<title>Performance requirements for semitransparent DWDM networks</title>

Abstract

Required limits of transmission distance, nodes cascadability and grade of transparency (number of regenerators) are presented to implement semi-transparent DWDM backbone networks. Results are based on OSNR performance of three realistic optical network scenarios. Optical transmission impairments are key issues for transparent optical networks. To improve transmission in an optical network one can use forward error correction (FEC), Raman amplification, robust modulation formats tolerant to non-linear effects and noise, optimised dispersion maps, semi-transparent OXC architectures with selective 3R or 2R regeneration and reduction of losses in the optical cross connector (OXCs) architectures. In a typical optical network with mesh topology, a transmitted optical signal is expected to traverse several nodes connecting any source-destination pair. The cascadability limit of transparent optical cross-connect (OXC) nodes and the transmission distance between OXC nodes are crucial network design parameters. The required limits of transmission distance, OXC nodes cascadability and number of regenerators per node are presented for DWDM backbone networks. OXC architectures with low loss components and cost effective distributive amplification is required to facilitate a high OSNR and reduce the regeneration rate of semi-transparent networks. OXC architectures with OSNR below 36.7 dB are capable of reducing the regeneration rate to 13% for realistic network topologies.