Dense wavelength division multiplexing (DWDM) systems are highly attractive in today's communication scenario, since they offer large transmission capacity and also achieve higher spectral efficiency. A scheme to reduce four-wave mixing (FWM) cross talk by using optical spreading code-based channel frequency allocation to a set of unevenly spaced channels is proposed. This assignment scheme provides several advantages over previously proposed schemes. The performance of this scheme for equal and unequal spaced channels of 4- and 16-channel DWDM systems is analyzed for various coding formats, including return to zero, nonreturn to zero, carrier-suppressed return to zero, and vestigial-sideband return to zero. It is observed that unequal channel spacing provides an improvement in the Q factor for all coding formats, and it is also noted that the vestigial-sideband return to zero technique is more tolerant to FWM cross-talk components.
© 2007 Optical Society of AmericaPDF Article