Hi friend.
Currently, the OLT does not support direct statistics on the number of ONUs on the entire OLT.
Run the huawei(config)#display ont info 0 command, the number of all ONTs globally can be displayed. Each PON port has ONTs. The number of ONTs can be accumulated manually.
Run the huawei(config)#display statistic global command, the number of online ONTs collected by the system can be queried.
I hope I can help you.