OTN (Optical Transport Network) is the Layer 1 protocol standardized by the ITU-T Study Group 15 in order to carry multi-gigabit signals across a fiber-optical infrastructure. It supersedes legacy SONET/SDH technology and is designed to address the challenges of a high-speed multi-service telecommunications infrastructure. OTN provides higher speed interfaces and better packet transport capabilities than earlier technologies and is typically used in access, metro and long-haul networks to support higher quality and bandwidth demands of business and consumer customers.
An increasing demand for OTN technology is expected from the growing need for quality business services required from service providers. Service providers also need to accommodate leading edge applications for business customers such as video and Internet services. OTN is considered the technology offering the highest bandwidth scalability and Quality of Service (QoS) for enterprise customers and private lines services.
OTN introduces novel elements over older technologies such as SONET/SDH:
- Dedicated Forward Error Correction (FEC) area that implements digital signal processing algorithms. FEC algorithms improve the effective Bit Error Rate (BER) and overcome Signal to Noise Ratio (SNR) limitations of optically based links by orders of magnitude.
- Enhanced management and supervision capabilities provide the service providers with full visibility into multiple parameters of the quality of the service being rendered to their customers as well as sophisticated troubleshooting tools.
- Optimized for Ethernet services. OTN is an asynchronous technology that does not impose synchronization requirements. Furthermore, OTN transports its client signals in their entirety without stripping overhead information. For example, OTN can provide true transparent connectivity for Ethernet based services (FE, 1GE, 10GE, etc.)
- Operates with the basic granularity of a 1.25Gbps container, ODU0. OTN incorporates a mapping method known as GMP (Generic Mapping Procedure) that allows it to support the transparent transport of signals of arbitrary bitrates. For example, a 1GE Client Signal would be accommodated by an ODU0 bearer in its entirety, including code-words and ordered-sets.
- OTN is nowadays commonplace in metro and core networks. Through its large variety of customer interfaces, deploying OTN at the Access Layer can provide a seamless end-to-end Optical Data Unit (ODU) path between network endpoints and simplify overall network management and supervision as well as reduce OPEX and CAPEX expenditures.