The mission-critical nature of high-speed networks imposes stringent requirements for high availability. Resilience is achieved through highly reliable network nodes, and through network protection / restoration mechanisms that rely on various forms of redundancy and fault tolerance. Although data networks can be restored at the IP layer, carriers and enterprises alike, are increasingly relying on protection at the physical layer, to achieve fast and reliable recovery. Faulty network components (nodes or links) are quickly identified and restoration takes place by automatically bypassing them or replacing them with spares. Switchover from a failed component to a spare is called "Protection Switching’. 1:N protection switching, in which a single spare is used to protect several (N) components, was found to be most cost-effective. Furthermore, operational expenses of fiber-based (optical) networks can be minimized through the use of all-optical switches that are transparent to data rates and protocols, allowing easy network upgrades. This article discusses issues associated with optical equipment protection switching and describes a new breed of intelligent protection systems, based on Planar Lightwave Circuit (PLC) technology.