schemes in case of multiple failures. In path-protected mesh networks, some connections can be unprotected; others can be protected against single or multiple failures in various ways. A connection can be protected against a single failure by defining a backup path, diverse from the primary path taken by the connection over the mesh network. The backup path and associated resources can be dedicated to the connection (Dedicated Backup Path Protection, aka dedicated (1+1) path protection, Subnetwork Connection Protection (SNCP) in SDH networks, or UPSR in SONET ring networks), or shared among multiple connections (Shared Backup Path Protection), typically ones whose primary paths are not likely to fail at the same time, thereby avoiding contention for the shared resources in case of a single link or node failure. A number of other protection schemes such as the use of pre-emptible paths, or only partially diverse backup paths, can be implemented. Finally, multiple diverse routes can be designed so that a connection has multiple recovery routes and can recover even after multiple failures (examples of mesh networks across the Atlantic and Pacific oceans ). Transparency Traditional transport networks are made of optical fiber-based links between telecommunications offices, where multiple wavelengths are multiplexed to increase the capacity of the fiber. The wavelengths are terminated on electronic devices called transponders, undergoing an optical-to-electrical conversion for signal Reamplification, Reshaping, and Retiming (3R). Inside a telecommunications office, the signals are then handled to and switched by a transport switch (aka optical cross-connect or optical switch) and either are dropped at that office, or directed to an outgoing fiber link where they are again carried as wavelengths multiplexed into that fiber link towards the next telecommunications office. The act of going through Optical-Electrical-Optical (O-E-O) conversion through a telecommunications office causes the network to be considered opaque. When the incoming wavelengths do not undergo an optical-to-electrical conversion and are switched through a telecommunications office in the optical domain using all-optical switches (also called photonic cross-connect, optical add-drop multiplexer, or Reconfigurable Optical Add-Drop Multiplexer (ROADM) systems), the network is considered to be transparent. Hybrid schemes that leverage optical bypasses and provide limited O-E-O conversions at key locations across the network, are referred to as translucent networks. ROADM-based transparent optical mesh networks have been deployed in metropolitan and regional networks since the mid-2000s. In the early 2010s, operational long-distance networks still tend to remain opaque, as there are transmission limitations