Optical Transport Network (OTN) switching and transport play critical roles in supporting modern optical transport networks based on Wavelength Division Multiplexing (WDM) technology. OTN provides a flexible, scalable and efficient framework that can accommodate various services and line rates while minimizing operational complexity.

As global demand for high-speed business and wholesale services grows, centralized OTN switched networks are gaining prominence. According to a recent OMDIA forecast, the global market for OTN switching is expected to grow at a 4.3% compound annual growth rate (CAGR), with Asia Pacific and China leading the charge, followed by Europe, the Middle East and Africa (EMEA), and with North America seeing relatively slower adoption.

At metro aggregation, metro core and core sites, network operators are increasingly deploying centralized OTN switches with photonic line systems to realize several key benefits, including improved network efficiency, service transparency, scalable any-to-any service connectivity and network resiliency.

Let’s look at each of these benefits in more detail, aided by real-world examples that show how network operators are using OTN today.

Improved network efficiency and utilization

One of the key benefits of OTN switching is its ability to optimize network efficiency by enabling a mix of low- and high-rate traffic, reducing costs through a blend of electrical grooming and photonic transparency. OTN relies on standardized multiplexing with universal containers that transparently map services into specific sizes. The services can then be combined to enable higher data rates.

This service transparency allows operators to mix and match any service type and optimally “fill the pipes” to improve the utilization of wavelengths. Flexible OTN mapping, supported by the ODUflex feature, allows for granular service mapping down to 1.25G, which lets operators fill the wavelengths more efficiently.

A real-world example of this is a European operator that deployed equipment from Nokia, including the core WDM (1830 PSS) and P-OTN switch (1830 PSS-x) platforms, to enhance service delivery and bandwidth utilization at key locations across its network. By adopting centralized OTN switching, the operator achieved faster provisioning and better fiber utilization through efficient aggregation and grooming of traffic streams, which resulted in improved service quality for its customers. To learn more, see Case study: European operator deploys WDM/OTN technology.

Service transparency

OTN's ability to transparently carry multiple types of traffic—including Ethernet, wholesale OTN and SONET/SDH services—over optical light paths offers a crucial advantage for network operators. The technology provides a unified transport layer that allows operators to support a wide variety of services without requiring protocol-specific configurations. This flexibility simplifies network management and enables quick deployment of new services.

For instance, Swisscom modernized its optical network using Nokia WDM/OTN platforms and can now quickly roll out bandwidth-efficient and flexible business services across its network. These capabilities show how OTN's service transparency can meet growing market demands without requiring significant reconfiguration. For further details, refer to Case study: Swisscom Newton.

Scalable any-to-any service connectivity

The growing use of cloud, video and Internet of Things (IoT) services continues to drive up data usage. Network operators must scale their optical networks to keep pace with increasing capacity demands.

Centralized OTN switching helps operators accommodate higher data volumes by enabling seamless network scaling. Many operators are turning to centralized core OTN switching to scale their core optical network capacity because it allows for fast any-to-any service rollouts without blocking conditions. The switching occurs through a scalable backplane.

India provides a good case study of how OTN is helping to meet new capacity demands. Major hyperscalers and operators across the country are investing in their optical networks to address demand for wholesale connectivity, data center interconnect (DCI) and other business services. The launch of 5G services has further driven the need for robust optical transport networks.

Tier-1 operators in the region have adopted centralized OTN switches such as the Nokia 1830 PSS-24x platform to enable massive scaling, efficient traffic segregation and improved network protection—all of which are crucial for high-speed, high-capacity services. To learn more about the benefits of this approach, read Case study: Nokia builds multi-terabit optical network across India for Tier 1 operator.

Increased network resiliency and protection

Transport networks must be resilient to ensure continuous service delivery in the face of outages or network failures. OTN switching offers robust protection and restoration mechanisms, along with enhanced performance monitoring capabilities at the optical layer. These capabilities enable quick restoration and minimize service disruptions when failures occur.

For example, operators in the Asia Pacific region have deployed Multi-layer Restoration Networks (MRNs) that provide protection and restoration across different layers of their optical networks. These MRNs, supported by high-capacity Nokia OTN switches, offer enhanced resilience and service reliability. They ensure that, in the event of failures, networks remain operational with minimal impact on end users. To learn more, see Case study: Asia Pacific operator modernizes national optical network.

Evolution of OTN to beyond 100G

As demand for bandwidth grows, OTN has evolved to support client rates beyond 100 Gb/s (B100G). The ITU-T released a new standard in 2016 that introduced the OTUCn frame structure and followed in 2017 with the introduction of FlexO (flexible OTN), which provides an interoperable interface for OTUCn signals to enable data transport at rates of 100 Gb/s and higher.

These updates allow operators to scale their networks more easily to meet future capacity demands. As shown in Figure 1, the Nokia 1830 PSS-x portfolio supports B100G, offering up to 1 Tb/s line rate using the PSE-6s optical engine, which will enable networks to scale well into the future.

Figure 1. Nokia end-to-end OTN switching and transport

Conclusion

OTN switching is a vital component of modern optical networks because it offers a scalable, resilient and efficient solution for meeting the growing demand for high-capacity business and wholesale services. Its flexibility in accommodating various service types, combined with advanced protection mechanisms and scalability, ensures that operators can meet customer expectations for reliable, high-quality services today and be ready to support new services in the future.

For more information on our centralized OTN switching solution visit our 1830 PSS-x P-OTN Switching web page.