Optical hop number limits imposed by various 2 x 2 cross-connect node designs.

The success of transparent optical transport networks depends on the availability of optical cross-connect nodes (OXNs) that induce minimal impairments on the signals they cross-connect. This should extend the possible coverage and flexibility of path restoration within a meshed network topology by raising the upper bound on the achievable optical hop (traversable OXNs) number. We provide a brief survey and categorization of the currently proposed OXNs. Furthermore, the possible limits they impose on the number of hops are established by a series of transmission performance simulations. Microoptic and all-fiber OXNs are identified to be suitable for networks with a low connectivity and channel count. In case larger OXNs are needed, then microoptic and integrated OXNs provide a better option. The results obtained are applicable as guidelines for the deployment of future optical ring topologies.