Optical networks present a promising candidate for the next generation ultra-high-speed networks due to its potential ability to offer huge bandwidth at low costs. These networks should have the ability to maintain service continuity to end-users in presence of network failures. Therefore, survivability has become a critical issue for the next generation optical networks. In this book, we demonstrate the stat of the art survivability techniques used in highly-survivable optical networks with focus on restoration techniques as promising techniques in terms of capacity utilization and blocking probability. Mohamed A. Azim distinctive approach, explores a new survivability scheme employed in optical networks namely, Active Restoration (AR). The AR scheme combines the advantages of the proactive protection and reactive restoration techniques while trying to avoid their shortcomings as verified by extensive simulations and analytical models. The book presents a step-by-step guide to survivability techniques and analytical modeling that can help researchers to find relevant ideas and open research problems on network survivability as well as developing their analytical models.