arxiv: 2605.10724 · v1 · submitted 2026-05-11 · 🪐 quant-ph · cs.IT· math.IT

Recognition: no theorem link

Selective Placement of Hollow-Core Fibers for QKD and Classical Communication Coexistence

Giovanni Simone Sticca , Alessandro Gagliano , Memedhe Ibrahimi , Alberto Gatto , Francesco Musumeci , Massimo Tornatore

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Pith reviewed 2026-05-12 05:07 UTC · model grok-4.3

classification 🪐 quant-ph cs.ITmath.IT

keywords hollow-core fibersQKD coexistenceoptical networksquantum key distributionmetro topologynetwork upgrading

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The pith

Partially upgrading metro optical networks with hollow-core fibers can reduce the number of quantum modules needed for QKD by up to 49 percent.

A machine-rendered reading of the paper's core claim, the machinery that carries it, and where it could break.

The paper investigates the advantages of selectively replacing some conventional optical fibers with hollow-core fibers to enable better coexistence between quantum key distribution and classical data transmission. Using a model of a metro network, the authors find that upgrading 40 percent of the links achieves up to a 49 percent reduction in required quantum modules. This matters because it provides a cost-effective way to integrate secure quantum communications into existing infrastructure without replacing the entire network. A sympathetic reader would see this as a practical step toward scalable QKD deployment in urban settings.

Core claim

The central claim is that selective placement of hollow-core fibers in optical networks improves the coexistence of QKD and classical communication, allowing fewer dedicated quantum modules. Specifically, in a metro topology, upgrading 40% of links reduces the number of quantum modules by up to 49%.

What carries the argument

Selective placement of hollow-core fibers, which reduces noise and improves wavelength compatibility for QKD signals alongside classical traffic.

Load-bearing premise

The network model accurately reflects how hollow-core fibers improve coexistence and reduce the need for separate quantum modules.

What would settle it

A real-world deployment in a metro network where 40% of links are upgraded to hollow-core fibers, followed by counting the actual quantum modules required compared to the all-standard-fiber case.

Figures

Figures reproduced from arXiv: 2605.10724 by Alberto Gatto, Alessandro Gagliano, Francesco Musumeci, Giovanni Simone Sticca, Massimo Tornatore, Memedhe Ibrahimi.

**Figure 1.** Figure 1: Quantum channel allocation example in a hybrid SSMF/HCF network. possible configurations for fiber deployment (namely SSMFonly, hybrid SSMF/HCF, and HCF-only), where different combinations of band assignment can be used to achieve coexistence of classical and QKD channels, as shown in [PITH_FULL_IMAGE:figures/full_fig_p001_1.png] view at source ↗

**Figure 2.** Figure 2: shows the SKR as a function of span length for quantum channels transmitted in either the C- or O-band, under the assumption of full classical channel loading, for both SSMF and HCF. For each case, the shaded region represents the range of SKR values obtained over all quantum channels in the considered band, bounded by the best- and worstperforming channels. The results show that coexistence in the C-band… view at source ↗

**Figure 3.** Figure 3: Average cost (number of quantum modules) and unserved key rate as a function of the HCF budget, for different link length factors ( [PITH_FULL_IMAGE:figures/full_fig_p003_3.png] view at source ↗

**Figure 4.** Figure 4: Percentage of C-band quantum channels vs. HCF budget, averaged [PITH_FULL_IMAGE:figures/full_fig_p003_4.png] view at source ↗

read the original abstract

We investigate the benefits of partially upgrading optical networks with hollow-core fibers for QKD-classical communication coexistence. Results show that upgrading 40% of links in a metro topology can reduce the number of quantum modules by up to 49%.

Editorial analysis

A structured set of objections, weighed in public.

Desk editor's note, referee report, simulated authors' rebuttal, and a circularity audit. Tearing a paper down is the easy half of reading it; the pith above is the substance, this is the friction.

Referee Report

2 major / 1 minor

Summary. The manuscript investigates the benefits of selectively upgrading metro optical networks with hollow-core fibers (HCF) to improve coexistence between quantum key distribution (QKD) and classical communications. Through network modeling and optimization, it reports that upgrading 40% of links yields up to a 49% reduction in the number of required quantum modules.

Significance. If the underlying network model and its assumptions about HCF-enabled noise reduction hold under realistic conditions, the result could meaningfully lower the hardware costs and infrastructure barriers for QKD deployment in existing metro networks, providing a phased upgrade strategy for operators.

major comments (2)

[Abstract] Abstract: The central quantitative claim (40% upgrade yields up to 49% fewer quantum modules) is presented without any description of the network model, the specific parameters quantifying HCF coexistence benefits (e.g., allowable classical launch power, Raman/Brillouin noise reduction), or error analysis/validation data.
[Network modeling and results sections] Network modeling and results sections: The optimization credits HCF links with substantially lower nonlinear noise that directly reduces the need for dedicated quantum modules, but no calibration of these modeled crosstalk reductions against measured metro-scale coexistence data is provided; this assumption is load-bearing for the reported module savings.

minor comments (1)

[Throughout] Ensure consistent definition of acronyms (HCF, QKD) on first use and clarify any topology-specific assumptions in figure captions or text.

Simulated Author's Rebuttal

2 responses · 0 unresolved

We thank the referee for their constructive review and for highlighting areas where additional clarity would strengthen the manuscript. We address each major comment below and are prepared to make targeted revisions.

read point-by-point responses

Referee: [Abstract] Abstract: The central quantitative claim (40% upgrade yields up to 49% fewer quantum modules) is presented without any description of the network model, the specific parameters quantifying HCF coexistence benefits (e.g., allowable classical launch power, Raman/Brillouin noise reduction), or error analysis/validation data.

Authors: We agree the abstract is concise and omits model details to meet length limits. The network model, HCF noise parameters (including Raman/Brillouin suppression and allowable classical launch powers), and sensitivity/error analysis are fully described in Sections II and III. We will revise the abstract to include one sentence summarizing the modeling framework and key HCF assumptions while preserving the result statement. revision: partial
Referee: [Network modeling and results sections] Network modeling and results sections: The optimization credits HCF links with substantially lower nonlinear noise that directly reduces the need for dedicated quantum modules, but no calibration of these modeled crosstalk reductions against measured metro-scale coexistence data is provided; this assumption is load-bearing for the reported module savings.

Authors: The HCF crosstalk reductions are taken from published experimental measurements on hollow-core fiber coexistence (Raman noise suppression and nonlinear threshold improvements). As this is a network optimization study, we did not perform new metro-scale experiments. We will add an explicit subsection in the modeling section that (i) cites the specific measured values and references used, (ii) states the range of reported benefits, and (iii) includes a sensitivity analysis showing how module savings vary with the noise-reduction assumption. This directly addresses the load-bearing concern. revision: yes

Circularity Check

0 steps flagged

No circularity detected in network optimization results

full rationale

The paper derives its headline result (40% HCF upgrade yielding up to 49% fewer quantum modules) as the output of a metro-topology optimization model that takes HCF coexistence performance parameters as inputs and computes module counts. This is a standard simulation workflow with no evidence of self-definitional loops, fitted inputs renamed as predictions, or load-bearing self-citations that reduce the claim to its own premises by construction. The derivation remains self-contained as an independent modeling exercise whose validity rests on the accuracy of its external assumptions rather than tautological equivalence to the inputs.

Axiom & Free-Parameter Ledger

1 free parameters · 1 axioms · 0 invented entities

Based solely on the abstract, the central claim rests on unstated network simulation assumptions about fiber performance, crosstalk reduction, and module counting that are not detailed or justified here.

free parameters (1)

Optimal upgrade fraction
The 40% figure is presented as the level achieving the reported savings and is therefore a key parameter in the optimization.

axioms (1)

domain assumption Hollow-core fibers provide sufficient performance gains in coexistence scenarios to meaningfully reduce the number of required quantum modules.
This premise is implicit in the investigation of benefits for QKD-classical communication coexistence.

pith-pipeline@v0.9.0 · 5342 in / 1137 out tokens · 61629 ms · 2026-05-12T05:07:26.427479+00:00 · methodology

discussion (0)

Reference graph

Works this paper leans on

10 extracted references · 10 canonical work pages

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