Optical layer overhead alarm detection is implemented through optical layer overhead OOS.

Optical layer overhead alarm detection is implemented via the Optical Layer Overhead Out Of Service (OOS) mechanism. Alarms like R_LOS (Loss of Signal) and MUT_LOS (Multiple Loss of Signal) belong to the optical layer and are reported based on OOS detection. This approach helps isolate physical layer faults and informs higher layers for protection switching or maintenance. HCIP-Transmission emphasizes that OOS-based alarm detection is crucial for rapid fault localization and efficient network operation in optical transmission systems.