Optical Network Design and Implementation

SDH Multiplexing

It is very important to understand the SDH multiplexing hierarchy to truly understand and appreciate SDH. Multiplexing follows a rigid hierarchy in SDH. From an extremely high-level perspective, it is safe to say that low-level PDH signals are mapped to an SDH entity known as a container (C). The C is mapped along with POH bytes to form another entity known as a lower-order virtual container (VC). The lower-order VCs are aligned with tributary unit (TU) pointers to form entities known as tributary units (TUs). The TUs are multiplexed to form tributary unit groups (TUGs). The TUGs are further multiplexed to form higher-order VCs. These higher-order VCs are aligned with fixed byte-stuffing and administration units (AU) to form ...