196,160 research outputs found
Transient gain dynamics in saturated Raman amplifiers with multiple counter-propagating pumps
No full textA new block diagram of Raman amplifiers with
multiple backward pumps is proposed, for use in
commercial simulators. Transient computation
times are shorter by more than an order of magnitude
as compared with the full solution of the propagation equations
Polarization mode dispersion reduction in spun silica holey fibres
No full textWe report the fabrication of a spun holey optical fibre. Our experiments show that the complex air/glass transverse structure can be retained when the preform is spun during the fibre drawing process. Measurements of differential group delay (DGD) confirm that significant reductions in polarization mode dispersion (PMD) can be readily achieved using this approach
Transient gain dynamics in saturated Raman amplifiers
No full textThis paper provides a detailed analysis of transient gain dynamics in saturated Raman amplifiers
fed by wavelength division multiplexed (WDM) signals. Such dynamics are due to a pump saturation
effect, known as pump-mediated signal-to-signal crosstalk, which is equivalent to the well-known
cross-gain modulation in EDFAs. We provide for the first time a simple block-diagram model of the
Raman amplifier, whose state is represented by the relative pumps depletion sensed by the signals.
With such model, we are able to prove that the time constants of the Raman gain transients are of the
same order as the pump–signal walk-off times. For counter-propagating pumps, the model is very
accurate in predicting both the steady-state gain and the transient gain dynamics, with more than an
order of magnitude improvement in computation time with respect to the direct solution of the signals
and pumps propagation equations. The value of such model is therefore in the simulation of dynamic
WDM networking scenarios in which the input powers have large swings in time. The model also
extends to the co-propagating pump and well captures the time constants involved in the transients,
although the accuracy in the predicted power levels is worse than that of the counter-propagating
pump case
E-beam curing of epoxy based blends in order to produce high performance composites
No full textIn this work, blends of a difunctional epoxy monomer and a thermoplastic toughening agent are E-beam irradiated at two different dose rates and two different total absorbed doses. The influence of the processing conditions on the thermal properties and on the morphology of the obtained matrices has been investigated. In particular, it is shown how the increase of the dose rate causes an increase of the temperature during irradiation, thus inducing a simultaneous thermal and radiation curing. On the contrary, at low-dose rate the system mainly undergoes to radiation curing, thus making the cured material very sensible to a post-irradiation thermal treatment with a significant improvement of the thermal properties
New anti sars-cov-2 targets for quinoline derivatives chloroquine and hydroxychloroquine†
No full textThe rapid spread of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has created a severe global health crisis. In this paper, we used docking and simulation methods to identify potential targets and the mechanism of action of chloroquine (CQ) and hydroxychloroquine (HCQ) against SARS-CoV-2. Our results showed that both CQ and HCQ influenced the functionality of the envelope (E) protein, necessary in the maturation processes of the virus, due to interactions that modify the flexibility of the protein structure. Furthermore, CQ and HCQ also influenced the proofreading and capping of viral RNA in SARS-CoV-2, performed by nsp10/nsp14 and nsp10/nsp16. In particular, HCQ demonstrated a better energy binding with the examined targets compared to CQ, probably due to the hydrogen bonding of the hydroxyl group of HCQ with polar amino acid residues
Pulse radiolysis and theoretical investigation on the initial mechanism of e-beam polymerization of epoxy resins. The results obtained on (phenoxymethyl)oxirane
No full textThe radical cation of (phenoxymethyl)oxirane (PGE
.+) is generated by pulse radiolysis in dichloromethane solution and by direct
action of radiation on the title compound. In the pure system its UV–vis spectrum is characterized by two bands at 340 and 430 nm, such
that the electronic structure corresponds to a dipole bearing the positive charge on the phenoxy side. At the same time, the phenoxyoxirane
bridge is weakened. Then, the radical cation fragments into a phenoxonium ion and an oxyranylmethyl radical
(kPGEfragm = 1,16 x 10^7 s^-1). The latter immediately rearranges to an allyloxyl radical by ring opening. It is then conceived that the
action of onium salts, as radiation curing initiators of phenoxy-oxirane derivatives, occurs after epoxy ring opening
Study of Raman amplification properties in triangular photonic crystal fibers
No full textIn this paper, the Raman properties of triangular photonic crystal fibers (PCFs) are analyzed in order to design a fiber for Raman amplification with enhanced performances. By casting the Raman intensity propagation equations, the Raman effective area and the Raman gain coefficient are introduced-two meaningful parameters that take into account the overlap between the pump and signal profiles. The behavior of these two parameters is examined in silica PCFs as a function of the geometrical characteristics of the triangular lattice. The numerical results show that a proper design of the hole diameter and the spacing between air holes can minimize the Raman effective area and maximize the Raman gain coefficient. The paper then focuses on the PCFs with germania-doped core. It is found that, for a given PCF cross section and dimension of the doped region, the Raman gain coefficient increases linearly with the germania concentration. Moreover, by enlarging the doped region, it is discovered that a PCF with a germania-doped area internally tangent to the first ring of air holes has a maximum Raman gain coefficient. Finally, the calculated values of the Raman gain coefficient are compared with those of other highly nonlinear fibers presented in literature, showing that a well-designed triangular PCF can significatively improve the Raman gain performances
Raman Amplification Properties of Silica and Tellurite Photonic Crystal Fibers
No full textRaman properties of silica and tellurite photonic crystal fibers are investigated and compared. A significant increase in Raman gain coefficient is possible by tailoring the triangular lattice holes
Dispersion and non-linear properties of triangular photonic crystal fibers with large air-holes and small pitch
No full textProcessi di cura di resine epossidiche mediante radiazioni ionizzanti per la realizzazione si materiali compositi per il settore aerospaziale. Influenza delle condizioni operative sulle proprietà finali
No full text- …
