Performance analysis of CO-OFDM schemes based on multidimensional constellations for long-haul transmission

In this paper, we have examined two schemes based on Coherent Optical-Orthogonal Division Multiplexing (CO-OFDM) systems suitable for long-haul transmission. Both take advantage of the Dual Polarization Quadrature Phase-Shift Keying (DPQPSK) constellation. However, the optical transmission is done by time dimension in Time Diversity (TD)-DPQPSK scheme and by the polarization dimension in Polarization Diversity (PD)-DPQPSK scheme. Both schemes have been compared with the 4QAM conventional CO-OFDM system for Back to Back (B2B) configuration and after 1040 km and 2000 km fiber lengths. The TD-DPQPSK presents enhanced performance in terms of Optical Signal-to-Noise Rate (OSNR) and require half of the optical resources than PD-DPQPSK. Furthermore comparing the TD-DPQPSK scheme with the 4QAM system, the OSNR penalties decrease and the transmitted bit rate is doubled, for the TD-DPQPSK option.