Crosstalk Analysis in Quantum Networks: Detection and Localization Insights with photon counting OTDR

TL;DR

This paper demonstrates the use of photon counting OTDR to detect, localize, and analyze crosstalk in quantum networks, revealing its dependence on configuration and wavelength, and offering insights for improved network performance.

Contribution

It introduces a novel application of photon counting OTDR for precise crosstalk analysis in quantum networks, highlighting configuration and wavelength effects for better mitigation strategies.

Findings

Crosstalk depends strongly on optical switch configuration.

Crosstalk increases significantly at longer wavelengths.

Photon counting OTDR effectively localizes crosstalk sources.

Abstract

Optical crosstalk from sub-milliwatt classical-channel power into quantum channels presents a significant challenge in quantum network development, introducing substantial noise that limits the network's performance, scalability, and fidelity. Here we report a demonstration using photon counting optical time-domain reflectometry ({\nu}-OTDR) to precisely identify and localize crosstalk between separate channels within the same fiber and between separate fibers. The coexistence of classical and quantum signals in the same network necessitates the use of optical switches for efficient routing and control. Crosstalk characterization of an optical switch reveals that crosstalk depends strongly on cross connect configuration, with higher levels observed when connections are presumed to be physically closer and lower levels when further apart. Additionally, we found that crosstalk exhibits a pronounced wavelength dependence, increasing over tenfold at longer wavelengths. These findings demonstrate the value of {\nu}-OTDR in diagnosing and mitigating crosstalk in quantum networks. They highlight the importance of optimizing optical switch configurations and wavelength management to minimize noise, ultimately enhancing the scalability, fidelity, and overall performance of quantum networks. This work establishes a foundational approach to addressing crosstalk, paving the way for more robust and efficient quantum network designs.