KAZUICHI ICHIKAWA FLEXIBLE ROADM TECHNOLOGY
management functionalities facilitated through multi-vendor software-defined networking (SDN) controllers. The current challenges facing ROADM systems include limited interoperability between equipment from different suppliers. Variations in network configurations across vendors frequently result in increased costs and operational complexity during the integration of new components into existing systems. Furthermore, reliance on a single vendor for network equipment constrains competition, reduces innovation, and lowers system flexibility. This vendor dependency, commonly referred to as ’vendor lock-in,’ restricts overall interoperability within the network ecosystem. OpenROADM aims to address these limitations by providing a standardised framework that enhances vendor-neutral interoperability. OPENROADM SPECIFICATIONS OpenROADM addresses five types of hardware with optical interfaces, including pluggable optics, transponders, in-line optical amplifiers, transponders/switches, and the ROADMs themselves. Combined with software-based controllers, these devices can be managed through SDN controllers that utilise a common data model and Application Interface (API). Open APIs empower operators to develop custom network applications, enabling features like low latency and high reliability. By adopting the YANG language for data modelling and control methods, OpenROADM ensures compatibility and seamless integration across different vendors. Furthermore, contentionless and directionless switching capabilities in ROADM architectures, when orchestrated by SDN, effectively resolve wavelength conflicts and automatically reallocate routes throughout the network. This enhances redundancy and supports uninterrupted data continuity, even in the event of multiple failures. Integrating Optical Performance Monitoring (OPM) with SDN control allows the controller to optimise resource allocation and avoid deploying infeasible lightpaths. In addition, SDN provides a unified control layer, orchestrating protection and restoration schemes across both optical and higher network layers, thereby maximising network resilience and operational efficiency. EMERGENCE OF THE OPEN ZR+ STANDARD While huge data centres are distributed across multiple locations, the communication distance between them (data centre interconnects, DCI) is kept relatively short (about 80 to 120 km) to minimise latency. In addition, point-to- point connections are used between data centres. The Optical Internetworking Forum (OIF) has developed 400ZR as an interface specification specifically for this
DCI application. 400ZR also defines a transmission method with WDM, enabling the realisation of Internet Protocol (IP over DWDM) using high-density multiplex modulation. On the other hand, the optical interface of OpenROADM uses a communication protocol called Optical Transport Network (OTN), which has been standardised by ITU-T and can support data rates from 100 to 400 Gbps. However, the cost is also high.
Figure 3: Demo system and the role of Anritsu products at OFC 2024.
Although the two standards have different starting points, both use a digital coherent scheme suitable for WDM. For this reason, the hardware specifications of the corresponding optical transceivers have many parts in common, and a movement to integrate the standards has emerged. This led to the creation of the “OpenZR+” standard. This standard inherits the basic specifications of 400ZR while enabling DCI networking and longer-distance (around 480 km) communications. In December 2023, 600 Gbit/s and 800 Gbit/s specifications were added to the OpenROADM optical interface, while the OIF published the 800ZR standard in October 2024. Shortly, 800 Gbit/s specifications are expected to be added to OpenZR+. NEED FOR TESTING AGAINST ROADM To ensure interoperability between devices from different vendors, maintaining communication quality across individual devices and the network as a whole is essential. Rigorous testing is required to guarantee communication stability, prevent errors, and enhance reliability. Furthermore, real-time configuration adjustments and rapid recovery mechanisms are critical for maintaining network flexibility in the event of failures. Keeping pace with rapid technological advancements necessitates the adoption of testing solutions that can seamlessly adapt to emerging technologies and specifications.
were connected through the Add/Drop line of an Open ROADM system. This setup enabled the orchestration system to configure channel settings while monitoring critical network performance metrics, such as bit error rate, throughput, and latency, via the MT1040A. The unified system facilitated by the real-time evaluation of ROADM path changes based on performance quality data provides a framework for monitoring and adaptation.
ACCELERATING ROADM INNOVATION
The pursuit of flexibility, automation, and cost-efficiency for future ROADM technology will continue to drive the evolution of ROADM technology. Photonic integrated circuits (PICs), co- packaged optics, and advanced materials are instrumental in miniaturising and optimising ROADMs for future network demands. A notable recent trend is the push toward higher transmission speeds. In January 2024, OIF launched a project focused on the 1600ZR+ specification in response to market demand for enhanced ZR+ mode performance. Naturally, this development is expected to impact both OpenZR+ standards and OpenROADM specifications. Amid these advancements, it is important that the vendor ecosystem continues to actively participate in OpenROADM and offers products that contribute to the control and quality monitoring of optical communication networks.
ANRITSU AND OPENROADM Anritsu, in collaboration with
the University of Texas at Dallas, demonstrated advancements in OpenROADM/IP over DWDM (IPoDWDM) orchestration systems at OFC 2024 and SC24. Using the YANG model—a vendor-independent network control methodology developed by OpenROADM and IETF—their demonstration showcased networks integrated with an orchestration system managed by the University of Texas at Dallas. Two 400G ports on Anritsu’s Network Master Pro (400G Tester) MT1040A, equipped with embedded 400G OpenZR+ transceivers,
Kazuichi Ichikawa, Assistant Manager, Anritsu Corporation
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ISSUE 42 | Q3 2025
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