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Jitter and shimmer are measures of the fundamental frequency and amplitude cycle-to-cycle variations, respectively. Both features have been largely used for the description of pathological voices, and since they characterise some aspects concerning particular voices, they are expected to have a certain degree of speaker specificity. In the current work, jitter and shimmer are successfully used in a speaker verification experiment. Moreover, both measures are combined with spectral and prosodic features using several types of normalisation and fusion techniques in order to obtain better verification results. The overall speaker verification system is also improved by using histogram equalisation as a normalisation technique previous to fusing the features by SVM. This work has been supported by the Spanish Government under Grant AP2003-3598. The authors would like to thank Pascual Ejarque and Andrey Temko for his help in the fusion techniques used in this work. This work has been supported by the Spanish Government under Grant AP2003-3598. The authors would like to thank Pascual Ejarque and Andrey Temko for his help in the fusion techniques used in this work.

Measurements on fundamentally-driven and harmonically-driven mode-locked lasers show that these lasers have low timing jitter when the RF drive frequency is tuned to within the ‘locking bandwidth’ of the fundamental of the cavity resonance frequency, or a harmonic of the frequency. It is shown that the locking bandwidth is determined by a new parameter termed the ‘pull-in time’. The pull-in time is independent of the cavity length and the harmonic number of the drive.

The synchronisation mechanism of self-pulsating laser diodes is determined and it is shown how this results in a frequency-dependent phase difference between the electrical input and optical output. The time-to-lock of the electrical input to the optical output is examined, particularly with regard to the importance of the initial phase difference between the signals. The effect of synchronisation on timing jitter in self-pulsating lasers is also investigated.

Colloque avec actes et comité de lecture. internationale.; International audience; We propose in this paper a trade-off between hard and soft real-time guarantees to maintain an acceptable QoS guarantee in overload condition and maximize efficiently the utilization of network resources. The key of our solution is that many real-time applications are loss-tolerant, but the loss profile must be well defined since successive packet losses are not suitable. We use the concept of (m,k)-firm timing constraints to define a novel guaranteed loss-tolerant QoS. Therefore, we extend the basic WFQ algorithm to take into account the firm timing constraints to provide lower delay guarantees without violating bandwidth fairness or misusing network resources. The proposal is called (m,k)-WFQ. Using Network Calculus formalism, analytic study gives the deterministic delay bound provided by the (m,k)-WFQ algorithm for upper bounded arrival curve traffic. Theoretical results and simulations show a noticeable improvement on delay guarantee made by (m,k)-WFQ compared to standard WFQ algorithm without much degrading bandwidth fairness.

We report an experimental study which shows how time jitter in semiconductor lasers, which arises when such sources are switched from below to above threshold, is related to the actual operating conditions. The effect is observed both in distributed feedback and in Fabry–Perot lasers, even if in the latter case it becomes more and more negligible when the output power of the final state is increased.

Jitter accumulation on a high-bit-rate submarine optical link has been investigated through signal circulating experiments. One-, 6- and 12-repeater loops exhibit similar accumulation. The variance of the systematic jitter increases as the number of repeaters and the random jitter tends to saturate.

A jitter suppression method using simple pattern inversion at each regenerator is proposed. It is theoretically shown that this method is very effective for systematic jitter suppression. The results of a signal circulating experiment using a 446 Mbit/s optical regenerator agree with the theoretical estimation.

A novel optical regeneration scheme without using nonlinear clock recovery elements has been demonstrated in a transmission experiment at 2.4Gbit/s over 35 km of fibre. In this scheme, the clock is superimposed on the data signal at the transmitter end, and is separated from the composite signal by passive filters at the receiver end for data regeneration.

The accumulation and tolerance of timing jitter in digital networks is analysed for transmission links containing regenerators as well as dejitterizers and/or multiplexer—demultiplexer pairs, and for timing circuits employing phase-locked-loops. Both systematic pattern-dependent jitter and waiting-time jitter are taken into account. It is shown that, under practical circumstances, the total accumulated jitter can be adequately described by some simple equations and measurement data confirm these equations. An experimental relation between peak-peak jitter values over a long period and those over a short period is presented. The results of the analysis have led to the conclusion that the internationally recommended maximum permissible peak-peak jitter values at digital interfaces will never be reached in the Dutch digital network.

There has been renewed interest in pulse stuffing jitter because new multiplexer frame formats have to be designed for high-bit-rate optical fibre. The letter provides a simple derivation of the generalised pulse stuffing jitter formula, shown by Chow in 1973, for any phase change per pulse stuffing.

Two techniques to assess the performance degradation of optical communications systems due to jitter are compared: a Gaussian approximation and a precise calculation. It is shown that, depending on the jitter distribution, the approximation may either under- or overestimate the performance degradation caused by jitter by a significant amount.

For very high data rate optical communication systems, jitter is an impairment which may seriously degrade system performance. Assuming knowledge of the jitter statistics to be restricted to just the range and RMS value, the authors determine a new upper bound on the performance. For a certain class of signals, they derive a worst-case distribution (WCD) which consists of three Dirac impulses, located at the centre and at the extremes of the range. The usefulness of the WCD is demonstrated by means of examples which show that for many practical cases the new bound is tight. They show how the WCD may be combined with a modified Chernoff bound to obtain an overall upper bound on system performance which encompasses a comprehensive set of impairments including jitter.

The purpose of this paper is to develop relationships between the normalized far-field peak intensity (Strehl ratio) and system perturbations, such as mirror misfigure, piston errors, jitter, and polarization errors, for phased-array transmitters. Some of these sources of degradation are unique to phased arrays, whereas others are shared in common with single-aperture transmitters. It was found that for a phased array with many apertures, piston errors must be controlled to within ~λ/20 to ensure a Strehl ratio of 0.9. However, if adaptive optics is used to adjust the path lengths optimally in the free-space regions, then the gain lengths need only be controlled to within λ/(20δn) for a master-oscillator power-amplifier system. The factor δn = (δn/δk)δk is simply the variation of the gain’s index of refraction within one standard deviation in the wave number of the lasing lines. The results found for the effects of jitter are valid for arbitrary-shaped apertures as well as for arbitrary array patterns. For identical apertures and uncorrelated jitter among the apertures, the Strehl ratio is independent of the number of apertures and their arrangement. On the other hand, for correlated jitter, the far-field degradation is sensitive to the array pattern and is least sensitive for a close-packed array. Both the case of isolated perturbations for one element of the array and that of random errors in all the elements of the array are studied.

Unless proper control is exercised in limiting the amplitude of jitter in future digital networks, serious degradations can arise. The important sources of jitter are identified and described. Trie manner in which jitter accumulates in a digital network is discussed with particular emphasis being given to accumulation along transmission systems. A brief review is given of the current status of jitter studies within international organizations (CCITT and CEPT).† The jitter control and specification philosophy for digital networks and equipments based on the 2048-kbit/s hierarchy is outlined.

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Harmonics-to-noise ratios (HNRs) are affected by general aperiodicity in voiced speech signals. To specifically reflect a signal-to-additive-noise ratio, the measurement should be insensitive to other periodicity perturbations, like jitter, shimmer, and waveform variability. The ensemble averaging technique is a time-domain method which has been gradually refined in terms of its sensitivity to jitter and waveform variability and required number of pulses. In this paper, shimmer is introduced in the model of the ensemble average, and a formula is derived which allows the reduction of shimmer effects in HNR calculation. The validity of the technique is evaluated using synthetically shimmered signals, and the prerequisites (glottal pulse positions and amplitudes) are obtained by means of fully automated methods. The results demonstrate the feasibility and usefulness of the correction.