Polarization Division Multiplexing for SC-FDE Communications over Dispersive Optical Fibers

High order linear modulations, combined with coherent detection and signal processing at the receiver, are nowadays considered to reach the new capacity targets for the communications over the optical fibers. In order to reduce the computational complexity of the algorithms at the receiver, it has recently been proposed to compensate for the chromatic dispersion (CD) and polarization mode dispersion (PMD) in the frequency domain. Orthogonal frequency-division multiplexing (OFDM) and single-carrier with frequency domain equalization (SC-FDE) are two alternative coding strategies to support frequency domain signal processing. Compared to OFDM, SC-FDE is particularly interesting because it generates a lower peak-to-average power ratio (PAPR) waveform and it potentially facilitates the implementation of the transmitter. The goal of the present paper is to demonstrate how the SC-FDE system can further support polarization division multiplexing (PDM) to double the communication capacity. The SC-FDE PDM system is derived analytically and its performance is assessed by numerical simulations. It is shown that a 80 Gbps bit rate can be obtained in a 10 GHz bandwidth.