Study on Fiber Nonlinearities and Polarization Mode Dispersion on DWDM System

Abstract

The rapid worldwide growth of data and internet traffic in telecommunication networks has resulted in a sharp increase in the demand for transmission capacity. Efficient utilization of the existing optical fiber network is an answer to this growing demand. An important step to this end is the introduction of optical communication systems withterabitspersecondcapacity,whicharebasedonDenseWavelengthDivisionMultiplexing(DWDM)system. This DWDM system has brought a big leap of transmission capacity in optical communication systems. Some research groups have already demonstrated that it is possible to transmit almost aTbits/sbitrateoverthousandsofkilometers. Butsuchhigherdatatransmissionrates impose very strict requirements on the fiber plants and transmission systems. In particular the nonlinearity effects and polarization mode dispersion (PMD) can be a serious limitation on certain fiber links, particularly on links in older legacy networks. Recent papers written on this topic argue that even fibers made and deployed in the 1990 to 2001 time frame, may beunstableduetothechallengespresentedbythenonlinearityandPMDeffect. Asnetwork data rates continue to rise, it is becoming increasingly important to understand the nonlinearity and PMD effect and their potential impact in the network. PMD in optical fibers is consideredtobetheultimatelimitationinDWDMsystem. Manystudiesonfirstandhigherorder PMD compensation have already been reported, but most of them are based on single channel systems and the nonlinear effects in optical fibers such as Cross Phase Modulation (XPM), Four Wave Mixing (FWM) are overlooked. But in DWDM system the nonlinearity andPMDphenomenabothleadtopulsedistortionandsystemimpairmentswhichadversely limitthetransmissioncapacityofthefiber. Inthispaperanendeavorhasbeentakentocover thepracticalaspectsandimplicationsofnonlinearityandPMDeffectsonfibertransmission systems. A rigorous analysis has been carried out to quantify the effect of XPM and how they affect PMD impairments and mitigation.