Eavesdropper localization for quantum and classical channels via nonlinear scattering

TL;DR

This paper introduces a novel method for localizing eavesdroppers in optical fiber networks using nonlinear scattering, achieving centimeter-level precision and distinguishing fiber types, enhancing security in quantum and classical communications.

Contribution

The authors present a new eavesdropper localization technique employing stimulated Brillouin scattering, outperforming conventional methods and enabling fiber fingerprinting for security.

Findings

Achieves centimeter-level localization accuracy.

Outperforms conventional OTDR in detecting evanescent outcoupling.

Can distinguish fiber types for security fingerprinting.

Abstract

Optical fiber networks are part of important critical infrastructure and known to be prone to eavesdropping attacks. Hence cryptographic methods have to be used to protect communication. Quantum key distribution (QKD), at its core, offers information theoretical security based on the laws of physics. In deployments one has to take into account practical security and resilience. The latter includes the localization of a possible eavesdropper after an anomaly has been detected by the QKD system to avoid denial-of-service. Here, we present a novel approach to eavesdropper location that can be employed in quantum as well as classical channels using stimulated Brillouin scattering. The tight localization of the acoustic wave inside the fiber channel using correlated pump and probe waves allows to discover the coordinates of a potential threat within centimeters. We demonstrate that our approach outperforms conventional OTDR in the task of localizing an evanescent outcoupling of 1% with cm precision inside standard optical fibers. The system is furthermore able to clearly distinguish commercially available standard SMF28 from different manufacturers, paving the way for fingerprinted fibers in high security environments.