Testbed for ROADM and WXC based metro WDM networks

A testbed for metro wavelength division multiplexing (WDM) network is realized and tested. The testbed contains a reconfigurable optical add/drop multiplexer (ROADM) node, a 2×2 wavelength cross-connect (WXC) node, and two interconnected two-fiber bidirectional path protected switching ring networks (TF-BPSR). Both the ROADM and WXC node are bidirectional nodes, so they can select channels from the working and the protection ring networks simultaneously, and they support both protected and unprotected services. The ROADM node uses a flexible band tunable filter (FBTF) to drop a waveband from the input WDM signals and send the express channels directly to the output port. As a result, the physical impairment accumulated on the express channels can be minimized. It also has a modular structure, so additional modules can be cascaded to expand the capacity and functionality of the node without any interruption to current services. The WXC node is realized with interconnected ROADM modules that are comprised of wavelength selective switches (WSSes). Arbitrary wavelength or wavelength sets can be either dropped in the node or cross-connected in a non-blocking manner. Multiple services, such as OC-48 and OC-192 SONET signals, gigabit Ethernet streams carrying interactive movie signals, and live video broadcasting services, are carried in the network, dropped in the ROADM and WXC node, and switched between the two ring networks. The testbed is controlled by a websever based network management system that facilitates remote control and monitoring. Experiments demonstrate that the performance of the nodes and the testbed meets the requirement of the services.