Characterization and modeling of amplified spontaneous emission in unsaturated erbium-doped fiber amplifiers

The generation of amplified spontaneous emission (ASE) in erbium-doped fiber amplifiers (EDFAs) is characterized. A theoretical model, leading to closed-form analytical expressions for the backward and forward ASE power spectra, is developed for the unsaturated gain regime. This study shows that for the unsaturated gain regime, both power and spectral distributions of the ASE can be well described through the closed-form expressions, which require only measurable experimental parameters.<>     

Dynamic gain compensation in saturated erbium-doped fiber amplifiers

Dynamic compensation of low-frequency gain fluctuations in saturated erbium-doped fiber amplifiers is demonstrated. This compensation, based on a simple feedback-loop scheme makes it possible to reduce transient gain fluctuations efficiently across the whole amplifier bandwidth using only a low-power optical feedback signal. Such an, automatic gain control technique could be applied to suppress data packet interference due to traffic bursts in multiple-access networks, as well as in the implementation of long-haul fiber systems using erbium fiber amplifiers.<>     

The V-ATPase a3 Subunit: Structure,Function and Therapeutic Potential of an Essential Biomolecule in Osteoclastic Bone Resorption

This review focuses on one of the 16 proteins composing the V-ATPase complex responsible for resorbing bone: the a3 subunit. The rationale for focusing on this biomolecule is that mutations in this one protein account for over 50% of osteopetrosis cases, highlighting its critical role in bone physiology. Despite its essential role in bone remodeling and its involvement in bone diseases, little is known about the way in which this subunit is targeted and regulated within osteoclasts. To this end, this review is broadened to include the three other mammalian paralogues (a1, a2 and a4) and the two yeast orthologs (Vph1p and Stv1p). By examining the literature on all of the paralogues/orthologs of the V-ATPase a subunit, we hope to provide insight into the molecular mechanisms and future research directions specific to a3. This review starts with an overview on bone, highlighting the role of V-ATPases in osteoclastic bone resorption. We then cover V-ATPases in other location/functions, highlighting the roles which the four mammalian a subunit paralogues might play in differential targeting and/or regulation. We review the ways in which the energy of ATP hydrolysis is converted into proton translocation, and go in depth into the diverse role of the a subunit, not only in proton translocation but also in lipid binding, cell signaling and human diseases. Finally, the therapeutic implication of targeting a3 specifically for bone diseases and cancer is discussed, with concluding remarks on future directions.     

Highly-scalable load-balanced router with optical switch fabric

A novel load-balanced optical packet router architecture is proposed and demonstrated. High scalability and reduced complexity are achieved by using optical switch fabrics, FPGA-based 10 Gbit/s packet processors and no centralised scheduler.     

Diagnosis of liver metastases from colorectal adenocarcinoma. Comparison of spiral-CTAP combined with intravenous contrast-enhanced spiral-CT and SPIO-enhanced MR combined with plain MR imaging

BACKGROUND/AIMS: Doppler arterial resistance indices are used to evaluate alterations in arterial hemodynamics in the liver, spleen, and kidney. The purpose of this study was to determine the interobserver and interequipment variability of hepatic, splenic, and renal arterial Doppler resistance indices, and the influence of a cooperative training program of the operators on the reproducibility of the results. METHODS: In the first part of the study, hepatic (PI-L, RI-L), splenic (PI-S, RI-S), and renal (PI-K, RI-K) pulsatility and resistive indices were measured by echo-color-Doppler in eight control subjects and ten patients with cirrhosis by three operators using three different machines. In the second part of the study, measurements were taken by the three operators in nine controls and nine patients with cirrhosis, after cooperative training, with a single machine. RESULTS: Significant interobserver variability was present for all parameters except RI-L. Significant interequipment variability was present for all parameters except PI-S and RI-S. Only 0-3% of variance was equipment- or operator-related, while 58-72% was patient-related. Hepatic and renal coefficients of variation were similar in patients with cirrhosis and controls, while splenic coefficients of variation were higher in patients with cirrhosis than in controls. After training, differences among operators disappeared for all variables except RI-K, and the operator-related component of variance nearly disappeared for all parameters. CONCLUSIONS: Hepatic, splenic, and renal arterial resistance indices show small but significant interobserver and interequipment variability. Interobserver variability can be decreased to non-significant levels by a common training program. Thus, these indices can be widely applied to the study of arterial circulation in these organs.     

Digitally tunable channel dropping filter/equalizer based onwaveguide grating router and optical amplifier integration

We demonstrate a novel and powerful device that permits individual and simultaneous control of all the wavelength channels in a WDM system. The device is based on the monolithic integration of two identical waveguide grating routers with semiconductor optical amplifiers. By biasing appropriately the individual amplifier, each WDM channel can be amplified, detected or modulated. The device exhibits a channel bandwidth of 60 GHz, a channel spacing of 195 GHz and a crosstalk of -19 dB     

Wavelength conversion in a 1550-nm multifrequency laser

Wavelength conversion of input signals at data rates of 622 and to 1250 Mb/s was as demonstrated using an integrated multifrequency laser having 8 channels with 1.6-nm channel spacing.     

Characterization of a multiwavelength waveguide grating routerlaser

Measurements on a multiwavelength laser source that is based on the integration of semiconductor amplifiers with a waveguide grating multiplexer are reported. The source can emit cw simultaneously on 11 frequencies that are precisely spaced by 3.2 nm. Laser oscillation occurs on a single longitudinal mode with a 5 MHz line width. The 18 mm long cavity limits the direct modulation rate to several hundred Mbps     

WDM receiver by monolithic integration of an optical preamplifier,waveguide grating router and photodiode array

A high performance monolithic WDM receiver is demonstrated. The chip receives eight optical channels spaced by 200 GHz. An optical amplifier at the input of the device boosts the incoming signal. A fibre insertion DC responsivity of 0.5 A/W and crosstalk below -20 dB are achieved. The receiver has a small signal bandwidth of 3.5 GHz     

Electrically tunable semiconductor Fabry-Perot filter

A key component of Wavelength Division Multiplexed (WDM) networks is a tunable broadband wavelength demultiplexer, with good selectivity and high tuning speed. In this communication we report low waveguide loss InGaAsP Fabry-Perot filters, grown by Metal Organic Vapor Phase Epitaxy, with tuning ranges up to 3.07 nm (380 GHz). These filters have waveguides with bandgap wavelengths between 1.3 and 1.48 μm so that they are transparent at zero bias and at low tuning currents (<2 mA) for 1.55 μm light. Their performance is independent of light level and they should be capable of high speed operation