High-efficiency crystalline silicon technology development

The rationale for pursuing high efficiency crystalline silicon technology research is discussed. Photovoltaic energy systems are reviewed as to their cost effectiveness and their competitiveness with other energy systems. The parameters of energy system life are listed and briefly reviewed

Effect of side-mode suppression ratio on the performance of self-seeded gain-switched optical pulses in lightwave communications systems

The side-mode suppression ratio (SMSR) of self-seeded gain-switched optical pulses is shown to be an extremely important factor for the use of these pulses in optical communications systems. Experiments carried out involving pulse propagation through dispersion-shifted fiber and a bandpass optical filter demonstrate that, for SMSR values of less than 25 dB, the buildup of noise due to the mode partition effect may render these pulses unsuitable for use in optical communications system

Optical pulse generation at frequencies up to 20 GHz using external-injection seeding of a gain-switched commercial Fabry-Pérot laser

We demonstrate that by using strong external-injection seeding of gain-switched Fabry-Perot (FP) lasers, it is possible to generate optical pulses at repetition rates far in excess of the laser bandwidth. Experimental results illustrate the generation of optical pulses at frequencies up to 20 GHz from a FP laser with a 3-dB bandwidth of only 8 GHz. The optical pulses generated have a duration around 12 ps, and a spectral width of 40 GHz

Multiple RF carrier distribution in a hybrid radio/fiber system employing a self-pulsating laser diode transmitter

A self-pulsating laser diode is used to generate a multicarrier microwave optical signal for use in a hybrid radio/fiber system. The self-pulsation frequency of the laser is controlled by external light injection, and can be varied between 14-24 GHz. The hybrid radio/fiber system, employing the self-pulsation laser, is used to distribute two 155-Mb/s data signals on two radio frequency (RF) carriers (at 18.5 and 18.9 GHz). Experimental results show the overall system performance for both RF channels, and demonstrate that the performance is improved by around 17 dB compared with the case when the laser is used without external injection, and thus, does not self-pulsat

Development of highly flexible broadband networks incorporating wavelength division multiplexing and sub-carrier division multiplexing in a hybrid radio/fiber distribution system

A radio over fiber distribution system incorporating both SCM and WDM technologies is presented. The SCM signal contains five 155 Mbit/s data channels, centered around 18.5 GHz with 450 MHz spacing. This signal is directly modulated onto three high-speed lasers with emission frequencies spaced by 50 GHz. Bragg filters are employed at the receiver base station in order both to demultiplex the required optical channel, and to ensure that the detected signal is single side band (in order to overcome dispersion limitations on the link). Our results show negligible degradation in system performance for the demultiplexing of the WDM signal compared with the back-to-back performance curves

Continuous repetition rate tuning with timing window independent self-seeding of a gain-switched Fabry-PÉrot Laser

In this work, we propose a novel self-seeding technique that yields timing window independent operation allowing continuous repetition rate tuning of the self-seeded gain-switched (SSGS) laser. This is achieved by employing a highly linearly chirped fiber Bragg grating (LC FBG) as a wavelength selective element. The reflected gain-switched pulses are dispersed to such an extent, that temporal overlap occurs between them. This overlap creates a pseudo continues wave like signal that is re-injected into the gain-switched laser

Tied factor analysis for face recognition across large pose differences

Face recognition algorithms perform very unreliably when the pose of the probe face is different from the gallery face: typical feature vectors vary more with pose than with identity. We propose a generative model that creates a one-to-many mapping from an idealized “identity” space to the observed data space. In identity space, the representation for each individual does not vary with pose. We model the measured feature vector as being generated by a pose-contingent linear transformation of the identity variable in the presence of Gaussian noise. We term this model “tied” factor analysis. The choice of linear transformation (factors) depends on the pose, but the loadings are constant (tied) for a given individual. We use the EM algorithm to estimate the linear transformations and the noise parameters from training data. We propose a probabilistic distance metric that allows a full posterior over possible matches to be established. We introduce a novel feature extraction process and investigate recognition performance by using the FERET, XM2VTS, and PIE databases. Recognition performance compares favorably with contemporary approaches

Wavelength tunable lasers in future optical communication systems

Monolithic tunable lasers (TL) have been an important component in dense wavelength division multiplexed (DWDM) systems mainly because of their ability to reduce inventory costs associated with different part numbers for fixed wavelength distributed feedback (DFB) lasers. Moreover, the use of wavelength agile laser diodes in DWDM networks has gained a lot of interest in recent years, due to emerging new applications such as optical switching and routing, which require fast switching lasers in the nanosecond regime (Coldren et al., 2000). Employment of such lasers as tunable transmitters in wavelength packet switched (WPS) networks is one of the possible applications of these devices. In such systems, the information to be transmitted could be encoded onto a destination dependent wavelength and the routing of traffic could be performed on a packet-by-packet basis. The utilization of TLs in an optical switching and routing environment would put stringent requirements on its performance. This would include increased tuning range, high side mode suppression ratio (SMSR), reduced switching time and excellent wavelength stability. The sampled-grating distributed Bragg reflector (SG DBR) TL proves to be an ideal candidate, due to its large tuning range (40 nm), high output power (10 dBm), high side mode suppression ratio (SMSR > 30 dB) and simplicity of integration

A Brief Nomenclatural Review of Genera and Tribes in Theaceae

The angiosperm family Theaceae has been investigated extensively with a rich publication record of anatomical, cytological, paleontological, and palynological data analyses and interpretation. Recent developmental and molecular data sets and the application of cladistic analytical methods support dramatic changes in circumscription at the familial, tribal, and generic levels. Growing interest in the family outside the taxonomic and systematic fields warrants a brief review of the recent nomenclatural history (mainly 20th century), some of the classification systems currently in use, and an explanation of which data support various classification schemes. An abridged bibliography with critical nomenclatural references is provided