Check whether POS optical module and fiber can be used or not, the commonest way is to use flange loop at ODF. But the protocol is nkt up when looping.
1. Loop with hardware device, the protocol cannot be up.
2. Change encapsulation protocol of link layer as HDLC. The protocol layer is up and the loop succeeds. The module and fiber can be used.
Normally the physical layer and protocol layer are up when looping. However, Huawei's router POS interface default encapsulation of link layer is PPP, the protocol cannot be up. Change encapsulation protocol of POS interface link layer as HDLC, and then the link protocol can be up.
When default encapsulation protocol of POS link layer is PPP, the protocol can be up even looping with hardware device.