TIM DOIRON AI DATA CENTRES
fibre. Faster transmission enables signals to travel longer distances with the same latency. This extended reach significantly increases where AI and cloud operators can build data centres, more than doubling the usable real estate around major metro areas. HCF also has the potential for wider- band transmission beyond conventional C and L bands, enabling more capacity per fibre for DCI and scale-across networks. However, despite these advantages, HCF carries a higher cost than silica fibre, and operational challenges, such as field-repair techniques, need to evolve. Early trials and deployments are underway using today’s coherent optical engines and OLS platforms. In parallel, leading vendors are researching and experimenting with optical engine, amplifier and line system optimisations for the HCF ecosystem to not only replace glass fibre with hollow core, but to maximise transmission capacity and minimise cost and complexity over the long term.
Figure 2. The thin transponder: operational consistency for coherent pluggables
centre connectivity services may use a combination of embedded and pluggable coherent technologies throughout their network to cover the breadth of customers, distances and fibres. While the power, space and economic benefits available from coherent pluggables are important, retaining operational and feature consistency throughout the network remains paramount. That is where thin transponders come in. Thin transponders are cost- and power-optimised sleds or modules that host anywhere from six to 32 client- and line-side pluggables per module. Thin transponders leverage industry standard QSFP-DD and OSFP pluggable form factors, provide a clear demarcation between client- and line-side traffic, deliver operational consistency across the optical transport layer and support incremental features like encryption and virtual bandwidth where client traffic can be split across multiple line-side interfaces (Figure 2). As an example, three 400G clients can be delivered across 2,000 km over two coherent pluggables running at 600 Gb/s each. Thin transponders demonstrate how streamlined, focused designs can deliver outsized benefits, delivering up to 50% of the footprint and 40% of the power and economic benefits of IPoDWDM while eliminating operational complexity and inconsistency. Coherent pluggables combined with thin transponders provide a cost-, space- and power-efficient solution for telecommunication providers who are delivering high-capacity DCI and scale- across connectivity for AI and cloud customers throughout the metro and portions of the long-haul network. HYPERSCALE THE LINE SYSTEM The increasing demand for optical transport capacity in DCI and scale across networks is remarkable. Day one deployments are driving full C band and C + L band implementations per fibre pair. And with optical engine spectral efficiency gains plateauing, network operators
are deploying multi-fibre transmission architectures to secure the hundreds of terabits of capacity they need today and tomorrow. Accelerating transmission demands cannot be met with outdated optical line systems (OLSs). To deploy hyperscale capacity between data centres, a hyperscale OLS is needed. Two OLS innovations are being developed to meet the cost, power and space demands of multi-rail (or multi- fibre) deployments. High-port-count, direct-attach ROADMs that can multiplex 64 or more wavelengths onto a fibre enable full C+L band transmission with a single compact sled or module. Using 800G ZR/ZR+ pluggables, this solution delivers over 50 Tb/s. If combined with more spectrally efficient 1.2 Tb/s embedded optical engines, the solution delivers 76.8 Tb/s, or 50% more capacity. The tradeoff is that the embedded optical engines require additional space and power. The second OLS innovation relates to signal amplification. Optical transport solutions, including those for DCI and scale-across networks, require amplification approximately every 60 to 100 kilometres using in-line amplifiers (ILAs). In many instances, these ILAs are deployed in small huts with significant space and power constraints. With multi- rail deployments, the network cannot meet the scaling demands by using today’s ILAs, which only support a single fibre pair or direction per module. A combination of integration and innovation is delivering a new generation of bidirectional ILAs that support four or even eight fibre pairs in the same footprint. CHANGE THE MEDIUM Hollow core fibre (HCF) has existed for more than two decades, but Microsoft’s acquisition of Lumenisity in 2022 marked a major step forward in its maturity and commercial viability. One of HCF’s most compelling advantages is its ability to reduce latency: light travels up to 47% faster in HCF than in traditional silica
BUILDING THE OPTICAL FOUNDATION
In the era of AI-driven data centre growth, meeting escalating connectivity demands requires an innovative optical toolbox. Advancements in coherent pluggables,
thin transponders, hyperscale and multi-rail optical line systems and
emerging technologies such as hollow core fibre, collectively enable operators to flexibly scale capacity both now and in the future. Together, these innovations help the industry to efficiently support massive XPU clusters and multifibre network architectures while optimising cost, power and deployment flexibility.
Tim Doiron, Vice President, Solution Marketing | Nokia
www.opticalconnectionsnews.com
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ISSUE 43 | Q1 2026
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