Comparitive Analysis of 8-DPSK and 16-QAM Digital Modulation, using RoF for Hybrid WDM-TDM PON [ ]


Hybrid WDM-TDM Passive optical networks (PON) combine both wavelength division multiplexing (WDM) and time division multiplexing (TDM) into a single PON, offering reduced cost, high scalability and increased data rates, hence hybrid PONs are currently effective solutions. The objective of this paper is to investigate and analyse various digital modulation schemes in conjuction with the hybrid WDM-TDM architecture, and implement a PON with efficient performance at 2.5 Gbps data rate, while trying to reduce costs. Radio-over-fiber technlogy (RoF) is used as it allows direct transmission of radio frequency (RF) through the fiber without the need of frequency conversion at the reciever. Digital modulation techniques like QPSK, M-PSK, M-QAM provide high spectral efficiency and better utilization of bandwidth. In this paper, 8-DPSK and 16-QAM are investigated for 2.5 Gbps, 4 Gbps and 5 Gbps, for a standard single mode fiber length of 25 km, and the performance is compared for hybrid PON architecture. It is shown that 16-QAM offers better performance at higher data rates. The performance analysis is based on eye diagrams, constellation diagrams, OSNR, and received optical power. OptiSystem simulation software package is used for simulation.