How to Select the Upstream Clock Source for the STM-1 Interface of an OLT

Usually, an OLT selects the line clock of the STM-1 interface as the system clock, and the entire SDH network is with the same clock source. This requires less VC12 adjustment. 

Versions earlier than V800R006C02SPC103 use the line clock of the STM-1 interface as the system clock, but the service cannot be provisioned. Therefore, the OLT of this version does not select the line clock of the STM-1 interface as the system clock; 

Versions later than V800R006C02SPC104 select the line clock of the STM-1 interface as the system clock.