Widely tunable wavelength exchange in anomalous-dispersion regime

We demonstrate the 10-Gb/s wavelength exchange with two pumps in the anomalous-dispersion region. Results show that performance degradation caused by Raman gain is avoided so that a nearly complete exchange can be achieved. In this letter, we also investigate the tunability of wavelength exchange for the first time to the best of our knowledge. Complete wavelength exchange is achieved with tuning range >15 nm. A bit-error rate of <10-9 is maintained with power penalties of ∼2 dB using 27-1 pseudorandom bit sequence (PRBS). © 2007 IEEE.published_or_final_versio

A comprehensive study on the dynamic range of wavelength exchange and its impact on exchanged signal performance

Effects of the incomplete signal exchange on the dynamic range performance of type II wavelength exchange (WE II, i.e. both pumps are in anomalous dispersion region) are investigated analytically and experimentally. The dynamic range here is defined as the tolerable operational range of the signal power to maintain a nearly complete WE performance. We studied the case of equal signal powers (balanced signal powers) as well as the case of unequal signal powers (imbalanced signal powers). It is demonstrated that the beating between exchanged signal and residual one and the extinction ratio degradation due to the existence of residual power at original channel is the major source of the signal quality degradation after WE II. The experimental results demonstrated dynamic range ∼17 dB with bit-error rate (BER) < 10-9 could be maintained with power penalty of <2 dB in the case of balanced signal powers. In the case of imbalanced signal powers, the dynamic range was <8 dB with the power penalty incurred of ∼2 dB in the worst case. © 2009 IEEE.published_or_final_versio

Dynamic range of wavelength exchange in highly nonlinear dispersion-shifted fiber

We investigate the signal dynamic range of wavelength exchange using 10Gb/s 231-1 PRBS. Data exchanging between two wavelengths is achieved with signal dynamic range ∼20dB. Bit-error-rate of <10-9 is maintained with power penalties of <2dB. © 2008 Optical Society of America.published_or_final_versio

Equatorial Pacific coral geochemical records show recent weakening of the Walker Circulation

Equatorial Pacific ocean-atmosphere interactions affect climate globally, and a key component of the coupled system is the Walker Circulation, which is driven by sea surface temperature (SST) gradients across the equatorial Pacific. There is conflicting evidence as to whether the SST gradient and Walker Circulation have strengthened or weakened over the late twentieth century. We present new records of SST and sea surface salinity (SSS) spanning 1959–2010 based on paired measurements of Sr/Ca and δ18O in a massive Porites coral from Butaritari atoll in the Gilbert Islands, Republic of Kiribati, in the central western equatorial Pacific. The records show 2–7 year variability correlated with the El Niño–Southern Oscillation (ENSO) and corresponding shifts in the extent of the Indo-Pacific Warm Pool, and decadal-scale signals related to the Pacific Decadal Oscillation and the Pacific Warm Pool Index. In addition, the Butaritari coral records reveal a small but significant increase in SST (0.39°C) from 1959 to 2010 with no accompanying change in SSS, a trend that persists even when ENSO variability is removed. In contrast, larger increases in SST and SSS are evident in coral records from the equatorial Pacific Line Islands, located east of Butaritari. Taken together, the equatorial Pacific coral records suggest an overall reduction in the east-west SST and SSS gradient over the last several decades, and a recent weakening of the Walker Circulation. © 2014, American Geophysical Union. All Rights Reserved

14.23 Wet chemical methods (pH, electrical conductivity, ion-selective electrodes, colorimetric analysis, ion chromatography, flame atomic absorption spectrometry, inductively coupled plasma-atomic emission spectroscopy, and quadrupole inductively coupled plasma-mass spectrometry)

A summary of wet chemical methods commonly used in geomorphological studies is presented. Instructions and tips are provided for the determination of pH and electrical conductivity in the laboratory. General information is presented about the principles of ion-selective electrodes, colorimetric analysis, ion chromatography, FAAS, ICP-AES, and Q-ICP-MS, together with some examples. References to specialized textbooks and standard analytical methods are provided for each analytical technique. © 2013, Elsevier Inc

Gain optimization of Raman-mediated fiber optical parametric amplifiers

Fiber optical parametric amplifiers (OPAs) and Raman amplifiers (RAs) are both based on the third-order nonlinear susceptibility of glass fibers. Recently, there have been some efforts to combine these two nonlinear phenomena in order to extend the amplification and wavelength conversion windows to the S-band, or to lower the required parametric pump power in order to achieve the same signal gain. We propose a new technique utilizing these two amplication principles in a single piece of highly-nonlinear dispersion-shifted fiber (HNL-DSF). We call this Raman-mediated fiber OPA (RM-OPA), which is different from the previous Raman-assisted OPA (RA-OPA) work. The previously investigated RA-OPA required an extra Raman pump with power around 1 W, on top of the erbium-doped fiber amplifier (EDFA) required to amplify the OPA pump. Therefore, Raman amplification was simply employed as a power booster for the OPA pump, i.e. RA "assists" OPA. On the other hand, our new approach does not require an extra EDFA as pre-amplifier, and the single piece of HNL-DSF provides both RA and OPA effects. In other words, there is essentially no parametric amplification without the presence of the Raman pump. While combining RA and OPA have been investigated both analytically and experimentally before, it involved only introducing some extra Raman terms in the nonlinear Schrödinger equations (NLSE) additively, which is sufficient for the case when one pump is used to amplify the signal (and idler) through both RA and OPA. However, the situation is significantly different here, where the parametric pump is amplified by the RA, while the OPA gain varies along the gain medium as the parametric pump power itself is a function of the distance along the HNL-DSF. In this paper, we will present an approximate analytical model for this RM-OPA, in a co-propagating configuration. Through certain simplifying assumptions, we produce closed-form equations allowing intuitive insights into the RM-OPA operation, given the coupling amongst the parametric pump, Raman pump, signal and idler. These equations provide a framework for optimizing such kind of fiber amplifiers. Important RM-OPA design guidelines are also discussed.link_to_subscribed_fulltex

Performance of Wavelength Exchange in Anomalous-dispersion Region

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High Extinction Ratio of Switched Packets by Two-Stage Four Wave Mixing in Highy Nonlinear Dispersion-Shifted Fiber

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All-optical packet switching by pulsed-pump wavelength exchange in a highly nonlinear dispersion-shifted fiber

We demonstrate experimentally for the first time successful switching of packets based on wavelength exchange with two pulsed pumps located at the anomalous-dispersion region. Simultaneous packet switching between different wavelengths at same timeslot is achieved. © 2007 Optical Society of America.link_to_subscribed_fulltex

Separation and measurement of thorium, plutonium, americium, uranium and strontium in environmental matrices

A technique for the isolation of thorium (Th), plutonium (Pu), americium (Am), uranium (U) and strontium (Sr) isotopes from various environmental matrices has been adapted from a previously published method specific to water samples (Maxwell, 2006). Separation and isolation of the various elemental fractions from a single sub-sample is possible, thereby eliminating the need for multiple analyses. The technique involves sample dissolution, concentration via calcium phosphate co-precipitation, rapid column extraction using TEVA™, TRU™ and Sr-Spec™ resin cartridges, alpha spectrometry for Th, Pu, U and Am and Cerenkov counting for Sr. Various standard reference materials were analysed and chemical yields are in the range of 70–80% for Th, Am, U and Sr and 50–60% for Pu. Sample sizes of up to 10 L for water, 5 g for dry soil and sediment and 10 g for dry vegetation and seaweed can be processed using this technique. Copyright © 2010 Elsevier Ltd. All rights reserved