Tutorial Optical Transport Network (OTN)

Optical Transport Network (OTN) Tutorial

Tutorial Optical Transport Network (OTN)

tutorial for Optical Transport Network standards and their applications. The objective is to provide the telecommunications engineers with a document that forms the basis for understanding OTN.

There are many standards that fall under the umbrella of “OTN”. This document focuses on Layer 1 standards. Therefore, it does not describe the Physical or Optical layers. Furthermore, it doesn’t describe any layers implemented in Software. Thus this document only describes the digital layer that could be implemented in ASIC. The Optical Transport Hierarchy OTH is a new transport technology for the Optical Transport Network OTN developed by the ITU. It is based on the network architecture defined in ITU G.872 "Architecture for the Optical Transport Network (OTN)" G.872 defines an architecture that is composed of the Optical Channel (OCh), Optical Multiplex Section (OMS) and Optical Transmission Section (OTS). It then describes the functionality that needed to make OTN work. However, it may be interesting to note the decision made during G.872 development as noted in Section 9.1/G.872 : “During the development of ITU-T Rec. G.709, (implementation of the Optical Channel Layer according to ITU-T Rec. G.872 requirements), it was realized that the only techniques presently available that could meet the requirements for associated OCh trace, as well as providing an accurate assessment of the quality of a digital client signal, were digital techniques….” “For this reason ITU-T Rec. G.709 chose to implement the Optical Channel by means of a digital framed signal with digital overhead that supports the management requirements for the OCh listed in clause 6. Furthermore this allows the use of Forward Error Correction for enhanced system performance. This results in the introduction of two digital layer networks, the ODU and OTU. The intention is that all client signals would be mapped into the Optical Channel via the ODU and OTU layer networks.” Currently there are no physical implementations of the OCh, OMS and OTS layers. As they are defined and implemented, they will be included in this tutorial.