Optical layer survivability: a comprehensive approach

Summary form only given. Summary form only given. To many, the rapid deployment of dense-wavelength-division multiplexing (DWDM) line systems in world-wide telecommunications networks heralds a new age-the age of Optical Networking. While line systems in and of themselves support little in terms of networking functionality, DWDM line systems with wavelength add/drop capability are being deployed, and demonstrations (and lab/field trials) of optical network elements with nodal features, such as WDM add/drop multiplexers and optical cross-connects are being reported. The ability to add, drop, and in effect construct wavelength-switched and wavelength-routed networks, facilitated by these WDM optical nodal elements, does indeed herald the dawning of an age of optical networking. As such, it presents an attractive opportunity to design survivable optical WDM network architectures, using WDM optical nodal elements as tools analogous to those currently used at the electrical (e.g., SONET/SDH) layer. The emergence of survivable WDM optical network architectures will likely mirror the emergence of SONET/SDH survivable architectures. Both SONET/SDW and WDM optical survivable architectures have been classified as either protection switching or restoration architectures, wherein the distinction between the two has largely been based upon differences in restoral time frame, and degree of autonomy. Providing survivability, either in the form of protection switching, restoration, or some combination of both, at the optical layer is inherently attractive.