This paper surveys recent progress in optical protection rings with the focus on transparent optical protection rings. Generic requirements and attributes for optical protection rings, different optical protection ring architectures such as dedicated and shared protection rings in both the optical channel layer and the optical multiplex section layer are described. In particular, optical channel shared protection rings are discussed in detail including node architecture designs, ring protocols, triggers and messaging channels. Feasibility studies and experimental results from Corning Incorporated and other companies are reviewed. The paper also discusses how protection switching times scale with number of nodes and number of wavelengths, and shows examples of applications using the scaling rules for practical optical networks such as metro, regional and long haul ring network. Finally, the paper discusses remaining issues and future developments in the optical protection ring area.
"Optical protection ring architectures and applications", Proc. SPIE 4872, Optical Transmission Systems and Equipment for WDM Networking, (8 July 2002); doi: 10.1117/12.475126; https://doi.org/10.1117/12.475126