Wavelength conversion in optical transport networks

The introduction of optical technology in the path layer of a transport network is analyzed; in particular, the impact of all-optical wavelength conversion is examined. Two basic optical cross-connect schemes based on space switching and on wave-length switching, respectively, and two types of wavelength converters are considered. The wavelength converters are, respectively, based on four-wave miring (FWM) in semiconductor optical amplifiers (SOAs) and on cross-phase modulation (XPM) obtained by two SOAs put in an interferometric configuration. An analysis of transmission performances of optical transport networks employing both types of wavelength conversion and both the node architectures is reported. The performances are evaluated by means of a system modeling that facilitates considering physical phenomena occurring during transmission and all the important transmission impairments. The analysis reveals that both the types of converters can be employed with different features and limitations, according to the considered network and switching architecture.     

Polarization modulated coherent optical communication systems

Polarization modulated coherent optical communication systems are interesting for low-phase noise-induced penalty and insensitivity to the fluctuations of the field state of polarization if a suitable tracking is adopted. In this paper, sever kinds of binary and multilevel polarization modulated systems are presented based c Stokes parameters detection. Quantum limit performance is determined and phase noise-induced penalty is evaluated both in the presence of a sample and hold decision device and in case of postdetection filtering.     

Solid state catalytic tritiation: Isotopic exchange and tritium addition in high specific activity synthesis

Solid state catalytic saturation of double bond with hydrogen, deuterium and tritium is a valid route to incorporate selectively isotopes in specific positions. We studied the best fitting of all parameters that rule the radioactive yield of tritiation of an unsatured substrate, to guarantee the maximum incorporation of labeled atom in the product at room temperature. The wise choice of experimental parameters allowed very high radiochemical yields. The number of tritium exceeded the statistical presence of two atoms. Relative magnitudes for addition and exchange kinetic constants are provided.     

A facile synthesis of N-C linked 1,2,3-triazole-oligomers

The synthesis of the title oligomers was performed by means of an iterative sequence of 1,3-dipolar cycloaddition reactions of appropriate azides, starting from commercial 4-bromo-1-butyne as a key intermediate.     

Simulation of Transmissions Through Optical Transport Networks

The introduction of optical technologies in the path layer of the transport network allows the network communication capacity and nodes throughput to be greatly increased. Optical networks covering large geographic areas and information super highways are coming in the not too distant future. For these reasons it is necessary to analyze the transmission of high-speed signals that transport high volumes of traffic throughout large-area networks. Simulation is an effective tool for this analysis, allowing one to take into account the complex nonlinear behavior of the long optical links and of some optical devices as wavelength converters. This article discusses two different approaches to the simulation of transmission through optical networks: the semi-analytical approach and the complete simulation. Advantages and disad vantages of each approach are considered, and the results obtained by different simulation software implementing the two approaches are compared.     

Anisotropy studies of ultrafast dipole reorientations

Various ways in which the anisotropy can be used to understand ultrafast processes are presented and discussed. Examples include molecular reorientation, energy transfer between identical systems, excitation dynamics in polymers, reactant product alignment, protein dynamics and internal motions in fluxional molecules.     

A water isotope (2H, 17O, and 18O) spectrometer based on optical feedback cavity-enhanced absorption for in situ airborne applications

Measurements of the isotopic composition of water are thought to help explain stratospheric aridity and related issues in atmospheric sciences. Simultaneous in situ measurements of ²H/¹H, ¹⁷O/¹⁶O, and ¹⁸O/¹⁶O at high spatial resolution are required for this purpose. We present the design and laboratory performance of a device that will be used on high-altitude research aircraft. It is based on optical feedback cavity-enhanced spectroscopy (OF-CEAS), with better sensitivity than traditional multi-pass arrangements. It utilizes a near-infrared laser source, avoiding the need for cryogens. We demonstrate an airborne precision during tropospheric flight conditions of 1 ‰, 3 ‰, and 9 ‰ for δ¹⁸O, δ¹⁷O, and δ²H, respectively, for 30-s averaged data and a water concentration of about 200 ppm. With recent improvements we expect to remain within a factor of about three of these values under true stratospheric conditions (water mixing ratio ∼10 ppmv). PACS 07.88.+y; 42.55.Px; 42.62.Fi; 92.60.Hd; 92.60.Jq