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Nonlinear penalty suppression through the use of optical add drop multiplexers

A study of WDM systems that utilize a number of optical add drop multiplexers (OADMs) to enable transparent add and drop of wavelengths at specific network locations as required by the traffic demands were presented in this paper. Through extensive simulation results it will be shown that the presence of OADMs and in particular the optical filtering associated with them improves the overall system performance. This is due to that in the case of systems suffering by nonlinear effects, periodic optical filtering assists in suppressing the spectral broadening imposed by nonlinear interactions between the WDM channels and therefore suppresses the associated penalty. This is in contrast to the effect of optical filtering in linear systems, where it introduces spectral narrowing and hence transmission penalties. The effect of nonlinear suppression directly impacts the power level that can be tolerated by the system before nonlinear penalties start degrading the overall performance. In such systems higher launch power can be used supporting improved optical signal to noise ratio and suppressed nonlinear penalties providing a significant improvement in the overall system performance. A large number of simulations have been run in order to identify the optimum operating point in terms of launch power in this type of systems. The analysis focuses on 10 Gbit/s systems supporting 100 GHz and 50 GHz channel spacing. A number of scenarios supporting varying transmission distances, different number of OADMs and various optical filter bandwidths are studied and compared. Significant attention is paid on the interplay of the variety of impairments and the identification of suitable trade-offs to ensure optimized system performance.