Things about OTN Layer Protection for Reliable Connectivity

Updated on Jun 5, 2023 by

As the criticality of optical transport networks necessitates robust protection mechanisms to ensure uninterrupted communication, OTN layer protection, including OCH, OMS, and OTS protection, plays a vital role in safeguarding optical communication paths. This article delves into the various aspects of OTN layer protection and highlights its significance in maintaining reliable connectivity.

Overview of Optical Transport Network Layers

Optical Transport Network (OTN) serves as the backbone of modern communication infrastructures. It encompasses a complex architecture comprising optical channels, multiplex sections, and transport sections. The OCH layer handles individual client signals; the OMS layer is the part between the OMU/ODU, aggregating multiple OCHs onto a common wavelength; and the OTS layer represents the physical layer of the optical network, and encompasses the actual optical fibers, transmission equipment, and line amplifiers. OTN system provides comprehensive network-level protection schemes to meet the reliability of each layer of the OTN network.

Optical Transport Network Layers

OTS Protection: Ensuring Transport Section Continuity

OTS (Optical Transport Section) protection, also called OLP (Optical Line Protection), offers a comprehensive approach to protecting transport sections in an OTN. Transport sections encompass multiple OMSs or optical multiplex sections. By dividing the network into transport sections, OLP ensures continuity even in the face of significant failures. Backup sections are established to maintain communication during disruptions, providing an additional layer of redundancy. OLP protection offers robust protection for multiple channels and sections, ensuring the overall resilience of the optical network.

OLP uses 1+1 dual transmission and selective reception, or 1:1 selective transmission and selective reception to protect the working optical fiber. Among them, the 1+1 scheme adopts the single-ended switching mode, and the 1:1 scheme adopts the double-ended switching mode (the principles of 1+1 and 1:1 described later are similar). In the case of OLP protection, there is no need to switch the protocol, so its switching speed is very fast, generally less than 50ms.

1+1 OLP

OMS Protection: Section-Level Resilience

OMS (Optical Multiplex Section) protection expands the scope of protection by safeguarding entire multiplex sections. In this method, multiple optical channels are grouped within an optical multiplex section. OMS protection ensures simultaneous protection for all channels within a section. If the primary section encounters a failure or disruption, traffic is automatically switched to the backup section, guaranteeing uninterrupted connectivity. This section-level resilience is vital for networks where multiple channels need synchronized protection.

Generally, there is only the form of 1+1 for the OMS protection scheme used to protect routes between OTM/ OADM. Although the protection switching protocol is not required, the switching time may not be less than 50ms due to the complexity of network networking involved.

1+1 OMS

OCH Protection: Safeguarding Individual Optical Channels

OCH (Optical Channel) protection focuses on securing individual optical channels within an OTN. Each optical channel, carrying specific wavelengths of light, plays a crucial role in data transmission. OCH protection involves the setup of redundant paths for each channel. In case of primary path failure or disruption, the system automatically switches the traffic to the backup path, ensuring seamless communication. 1+1 and 1:N protection modes can be implemented at the OCH layer, providing dedicated protection to each channel, minimizing service interruptions, and enhancing network reliability.

1+1 OCH

Best Practices for Implementing OTN Layer Protection

Implementing OTN layer protection requires careful consideration of network requirements and adherence to best practices.

  • Evaluating the network's specific needs helps determine the most suitable protection methods.

  • Redundancy planning is crucial, involving the identification of primary and backup paths, as well as fault detection mechanisms to detect and react to failures swiftly.

  • Proactive maintenance and monitoring are essential to identify potential issues and optimize network performance.

  • Collaborating with equipment vendors ensures seamless integration and compatibility, enabling efficient protection mechanisms.


OTN layer protection, including OCH, OMS, and OLP protection, plays a critical role in maintaining reliable connectivity in optical networks. By safeguarding individual channels, multiplex sections, and transport sections, these protection mechanisms ensure uninterrupted communication, minimize downtime, and enhance overall network resilience. Implementing these protection measures, combined with best practices, paves the way for robust and efficient optical networks capable of meeting the growing demands of the digital age.

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