FADY MASOUD COHERENT PLUGGABLES
THE RISE OF COHERENT PLUGGABLES: WHAT’S NEXT?
As the demand for bandwidth continues to increase and the need to reduce the cost of optical transport becomes more pressing, a new breed of pluggable optics has emerged – 400G coherent pluggables. Fady Masoud , Senior Director, Solutions Marketing, Infinera reads the runes.
T his new generation leverages 7-nm CMOS technology and cutting-edge opto- electronics to deliver 400 Gbps in pluggable form factors such as QSFP-DD and CFP2, thus redefining business and network economics by reducing power consumption, simplifying the network, and enhancing service flexibility, all of which contribute to a significant reduction in total cost of ownership. However, deploying coherent pluggables comes with its own set of challenges that need to be addressed to unlock their full potential. These include: Complex in-host management: When deployed in a host device other than a WDM platform, the management of current coherent pluggables represents organisational and operational challenges. Organisational challenges arise in terms of which team (optical or IP) will manage the coherent pluggables, normally part of the optical network but now hosted in the IP domain. Operational challenges can also be exacerbated as new features and capabilities are added to coherent pluggables. Today’s host devices generally have limited management schemes supporting basic functions, such as setting laser frequency, spectrum width and launch power. Deployment over single fibre: PON networks, which use a single fibre for service delivery, are rapidly becoming the access technology of choice across the globe. While PON networks are highly suitable for residential services, the technology falls short in keeping up with the ever-increasing demand for capacity triggered by next-generation business services and 5G mobile transport. Access networks for enterprise services can greatly benefit from the high capacity enabled by coherent pluggables; however, coherent pluggables cannot be deployed
over a single fibre because the technology uses the same wavelength frequency for each transmission direction. Deployment over legacy Infrastructure: Today’s optical infrastructure is the result of more than 25 years of network buildouts and expansions; hence, it consists of a mix of technologies and capabilities including ROADMs, optical amplifiers and filters. The network may only support 50 GHz fixed grid, or it may support variable flexible-grid channel assignments. To deploy and operate broadly in such diverse environments requires coherent pluggables to be flexible and programmable. Lack of troubleshooting tools: Issues that may arise during the deployment and operation of coherent pluggables can be challenging due to the lack of specialised tools and diagnostics specifically designed for these advanced transceiver modules. Lack of automation features: Manual operations cannot keep up with the growing number of end sites and constant service churn of today’s metro networks. Emerging coherent pluggables must support automation features to accelerate service turn-up, streamline network operations, and reduce human error. RAISING THE BAR WITH INTELLIGENT COHERENT PLUGGABLES A new breed of intelligent coherent pluggables, such as XR optics, driven by the Open XR Optics forum, has been introduced to the optical networking market to overcome the operational challenges mentioned above. They leverage digital subcarriers to enable higher optical performance; new optical configurations like point-to-multipoint, including a 4 x 100G coherent breakout; and new deployment models, such as single-fibre working. They also offer
numerous optical transport features that for the longest time have been limited to fully featured optical transport platforms. The operational challenges that face coherent pluggables today touch every aspect of the service delivery cycle. To overcome these challenges the new generation of coherent pluggables was designed and built around the principle of complete and remote software programmability. Key functions can be set through software to enable successful deployment and optimised performance over any given link in any given application. Programmable functions include modes (ZR, ZR+, XR), baud rate, spectrum, launch power, modulation, transmission fibre (single fibre or fibre pair), and traffic flows (asymmetrical, symmetrical). The combination of software programmability, embedded system- level features, and a new paradigm for management overcome current operational challenges with: Enhanced optical performance: By leveraging vertical integration and software-configurable building blocks, this generation of coherent pluggables delivers record-breaking optical performance by tuning each building block, such as the digital signal processor (DSP) and the transmit-receive optical sub-assembly (TROSA), around the optimal performance for each application. This translates into significant capex/opex savings for network operators enabled by network simplification and the elimination of regen sites and their associated costs. Easier management: To overcome the complex management challenge, the Open XR Forum published specifications for a dual management approach. Coherent pluggables can be managed through the host device for basic configurations like setting frequency, power, and modulation but can also be
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| ISSUE 38 | Q3 2024
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