arXiv subjects
Publications and source records attributed to Florian Honz.
We deploy shortwave-QKD over short-reach in-house/datacom architectures and show that few-mode propagation and speckle-selective loss severely impact the QKD performance. We accomplish 12 kb/s secure-key generation in presence of 50 co-existing data channels.
We present a single-chip photonic QKD transmitter fabricated on a silicon platform. We achieve secure-key generation over 45.9km of field-deployed fiber and prove its operation along 32 WDM channels, by sourcing light without III-V materials.
We demonstrate robust light coupling between two single-mode fibers for an out-door FSO link through a focal plane array beamformer with 61 fine-pitched fiber cores as antenna elements. We show that favourable coupling conditions are established for this 10Gb/s Fi-Wi-Fi bridge after rough initial pointing.
We demonstrate focal plane array beamforming for semi-blind deployments of free-space optical QKD links. We accomplish a secure-key rate of 1.2 kb/s at a QBER of 9.1% over a 63-m out-door link during full sunshine.
We present a full-duplex 10Gb/s FSO bridge between two single-mode ports, utilizing centralized beamforming and simultaneous channel sounding. We further mitigate turbulence-induced fading through diversity reception enabled by wavelength-set coding.
Terrestrial free-space optical (FSO) links are an ideal candidate to extend the bandwidth continuum offered by fiber networks, yet at the expense of unfavorable cost credentials due to highly complex opto-mechanical setups. As a response to this challenge, we present a simple fiber-based focal plane array (FPA) architecture which contributes beamforming functionality to an FSO link that bridges the gap between two single-mode fiber ports. Through use of space-switched and wavelength-routed beamforming networks, which together with a photonic lantern provide a compact arrangement of up to 61 fine-pitched optical antenna elements on a fiber tip, we experimentally demonstrate that our FPA can assist the channel optimization of an FSO link after rough initial beam pointing. We show that favorable coupling conditions can be accomplished between two standard single-mode fibers, which enables us to successfully retain the fiber continuum by achieving error-free 10 Gb/s/λ data transmission in a space-switched out-door fiber-wireless-fiber scenario.
We show simplified DPS-QKD using a SiN micro-ring resonator operated at 852 nm. A raw-key rate of up to 25.3 kb/s is reached at a QBER suitable for secure-key extraction. Short-reach QKD operation is maintained for zero-touch link layouts with C-band telecom fiber.
We demonstrate QKD and data communication over an out-door free-space link where large-core fiber substitutes active alignment. We further prove E-band QKD as stable and robust under full daylight, despite the loss of spatial filtering.
We implement a silicon-on-insulator light emitter as optical supply for a QKD transmitter and transfer it to an electronic BiCMOS wafer. A secure key is established over short reach in co-existence with shortwave data transmission.
We evaluate large-core FSO links where excellent coupling pairs with bandwidth fading due to multi-mode propagation. The 10-Gb/s/λ limit for 105-μm double-clad fibers is mitigated by spectral launch tuning, restoring 84% of single-clad 25-Gb/s/λ capacity.
We demonstrate a novel transmitter concept for quantum key distribution based on the polarization-encoded BB84 protocol, which is sourced by the incoherent light of a forward-biased Ge-on-Si PIN junction. We investigate two architectures for quantum state preparation, including independent polarization encoding through multiple modulators and a simplified approach leveraging on an interferometric polarization modulator. We experimentally prove that the Ge-on-Si light source can accommodate for quantum key generation by accomplishing raw-key rates of 2.15 kbit/s at a quantum bit error ratio of 7.71% at a symbol rate of 1 GHz. We further investigate the impact of depolarization along fiber-based transmission channels in combination with the broadband nature of the incoherent light source. Our results prove the feasibility of a fully-integrated silicon quantum key distribution transmitter, including its light source, for possible short-reach applications in zero-trust intra-datacenter environments.
As quantum key distribution has reached the maturity level for practical deployment, questions about the co-integration with existing classical communication systems are of utmost importance. To this end we demonstrate how the co-propagation of classical and quantum signals can benefit from the development of novel hollow-core fibers. We demonstrate a secure key rate of 330 bit/s for a quantum channel at 1538 nm in the presence of 25 x 10 Gb/s classical channels, transmitted at an aggregated launch power of 12 dBm, spanning over the C+L-band in the same hollow-core fiber link. Furthermore, we show the co-integration of the classical key-distillation channel onto this fiber link, turning it into a bidirectional fiber link and thereby mitigating the need for multiple fibers. We believe this to be an important step towards the deployment and integration of hollow-core fibers together with DV-QKD for the inherently secure telecom network of the future.
We investigate a polarization-encoded BB84-QKD transmitter that is simplified from an architectural and technological point-of-view, demonstrating a silicon emitter sourcing a low-complexity polarization modulator for secure-key generation at a raw-key rate of 2.8kb/s and QBER of 10.47%, underpinning the feasibility of an all-silicon QKD transmitter.
We investigate the behavior of a Ge-on-Si light source and demonstrate its feasibility for polarization-encoded discrete-variable quantum key distribution following the BB84 protocol, enabling a potential "all-silicon" QKD scheme which can operate well below the necessary QBER limit and successfully generate secret keys.
We demonstrate a polarization-encoded BB84 transmitter sourced by a SiGe light source and show that such a potentially "all-silicon" QKD scheme can operate well below the QBER threshold at which secret keys can be established.
We demonstrate a simplified out-door FSO link with modal split for down-/uplink and confirm its long-term stability without active beam tracking. We further prove the duality of modal and directional split through penalty-free full-duplex transmission.
We experimentally compare a loss-optimized coherent heterodyne and a bandwidth-blessed intradyne CV-QKD architecture. We find the former to prevail performance-wise for medium/long link reach, while the latter features a 5-9 dB higher secure-key rate over short reach.
We successfully integrate coherent one-way QKD at 1538 nm in a 7.7 km long hollow-core fiber link with 17 EDFA-boosted C-band data channels from 1540.56 to 1558.17 nm, aggregating a power of 11 dBm. QKD operation proves successful despite the wideband layout of classical channels.