How SDH works?

The frame structure defined by SDH standard is called STM-n frame. 'n' in STM-n represents the number of AU-3s present in a frame, The number of AU-3 present in STM-n frame structure is 3 times the value of n. The AU-3 and related terms will be explained in the next frame with the complete frame structure.

How STM-n works?

The STM-n frames will be multiplexed in such  a way that one single clock is sufficient to separate the multiplexed payload.This makes the implementation of multiplexing and demultiplexing techniques easier.

I know that this is not sufficient for understanding the working of SDH. I don't want to confuse you right now without the frame structure. So, in the next post I will explain it with the frame structure. As of now, be clear that SDH mux/demux is simpler to implement.