Orthogonal Frequency Division Multiplexing for Spectrally Efficient Nyquist WDM Systems

In order to meet the increasing demand on high data rate in the backbone optical networks, we choose offset QAM Nyquist Wavelength Division Multiplexing (OQAM N-WDM) as the technique to increase the spectral efficiency (SE) of fiber-optic WDM transmission systems. To get intersymbol interference (ISI)-free transmission, root-raisedcosine (RRC) pulses are used in the transmitter. To get interchannel interference (ICI) free transmission, OQAM is employed as modulation scheme enabling the multiplexing of the users channels with a spacing equal to the symbol rate and thus achieving the highest SE. The performance is evaluated for this system propagating over a linear chromatic dispersion (CD) channel. Simulation results show that the required optical SNR (ROSNR) at BER of 10(exp -3) for backto- back connection of the transmitter and receiver meets the theoretical value of OSNR for QPSK transmission i.e. ROSNR = 13.3 dB.