Implications of fiber grating dispersion for WDM communication systems

For high bit-rate dense wavelength-division multiplexed (DWDM) applications fiber grating dispersion for the transmitted adjacent channels is shown to be detrimental and ultimately leads to a penalty. We consider design criteria for fiber grating filters in DWDM systems using both Gaussian pulses and super-Gaussian pulses that approximate square pulses that are more common in nonreturn-to-zero (NRZ) systems.     

Compression of optical pulses spectrally broadened by self-phase modulation with a fiber bragg grating in transmission

We demonstrate experimentally the compression of optical pulses, spectrally broadened by self-phase modulation occurring in the rod of a mode-locked Q-switched YLF laser, with an unchirped, apodized fiber Bragg grating in transmission. The compression is due to the strong dispersion of the Bragg grating at frequencies close to the edge of the photonic bandgap, in the passband, where the transmission is high. With the systems investigated, an 80-ps pulse, which is spectrally broadened, owing to self-phase modulation, with a peak nonlinear phase shift of D? = 7, is compressed to approximately 15 ps, in good agreement with theory and numerical simulations. The results demonstrate that photonic bandgap structures are promising devices for efficient pulse compression.     

When reality monitoring fails: The role of imagination in stereotype maintenance.

Research on reality monitoring (the process by which people distinguish memories of real events from memories of imagined events) suggests that the occurrence of imagined events can inflate the perceived frequency of corresponding real events. Two experiments examined how such failures in reality monitoring can contribute to the maintenance of social stereotypes. When subjects imagined members of occupational groups in the initial experiment, they tended to incorporate stereotyped traits into their imaginations, with specific traits determined by the contexts being imagined. This suggests that imagined events do correspond with stereotype-confirming real events. In the second experiment, subjects read sentences that presented traits (stereotyped and nonstereotyped) in association with occupations with uniform frequency. They also imagined members of each occupation in situations relevant to particular stereotypic traits. In subsequent judgments of presentation frequency, subjects overestimated their exposure to stereotypic occupation–trait combinations, which replicated earlier studies. Subjects further overestimated the presentation frequency of imagined stereotypic combinations, which indicated the failure to distinguish self-generated images from actual presentations. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Using causal persuasive arguments to change beliefs and teach new information: The mediating role of explanation availability and evaluation bias in the acceptance of knowledge.

In this article processes by which causal arguments effect change in established beliefs were explored. The hypothesis that explanation availability mediates belief change in response to causal arguments was tested in 2 experiments. Persuasive communications used causal evidence, noncausal (statistical) evidence, or both to argue that AIDS is not transmissible by casual contact. Results supported the authors' hypothesis. Causal arguments produced the greatest belief change, with the effect mediated by explanation availability. Causal arguments were also less subject to evaluation bias, consistent with a cognitive interpretation of the biased assimilation phenomenon (in which evidence in favor of one's position is evaluated more favorably than evidence in opposition). Experiment 2 replicated the basic effects with dependent measures (including a measure of behavioral commitment) obtained 3 weeks after presentation of the communications. These results suggest that a causal component strengthens the educational potential of persuasive arguments. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Pension integration and Social Security reform

There was a steady increase in the number of hours worked by nursing personnel in California hospitals from 1977 through 1996, mostly due to an increase in the number of hours worked by registered nurses (RNs). The hours worked by nursing personnel and RNs per case-mix adjusted discharge and per adjusted patient day also have increased. Possible explanations for the discrepancy between perceptions of declining nursing staffing and the data are discussed.     

Resonators and materials for organic lasers based on energytransfer

Optically pumped lasers have been fabricated with organic/polymeric materials capable of charge transport. The active materials employed are doped films with small molecule hosts and dye, oligomer, and conjugated polymer emitters. In these materials, the excited states created in the host are transferred nonradiatively to the guest molecules which are the emitters. This energy transfer results in very low absorption losses at the emission wavelength and relatively low-threshold powers for the onset of stimulated emission. Such gain media have been successfully included in many types of resonators including whispering-gallery mode, photonic bandgap, and distributed Bragg reflector (DBR) based resonators. A number of novel patterning and fabrication procedures have been developed for organic-based lasers     

Room temperature operation of microdisc lasers with submilliamp threshold current

Electrically pumped whispering-gallery mode microdisc lasers with singlemode operation and submilliamp threshold current at room temperature are demonstrated. The device consists of an InGaAs/InGaAsP multiple quantum well (MQW) structure formed into a 2-10 mu m diameter disc approximately 0.1 mu m thick. These microdiscs are supported on an InP pedestal.<>     

Nonlinear pulse propagation in long-period fiber gratings: theoryand experiment

In this paper, we discuss theoretical and experimental aspects of nonlinear pulse propagation in long-period fiber gratings. We derive nonlinear coupled mode equations for co-propagating core and cladding modes in a long-period fiber grating and show that the intensity dependent index can be used to tune the mode coupling, thereby creating a mechanism for pulseshaping and all-optical switching. Extensive numerical simulations, which describe the nonlinear pulse dynamics, are compared with experiments. We discuss the application of these nonlinear effects to signal processing in all-optical fiber communications