Design And Upgrading Of Metropolitan Area Networks Based On Coarse Wavelength Division Multiplexing

The rapid growth of traffic and bandwidth mainly in the metropolitannetworks demands to the carriers the use of a flexible infrastructure in order toattend the end users needs. Coarse Wavelength Division Multiplexing (CWDM)has recently emerged as an inexpensive technique for increasing the capacityand flexibility of metropolitan area/regional optical networks. The CWDMsystems characterized by wider channel spacing than Dense WDM are morecost-effective for metropolitan applications. CWDM is well suited for metroapplications (e.g. CWDM local rings that connect central offices to majorDense WDM metro express rings). The CWDM application in the metropolitannetworks needs an accurate analysis due to the specifics needs that theenvironment presents, as higher costs sensitivity and the high availability ofcommercial components and fibers.This paper compares the performances of different types of fibers usedin the CWDM system, evaluates their advantages and shortages according tothe experiments data. Both standard SMF and NZ-DSF are reliable to thepresent network. Two types of low-water-peak fibers G.652C/D and G.655B/Care superior on full spectrum transmission and best suit the upgrade of futurenetwork. Other unprevailing fibers such as dispersion-shifted fiber, negativedispersion (flattened) fiber used in CWDM are also compared.In this paper, by means of an Optical Communication System DesignSoftware, we study a CWDM metro network configurations, with directlymodulated lasers (DMLs) operating at either 2.5Gbit/s or 10Gbit/s, in order toincrease the aggregate capacity and maximize the error-free transmissionlength with different types of fibers. It is demonstrated for the first time how toenhance CWDM metro networks performances by appropriate choice ofproper fibers using inexpensive DMLs with inherent chirp. It has shown thatwhen DMLs are used the CWDM system performance is function of the fiberattenuation, dispersion value as well as channel wavelength. Exactconnections between such variations are numerically analyzed and elaborated, which are very helpful to optimization design or upgrade of CWDM metronetworks.Optimization of CWDM metro network optical layer engineering studieshave been recently presented, however most of them have been limited toeither complex transmitters or amplified links. In this work we demonstrate forthe first time how to enhance metropolitan CWDM Capacities by appropriatechoice of proper fibers and careful characterization of directly modulatedtransmitter with inherent chirp.In this article, we use a range of DML parameters and simulation modelsthat have been benchmarked with experimental data to show that a properengineering methodology and appropriate choice of fiber is needed in orderfor uncompensated CWDM to support metropolitan network reach.