Colorless tunable optical dispersion compensator based on a silica arrayed-waveguide grating and a polymer thermooptic lens

We present a colorless tunable optical dispersion compensator (TODC) comprised of a silica arrayed-waveguide grating (AWG) directly coupled to a polymer thermooptic lens. Using silica for the AWG allows it to be low loss and manufactured by a standard process, and using polymer for the thermooptic lens allows it to have a large tuning range and low electrical power consumption. This hybrid TODC is fully solid-state and scales to a large figure-of-merit (dispersion range times bandwidth squared). We demonstrate a version with 100-GHz free-spectral range and 1300-ps/nm tuning range with a 3-dB bandwidth >39 GHz and a lens power consumption <74 mW.     

Arrayed waveguide dynamic gain equalization filter with reducedinsertion loss and increased dynamic range

We present an arrayed waveguide dynamic gain equalization filter with less than 4.5-dB insertion loss and greater than 14-dB dynamic range over the C-band resulting from three improvements: a circulator and polarization splitter combined into one, used to make the device polarization insensitive; segmentation in the star coupler transition regions; and an exponential control wavelength distribution     

Flexible waveband optical networking without guard bands using novel 8-skip-0 banding filters

Novel five-band 8-skip-0 band filters realized in silica waveguide planar lightwave circuit technology were successfully used to demonstrate versatile wavelength-division-multiplexed (WDM) optical networking. Forty C-band channels spaced 100 GHz apart grouped in five bands of eight channels each allowed WDM networking without loss of any channel within the available optical bandwidth. We demonstrate simultaneous transport of 10 and 40 Gb/s with rate-appropriate optical add-drop nodes.     

Low-threshold nine-channel waveguide grating router-basedcontinuous wave transmitter

This paper demonstrates a nine-channel waveguide grating router-based laser with low (18-22 mA) thresholds, which we believe to be a record for a monolithically integrated multiwavelength laser with a 1.1-cm long cavity and a single nondistributed amplifier. This result was achieved through a combination of techniques including reduced intracavity loss, improved router design and optimal active/passive transitions     

Global roundings of sequences

For a given sequence a=(a₁,…,an) of numbers, a global rounding is an integer sequence b=(b₁,…,bn) such that the rounding error |_∑i∈I(ai−bi)| is less than one in all intervals I⊆{1,…,n}. We give a simple characterization of the set of global roundings of a. This allows to compute optimal roundings in time O(nlogn) and generate a global rounding uniformly at random in linear time under a non-degeneracy assumption and in time O(nlogn) in the general case.     

Induction of maternal behavior in rats: Effects of pseudopregnancy termination and placenta-smeared pups.

The onset of maternal behavior in Long-Evans rats was examined after pseudopregnancy (PsP) termination, both with and without exogenous estrogen administration, and in response to either clean or placenta-smeared stimulus pups. Natural (spontaneous) PsP termination was as effective in hastening the onset of maternal behavior as ovariectomy plus estrogen injection. If clean foster pups were presented as soon as pseudopregnancy terminated (first proestrus or cornified smear), maternal behavior was exhibited within 2 days; placenta-smeared foster pups presented at the same time elicited maternal behavior within 2 hr. The combination of initiating maternal-behavior testing immediately after the natural termination of pseudopregnancy and proffering placenta-smeared pups apparently simulates the hormonal milieu as well as the environmental cues present at parturition, noninvasively, producing optimal conditions for the rapid induction of maternal behavior. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Electrical resistance drift of molybdenum silicide thin film temperature sensors

For a thermometer to be of practical use, its accuracy of temperature indication must be within a tolerable range. In this paper, patterned molybdenum disilicide (MoSi₂) thin film temperature sensors were fabricated to study their thermoresistance, i.e. resistance vs. temperature (R-T) characteristics. The R-T characteristic of MoSi₂ thin films exhibits a positive deviation from linearity (termed “superlinearity”) instead of showing a simple linearity as for most metals. This superlinear behavior was attributed to thermal expansion and the consequent decrease in the Debye characteristic temperature of MoSi₂. For long-term duration at elevated temperatures, the variation in thickness and composition of the sensor film due to oxidation and other factors may produce drift in the electrical resistance. In this study, the electrical resistance drifts of the sensors as a function of time at temperatures of 1200, 1300 and 1350 °C are presented. For the sensor film tested at 1300 °C, the resistance drift due to the thickness change of the sensor layer was well corrected with the help of an analysis of the oxidation rate of the sensor material. On the other hand, the in-depth composition profile analyzed by Auger electron spectroscopy (AES) indicated no significant composition variation, implying that we could neglect the correction factor for the composition variation in the present study. After the thickness factor was corrected for, a minor drift was still observed; this was also found for the same sensor film tested in an Ar ambient. The exact source of the minor drift is not well understood; further investigations are required.     

Orthogonal polarization fiber gyroscope with increased stability and resolution

The orthogonal polarization fiber gyroscope (OPFG) is an interferometric fiber gyroscope design that requires no phase bias in the fiber ring and is insensitive to light-source intensity noise. However, in the original OPFG [Hitachi Rev. 33, 215 (1984)], environmental changes caused first-order false rotation signals. We propose and experimentally verify modifications that eliminate the first-order sensitivity to environmental changes and that improve the gyroscope's resolution as well. We believe that this modified OPFG is the first interferometric fiber gyroscope capable of stable, high-sensitivity measurement that contains only reciprocal optical elements.