Performance of Modulation Formats on Dwdm Optical Systems

The need for higher transmission rate in Dense Wavelength Division optical systems necessitates the selection of a suitable modulation format for the efficiency of the optical system and has been a key issue in recent research (Vassilieva et al 2001). Generally modulation formats are classified into On Off Keying (OOK) and Phase Shift Keying (PSK) techniques (Idler et al 2003). Over the last few years, novel modulation formats with improved performance than the NRZ scheme have been suggested and investigated, (Matsuda et al 1998). From the literature it is found that by adapting a Return-to-Zero (RZ) format we can improve the receiver sensitivity and non-linear tolerance (Winzer and Kalmar 1999, Caspar et al 1999), but at the extra cost of one additional modulator and drive circuitry in the transmitter.