IHAP (independent hybrid amplitude/phase modulation). Return to zero (RZ) pulse profiled QDPASK signal is added to the chaotic waveform and successfully retrieved. IHAP modulation of chaos is carried out and successful recovery of data is shown along with comparison with RZ-QDPASK. Successful recovery of message encoded in both schemes is shown heralding in improvement of bit rate 3 times than the ordinary chaotic optical communication system with only amplitude encoding.