Which layer of a SONET maps the signals into an SPE?

The path layer is responsible for mapping the signals into a synchronous payload envelope (SPE) within the SONET (Synchronous Optical Networking) framework. The primary function of the path layer is to encapsulate and manage the payload data for transport through the SONET network. It allows for the efficient handling of various types of data while ensuring that they are compliant with SONET's timing and structure requirements.

In the context of SONET, the payload goes through several stages of encapsulation as it moves from the data source to the physical medium. The path layer plays a crucial role in this by allowing compatibility between different types of data streams and ensuring they are formatted correctly. This mapping process involves assigning pointers and determining the actual start and end of the data within the envelope, making it integral to the overall performance and efficiency of the SONET system.

Understanding the function of the path layer is essential for grasping how SONET structures its data and manages data payloads across long distances in a reliable manner.