Fiber-optic voltage sensor based on a Bi12TiO20 crystal

A fiber-optic voltage sensor based on the longitudinal Pockels effect in a Bi(12)TiO(20) crystal is described. The use of a special backreflecting prism as a phase-retarding element is shown to improve the sensitivity and temperature stability of the sensor. A comparison between the temperature properties of the glass backreflecting prism and that of a quarter-wave plate is derived. The sensor demonstrates temperature stability of +/-1.5% from -20 degrees C to 60 degrees C and sensitivity of 0.145% per 1 V(rms) at 850 nm without the use of an additional temperature control channel.     

Continuous-wave and giant-pulse operations of a single-frequency erbium-doped fiber laser

We present a compact diode-pumped single-frequency single-polarization erbium-doped fiber laser with fiber Bragg gratings (FBGs) written in the active fiber itself. The single-polarization regime was obtained by applying uni-axial stress to one of the two FBGs forming the cavity. The laser is shown to operate in two regimes-quasi-continuous-wave regime with a few-percent of modulation in the output power and a giant-pulse regime accessible under sinusoidal pump modulation.     

The intensity dependent refractive index change of bacteriorhodopsin measured by the Z-scan and phase-modulated beams techniques

A comparative analysis of intensity dependent refractive index change of a thin polymer bacteriorhodopsin (bR) film by the Z-scan and phase-modulated beams techniques is given. The analysis is conducted at two excitation wavelengths, λ=543 and 633 nm, corresponding to the opposite slopes of the bR ground-state absorption band resulting in opposite signs of the refractive index change. A three-level model of the bR photo-cycle is proposed to describe the experimental data.     

Experimental characterization of the bifurcation structure in an erbium-doped fiber laser with pump modulation

The bifurcation structure of phase space is investigated experimentally in an erbium-doped fiber laser with a sinusoidal pump modulation. We demonstrate a rich variety of bifurcations and dynamical states which appear in primary saddle-node bifurcations and discuss their relation to the main laser resonance. The systematic organization of coexisting attractors allows one to predict the behavior of the fiber laser, when initial conditions are allowed to evolve to their final states.     

Threshold of a Symmetrically Pumped Distributed Feedback Fiber Laser With a Variable Phase Shift

In this paper, we study, both theoretically and experimentally, the threshold characteristics of a distributed feedback fiber laser that depend on the value of a phase shift introduced into the fiber Bragg grating structure. We show that as the phase shift possesses a noticeable birefringence, the laser oscillates at any phase shift value. We also reveal that the laser threshold is different for the cavity eigen polarizations and depends on the phase shift value. We derive a simple analytical formula to calculate the laser threshold in the case of pi phase shift; this formula can be utilized to estimate a minimal threshold value for the laser with certain active fiber and Bragg grating parameters. The developed theory allows us to fairly model the experimentally measured dependence of the laser threshold on induced phase shift value.     

A simulation system for power installations

Problems of constructing dynamic computer models for training personnel are considered on the basis of developments by OAO Chelyabenergo.     

On the development of national standards for magnetic and eddy-current nondestructive inspection of steel pipes

Comparative analysis of the technical level of different nondestructive-testing methods (ultrasonic, magnetic, and eddy-current) used in the production of seamless and HFC welded pipes is performed. To increase the quality of pipes produced for operation under elevated pressure and to unify nondestructive-testing methods and facilities used, standards for magnetic and eddy-current inspection are developed in accordance with the stated foreign acceptance levels.     

Simultaneous Switching of the Q -Value and Operation Wavelength in an Erbium-Doped Fiber Laser

We report a pulsed erbium-doped fiber laser with simultaneous switching of the laser cavity Q-value and generation wavelength. The laser generates a train of short pulses with adjacent pulses alternately being on one of two fixed wavelengths. This regime is realized at periodical modulation of physical length of overwritten fiber Bragg gratings composing the laser cavity