The design of an optical network's physical topology determines its performance through its graph properties. However, the intelligent and automated design of scalable optical networks remains challenging due to the computational complexity of traditional optimisation methods, deterministic graph generators, and the lack of proper training data. In this paper, we introduce Topology Architect, the first generative AI model for optical network design, capable of generating core topologies from only node counts and geographic coordinates. It is an unsupervised learning framework trained on real networks from our dataset, Topology Bench. The model achieves up to 95% graph similarity, as measured by Wasserstein distances to real networks, and generates user-defined topologies in less than a second. Topology Architect captures the data variability in the latent space 20 times better than a graph's mathematical properties alone. It implicitly integrates multi-objective design principles, scales across different sizes, and presents a novel framework for optical network topology generation.

We report a field trial of chip-based QKD over 28.5km of deployed G.652 fibre, integrated using RFC 8784 with Juniper routers, with concurrent IPsec tunnels consuming independent keys. This illustrates practical quantum-resilient transport layer communication.

The first part of this special issue contains five papers addressing different aspects of good benchmarking practices in optical network research. We start with a brief introduction, followed by an overview of the papers and an invitation to contribute to the second part.

Graph representation learning on real-world optical core networks outperforms edge prediction heuristics by 10 times, achieving up to 93.4% accuracy on BT(UK), COST(EU), and CORONET(USA) by learning from 10% training data.

We numerically compare the performance benefits and viability of deploying hollow-core-fibre (HCF) and ultra-low-loss (ULL) fibre in metro-core optical network considering practical traffic growth, limitations of transceiver OSNR and output power from commercial optical amplifiers.

We describe a London Quantum-Secured Metro Network using Quantum Key Distribution between three London nodes together with customer access tails. The commercially-ready solution is fully integrated into the BT network and on-boarded its first customer.

We analytically compare HCF with SSMF in point-to-point core networks of BT-UK and TIM-Italy using GN model. HCF reduces line-amplifiers and high power consuming 400ZR+ links, allowing 400ZR, C+L WDM transmission at 23dBm input power.

We review and discuss the practicalities of integrating Quantum Key Distribution within the service provider fiber network. © 2022 The Authors.

We use an FPGA-based real-time coherent transceiver prototype with continuous µs-level state-of-polarization readouts and a commercial DAS system to perform fiber s ensing. Link monitoring and active detection of link tampering is demonstrated using both systems, showing how SOP-based sensing complements DAS in metro environments.

We report characterisation of ISRS, Kerr-nonlinearity and the first demonstration of error-free DWDM transmission with 38×400G signals using commercial 400ZR QSFP-DD modules through a field deployable 10.25km hollow-core NANF cable with <1.2dB/km loss from 1525-1625nm.

We propose a new metric called hubbedness to describe traffic flow in modern optical networks. We compare theoretical savings of point-to-multipoint vs point-to-point transceivers and find significant savings for a wide variety of traffic patterns when optical transceivers of sufficiently high data rates are available.

We report how hollow core fibres low latency can be used to increase the physical distance on an eCPRI based Radio Access Network (RAN) fronthaul link. We show an increase out to 43km on a commercial open RAN system.

We demonstrate how the 5G network slicing model can be extended to address data security requirements. In this work we demonstrate two different slice configurations, with different encryption requirements, representing two diverse use-cases for 5G networking: namely, an enterprise application hosted at a metro network site, and a content delivery network. We create a modified software-defined networking (SDN) orchestrator which calculates and provisions network slices according to the requirements, including encryption backed by quantum key distribution (QKD), or other methods. Slices are automatically provisioned by SDN orchestration of network resources, allowing selection of encrypted links as appropriate, including those which use standard Diffie-Hellman key exchange, QKD and quantum-resistant algorithms (QRAs), as well as no encryption at all. We show that the set-up and tear-down times of the network slices takes of the order of 1-2 minutes, which is an order of magnitude improvement over manually provisioning a link today.

We seamlessly integrate quantum key distribution with >1Mb/s secure bit rate into a smart-manufacturing production network. This provides a 10Gb/s quantum key encrypted link with long-term stable operation, compatible with national network infrastructure.

Acknowledging the predominantly hubbed traffic profile in the metro, we apply digital subcarrier multiplexing techniques to 400Gb/s coherent pluggable optics, enabling a point-to-multipoint architecture which shows TCO savings of 76% over a five-year period compared to a traditional architecture based on ROADMs and point-to-point transponder

The introduction of ZR/ZR+ optics means that WDM optics can now be integrated into IP routers in a cost-effective manner without reducing IP router port density. We present a model comparing the costs of building a national network with these new modules to traditional transponders.

This paper describes a demonstration of an end-to-end, SDN-controlled Video Contribution Network providing dynamic service set-up, using optical switching to enable flexible provisioning of resources. We show seamless operation of legacy and future technologies.

Our network model shows that the 3dB width of the Gaussian spectrum intensity profile in WSSs needs to be < 6GHz for realising the similar to 30% capacity increase in a WDM ring network as promised by the flexible-spectrum standard.

We proposed and showcased an X-Haul architecture converging front- and backhaul for 5G networks. The solution leveraged agile functional placement and hosting for cell sites and agile optical transmission based on the wavelength-agnostic WDM technology.

We show that the WSS passband shape needs to be optimized to the 3.6th and 3.2th Super-Gaussian orders in BT-UK and PAN-Europe networks, respectively, for realizing the 30% capacity increase promised by the flexible-spectrum standard.