SONET (Synchronous Optical Networking) is used for transferring multiple digital bit data streams via lasers or light-emitting diodes (LEDs) through the one optical fiber. This is SONET's function, and it is therefore essentially focused on the physical medium of the process, being concerned with media, signal and binary transmission. OSI (Open Systems Interconnection), on the other hand, is an abstract description for the design model of a 'background' computer network protocol, using different syntax and semantics to communicate between its different levels or 'layers'.

An OSI system is a 'seven-layer/level' design model: Physical Layer Data Link Layer Network Layer Transport Layer Session Layer Presentation Layer Application Layer At its first level, i.e. the Physical Layer, SONET is just an example one of the many systems that could be appropriately enhanced by an OSI-modelled/structured program.