Multi-band elastic optical networks are a promising alternative to meet the bandwidth demand of the ever-growing Internet traffic. In this letter, we propose a family of band allocation algorithms for multi-band elastic optical networks. Employing simulation, we evaluate the blocking performance of 3 algorithms of such a family and compare their performance with the only heuristic proposed to date. Results show that the three new algorithms outperform the previous proposal, with up to one order of magnitude improvement. We expect these results to help advance the area of dynamic resource allocation in multi-band elastic optical networks.

This paper studies the impact of demand-prioritization on Space-Division Multiplexing Elastic Optical Networks (SDM-EON). For this purpose, we solve the static Routing, Modulation Level, Spatial Mode, and Spectrum Assignment (RMLSSA) problem using 34 different explainable demand-prioritization strategies. Although previous works have applied heuristics or meta-heuristics to perform demand-prioritization, they have not focused on identifying the best prioritization strategies, their inner operation, and the implications behind their good performance by thorough profiling and impact analysis. We focus on a comprehensive analysis identifying the best explainable strategies to sort network demands in SDM-EON, considering the physical-layer impairments found in optical communications. Also, we show that simply using the common shortest path routing might lead to higher resource requirements. Extensive simulation results show that up to 8.33% capacity savings can be achieved on average by balanced routing, up to a 16.69% capacity savings can be achieved using the best performing demand-prioritization strategy compared to the worst-performing ones, the most used demand-prioritization strategy in the literature (serving demands with higher bandwidth requirements first) is not the best-performing one but the one sorting based on the path lengths, and using double-criteria strategies to break ties is key for a good performance. These results are relevant showing that a good combination of routing and demand-prioritization heuristics impact significantly on network performance. Additionally, they increase the understanding about the inner workings of good heuristics, a valuable knowledge when network settings forbid using more computationally complex approaches.

Space division multiplexing (SDM) systems using few-mode fibers (FMF) are essential for next-generation fiber optic communications. Optical amplifiers with low noise, minimal differential modal gain (DMG), and minimal differential spectral gain (DSG) are essential for these systems. In this work, we present a method to design and optimize a two-stage few-mode erbium-doped fiber amplifier (FM-EDFA) using a joint DMG-DSG minimization approach. This methodology involves the pumping profile design and the gain flattening filter design. Simulation results show the two-stage FM-EDFA achieves DMG and DSG below 2.8 dB and 0.42 dB, respectively, with an optical signal-to-noise ratio above 19 dB across the C-band, enabling a system capacity of 48.6 Tbps. This work reveals the effectiveness of this two-stage FM-EDFA for optical amplification in the context of SDM systems.

The Loop-Back Quantum Key Distribution (LB-QKD) protocol establishes a bidirectional architecture in which a single photon travels forth and back through the same optical channel. Unlike conventional one-way schemes such as BB84, Alice performs both state preparation and measurement, while Bob acts as a passive polarization modulator and reflector. This design eliminates detectors at Bob’s side, minimizes synchronization requirements, and enables compact, low-power implementations suitable for quantum-mobile and IoT platforms. An extended three-basis configuration $\{X,Y,Z\}$ is introduced, preserving the simplicity of the two-basis scheme while improving noise tolerance through enhanced orthogonality-based filtering. Analytical modeling shows that the effective protocol error decreases from $E_{\mathrm{protocol}}^{\left(2\right)}=e/2$ to $E_{\mathrm{protocol}}^{\left(3\right)}=e/3$, achieving a 33% improvement in noise resilience. Despite its slightly lower sifting efficiency ($\eta =1/6$), the total information gain reaches $G=0.26$ bits per pulse, maintaining post-sifting throughput comparable to BB84. The protocol doubles the tolerable QBER of conventional QKD, sustaining secure operation up to $22\%$ for two bases and approximately $47.58\%$ for three bases. Its passive, self-verifying architecture enhances resistance to man-in-the-middle, photon-number-splitting, and side-channel attacks, providing a scalable and energy-efficient framework for secure key distribution and authentication in next-generation mobile and distributed quantum networks.

Network virtualization is a key enabling technology for “Infrastructure as a Service” provisioning, increasing the flexibility and cost savings offered to customers. By extending the concept of server virtualization to the network infrastructure, the allocation of different, independent virtual networks over a single physical network is carried out on demand. A fundamental challenge in network virtualization systems is to choose which physical nodes and links to use for hosting virtual networks in the physical infrastructure, known as the “virtual network allocation” problem. All virtual network allocation proposals on elastic optical networks assume a centralized operation, deploying a single node with access to the network state global information and assigning resources accordingly. However, such configuration might exhibit the inherent problems of centralized systems: survivability and scalability. In this paper, we present a distributed protocol for resource discovery, mapping, and allocation of network virtualization systems. The distributed protocol is generic enough as to be used with different substrate networks. However, in this paper, it has been adapted to work over an elastic optical network infrastructure, where further considerations regarding the spectrum continuity and contiguity constraints must also be taken into account. The distributed protocol is based on the concept of alliances: upon the arrival of a virtual network request, agents located in the physical network nodes compete to form the first alliance able to host the virtual network. Because the first alliances to be formed are also the ones composed by nearby nodes, a good network resource usage is achieved. The feasibility of the distributed protocol was studied by evaluating its ability to successfully establish virtual networks within acceptable time and with low bandwidth consumption from the coordination messages.

ZR+ pluggables have the potential to transform the optical core landscape, paving the way for new, to our knowledge, network services enabled by a reconfigurable infrastructure. However, reconfigurability brings challenges. One of the challenges among them is the fast and accurate planning tools for networks with stochastic demands. In this paper, we introduce SPRINT: a fast and accurate planning engine for ZR+-enabled hop-by-hop IPoWDM networks. By leveraging a novel, to the best of our knowledge, recurrence-based approach, SPRINT can determine the location and number of ZR+ pluggables needed across an IPoWDM network to meet a target quality of service at a very low computational cost. We compared SPRINT to conventional simulation-based dimensioning techniques in real-world network topologies exhibiting different structural, spatial, and spectral features under different traffic loads. Results show SPRINT is up to four orders of magnitude faster while maintaining a high average accuracy of 90%. This speedup is critical when evaluating a number of envisaged scenarios, while accuracy is key to avoid the high cost of overprovisioning. SPRINT supports both uniform and non-uniform dimensioning strategies, providing flexibility in resource allocation and cost reductions in network planning. By addressing the lack of open fast dimensioning tools for hop-by-hop IPoWDM networks, this work contributes to the advancement of the design of next-generation ZR+-based optical networks.