10.3. RAPID ADVANCES IN DENSE WAVELENGTH DIVISION MULTIPLEXING TECHNOLOGY

Optical networks using WDM technology, which divides the enormous fiber bandwidth into a large number of wavelengths (100 or more, each operating at 2.5 Gbps or higher), is a key solution to keep up with the tremendous growth in data traffic demand. However, as the WDM transmission technology matures and fiber deployment becomes ubiquitous, the ability to manage traffic in a WDM network is becoming increasingly critical and complicated. In particular, the rapid advance and use of DWDM technology has brought about a tremendous increase in the size (number of ports) of photonic (both optical and electronic) cross-connects, as well as the cost and difficulty associated with controlling and management of such large cross-connects. Hence, despite the remarkable technological advances in building PXC systems and associated switch fabrics, the high cost (both CAPEX and OPEX) and unproven reliability of huge switches have hindered their deployment [3].

Recently, the concept of WBS has been proposed to reduce this complexity to a reasonable level. The main idea of WBS is to group several wavelengths together as a band and switch the band (optically) using a single port. In this way, not only can the size of DXCs (OEO, grooming switches) be reduced, because bypass (or express) traffic can now be switched optically, but also, the size of OXCs that traditionally switch at the wavelength level can be reduced because of the bundling of lightpaths into bands in WBS networks. The following section focuses on the use of WBS to reduce the size of the MG-OXC [3], which is part of the multigranular PXC (Fig. 10.12) [3].