Pulse Width Variation Research Articles

Bandwidth and modal noise effects in fused-head-end multimode fiber passive components

Passive multimode fiber components, particularly 1-to-2 splitters/couplers, manufactured using the fused-head-end technique, are tested under network conditions. The mode power transfer matrix and its effects on the network are discussed. The modification of the pulse mode spectrum in the splitter is analyzed by studying the pulsewidth variation and the transmitted pulse power for components at the near and far end of a long length of fiber. The modal noise generated in such passive fiber components is determined, and the modal noise ratio (MNR) and the modal noise susceptibility (MNS) are introduced as figures of merit characterizing modal noise sources and multimode fiber passive components, respectively. >

Rupture characteristics and tomographic source imaging of ML ∼ 3 earthquakes near Anza, southern California

The rupture characteristics of several ML ∼ 3 earthquakes near Anza, California, are determined from time domain analysis of path‐corrected, displacement pulses. These pulses are corrected for propagation effects (apparent attenuation, scattering, site resonance) using the waveforms of adjacent small events (ML ≤ 2.1) as empirical Green's functions. The earthquakes studied occurred during two swarm sequences near Cahuilla, in an area characterized by swarm activity at shallow depth (< 5 km). The data consist of seismograms recorded by the Anza seismic network, a high dynamic range local array with digital telemetry. The waveforms of adjacent small events (ML ≤ 2.1) are deconvolved from those of the ML ∼ 3 events to yield the source time functions of the larger earthquakes. The ML ∼ 3 earthquakes display a variety of rupture modes, similar to those reported for large shocks but over much shorter time scales and distances. Events with single and multiple ruptures are observed. Relative locations of the subevents are obtained from azimuthal differences in the time separation of pulses in the deconvolved displacement waveforms. Some events (as small as ML 2.4) display unilateral rupture propagation, as manifested by azimuthal variations in the pulse widths of the deconvolved displacement pulses. A tomographic back projection technique is applied to the deconvolved displacement pulses to image the slip velocity on the fault as a function of time after nucleation and distance along the fault, using a one‐dimensional fault model. The tomographic inversion for one of the events (ML 2.4) reveals a unilateral rupture with rupture velocity about equal to the shear wave velocity (Vs) and fault length of 300 m. A similar inversion for an ML 3.7 event resolves two subevents separated by about 200 m and yields an average rupture velocity of 0.8Vs. These rupture velocities are similar to those reported for large earthquakes, indicating that rupture velocity is independent of seismic moment down to 3.1 × 1019 dyn cm, the smallest event studied. There are clear variations in pulse width for neighboring events with similar seismic moments, implying significant differences in static stress drops. Factor of five variations in stress drop (11–61 bars) are calculated for events within 200 m of each other. Thus the stress and/or strength along this fault zone varies considerably over distances of hundreds of meters.

A GaAs data switching IC for a gigabits per second communication system

A GaAs monolithic 4/spl times/4 switching circuit has been developed for high-speed digital communication systems. This switching IC, which has built-in address decoders, is completely ECL-compatible. Dynamic performance measurements on the chip mounted in a 32-pin flat package prove that it correctly switches pseudorandom data transmitted at more than 2 Gb/s, switching in 1 ns. The pulsewidth variation is only /spl plusmn/60 ps at 2 Gb/s. Very stable operation is observed from 0 to 70/spl deg/C ambient temperature for supply voltage fluctuations of /spl plusmn/5%.

Spectral and temporal study of picosecond-pulse propagation in a single-mode optical fibre

The power-dependent pulsewidth variations for input 85 ps pulses from a cw mode-locked Nd: YAG laser propagating through 125 m of single-mode optical fibre have been examined using a Synchroscan streak camera. Simultaneous spectral and temporal measurements provide information as to the optimum parameters for pulse compression in fibres.

Importance of frequency and pulse with in field stimulation of the mouse vas deferens: different behaviour of twitch-inhibiting drugs.

The effect of six twitch-inhibiting drugs on the stimulus-response relationship in the field-stimulated mouse vas deferens was compared by means of stimulus response curves which were obtained in two ways, that is, variation of frequency at constant pulse width and variation of pulse width at constant frequency. The twitch-inhibiting potency (in the range of maximal twitch responses) differed with the type of stimulation in a way permitting two groups of substances to be defined: group A (tetrodotoxin, procaine, verapamil) was more effective on frequency-response curves and group B (FK 33-824, clonidine, nifedipine) on pulse-width response curves; the latter applied also to subnormal calcium concentrations in the bath solution. The results suggest that the effect of inhibitory drugs on the field-stimulated vas of the mouse varies greatly with the type of field stimulation.

The choice of optimum parameters of a toroidal charge monitor for precision measurements

An analysis of errors connected with beam pulse width variation and instrument noise characteristics has been carried out for charge monitoring of a pulsed accelerator beam traversing an experimental target. The formulae necessary for the selection of optimum monitor and preamplifier parameters for a given range and required accuracy are presented.

Multifrequency timing measurements on the millisecond pulsar PSR 1937+214

view Abstract Citations (45) References (15) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Multifrequency timing measurements on the millisecond pulsar PSR 1937+214. Cordes, J. M. ; Stinebring, D. R. Abstract Measurements at four radio frequencies show to high accuracy that interstellar dispersion and scattering produce the only frequency-dependent time delays in pulse arrival times. The dispersion measure is DM = 71.0440 + or - 0.0002 pc per cu cm. All frequencies are emitted from the same altitude to within + or - 2 km, but the variation of pulse width with frequency proportional to f exp -1.5 at low frequencies implies beaming is strongly frequency dependent. The interpulse to main pulse separation (174 deg) appears to be independent of frequency. Dual-frequency monitoring should allow intrinsic timing activity or timing variations due to gravity wave backgrounds to be distinguished from changes in dispersion measure. Publication: The Astrophysical Journal Pub Date: February 1984 DOI: 10.1086/184201 Bibcode: 1984ApJ...277L..53C Keywords: Interstellar Extinction; Pulsars; Pulsed Radiation; Radio Astronomy; Stellar Radiation; Time Measurement; Gravitational Waves; Magnetospheres; Multipath Transmission; Plasma Turbulence; Stellar Gravitation; Time Lag; Astrophysics full text sources ADS | data products SIMBAD (1)

An iterative linear method for calculation of spin-lattice relaxation times

A simple algorithm for the calculation of spin-lattice relaxation times which can be run in a programmable calculator is presented. As was suggested by H. Hanssum et al., an experimentally determined inhomogeneity parameter ( I) can be used with this procedure to compensate for imperfections in the RF field. The effects of variation of pulse width and repetition rate on both I and T 1 are investigated with simulated and experimental data sets. The superiority of this approach over three-parameter nonlinear fitting methods is demonstrated by comparisons between data sets generated with different pulse flip angles and sample volumes.

Pulse distortion in optical fibers with transverse offset splices

A method for calculating the pulse distortion in a spliced multimode optical fiber vs transverse misalignment is presented. Measurements on two graded-index and one step-index fibers are shown. In graded-index fibers both theory and experiment show a rapid decrease of the rms pulse width for large offsets. For smaller offsets some discrepancies are observed. These are remedied to some extent by considering unequal mode excitation conditions. Different lengths of the two spliced sections are investigated as well. In the step-index case the experiments show no variation in the rms pulse width as predicted by the theory.

Pulse-width stabilization of a synchronously pumped mode-locked dye laser

Using an analog feedback loop acting on the mode-locker frequency of a synchronously pumped mode-locked dye laser, we have observed a substantial decrease of pulse-width variations at frequencies up to 10 kHz at the cost of an increase in higher-frequency noise. A digital loop acting on the cavity length decreased noise at low frequencies. Using these methods, we have generated reproducible and stabilized frequency-tunable subpicosecond pulses, and have determined the effects of noise in the mode-locking frequency of the pumping Ar+ laser and drift in the cavity length of the dye laser.

Pulse synchronization of intestinal myoelectrical models.

Electrical stimulation of the stomach and small intestine in animals has been shown to give a "pacing" effect, whereby the normal frequency of the myoelectrical slow-waves can be altered to that of the pulse stimulus if it has a frequency close to that of the natural rhythm. In this paper the effect of pulse stimulation on three different types of models used for gastrointestinal studies is investigated. Each of the models is an electronic implementation comprising coupled oscillators, where the unit oscillators are either based on van der Pol's equation, Hodgkin-Huxley type equations, or a relaxation switching circuit. The synchronization range is investigated for each model for variations in stimulus pulse height and width. The effect of the number of oscillators in a chain, the waveshape of the individual oscillators, and the coupling between oscillators are also studied. It is shown that the relaxation model has different synchronization characteristics than the other two models. These differences are that a weakly coupled system is easier to synchronize than a strongly coupled system, that increasing pulsewidth does not always increase the pacing band, phase lead cannot be induced, and the synchronization-band can be entirely above the unpaced system frequency.

Variations in initial pulse width as a function of anelastic properties and surface geology in central California

Initial P -wave pulse widths (first break to first zero crossing) from quarry blasts within a narrow magnitude range were measured at epicentral distances of 5 to 100 km on seismograms from the USGS central California array. Pulse width is related to spectral shape and assuming a constant source should change as a function of travel time (distance) and anelastic properties. In this geologically complex region no simple systematic change with distance was observed but an excellent correlation with station surface geology and fault proximity was shown. Consistently shorter pulse widths were associated with stations on the granitic Salinian side of the San Andreas fault while larger and more varying pulse widths were associated with station on the Franciscan side and along the San Andreas fault itself. Stations along or near the Calaveras and Sargent faults showed shorter pulse widths than those along the San Andreas. When a second quarry source was used similar pulse widths were measured at most stations. Those stations that had significantly different pulse widths could be associated with propagation paths through anomalous features (a metamorphosed limestone pendant and a deep sedimentary trough). Preliminary quantitative estimates of attenuation using a simple model of Gladwin and Stacey (1974) and Ramana and Rao (1974) include a granitic basement Q greater than 200 (possibly less than 800), and a Q of 19 to 28 for the upper crust associated with the Franciscan Formation assuming a previously estimated Q of 40 to 250 for the upper crust associated with the Gabilan granite. Pulse width measurements are a promising method for measuring variations in anelastic properties that are not affected by scattering or lateral refractions.

A Load Insensitive DC/DC Converter for Supply of Telephone Exchanges

The output waveform in thyristor choppers and inverters with parallel capacitor commutation is load sensitive. This can limit the applicability of such circuits where extreme pulse width variation is needed. A solution of the problem is shown on an example of a d.c. converter for the supply of telephone exchanges.

Multichannel remotely programmable logic delay system

A remotely programmable logic delay system is described consisting of up to 16 independent electronic delays for fast NIM pulses—each having a delay capability of 0–101 ns. Each delay can be set locally at the delay unit or remotely from a two-wide CAMAC unit which permits front-panel manual or computer selection of any delay channel and its delay. Individual delay settings over the full range show less than a ±1 ns maximum accumulated error from their nominal settings for typical NIM pulse widths down to 6 ns fwhm at instantaneous rates up to 50 MHz. Pulse-width variations between input and output are less than ±1 ns for the same pulse widths and rates.

Fast, high-current pulse generator with variable amplitude and width

A simple pulse generator, providing continuous variation of current amplitude (0.1–35 A) and pulse width (100–700 nsec) is described. This pulser has been used for operating injection lasers at repetition rates up to 5 kHz.

Scaling Laws for SGEMP

Scaling laws for the nonlinear system-generated electromagnetic pulse (SGEMP) problem are defined and resulting implications for theory and experiments are explored. The scaling laws are used to present calculations in a scaled format which permits display of responses to a wide range of variations in fluence, spectrum, pulse width, and characteristic dimension. Interesting trends in the solutions as a function of these excitation parameters are noted and discussed.

The effect of spatial and temporal laser beam characteristics on two-photon absorption

We present calculations which indicate possible sources of error in the determination of two-photon absorptivity introduced by the choice of experimental conditions. Both the direct absorption experiment and the two-photon excitation experiment are considered. We include the effects of beam alignment, diffraction-limited focusing, and pulse width variation on the observed two-photon absorptivity.

Measurement techniques for assessing the influence of electromagnetic fields on implanted pacemakers.

A method is described for assessing quantitatively the influence of electromagnetic fields on the function of implanted cardiac pacemakers. This influence may occur either indirectly by the action as an antenna of the catheter, or directly by induction into the pacemaker's electronic circuit. The technique comprises: measurement of the influence of electric voltages of various frequencies applied directly across the generator's output connections; determination of the aerial factor of the catheter configuration; combination of the data acquired to a diagram of overall sensitivity of the combination, in which a 10% variation of maximum output pulse amplitude, pulse width, or repetition rate of the pacemaker, whichever occurs first, has been chosen as a limit; comparison of this sensitivity/frequency curve with the electromagnetic field strength produced by several commonly used apparatus; and measurement of the direct influence of fields on the pacemaker itself. It is concluded, that disturbance of pacemaker action may occur in the vicinity of apparatus designed to produce electromagnetic fields, such as broadcast transmitters, diathermy applicators, and radar sets. Normal household appliances appear to be safe in the respect investigated.

Linear voltage-amplitude to pulse-width conversion utilizing a controlled unijunction monostable multivibrator

A circuit that achieves linear wide-range voltage-amplitude to pulse-width conversion is presented. The circuit combines a unijunction transistor operating in an inverted mode, a field- effect transistor, and an integrated circuit flip-flop to obtain highly linear conversion. Other advantages are low-ments, excellent interface characteristics, asynchronous operation, simplicity, and a wide range of pulse-width variation. The circuit operation is discussed, and major design equations are derived. In the experimental circuit that is included, linearity of conversion is within 0.5 percent of full scale pulse width. The pulse width is controllable over the range of 85 to 6 ms for a control voltage variation of 0 to 1.6 volts.

Dynamics of a Repetitively Pump-Pulsed Nd:YAG Laser

Laser pulse dynamics in a repetitively pump-pulsed Nd:YAG laser are examined. Analytic expressions for the laser pulse height and pulse width for a pump-pulsed laser are given, and the variation of the pulse height and width with pump power, cavity length, and cavity loss in the pump-pulsed mode is compared to the variation in the Q-switched mode. By pulsing a xenon pump lamp (with the lamp discharge maintained at a subthreshold value between pulses), 200 W, 200 nsec laser pulses were generated at repetition rates of several hundred per second. The predicted variation of the laser pulse height, width, and delay with pulsed pump power was verified. Using currently available YAG material and pump cavities, it is shown that 3600 W, 200 nsec laser pulses should be available at 50 kW pulsed pump powers.