Abstract
The theory of nonlinear systems based on frequency domain analysis using Volterra series is shown to provide an appropriate means of assessing laser distortion which includes the effects of laser resonance. Hence, it is an appropriate and tractable means of assessing the performance of optical subcarrier multiplexed (SCM) systems. Based on this analysis the performance of SCM systems is examined, with calculation of the carrier-to-intermodulation ratio for an eight-channel SCM system providing an illustrative example.

Abstract
Analytic techniques proposed for distortion analysis are shown not to predict adequately the higher order terms generated by a semiconductor laser diode of relevance to the design and dimensioning of subcarrier multiplexed optical communications systems. A modified analysis which avoids this deficiency is outlined and illustrative results are presented.

Abstract
An algorithm for coding image sequences based on the segmentation of the differential image into variable size and variable shape blocks is described. The differential image is split into 4 × 4 blocks, that are grouped to form square and rectangular macro blocks of several areas. Each macro block is then vector quantised. Simulation results presented show that compression rates and subjective quality compare favourably with methods previously described.

Abstract
The use of power Darlington transistors for an inverter of a 40-kVA uninterruptible power supply (UPS) system is discussed, and the storage time, dead time, and switching aid network contributions to the total harmonic content of the output voltage are examined. A review of common switching aid circuits, for nominal and short-circuit conditions, is presented, and their limitations are discussed. A solution, conceived specifically for power Darlington transistors, is presented. The solution that fits the most relevant characteristics of this technology is analyzed regarding commutation under nominal conditions, commutation under short-circuit conditions, and contribution to harmonic distortion in the output voltage. Conclusions are drawn about the optimal switching frequency for this type of application. The discussion and conclusions are supported by experimental and simulation results.

Abstract
Image processing can be supported by efficient thick holographic recording media such as photorefractive crystals. A numerical analysis is presented showing how low- and band-pass tunable filtering as well as frequency color coding can be performed with reflection holographic gratings recorded in photorefractive crystals.