Performance enhancement of 12 × 160 Gbps (1.92 Tbps) WDM optical system for transmission distance upto 8000 km with differential coding

In the past few years the demand for high capacity optical transport platform is rapidly increasing. It has drawn the attention of the researchers. The optical networks with the capacity of the order of Tbps are evolving. The capacity of individual optical channel is increasing towards 100 Gbps and beyond. In this paper, we demonstrate design and performance of 1.92 Tbps WDM Optical System. Three CW lasers are used to generate optical carriers. Twelve sub carriers, each spaced 80 GHz apart are produced using two dual tone generators. Each subcarrier carries information at transmission rate of 160 Gbps to enhance the spectral efficiency to 2 b/s/Hz. The analysis is carried out for 12 × 160 Gb/s (1.92 Tb/s) PDM-QPSK WDM optical system considering three different cases that is without coding, with gray coding and with differential coding for 100 km transmission distance. Extensive simulations are carried out to evaluate symbol error rate, error vector magnitude and Q-factor in each case. From the comparison, it is observed that the system with differential coding gives better performance in comparison with other two cases. An improvement in Q-factor with differential coding is achieved in the range of 2 to 5 dB with respect to other two cases. It is also shown that the transmission distance for PDM-QPSK WDM optical system with differential coding can be extended upto 8000 km keeping the Q factor above the FEC limit requirement (BER value 3.8 × 10-3).