Optical angular momentum in air core fibers

As data consumption continues to grow, the backbone of the internet, comprising single mode fiber (SMF)-based infrastructure, is fundamentally limited by nonlinear optical effects. One strategy to address this bottleneck, space division multiplexing (SDM), utilizes multiple modes in a single fiber as independent data channels. Orbital Angular Momentum (OAM) carrying modes, which have twisting phase fronts tracing out helices as the beams propagate, have recently received tremendous attention as a means of achieving low-crosstalk, digital signal processing (DSP)-free transmission with enhanced capacity. Terabit-scale transmission using 4 OAM modes over 1.1km has been demonstrated, but questions remain – how many OAM modes can fibers support, and how stable is propagation over longer lengths? In this thesis, we investigate angular momentum carrying modes in a novel class of fibers featuring an air core. We find that high-order OAM states, although arising in degenerate pairs, counterintuitively resist mode coupling due to OAM conservation, pointing to a unique stability inherent to OAM modes in fibers. We achieve OAM propagation up to 13.4km lengths, and achieve mode purities greater than 15dB at data-center length-scales. We use these fibers to transmit wavelength-division multiplexed data with 25 GHz channel spacing, 10 GBaud rates and quadrature-phase-shift keyed modulation formats in 12 modes simultaneously, over 1.2km, and over a large number of wavelengths across the C-band (1530-1565nm). However, transmission over every mode in every channel of the C-band was prevented by the accidental degeneracy of OAM states with undesired modes. To achieve a larger ensemble of stable modes over a larger wavelength range, we study new fiber designs that avoid this accidental degeneracy problem. We find that the most scalable modal eigenbasis is a set of states that carry non-integer amounts of average OAM, also called spin-orbit coupled modes in analogy with similar effects observed in atomic physics. We demonstrate excitation and transmission of 24 such modes over device lengths (10m). The achievement of a record number of uncoupled modes in fibers confirms the viability of angular momentum states as data carriers, and potential applications include links in data centers, high capacity optical amplifiers, and quantum communications links.2017-09-09T00:00:00

2011 Nutritional Assessment Guidelines : information

Careful assessment of nutritional needs of dogs and cats must be taken into consideration in order to maintain optimum health, be part of a treatment regimen for a diseased state, or to maximise the quality of life in all animals. Therefore, the goal of these WSAVA Guidelines is that a nutritional assessment and specific nutritional recommendation be made on every patient on every visit. This will become known as the 5th Vital Assessment (5VA), following the four vital assessments of temperature, pulse, respiration and pain that are already addressed on each patient interaction. Routinely doing a brief screening evaluation of the nutritional status during history taking and the physical examination can be seamlessly performed as part of every patient exam. Nutrition-related risk factors that can be easily identified from the history and physical examination include age (growing or old), suboptimal body condition score (overweight or thin), muscle loss, atypical or homemade diet, medical conditions, or changes in appetite. An extended evaluation would follow, if one or more risk factors is identified on screening. These guidelines provide criteria to evaluate the animal and the diet, as well as key feeding and environmental factors. In addition, recommendations for interpretation, analysis, and action are included so that a plan for optimising the animal's nutritional status can be instituted. Client compliance with nutritional recommendations requires input from the veterinarian, veterinary technicians/nurses, and the hospital staff. A team approach to continuous nutritional education, implementation of appropriate protocols, and focused client communication, utilising these WSAVA Nutritional Guidelines, are key components to reach this 5VA goal