OTN

Optical Transport Network (OTN) is a set of ITU-T standards that defines a transparent, scalable framework for carrying client signals over optical networks. It provides a digital wrapper and a hierarchical framing structure that enable efficient multiplexing, performance monitoring, and error management across long-haul and metro DWDM links. OTN is designed to accommodate diverse client technologies while preserving their characteristics and timing.

In the OTN architecture, client data is mapped into Optical Data Units (ODUs) and then carried within Optical Transport Units (OTUs) on optical channels. The OTU frame includes overhead for framing, management, performance monitoring, and forward error correction, which helps improve transmission reliability. The framework supports a hierarchy of payload and transport containers (ODUk and OTUk) that allows rate-compatible aggregation of multiple signals and flexible provisioning of services across the network.

Standards within the ITU-T family, such as G.709, define the framing, multiplexing, and protection mechanisms of OTN, while others address network architecture and performance characteristics (e.g., G.872). These specifications collectively enable interoperability among equipment from different vendors and promote scalable, multi-service transport.

OTN is widely deployed in telecom operator networks to transport Ethernet, Fibre Channel, SDH/SONET, and other client signals with high efficiency and robust management. It supports features such as optical channel data transmission, fault management, and restoration, making it suitable for backbone and metropolitan networks. Compared with traditional SDH/SONET, OTN emphasizes transparent transport, improved error protection, and scalable rate advancement.