Real-time OCh-OMS protection scheme selection

Optical channel (OCh) shared protection is considered the best scheme to implement protection in optical networks due to its high efficiency. Moreover, protection resources can be used to transport extra-traffic under normal conditions. Nevertheless, the switching time of the currently available wavelength selective switches (WSS), the key component to build reconfigurable optical nodes, prevents from protecting the complete set of affected lightpaths within 50 ms after fault detection. In this paper we propose a real-time mechanism to decide, on the basis of the current number of lightpaths to protect, whether the protection scheme to apply is either at the OCh level or at the link level. When protecting at the OCh level, some part of the not affected extra-traffic will be saved, whereas all extra-traffic will be pre-empted protecting at the link level. The objective of the proposed mechanism is to maximize the total transported traffic while keeping the protection times under the 50 ms objective. The performance of the proposed mechanism has been experimentally evaluated.