Large-scale and nonblocking OXC using a hybrid of WSSs and OCSs

Abstract

The surge in Internet traffic is driving traditional single-fiber fixed-grid optical networks to change toward multi-fiber flex-grid networks with fewer wavelengths per fiber. Designing a large-scale optical cross-connect (OXC) to adapt to these changes is challenging because the scalability of standard OXCs is limited by the port count of the wavelength-selective switch (WSS). The existing proposals either suffer from high insertion loss, lack a nonblocking property, or cannot support flexible grids. To this end, we propose a class of heterogeneous OXCs, using WSSs and port-level optical circuit switches (OCSs). Our idea is to employ WSSs to handle wavelength switching and OCSs to scale up the dimension of the OXC. In the context of flexible grids, we prove the conditions under which the heterogeneous OXCs are nonblocking on the line side, and colorless, directionless, and contentionless on the add/drop side. Also, our analysis shows that the port count of WSSs required by our proposals is governed only by the number of wavelengths in the network, rather than the dimension of the OXC. Also, our designs have low loss and a small filtering effect, as each lightpath only needs to pass through up to two WSSs in the OXC.