1,721,215 research outputs found
SELF-PULSING, SPECTRAL BISTABILITY, AND CHAOS IN A SEMICONDUCTOR-LASER DIODE WITH OPTOELECTRONIC FEEDBACK
No full textWe observed experimentally.self-pulsing, subharmonic generation, spectral bistability, and chaos in a stable semiconductor laser diode with delayed optoelectronic feedback. The laser diode emits 200 ps optical pulses with 1.1 GHz repetition rate in the self-pulsing region, and the bistable region is critically dependent on the closed loop gain of the system. Theoretical explanations of observed experimental results are also given
Parametric amplification in a directly modulated semiconductor laser
No full textWe investigate the parametric amplification and its saturation characteristics in a directly modulated semiconductor laser. The parametric gain depends on the resonance frequency shift that occurs due to the pump modulation current and the bias current. Also, the parametric gain is a strong function of the phase between the signal and the pump modulation currents. The saturation characteristic of the parametric amplification occurs at a large signal modulation current due to depletion of the pump by an amplified optical signal. We explain the observed behaviors using the analytic results of the nonlinear rate equations of the semiconductor laser
SIMPLE ASK TRANSMITTER USING A 790 NM SELF-PULSATING LASER-DIODE FOR LOCAL-AREA NETWORKS
No full textA simple amplitude shift keying (ASK) optical link is demonstrated by using a low-cost self-pulsating laser diode and an envelope detector for a low-cost broadband local area network. A link sensitivity of -22 dBm was achieved at 200 Mbit/s. Because the self-pulsation frequency can be tuned by the bias current, frequency division multiplexing can be simply implemented for multiuser applications
Design of a LiNbO3 ribbon waveguide for efficient difference-frequency generation of terahertz wave in the collinear configuration
No full textWe propose and investigate a ribbon waveguide for difference-frequency generation of terahertz (THz) wave from infrared light sources. The proposed ribbon waveguide is composed of a nonlinear optic crystal and has a thickness less than the wavelength of the THz wave to support the surface-wave mode in the THz region. By utilizing the waveguide dispersion of the surface-wave mode, the phase matching condition between infrared pump, idler and THz waves can be realized in the collinear configuration. Owing to the weak mode confinement of the THz wave, the absorption coefficient can also be reduced. We design the ribbon waveguide which uses LiNbO3 crystal and discuss the phase-matching condition for DFG of THz wave. Highly efficient THz-wave generation is confirmed by numerical simulations. (C) 2007 Optical Society of America
Effects of pre-chirping on the repeaterless dispersion-managed transmission system
No full textThe authors numerically investigate the interaction of pre-chirping and self-phase modulation in dispersion-managed 10Gbit/s transmission. The pre-chirping suppresses the chirping induced by self-phase modulation in the post-compensation scheme, while enhancing the signal distortion caused by self-phase modulation in the pre-compensation scheme. They also explain the physical mechanism of signal distortion in a high power dispersion compensated transmission system
A system-level investigation into the functional role of RKIP in the ERK and NF-kB signaling networks
No full textInterlinked Coupled Positive Feedback Loops Mediated by RKIP Coordinate the Dynamic Behavior of Extracellular Signal-Regulated Kinases
No full textInvestigations into the analysis and modeling of the TNF alpha-mediated NF-kappa B-signaling pathway
No full textIn this study, we propose a system-theoretic approach to the analysis and quantitative modeling of the TNFalpha-mediated NF-kappaB-signaling pathway. Tumor necrosis factor alpha (TNFalpha) is a potent proinflammatory cytokine that plays an important role in immunity and inflammation, in the control of cell proliferation, differentiation, and apoptosis. To date, there have been numerous approaches to model cellular dynamics. The most prominent uses ordinary differential equations (ODEs) to describe biochemical reactions. This approach can provide Lis with mathematically well-founded and tractable interpretations regarding pathways, especially those best described by enzyme reactions. This work first introduces a graphical method to intuitively represent the TNFalpha-mediated NF-kappaB-signaling pathway and then utilizes ODEs to quantitatively model the pathway. The simulation Study shows qualitative validation of the proposed model compared with experimental results for this pathway. The proposed system-theoretic approach is expected to be further applicable to predict the signaling behavior of NF-kappaB in a quantitative manner for any variation of the ligand, TNFalpha
System-level investigations into the functional role of RKIP in the Ras-Raf-MEK-ERK signal transduction pathway
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