DPT is an #optical networking technology that utilises SONET/SDH framing and employs intelligent protection switching in the event of fibre facility or node failure or signal degradation. Electrical signals and light can be converted to each other form via Fibre-Optic Transmission Systems (FOTS), whihc is a Modulator. It uses a bidirectional, counterrotating ring structure for metro applications, and a star structure with a central switching device for service point-to-point backbones.