Gain equalization by mitigating self-filtering effect in a chain ofcascaded EDFA's for WDM transmissions

A simple method of alternatively using high-inversion and moderate-inversion erbium-doped fiber amplifiers (EDFA's) in an optical amplifier chain is presented to mitigate the self-filtering effect and equalize both signal power and signal-to-noise ratio (SNR) of multiple wavelength channels in wavelength-division multiplexing (WDM) transmission systems. The performance of the compensated system with alternatively used high- and moderate-inversion amplifiers is compared with the uncompensated ones where only moderate- or high-inversion amplifiers are employed. The result shows that the compensated system has a flatter gain profile, a lesser signal power spread, and SNR degradation     

The material properties of sulphonated phenolic resin reinforced cement mortars

The material properties of new sulphonated phenolic resin (SP) reinforced cement mortars have been investigated. SP was found to promote the dispersion of cement particles and to interact with Ca(OH)₂. As a result, the resulting mortars exhibit better workability, more compact structure and higher compressive strength than plain mortars. The mortar with 1 wt% SP present after 28 days curing exhibits a compressive strength of 66MPa, which is about 18% higher than that of plain mortar.     

Geometric and algebraic errors in calculating a transducer'sspatial impulse response

Two types of errors resulting from the numerical evaluation of a transducer's spatial impulse response function have been identified, One is geometric and is due to the mismatch between the emulated piston surface (approximated using many small planar elements) and the true surface. The other error is algebraic and is due to the inexact formulation of the response of the emulated surface. The deviations from the true response were calculated for three different pistons. The results indicate that the shape and placement of the elements are important for the computational accuracy     

Fourier-transform-limited pulses from gain-switched distributed-Bragg-reflector lasers using simultaneous modulation of gain and phase sections

Fourier-transform-limited pulses ( Delta tau . Delta nu approximately=0.35) have been obtained from a microwave-modulated DBR laser at 1.56 mu m. The chirp of the gain-switched pulse is compensated for by applying a fraction of the microwave signal to the phase section, thereby creating an instantaneous frequency shift of opposite sign. The generation of short coherent pulses from such a monolithic source can be of great interest for long haul soliton transmission.<>     

Correlation between synthesis conditions, coherently diffracting domain size and cubic phase stabilization in barium titanate

The Constant Rate Thermal Analysis method has been used under different experimental conditions to obtain barium titanate powder of very small grain size. Both a crystallographic and a dielectric study ham been carried out on samples sintered at different temperatures. It is deduced that the formation of small coherently diffracting domains is improved by the generation of oxygen vacancies and the cubic phase stabilization depends on the coherently diffracting domain size rather than on the particle size.