Transparent ultra-long-haul DWDM networks with "broadcast-and-select" OADM/OXC architecture

We describe an experimental realization of ultra-long-haul (ULH) networks with dynamically reconfigurable transparent optical add-drop multiplexers (OADMs) and optical cross-connects (OXCs). A simple new approach to dispersion management in ULH dense-wavelength-division-multiplexing (DWDM) transparent optical networks is proposed and implemented, which enables excellent transmission performance while avoiding dispersion compensation on a connection-byconnection basis. We demonstrate "broadcast-and-select" node architectures that take full advantage of this method. Our implementation of signal leveling ensures minimum variations of path-averaged power among the wavelength-divisionmultiplexing (WDM) channels between the dynamic gain-equalizing nodes and results in uniform nonlinear and spontaneousemission penalties across the WDM spectrum. We achieve 80*10.7-Gb/s DWDM networking over 4160 km (52 spans*80 km each) of all-Raman-amplified symmetric dispersion-managed fiber and 13 concatenated OADMs or 320*320 wavelength-port OXCs with 320-km node spacing. The WDM channels use 50-GHz grid in C band and the simple nonreturn-to-zero (NRZ) modulation format. The measured Q values exhibit more than a 1.8-dB margin over the forwarderror correction threshold for 10/sup -15/ bit-error-rate operation. We compare these results with point-to-point transmission of 80*10-Gb/s NRZ WDM signals over 4160 km without OADM/OXC and provide detailed characterization of penalties due to optical signal-to-noise-ratio degradation, filter concatenation, and crosstalk.