60 research outputs found
Experimental Demonstration of Dual Polarization Nonlinear Frequency Division Multiplexed Optical Transmission System
Multi-eigenvalues transmission with information encoded simultaneously in
both orthogonal polarizations is experimentally demonstrated. Performance below
the HD-FEC limit is demonstrated for 8-bits/symbol 1-GBd signals after
transmission up to 207 km of SSMF
Experimental Satellite Quantum Communications
Quantum Communications on planetary scale require complementary channels
including ground and satellite links. The former have progressed up to
commercial stage using fiber-cables, while for satellite links, the absence of
terminals in orbit has impaired theirs development. However, the demonstration
of the feasibility of such links is crucial for designing space payloads and to
eventually enable the realization of protocols such as quantum-key-distribution
(QKD) and quantum teleportation along satellite-to-ground or intersatellite
links. We demonstrated the faithful transmission of qubits from space to ground
by exploiting satellite corner cube retroreflectors acting as transmitter in
orbit, obtaining a low error rate suitable for QKD. We also propose a two-way
QKD protocol exploiting modulated retroreflectors that necessitates a minimal
payload on satellite, thus facilitating the expansion of Space Quantum
Communications
Dual polarization nonlinear Fourier transform-based optical communication system
New services and applications are causing an exponential increase in internet
traffic. In a few years, current fiber optic communication system
infrastructure will not be able to meet this demand because fiber nonlinearity
dramatically limits the information transmission rate. Eigenvalue communication
could potentially overcome these limitations. It relies on a mathematical
technique called "nonlinear Fourier transform (NFT)" to exploit the "hidden"
linearity of the nonlinear Schr\"odinger equation as the master model for
signal propagation in an optical fiber. We present here the theoretical tools
describing the NFT for the Manakov system and report on experimental
transmission results for dual polarization in fiber optic eigenvalue
communications. A transmission of up to 373.5 km with bit error rate less than
the hard-decision forward error correction threshold has been achieved. Our
results demonstrate that dual-polarization NFT can work in practice and enable
an increased spectral efficiency in NFT-based communication systems, which are
currently based on single polarization channels
Experimental single photon exchange along a space link of 7000 km
Extending the single photon transmission distance is a basic requirement for
the implementation of quantum communication on a global scale. In this work we
report the single photon exchange from a medium Earth orbit satellite (MEO) at
more than 7000 km of slanted distance to the ground station at the Matera Laser
Ranging Observatory. The single photon transmitter was realized by exploiting
the corner cube retro-reflectors mounted on the LAGEOS-2 satellite. Long
duration of data collection is possible with such altitude, up to 43 minutes in
a single passage. The mean number of photons per pulse ({\mu}sat) has been
limited to 1 for 200 seconds, resulting in an average detection rate of 3.0 cps
and a signal to noise ratio of 1.5. The feasibility of single photon exchange
from MEO satellites paves the way to tests of Quantum Mechanics in moving
frames and to global Quantum Information.Comment: 5 pages, updated versio
Coagulation properties and Nostrano di Primiero cheese yield of milk from Brown grazing cows of different k-casein genotype
Propriet\ue0 di coagulazione e resa in Nostrano di Primiero del latte di vacche Brune al pascolo con differente genotipo per la k-caseina \u2013 Il latte prodotto in alpeggio da 16 bovine di razza Bruna Italiana con diverso genotipo per la k-caseina, 8 AA e 8 BB, \ue8 stato analizzato per composizione e caratteristiche reologiche. Lo stesso latte \ue8 stato trasformato in formaggio del tipo Nostrano di Primiero. La composizione del latte e il tempo di coagulazione (r) sono risultati simili tra i due tipi genetici, cos\uec come la composizione del siero e la resa in formaggio. Il tempo di rassodamento del coagulo (k20) e la sua consistenza (a30) sono risultati invece migliori per il tipo genetico BB rispetto all\u2019AA (4,2 min vs 7,9 min e 32,9 mm vs 25,2 mm)
End-to-end optimization of coherent optical communications over the split-step Fourier method guided by the nonlinear Fourier transform theory
Optimizing modulation and detection strategies for a given channel is
critical to maximize the throughput of a communication system. Such an
optimization can be easily carried out analytically for channels that admit
closed-form analytical models. However, this task becomes extremely challenging
for nonlinear dispersive channels such as the optical fiber. End-to-end
optimization through autoencoders (AEs) can be applied to define
symbol-to-waveform (modulation) and waveform-to-symbol (detection) mappings,
but so far it has been mainly shown for systems relying on approximate channel
models. Here, for the first time, we propose an AE scheme applied to the full
optical channel described by the nonlinear Schr\{"o}dinger equation (NLSE).
Transmitter and receiver are jointly optimized through the split-step Fourier
method (SSFM) which accurately models an optical fiber. In this first numerical
analysis, the detection is performed by a neural network (NN), whereas the
symbol-to-waveform mapping is aided by the nonlinear Fourier transform (NFT)
theory in order to simplify and guide the optimization on the modulation side.
This proof-of-concept AE scheme is thus benchmarked against a standard
NFT-based system and a threefold increase in achievable distance (from 2000 to
6640 km) is demonstrated
Dual-polarization nonlinear Fourier transform-based optical communication system
New services and applications are causing an exponential increase in Internet traffic. In a few years, the current fiber optic communication system infrastructure will not be able to meet this demand because fiber nonlinearity dramatically limits the information transmission rate. Eigenvalue communication could potentially overcome these limitations. It relies on a mathematical technique called “nonlinear Fourier transform (NFT)” to exploit the “hidden” linearity of the nonlinear Schrödinger equation as the master model for signal propagation in an optical fiber. We present here the theoretical tools describing the NFT for the Manakov system and report on experimental transmission results for dual polarization in fiber optic eigenvalue communications. A transmission of up to 373.5 km with a bit error rate less than the hard-decision forward error correction threshold has been achieved. Our results demonstrate that dual-polarization NFT can work in practice and enable an increased spectral efficiency in NFT-based communication systems, which are currently based on single polarization channels
Probabilistically Shaped 4-PAM for Short-Reach IM/DD Links with a Peak Power Constraint
Probabilistic shaping for intensity modulation and direct detection (IM/DD)
links is discussed and a peak power constraint determined by the limited
modulation extinction ratio (ER) of optical modulators is introduced. The input
distribution of 4-ary unipolar pulse amplitude modulation (PAM) symbols is
optimized for short-reach transmission links without optical amplification nor
in-line dispersion compensation. The resulting distribution is symmetric around
its mean allowing to use probabilistic amplitude shaping (PAS) to generate
symbols that are protected by forward error correction (FEC) and that have the
optimal input distribution. The numerical analysis is confirmed experimentally
for both an additive white Gaussian noise (AWGN) channel and a fiber channel,
showing gains in transmission reach and transmission rate, as well as rate
adaptability.Comment: accepted for publication in Journal of Lightwave Technolog
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