Hi,
The common connection mode is as follows:
Service transmit direction: SDH signals --> LSX --> M40V --> OBU1--> FIU--> Line.
Service receive direction: Line--> FIU--> OAU1-->D40 --> LSX--> SDH signals.
For more details, please click:
https://forum.huawei.com/enterprise/en/introduction-to-common-wdm-signal-flows/thread/532261-875
Thanks!