Loss of Signal (LOS) is an alarm state generated by networking equipment when the physical optical or electrical signal drops below the minimum detection threshold. On fiber optic gear, an LOS alarm usually means a severed cable, a dirty connector, or a failed transceiver laser. It triggers automatic protection switching in resilient networks to reroute traffic.
Heard on the job
The router just threw an LOS alarm on port 4, so check if the fiber got bumped in the patch panel.
Also heard as
- loss of signal