| Abbreviation | Definition |
|---|---|
| OLP | On-Line Provisioning |
| OLT | Optical Line Terminal |
| OLTS | Optical Loss Test Set |
| OM | Operational Measurement |
| OMC | Operations and Maintenance Center |
| OMC | Optical Multi-Channel |
| OMCI | ONU Management and Control Interface |
| OMPI | Open Message Passing Interface |
| OMS | Olympic Messaging System |
| OMSN | Optical Multi-Service Node |
| ONAL | Off Network Access Line |
| ONAL | Off-Network Access Line |
| ONU | Optical Network Unit |
| OOA | Out Of Area |
| OOF | Out Of Frame |
| OOS | OTM (Optical Transport Module) Overhead Signal |
| OOS | Out Of Service |
| OOS | Out Of Synchronization |
| OOS-AU | Out Of Synchronization - Autonomous Unit |
| OOS-AUMA | Out Of Synchronization - Autonomous Unit - Manual Override |