NUMERICAL SIMULATION
Numerical Model
The numerical model of the DP-16QAM transmission system illustrated in
Fig. 3 is implemented with OptiSystem 18. For a single-channel
transmission, a symbol rate of 14 GBaud is chosen to transmit at a high
bit rate of 112 Gbit/s. Considering a ~4% ethernet
overhead and ~7% forward error correction (FEC)
overhead translates into about 100 Gbit/s net data rate. At the
transmitter, a polarization beam splitter (PBS) separates the two
polarization states of the output of a continuous-wave (CW) laser
operating at a wavelength of 1550 nm and a narrow linewidth of 0.1 MHz.
The laser power is swept from 7 dBm to 15 dBm. Using two identical
LiNbO3 Mach-Zehnder Modulators (MZM), the and polarization respectively
modulates symbols from two 16-QAM modulators fed by a data stream of 215
– 1 pseudo-random bit sequence (PRBS). A polarization beam combiner
(PBC) then recombines the two polarization signals, after which the
signal is transmitted over a standard single-mode fiber of up to 4,000
km (50 spans 80 km).