Hybrid wavelength and sub-wavelength routed optical networks

Although wavelength routing has many advantages, it also has some inflexibilities. For one thing, the routing granularity is large, which could lead to waste of bandwidth when demand is fractional in the units of wavelengths. For another, full connectivity in a large network puts a serious stress on the number of wavelengths required in the network. To solve these problem, we propose a hybrid wavelength and sub-wavelength routing scheme, which provides, in addition to a set of dedicated wavelength channels where normal wavelength routing takes place, a pool of shared wavelength channels where sub-wavelength routing is performed. The hybrid scheme is designed to strike a right balance between the benefits of optical bypass and multiplexing gain. The problem involves optimal routing and traffic grooming in a mesh network. We formulated the problem in the hybrid scheme using integer linear programming, and studied its performance under different cost scenarios using a prototype network. Our result shows the hybrid scheme can invariably achieve lower total system cost, and is especially effective where the tension between the benefits of optical bypass and multiplexing gain is most intense. The proposed hybrid scheme provides a cost-effective and flexible way for network service providers to accommodate diverse customer bandwidth demand granularities, and offers a smooth migration path to integrate existing opaque network elements with newly introduced all-optical ones.