Concentration-dependent 4I13/2 lifetimes inEr3+-doped fibers and Er3+-doped planar waveguides

We report on the concentration- and pump-dependent lifetimes of the spontaneous emission in Er³⁺-doped fibers and Er³⁺ -doped waveguides. In addition, we measure the concentration dependence of the 550-nm fluorescence due to excited state absorption (ESA)     

Over 1100 nm wavelength tuning in superstructure grating (SSG) DBR lasers

A broad range tuning of over 100 nm in tunable DBR lasers with superstructure grating (SSG) is reported. The SSG reflectors for 100 nm were designed and patterned by electron beam lithography. 1.55 mu m DBR lasers with SSG reflector operate in a single mode with a tuning range of 83 nm under CW conditions. With inclusion of the multimode operating region, the tuning range becomes as wide as 103 nm.<>     

Properties of nitrogen-implanted SOI substrates

Properties of nitrogen-implanted silicon-on-insulator (SOI) substrates prepared by implanting different doses of 200 keV nitrogen into 50-70 Ω-cm, p-type silicon substrates at a temperature of 500°C were studied. The distribution of nitrogen was studied using Auger electron spectroscopy. The electrical properties of the active overlayer were studied using Hall-effect measurements and capacitance-voltage depth profile analysis. The insulating integrity of the buried nitride was studied by directly measuring the leakage current from top to bottom through the substrate. Additionally, electric field strength and surface roughness measurements were performed. Nitrogen concentrations in the buried layer increased from below to above the stoichiometric value for Si₃N₄ for increasing dose in the range studied. Nitrogen-related n-type doping is observed in all samples examined, and the magnitude of the doping increased with the increasing implant dose. Insulating buried nitride layers are formed only in samples implanted with very high doses     

Erbium-doped phosphosilicate glass waveguide amplifier fabricated by PECVD

An Er-doped waveguide amplifier fabricated by plasma enhanced chemical vapour deposition is described. A maximum net gain of 5 dB and a gain coefficient of 0.67 dB/cm are obtained in a 0.48 wt.% Er-doped waveguide pumped at 420 mW at a wavelength of 0.98 mu m. The 0 dB gain threshold is 23 mW.<>     

Effects of strain on the high speed modulation of GaAs- andInP-based quantum-well lasers

A small-signal numerical analysis of pseudomorphic GaAs- and InP-based Fabry-Perot quantum-well lasers using calculated optical gain spectra with strain effects included is reported. Examination of the effect of lifetime broadening shows that the resonance frequency increases at a rate of ~250-MHz/meV reduction in the lifetime broadening for a GaAs-based strained layer laser. The modulation speed is limited by either device heating or facet damage. If the limitation is imposed by the optical power then the modulation speed increases as the laser cavity becomes shorter and the number of quantum wells increases. If the limitation is imposed by the injection current density, however, then the modulation speed decreases for the laser with shorter cavity length. The highest modulation speed is given by an optimum well number. A resonance frequency of ~16 GHz is predicted for a pseudomorphic GaAs-based laser with 30% excess In and average output power of ~5 mW     

A 320 MFLOPS CMOS floating-point processing unit for superscalarprocessors

A CMOS pipelined floating-point processing unit (FPU) for superscalar processors is described. It is fabricated using a 0.5 μm CMOS triple-metal-layer technology on a 61 mm² die. The FPU has two execution modes to meet precise scientific computations and real-time applications. It can start two FPU operations in each cycle, and this achieves a peak performance of 160 MFLOPS double or single precision with an 80 MHz clock. Furthermore, the original computation mode, twin single-precision computation, double the peak performance and delivers 320 MFLOPS single precision. Its full bypass reduces the latency of operations, including load and store, and achieves an effective throughput even in nonvectorizable computations. An out-of-order completion is provided by using a new exception prediction method and a pipeline stall technique     

Highly efficient and tunable Nd/sup 3+/ doped fluoride fibre laser operating in 1-3 mu m band

A highly efficient and tunable Nd/sup 3+/ doped fluoride fibre laser operating in the 1.3 mu m band pumped at 0.8 mu m is demonstrated. The pump laser is a titanium sapphire laser and the tuning element is a dielectric multicoated bandpass filter inserted in the cavity. The oscillation wavelength was successfully tuned from 1.315 to 1.348 mu m for the first time.<>     

Scale and rotation invariant pattern recognition using complex-log mapping and augmented second order neural network

A scale and rotation invariant pattern recognition system using complex-log mapping (CLM) and an augmented second order neural network (SONN) is proposed. CLM is very useful for extracting the scale and rotation invariant features. The results are, however, given in a wrap-around translated form. This problem is solved with an augmented SONN. Experimental results show that the proposed system has improved recognition performance.<>     

MetaRing-a full-duplex ring with fairness and spatial reuse

The design principles of a ring network with spatial bandwidth reuse are described. A distributed fairness mechanism for this architecture, which uses low latency hardware control signals, is presented. The basic fairness mechanism can be extended for implementing multiple priority levels and integration of asynchronous with synchronous traffic. The ring is full-duplex and has two basic modes of operation: buffer insertion mode for variable-size packets and slotted mode for fixed-size packets or cells. Concurrent access and spatial reuse allow simultaneous transmissions over disjoint segments of a bidirectional ring and can increase the effective throughput by a factor of four or more. The combination of a full-duplex ring, spatial reuse, a reliable fairness mechanism, and the exploitation of advent in fiber-optic technology are the basis for the MetaRing network architecture     

On self-routing in Clos connection networks

A self-routing connection network is a switching device where the routing of each switch can be determined in terms of the destination addresses of its inputs alone, i.e. independent of the routing information regarding the other switches in the network. One family of connection networks that were considered in the literature for self-routing are Clos networks. Earlier studies indicate that some Clos networks can be self-routed for certain permutations. In this paper, it is proved that the only category of Clos networks that can be self-routed for all permutations are those with at most two switches in their outer stages