Transparent ultra-long-haul DWDM networks with "broadcast-and-select" OADM/OXC architecture

We describe an experimental realization of ultra-long-haul (ULH) networks with dynamically reconfigurable transparent optical add-drop multiplexers (OADMs) and optical cross-connects (OXCs). A simple new approach to dispersion management in ULH dense-wavelength-division-multiplexing (DWDM) transparent optical networks is proposed and implemented, which enables excellent transmission performance while avoiding dispersion compensation on a connection-by-connection basis. We demonstrate "broadcast-and-select" node architectures that take full advantage of this method. Our implementation of signal leveling ensures minimum variations of path-averaged power among the wavelength-division-multiplexing (WDM) channels between the dynamic gain-equalizing nodes and results in uniform nonlinear and spontaneous-emission penalties across the WDM spectrum. We achieve 80/spl times/10.7-Gb/s DWDM networking over 4160 km (52 spans/spl times/80 km each) of all-Raman-amplified symmetric dispersion-managed fiber and 13 concatenated OADMs or 320/spl times/320 wavelength-port OXCs with 320-km node spacing. The WDM channels use 50-GHz grid in C band and the simple nonreturn-to-zero (NRZ) modulation format. The measured Q values exhibit more than a 1.8-dB margin over the forward-error correction threshold for 10/sup -15/ bit-error-rate operation. We compare these results with point-to-point transmission of 80/spl times/10-Gb/s NRZ WDM signals over 4160 km without OADM/OXC and provide detailed characterization of penalties due to optical signal-to-noise-ratio degradation, filter concatenation, and crosstalk.     

Experimental realization of ‘universal homodyne tomography’ with a single local oscillator

We report preliminary experimental measurement of the twin-beam quantum state via optical homodyne tomography using a single local oscillator. The experiment is a realization of the recently reported ‘universal homodyne tomography’ technique. The results agree well with theoretical predictions and reveal the non-classical photon-number correlation between the signal and idler photons of the twin-beam state.     

Mechanism of terahertz photoconductivity in semimetallic HgTe/CdHgTe quantum wells

Terahertz photoconductivity in magnetic fields in semimetallic HgTe/CdHgTe quantum wells has been studied. The main contribution to photoconductivity comes from a signal that appears as a result of electron-gas heating. It is shown that, with the cyclotron resonance conditions satisfied, the photoconductivity signal is composed of cyclotron-resonance and bolometric components. However, in this case too, the bolometric contribution predominates.     

Analytical solution to inverse kinematic problem for 6-DOF robot-manipulator

Analytical solution to inverse kinematic problem for 6-DOF (Degree Of Freedom) robot-manipulators is considered. Well-known approaches to solving the problem involve geometrical and numerical methods. In this paper we discuss the solution technique based on deriving the system of nonlinear equations and solving it in the general view.     

Mechanism of the photoelectromagnetic effect in two-dimensional systems in quantizing magnetic fields

A new mechanism of the photovoltaic effect in a terahertz frequency range is proposed that is capable of explaining the features of terahertz photocurrents observed previously in asymmetric InAs quantum wells and double GaAs quantum wells in an external tilted magnetic field. It is shown that, in the asymmetric semiconductor heterostructures occurring in a tilted magnetic field, an edge photocurrent is generated due to the absorption of radiation on the electron transitions between Landau levels. A new approach to the creation of highly sensitive terahertz photodetectors based on asymmetric semiconductor heterostructures is proposed.     

Tests of a P-67 boiler for an 800 MW unit

The rebuilding of the P-67 boiler for an 800 MW unit at the Berezovskaya GRéS, as well as changes in the thermal engineering characteristics of the coal from the Berezovskii-1 seam and its slagging properties, are described. The results of balance tests of the boiler and changes in the thermal efficiency of heating surfaces during 2006 – 2008, including after mechanical cleaning and modernization of the combined cleaning system, as well as with coal dust coarsening and loading of the lower burner layers and downward blast, are discussed.     

Photon statistics of single-mode zeros and ones from an erbium-doped fiber amplifier measured by means of homodyne tomography

We report measurement of the photon-number distributions of zeros and ones that emerge from an erbium-doped fiber amplifier (EDFA) in an on-off modulated communication system. Single-mode single-photon resolution was achieved by employing the method of optical homodyne tomography. The measured distributions agree with the quantum predictions of a Bose-Einstein distribution for the zeros and a Laguerre (noncentral negative binomial) distribution for the ones over a dynamic range up to 40 dB. The resulting noise figure of the amplifier compares well to that measured by an optical spectrum analyzer.     

The Influence of Metal Grids on the Ion-Beam Characteristics in a Laser-Plasma Source

Instruments and Experimental Techniques - The influence of metal grids on the characteristics of particles extracted from a plasma was investigated in the course of development of the laser-plasma...