# OTN Alarms & Errors

I would recommend you this PDF: [https://www.veexinc.com/en-us/Download/TechnicalNotes/66840002](https://www.veexinc.com/en-us/Download/TechnicalNotes/66840002)

* OOF: Out of Frame; 帧失步
* LOF: Loss of Frame; 帧丢失
* OOM: Out of Multiframe; 复帧失步
* LOM: Loss of Multiframe; 复帧丢失
* LOS: Lost of Signal; 信号丢失
* AIS: Alarm Indication Signal; 告警指示信号: 当上游有LOS时，下游AIS告警\(接收到全1码\)
* FTFL: fault type and fault location

