SONET Layers :

SONET has four optical interface layers. They are:

¨ Path Layer,

¨ Line Layer,

¨ Section Layer,

¨ Photonic Layer.

Path Layer : The Path Layer deals with the transport of services between the PTE. The main function of the Path Layer is to map the signals into a format required by the line layer . Its main functions are :

· Reads ,

· Interprets ,

· Modifies the path overhead for the performance and automatic protection switching.

Line Layer : The line layer deals with the transport of the path layer payload and its overhead across the physical medium. The main function of the line layer is to provide synchronization and to perform multiplexing for the path layer . Its main functions are :

· Protecting Switching ,

· Synchronization ,

· Multiplexing ,

· Line maintenance ,

· Error Monitoring .

Section Layer : The section layer deals with the transport of an STS-N frame across the physical medium. Its main functions are :

· Framing ,

· Scrambling ,

· Error Monitoring ,

· Section Maintenance.

Photonic Layer : The Photonic layers mainly deals with the transport of bits across the physical medium. Its main functions are :

· Wavelength ,

· Pulse Shape ,

· Power Levels.