Solitary Waves in Optical Fibers Governed by Higher Order Dispersion

An exact solitary wave solution is presented for the nonlinear Schrodinger equation governing the propagation of pulses in optical fibers including the effects of second, third and fourth order dispersion. The stability of this soliton-like solution with sech2 shape is proven by the sign-definiteness of the operator and an integral of the Sobolev type. The main criteria governing the existence of such stable localized pulses propagating in optical fibers are also formulated. A unique feature of these soliton-like optical pulses propagating in a fiber with higher order dispersion is that their parameters satisfy efficient scaling relations. The main soliton solution term given by perturbation theory is also presented when absorption or gain is included in the nonlinear Schrodinger equation. We anticipate that this type of stable localized pulses could find practical applications in communications, slow-light devices and ultrafast lasers.Comment: 4 pages 3 Figure

Experimental Potentials for the XΣ+2 and AΠ2 States of NaHe

Experimental potentials for the XΣ+2 and AΠ2 states of the NaHe molecule are presented. The potentials are generated from the temperature dependence of the red wing of the Na resonance line perturbed by He. For the AΠ2 state an unexpectedly large value is obtained for De=480(50) cm−1at Re=4.4(2)a0. The physical basis for this result, which indicates an important role for the internal structure of the rare gas in determining the repulsive part of the alkali-rare-gas interaction, is discussed

Characterization of 1.55-μm pulses from a self-seeded gain-switched Fabry-Pérot laser diode using frequency-resolved optical gating

The intensity and frequency chirp of picosecond pulses from a self-seeded gain-switched Fabry-Perot laser diode have been directly measured using the technique of frequency-resolved optical gating. Measurements over an output sidemode suppression ratio (SMSR) range of 15-35 dB show that higher SMSR's are associated with an increasingly linear frequency chirp across the output pulses. This complete pulse characterization allows the conditions for optimum pulse compression to be determined accurately, and indicates that transform-limited, pedestal free pulses can be obtained at an SMSR of 35 dB

Characterization of nonlinear switching in a figure-of-eight fiber laser using frequency-resolved optical gating

The measurement technique of frequency-resolved optical gating is applied to determine the nonlinear switching characteristics of a passively modelocked figure-of-eight erbium-doped fiber laser. By completely characterizing the intensity and phase of the laser output pulses, the intracavity fields in the nonlinear amplifying loop mirror of the laser cavity are determined by numerical propagation using the nonlinear Schrodinger equation. Excellent switching of 95% can be achieved as a result of uniform phase characteristics developed by pulses propagating in the nonlinear amplifying loop mirror

Complete characterization of ultrashort pulse sources at 1550 nm

This paper reviews the use of frequency-resolved optical gating (FROG) to characterize mode-locked lasers producing ultrashort pulses suitable for high-capacity optical communications systems at wavelengths around 1550 nm, Second harmonic generation (SHG) FROG is used to characterize pulses from a passively mode-locked erbium-doped fiber laser, and both single-mode and dual-mode gain-switched semiconductor lasers. The compression of gain-switched pulses in dispersion compensating fiber is also studied using SHG-FROG, allowing optimal compression conditions to be determined without a priori assumptions about pulse characteristics. We also describe a fiber-based FROG geometry exploiting cross-phase modulation and show that it is ideally suited to pulse characterization at optical communications wavelengths. This technique has been used to characterize picosecond pulses with energy as low as 24 pJ, giving results in excellent agreement with SHG-FROG characterization, and without any temporal ambiguity in the retrieved puls

Accuracy of Automated Blood Pressure Monitors

TACSM Abstract Accuracy of Automated Blood Pressure Monitors Harvey JM and Smith JD Health & Human Performance Laboratory; Department of Health & Kinesiology; Texas A&M University-San Antonio; San Antonio, TX Category: Undergraduate Advisor / Mentor: Smith JD ([email protected]) ABSTRACT The purpose of this study was to examine the accuracy of two automated blood pressure (BP) monitors (Omron Model #BP791IT, brachial and Life Source Model #UB-521, wrist; BR and WR respectively). This study was approved by the TAMU-SA IRB and 41 subjects (Age=26.8±7.3 yrs, Ht=167.9±3.3 cm, Wt=88.0±44.6 kg, BMI=28.2±6.4) reported to the lab after fasting for at least four hours and sat quietly for five minutes, after which blood pressure was measured using a mercury gauge (CRIT) by the investigator, then BR followed by WR. A repeated measures ANOVA test was used to explore for differences in mean arterial pressure (MAP) among the three readings. Two groups were formed by placing those above the CRIT systolic mean (126 mmHg) to represent a lower BP group (115.4±6.2 mmHg) and a higher BP group (137.3±8.33 mmHg), after which a 2 (group) X 3 (method of reading) factorial ANOVA was conducted to explore for differences between groups. Alpha was set at \u3c.05 for all tests. The repeated measures ANOVA indicated the BR (100.5±13.5 mmHg) and WR (101.7±13.7 mmHg) MAP were significantly greater than CRIT (95.5±10.6 mmHg), P\u3c.05. The factorial ANOVA indicated no significant interaction among group and method of reading (P\u3e.05), however, the main effect of method indicated significant differences between both instruments and CRIT in systolic readings (P\u3c.05), and a significant difference in diastolic readings between CRIT and WR only, P\u3c.05 (Table 1). Table 1. Seated Blood Pressure Readings among Manual (CRIT) and Automated (Brachial and Wrist) Methods Total (N=41) Lower Group (n=21) Higher Group (n=20) Systolic (mmHg) CRIT 126.1±12.2 115.4±6.2 137.3±8.3 BR 135.9±19.0 122.6±12.3* 149.2±14.8* WR 131.1±18.7 120.2±11.2* 144.5±17.3* Diastolic (mmHg) CRIT 80.2±10.4 74.6±6.8 86.1±10.3 BR 82.8±12.1 75.8±6.4 89.9±12.5 WR 86.9±12.5 78.3±6.4** 97.6±9.5** *Significantly different from Systolic CRIT, **Significantly different from Diastolic CRIT Although the readings between groups were not significantly different, differences between CRIT and BR (11.9 mmHg) and WR (7.2 mmHg) in the Higher Group tended to be greater than differences in the Lower Group (BR=7.2 mmHg and WR=4.8 mmHg). Although consumers, doctors, and other professionals may rely heavily on the use of automated blood pressure monitors for getting a quick blood pressure reading, the results may not be as accurate as they should be. These implications could be more severe for those with higher BP’s, especially when using BR

Characterization of 40-Gbit/s pulses generated using a lithium niobate modulator at 1550 nm using frequency resolved optical gating

The characteristics of 40-Gbit/s pulses generated by exploiting the nonlinear characteristics of a Mach-Zender Lithium Niobate modulator are presented. A high spectral resolution frequency resolved optical gating apparatus has been developed to allow for the complete characterization of the intensity and phase of these pulses. The use of these measurements to simplify the design and optimization of an 80-Gbit/s pulse source, based on this 40-Gbit/s source followed by a nonlinear fiber compressor and multiplexer, is also demonstrated

80 Gb/s optimised pulse source using a gain-switched laser diode in conjunction with a nonlinearly chirped grating

The authors demonstrate the generation of transforms limited short optical pulses, which display excellent spectral and temporal qualities by employing a novel technology, based on an externally injected gain-switched laser in conjunction with a non-linearly chirped grating. Using this technique, 3.5 ps optical pulses, exhibiting a time bandwidth product of 0.45, are generated, which are suitable for use in high-speed 80 Gb/s OTDM communications systems