Degradation of DC characteristics of InGaAs/InP singleheterojunction bipolar transistors under electron irradiation

The effects of high-energy (~1 MeV) electron irradiation on the dc characteristics of InGaAs/InP single heterojunction bipolar transistors (SHBT's) are investigated. The device characteristics do not show any significant change for electron doses <10¹⁵/cm². For higher doses, devices show a decrease in collector current, a degradation of common-emitter current gain, an increase in collector saturation voltage and an increase in the collector output conductance. A simple SPICE-like device model is developed to describe the dc characteristics of SHBT's. The model parameters extracted from the measured dc characteristics of the devices before and after irradiation are used to get an insight into the physical mechanisms responsible for the degradation of the devices     

Simultaneous Compensation of Polarization Mode Dispersion and Chromatic Dispersion Using Electronic Signal Processing

In this paper, we study the performance of 10.7-Gb/s nonreturn-to-zero (NRZ) and return-to-zero (RZ) on-off keying signals in the joint presence of first-order polarization mode dispersion (PMD) and chromatic dispersion (CD) based on optical signal-to-noise ratio penalty measurements. Our investigations show that the tolerance of RZ to first-order PMD is severely reduced by the presence of typical values of residual CD. Three different receiver strategies are studied: 1. unequalized threshold detection; 2. combined feed-forward and decision-feedback equalization; and 3. maximum-likelihood sequence estimation (MLSE). In all three cases, the presence of CD eliminates the advantage of RZ over NRZ in terms of PMD tolerance. For NRZ, we find that the MLSE improves the tolerance to first-order PMD by 60%-70%, even in the presence of residual CD.     

Real-time computation of disparity for hand-pair gesture recognition using a stereo webcam

This paper presents an algorithm for the real-time computation of disparity using video stereo images captured by a stereo webcam. This algorithm is designed to provide both real-time throughput and robust disparity estimation for real-world applications where computation is limited to a pre-defined region-of-interest (ROI). More specifically, this algorithm is used as part of a hand-pair gesture recognition application where the disparity is computed for two ROI around a hand-pair identified by the segmentation component of the recognition application. The developed algorithm provides the required relative difference in disparity with background at high frame rates for the hand-pair gesture recognition application. The results obtained with an inexpensive commercial VGA stereo webcam show a robust disparity computation of 20?ms/frame enabling real-time hand-pair gesture recognition at 25?fps with >90% recognition rate for a maximum hand speed of 40?cm/s and for hand distances between 30 and 150?cm away from the camera.     

Lasing transitions between self-localized barrier-state electronsand confined-state heavy holes in InGaAs-InGaAsP-InPmultiple-quantum-well lasers

We describe the operation of an InGaAs-InGaAsP multiple-quantum-well laser under the condition of very-high-carrier density. Internal Coulomb fields induce then a self localization of barrier-state electrons in the vicinity of the quantum wells. Under certain conditions, stimulated transitions are possible between these self-localized electrons and the second level of confined holes so that the laser changes its oscillation wavelength from approximately 1450 nm to the 1340 nm range. We predict this self induced laser transition using a detailed model of the quantum-well laser injection process and demonstrate it experimentally. We show that both drive current and temperature enhance this special transition and that controllable switching between the two is possible. We also demonstrate different modulation capabilities of the two transitions     

Terabit Transmission at 42.7-Gb/s on 50-GHz Grid Using Hybrid RZ-DQPSK and NRZ-DBPSK Formats Over 16 × 80 km SSMF Spans and 4 Bandwidth-Managed ROADMs

We demonstrate for the first time the use of asymmetric-bandwidth interleaver-based reconfigurable optical add-drop multiplexer (ROADM) to transmit 42.7-Gb/s channels on a 50-GHz grid. Differential binary phase shift keyed (DBPSK) format was used on the wide passband side and differential quadrature phase shift keyed (DQPSK) format was used on the narrow passband side of the ROADM. 25 channels with an aggregate capacity of 1-Tb/s were transported over 1280-km of standard single-mode fiber (SSMF) including 4 ROADMs.     

Tunable Optical Dispersion Compensator With Increased Bandwidth via Connection of a Mach–Zehnder Interferometer to an Arrayed-Waveguide Grating

We propose and demonstrate a novel colorless tunable optical dispersion compensator (TODC) consisting of a Mach-Zehnder interferometer (MZI) connected to an ar- rayed-waveguide grating with a thermooptic lens. The MZI approximately doubles the magnitude bandwidth at large dispersion settings. We demonstrate compensation of a 43-Gb/s nonreturn-to-zero signal dispersed over a range of -844 to + 1700 ps/nm. To our knowledge, +1700 ps/nm is the largest demonstrated dispersion compensation amount of a 40-Gb/s signal with a single TODC.