U.S. East Coast Trough Indices at 500 hPa and New England Winter Climate Variability

Using monthly gridded 500-hPa data, two synoptic indices are defined to better understand the principle mechanisms controlling intraseasonal to multiannual winter climate variability in NewEngland (NE). The “trough axis index” (TAI) is created to quantify the mean longitudinal position of the common East Coast pressure trough, and the “trough intensity index” (TII) is calculated to estimate the relative amplitude of this trough at 42.5°N. The TAI and TII are then compared with records for NE regional winter precipitation, temperature, and snowfall with the goal of understanding physical mechanisms linking NE winter climate with regional sea surface temperatures (SST), the North Atlantic Oscillation (NAO), and the Pacific–North American (PNA) teleconnection pattern. The TAI correlates most significantly with winter precipitation at inland sites, such that a western (eastern)trough axis position is associated with greater (lower) average monthly precipitation. Also, significant correlations between the TAI and both NE regional SSTs and the NAO suggest that longitudinal shifting of the trough is one possible mechanism linking the North Atlantic with NE regional winterclimate variability. The NE winter temperature is significantly correlated with the TII, regional SSTs, and the NAO. While the PNA also correlates with the TII, NE winter climate variables are apparently unrelated to the PNA index

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

Is New Hampshire\u27s climate warming?

This Carsey brief looks at temperature anomalies across New Hampshire and shows that not only is the state warmer than it has been in the past, but it is also warming faster than much of the planet. Sociologist Lawrence Hamilton, research associate professor Cameron Wake, and former NH state climatologist Barry Keim analyzed over 100 years of temperatures across the state to produce this data for the Carsey Institute in August 2010

Are there spurious temperature trends in the United States Climate Division database

The United States (U.S.) Climate Division data set is commonly used in applied climatic studies in the United States. The divisional averages are calculated by including all available stations within a division at any given time. The averages are therefore vulnerable to shifts in average station location or elevation over time, which may introduce spurious trends within these data. This paper examines temperature trends within the 15 climate divisions of New England, comparing the NCDC\u27s U.S. Divisional Data to the U.S. Historical Climate Network (USHCN) data. Correlation and multiple regression revealed that shifts in latitude, longitude, and elevation have affected the quality of the NCDC divisional data with respect to the USHCN. As a result, there may be issues with regard to their use in decadal- to century-scale climate change studies

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

Charge dynamics in the half-metallic ferromagnet CrO\u3csub\u3e2\u3c/sub\u3e

Infrared spectroscopy is used to investigate the electronic structure and charge carrier relaxation in crystalline films of CrO2 which is the simplest of all half-metallic ferromagnets. Chromium dioxide is a bad metal at room temperature but it has a remarkably low residual resistivity (\u3c5 \u3eμΩ cm) despite the small spectral weight associated with free carrier absorption. The infrared measurements show that low residual resistivity is due to the collapse of the scattering rate at ω\u3c2000 \u3ecm-1. The blocking of the relaxation channels at low v and T can be attributed to the unique electronic structure of a half-metallic ferromagnet. In contrast to other ferromagnetic oxides, the intraband spectral weight is constant below the Curie temperature

Ultra-narrow (sub-MHz) linewidth emission from discrete mode laser diodes

A class of laser which exhibits ultra-narrow sub MHz linewidth emission necessary for numerous applications in optical communications and sensors is described. The spectral performance of commercial discrete mode (DM) and distributed feedback (DFB) lasers is compared. The devices used in this work are asymmetrically coated ridge waveguide Fabry Perot lasers which incorporated etched slot features and emitting around lambda = 1.55 mum. The active region of the devices consisted of a strained compensated InAlGaAs MQW structure

Characterization of 1.55-μm pulses from a self-seeded gain-switched Fabry-Pérot laser diode using frequency-resolved optical gating

The intensity and frequency chirp of picosecond pulses from a self-seeded gain-switched Fabry-Perot laser diode have been directly measured using the technique of frequency-resolved optical gating. Measurements over an output sidemode suppression ratio (SMSR) range of 15-35 dB show that higher SMSR's are associated with an increasingly linear frequency chirp across the output pulses. This complete pulse characterization allows the conditions for optimum pulse compression to be determined accurately, and indicates that transform-limited, pedestal free pulses can be obtained at an SMSR of 35 dB

Frequency drift characterisation of directly modulated SGDBR tunable lasers

Tunable Lasers (TL) are rapidly becoming key components in Dense Wavelength Division Multiplexed (DWDM) systems, packet switched schemes and access networks. They are being introduced as alternatives to fixed wavelength sources to provide a greater degree of flexibility and to reduce large inventory [1]. The SGDBR laser is an ideal candidate due to its large tuning range (40 nm), high output power (10 dBm), large Side Mode Suppression Ratio (>30 dB) and its ability to be monolithically integrated with other semiconductor devices. Such integration could comprise of a Semiconductor Optical Amplifier (SOA), allowing for extended reach tunable operation, in a very compact and low cost footprint [2]. Thus far, external modulation has been the most popular modulation technique used with TLs. However, the addition of the modulator introduces loss to the transmitted signal due to high insertion and coupling losses. Addressing these short comings would result in increased cost and complexity of the transmitter. Alternatively, direct modulation is one of the simplest and cost efficient ways to modulate the lightwave signal. Hence, it is rational to investigate the performance of a directly modulated SGDBR laser in order to verify its usefulness in a WDM based access network scenario. Previous work in this area has mainly focused on bandwidth characterisation and transmission experiments [3, 4]. In this paper, we characterise the frequency drift associated with a directly modulated SGDBR laser incorporating a wavelength locker. Focus is placed on investigating the magnitude and settling time of this drift. In addition, we also demonstrate how the frequency drift has a detrimental effect on DWDM system performance when the modulated channel is passed through a narrow Optical Band-Pass Filter (OBPF) centred at the target emission frequency