Abstract
Power supply current monitoring is a promising technique for the development of new test methodologies for analog and mixed-signal circuits. The advantages of efficiency and reduced test time have already been recognized in the digital domain. This paper shows that improved test efficiency and detection confidence are obtained when both output voltage and power supply current are observed. Results found from the simulation of two circuits are presented comparing fault detection ratios and the amplitude of faulty response deviations when observing each one of these signals. Cross-correlation between output voltage and power supply current is presented as a means to perform a single mixed current/voltage testing operation, providing at the same time increased efficiency. It allows also for simplifications on test circuitry and processing, as reductions on the sampling rates and amplitude resolutions used to acquire the signals provide the same fault coverage levels obtained using higher fidelity measurements.

Abstract
The FM intermodulation characteristics of directly modulated semiconductor lasers of relevance to the design of subcarrier multiplexed applications are investigated. "Adiabatic" chirp which has previously not been considered is shown to have a large impact on the reduction of the distortion levels at frequencies below half the resonance frequency of the laser. Results are presented showing that, in contrast to previous suggestions, FM modulation may be advantageous, imposing less requirements on laser linearity than IM modulation.

Abstract
In this paper, we present an analytical approach to accurately assessing the performance of subcarrier multiplexed optical systems for the delivery of future mobile radio broadband services, The existence of a wide dynamic range of power levels in the return link, together with laser nonlinear distortion, represents a major problem and makes performance evaluation difficult. By modeling laser nonlinear distortion using Volterra series analysis, we show that the performance assessment of these systems becomes not only tractable, but also that they can be can be optimized based on the worst case condition, This analysis is performed here for the case of continuous phase frequency shift keying (CPFSK) modulation, for which we calculate the power spectral density (PSD) of the intermodulation products, The overall system performance is then investigated, and its dependence on laser bias and RIN is examined, As an illustrative example we consider a specific 50 channel CPFSK system occupying the bandwidth of 2 to 2.1 GHz.

Abstract
A detailed comparative experimental and theoretical study of nonlinear distortion in laser diodes is undertaken to provide practical proving of the effectiveness and utility of the Volterra series method. The observed harmonic and intermodulation distortion levels are compared with the results given by the Volterra series nonlinear laser model using intrinsic parameters extracted from reflection and small-signal frequency response measurements. Second-harmonic, two-tone and three-tone intermodulation distortion data are all found to be in good agreement with the theoretical results, providing endorsement of the Volterra series approach for the study of distortion in microwave subcarrier optical systems. © IEE, 1996.

Abstract
An efficient algorithm for dynamically multiplexing MPEG2 encoded video sources is presented. Sources are grouped into classes regarding different combined levels of spatial detail and amount of movement. Simulations were performed using different associations of sources belonging to distinct classes, different bit rates and GOP structures. The implications associated to a real implementation are analyzed and a modular architecture is proposed. Simulation results are presented and discussed, showing that sequences with higher spatial detail and motion are those which exhibit the higher quality improvements. These results are almost not affected by the non alignment, at GOP level, between video sequences.

Abstract