7.7 Shared Protection Based on Predeployed Subconnections

The paradigm of predeployed subconnections can be used to avoid issues with power-level transients. The notion of a subconnection was introduced in Chapter 4, where regenerations along a path effectively break the end-to-end connection into smaller subconnections. Both ends of a subconnection are terminated in the electronic domain, with optical bypass at the intermediate nodes. In Chapter 4, the design process started with a connection and broke it into subconnections for regeneration and wavelength assignment purposes. With subconnection-based protection, the process is reversed; subconnections are predeployed in a network and concatenated as needed to form end-to-end backup paths.

A predeployed subconnection refers to a lit wavelength that is routed between two transponders, where the capacity is not currently being used to carry traffic. Thus, the transponders have been predeployed in the network and turned on for purposes of future traffic. Using predeployed subconnections as a building block for rapidly accommodating dynamic traffic or rapidly recovering from a failure was proposed in [SiSB01]. Shared mesh protection based on predeployed subconnections is described below; further details can be found in [Simm07].

Consider the network shown in Fig. 7.18(a), where it is assumed that the nodes are equipped with OADM-MDs and edge switches. Two working paths are established as indicated by the dotted lines; i.e., along A-B-C-D and A-J-K-I. There are three predeployed protection subconnections as indicated by the dashed lines: A-F-G-H, H-D, and H-I. The transponders at the endpoints of the working paths as well...