synchronous payload envelope (Sonet) (SPE)

The Synchronous Payload Envelope (SPE) transports a part of the STS signal in Synchronous Optical Network(Sonet). It is used to transport Tributary Units( TU) over synchronous networks such as Synchronous Digital Hierarchy( SDH). Most often, this signal is assembled at the networkaccess point and disassembled again at the network end point.