Integrated polarization filter for 1550 nm based on a narrow waveguide section

The polarization filter that is presented in this publication is based on a narrow deepetched waveguide. The measured suppression of the TE mode is 20 dB. The achievedbandwidth is larger than 130nm (limited by the setup). The filter width for an operatingrange around 1550 nm is 0.5 μ

Effect of tube size and obstacles on explosion limits in flowing gases.

In a large pilot plant the upper explosion limit of ethene-air-nitrogen mixtures was experimented in 3.0-m-long and 21-, 50-, and 100-mm-dia. tubes at different flow rates, pressures, and temperatures. The upper explosion limit, influenced by the gas velocity, becomes smaller and shifts to higher oxygen concentrations for increasing flow rates. The results of these tubes could be correlated based on the tube Reynolds number. A cooling effect of the tube wall, which might influence the explosion region, was not observed. An increase in pressure lowers the critical oxygen content as does an increase in temperature, thus the explosion region becomes larger. Different obstacles were tested, which alter the hydrodynamics. Reaction fronts could only propagate for increased oxygen concentrations through a structured Sulzer laboratory gauze packing or a sudden reduction in diameter from 50 to 20 mm. In the experiment, where the tube was completely filled with glass spheres, propagation of reaction fronts through this packed bed was not possible, even at very low gas velocities and very high oxygen concentrations. In a deep dead zone connected to the tube, the gas was ignited and reacted without igniting the gas outside the dead zone. After some time the reaction stopped because of oxygen starvation. However, dead zones with another geometry, where renewal of the combustible gas can occur, still may be dangerous

Influence of hydrodynamics on the upper explosion limit of ethene-air-nitrogen mixtures

A large pilot plant was constructed to study the upper explosion limit of ethene-air-nitrogen mixtures under conditions of flow in a tube. Experiments were performed at pressures of 0.5, 1.0, and 1.5 MPa, gas temperatures between 298 and 573 K, and with ethene concentrations between 20 and 40 vol. %. A cylinder-symmetrical 2-D model developed simulated the experimentally obtained ignition and flame propagation phenomena. The commercial computational fluid dynamics code AEA-CFX 4.1 was used to solve this model, to which reaction kinetics for a scheme of two consecutive reactions were added. The model predicts the experimental explosion points within 0.5 vol. %. The explosion limit is influenced by the gas velocity: it becomes smaller and shifts to higher oxygen concentrations at increasing flow rates. In practice this means that partial oxidation reactions can safely be operated at high oxygen concentrations, provided the gas is kept flowing at high flow rates

All-optical InP-monolithically integrated WDM regenerator for PoISK signals

A monolithically integrated Indium Phosphide optical circuit performing WDM regeneration of Polarization Shift Keying signals is presented. The scheme is based on hardlimiting amplification in a saturated Semiconductor Optical Amplifier. A Q-factor improvement of around 2 is reported on two different wavelengths

A 40Gb/s InP-monolithically integrated DPSK-demodulator enhanced by cross-gain-compression in an SOA

We fabricated and experimentally tested a novel monolithically integrated Indium Phosphide optical circuit for differential phase-shift keying demodulation, which is robust to noise degradations of the received signal. The circuit consists of a one-bit-delay interferometer that demodulates the incoming signal and a semiconductor optical amplifier where the constructive and destructive demodulated outputs synchronously counter-propagate experiencing a reshaping effect. The novel optical circuit has been fabricated for 40 Gb/s signals, and the amplitude signal restoration is demonstrated by comparing the obtained output eye diagrams with those of a commercial fiber-based demodulator. We find a net improvement in the signal to noise ratio when the circuit is fed with a noisy input signal

Tunable two color emission in a compact semiconductor ring laser with filtered optical feedback

We report on an integrated approach to obtain two color emission from a semiconductor ring laser with filtered optical feedback. This feedback is realized on-chip by employing two arrayed waveguide gratings to split/recombine light into different wavelength chan nels. Semiconductor optical amplifiers are used in the feedback loop to control the feed back strength of each wavelength channel independently. Results show that the effective gain of the d(tferent anodes is the key parameter which has to be balanced to obtain two color emission. This can be aclueved by tuning the injection current in each amplifie