OTN Layer Protection Introduction

Considering the critical role of optical transport networks, robust protection mechanisms must be implemented to ensure communication continuity. Therefore, OTN layer protection (covering OCH, OMS, and OTS protection) is critical in guaranteeing the stability of optical communication paths. This article will comprehensively explore various aspects of OTN layer protection and highlight its importance in maintaining reliable connectivity.

OTN Layers Definition

Optical transport network (OTN) is the backbone of modern communication infrastructure, which consists of a complex system of optical channels, multiplexing sections, and transmission sections. The OCH layer is responsible for processing individual client signals; the OMS layer acts between the OMUs and the ODUs to integrate multiple OCHs into a standard wavelength; and the OTS layer covers the physical layer of the optical network, which includes the actual optical fiber, transmission equipment, and line amplifier. OTN technology provides a comprehensive protection scheme to ensure high reliability at all network layers.

Figure 1: Optical Transport Network Layers

OTS Protection: Ensuring the Continuity of the Transport Section

OTS (Optical Transport Section) protection, also known as OLP (Optical Line Protection), is a method of comprehensively protecting the transport sections of an OTN network. These transport sections consist of multiple OMS (Optical Multiplexing Sections). OLP enables continuity of communications in the event of a major outage by dividing the network into multiple transport sections. A pre-defined backup section maintains communications during an outage, providing additional redundancy. OLP protection enhances the overall resilience of the optical network by providing robust protection for multiple channels and scetions.

The way OLP protects the working fiber can be divided into two different transmission and receive modes, one is 1+1 dual-path transmission and selective receive, and the other is 1:1 selective transmission and selective receive. The 1+1 scheme uses single-ended switching, while the 1:1 scheme uses double-ended switching (both are similar in principle). Since switching protocols with OLP protection is unnecessary, switching is very fast, typically under 50 ms.

QSFPTEK offers high-quality QT850, QT860, and QT900 series OLP products that enable effective 1+1 or 1:1 protection. These products allow users to easily view information such as critical data, alarms, and reports in the field or remotely via network management. By monitoring the power status of the working fiber in real time, they ensure line protection for optical transport systems. With a compact and highly integrated design, these products save cabinet space and offers excellent optical performance for a variety of application scenarios.

Figure 2: 1+1 OLP

OMS Protection: Strengthening Section-Level Resilience

OMS (Optical Multiplexing Section) protection extends the scope of protection by protecting the entire multiplexing section in an OTN network. This method groups optical channels within an optically multiplexed section, ensuring that all channels are protected simultaneously. When the primary section fails or is interrupted, and automatically switches the traffic to the backup section, thus ensuring uninterrupted connectivity. This section-level resiliency is critical for networks that must simultaneously protect multiple channels.

Typically, OMS protection schemes, predominantly of the 1+1 form, protect routes between OTMs/OADMs. Although no switching protocols are required, due to the complexity of the network organization, the switching time may be at least 50 ms.

Figure 3: 1+1 OMS

OCH Protection: Individual Optical Channels Protection

OCH (Optical Channel) protection focuses on securing each optical channel in the OTN. Each optical channel carries a specific wavelength of light in the OTN layer and plays a crucial role in data transmission.OCH protection sets up redundant paths for each channel. If the primary path fails or is interrupted, the system automatically switches the traffic to the alternate path, ensuring communication continuity. Implement 1+1 and 1:N protection schemes at the OCH layer to provide dedicated protection for each channel, minimizing service interruptions and enhancing network reliability.

Figure 4: 1+1 OCH

The Consideration for Implementing OTN Layer Protection

Deployment measures for OTN layer protection need to consider the following factors based on the network requirements to achieve optimal protection for the network.

First, the level of protection confirmed for that network needs to be assessed to obtain the most appropriate protection approach.

Second, when designing the network, it is necessary to take into account the subsequent network development and deploy sufficient network redundancy planning for the network system, including the design of the primary and backup paths. The fault detection mechanism should also be confirmed in advance in order to detect faults in a timely manner and respond to protection.

Third, timely network maintenance and monitoring can help detect potential problems earlier and optimize network performance.

Finally, choosing a suitable equipment vendor can save you a lot of trouble. Working with an equipment vendor can ensure compatibility and seamless integration of the entire network, maximize network performance, and achieve efficient network protection mechanisms.

Conclusion

This article focuses on the protection mechanisms of the OTN protection layer, including OCH, OMS, and OLP protection. All these protection mechanisms can provide reliable connectivity for optical transport networks. These protection mechanisms are taken to protect individual channels, multiplexed sections, and transport sections to maintain uninterrupted transmission of network communications, reducing network downtime and providing increased resilience to the network. These protection measures are essential to build a stable optical communication network. Contact QSFPTEK to design the best OTN layer protection solution for you free of charge!