Y-cable protection is a path protection scheme that offers 1+1 protection. Differences between Y-Cable and SNC protection:
Y-Cable protection starts from the transponder. When a Y-cable connects two different transponders, the SNCs configured on each transponder act as the working and protected SNC.
Y-Cable protects the full Wavelength service represented by the ClientCircuit instance in the topology. The scope of SNC protection is limited to EMS. A logical entity, called ClientTrail, is created to represent the Working and protected paths.