2,877 research outputs found
Photon Counting OTDR : Advantages and Limitations
We give detailed insight into photon counting OTDR (nu-OTDR) operation,
ranging from Geiger mode operation of avalanche photodiodes (APD), analysis of
different APD bias schemes, to the discussion of OTDR perspectives. Our results
demonstrate that an InGaAs/InP APD based nu-OTDR has the potential of
outperforming the dynamic range of a conventional state-of-the-art OTDR by 10
dB as well as the 2-point resolution by a factor of 20. Considering the trace
acquisition speed of nu-OTDRs, we find that a combination of rapid gating for
high photon flux and free running mode for low photon flux is the most
efficient solution. Concerning dead zones, our results are less promising.
Without additional measures, e.g. an optical shutter, the photon counting
approach is not competitive.Comment: 12 pages, 13 figures, accepted for publication by IEEE Journal of
Lightwave Technolog
Practical free-space quantum key distribution over 1 km
A working free-space quantum key distribution (QKD) system has been developed
and tested over an outdoor optical path of ~1 km at Los Alamos National
Laboratory under nighttime conditions. Results show that QKD can provide secure
real-time key distribution between parties who have a need to communicate
secretly. Finally, we examine the feasibility of surface to satellite QKD.Comment: 5 pages, 2 figures, 2 tables. Submitted to Physics Review Letters,
May 199
Experimental quantum key distribution with simulated ground-to-satellite photon losses and processing limitations
Quantum key distribution (QKD) has the potential to improve communications
security by offering cryptographic keys whose security relies on the
fundamental properties of quantum physics. The use of a trusted quantum
receiver on an orbiting satellite is the most practical near-term solution to
the challenge of achieving long-distance (global-scale) QKD, currently limited
to a few hundred kilometers on the ground. This scenario presents unique
challenges, such as high photon losses and restricted classical data
transmission and processing power due to the limitations of a typical satellite
platform. Here we demonstrate the feasibility of such a system by implementing
a QKD protocol, with optical transmission and full post-processing, in the
high-loss regime using minimized computing hardware at the receiver. Employing
weak coherent pulses with decoy states, we demonstrate the production of secure
key bits at up to 56.5 dB of photon loss. We further illustrate the feasibility
of a satellite uplink by generating secure key while experimentally emulating
the varying channel losses predicted for realistic low-Earth-orbit satellite
passes at 600 km altitude. With a 76 MHz source and including finite-size
analysis, we extract 3374 bits of secure key from the best pass. We also
illustrate the potential benefit of combining multiple passes together: while
one suboptimal "upper-quartile" pass produces no finite-sized key with our
source, the combination of three such passes allows us to extract 165 bits of
secure key. Alternatively, we find that by increasing the signal rate to 300
MHz it would be possible to extract 21570 bits of secure finite-sized key in
just a single upper-quartile pass.Comment: 12 pages, 7 figures, 2 table
Streak camera receiver definition study
Detailed streak camera definition studies were made as a first step toward full flight qualification of a dual channel picosecond resolution streak camera receiver for the Geoscience Laser Altimeter and Ranging System (GLRS). The streak camera receiver requirements are discussed as they pertain specifically to the GLRS system, and estimates of the characteristics of the streak camera are given, based upon existing and near-term technological capabilities. Important problem areas are highlighted, and possible corresponding solutions are discussed
The Security of Practical Quantum Key Distribution
Quantum key distribution (QKD) is the first quantum information task to reach
the level of mature technology, already fit for commercialization. It aims at
the creation of a secret key between authorized partners connected by a quantum
channel and a classical authenticated channel. The security of the key can in
principle be guaranteed without putting any restriction on the eavesdropper's
power.
The first two sections provide a concise up-to-date review of QKD, biased
toward the practical side. The rest of the paper presents the essential
theoretical tools that have been developed to assess the security of the main
experimental platforms (discrete variables, continuous variables and
distributed-phase-reference protocols).Comment: Identical to the published version, up to cosmetic editorial change
Feasibility of Using Bandwidth Efficient Modulation to Upgrade the CMS Tracker Readout Optical Links
Plans to upgrade the LHC after approximately 10 years of operation are
currently being considered at CERN. A tenfold increase in luminosity delivered
to the experiments is envisaged in the so-called Super LHC (SLHC). This will
undoubtedly give rise to significantly larger data volumes from the detectors,
requiring faster data readout. The possibility of upgrading the CMS Tracker
analog readout optical links using a bandwidth efficient digital modulation
scheme for deployment in the SLHC has been extensively explored at CERN.
Previous theoretical and experimental studies determined the achievable data
rate using a system based on Quadrature Amplitude Modulation (QAM) to be
~3-4Gbit/s (assuming no error correction is used and for an error rate of
~10-9). In this note we attempt to quantify the feasibility of such an upgrade
in terms of hardware implementation complexity, applicability to the high
energy physics (HEP) environment, technological feasibility and R&D effort
required.Comment: CERN CMS Note. 16 pages, 10 figure
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