Near-IR (~1.5 µm) and mid-IR (~8 µm) laser heterodyne radiometers have been recently developed for ground-based remote sensing greenhouse gases in the atmospheric column. Field campaigns have been performed. The developed LHR instruments as well as the preliminary results of their applications to the measurements of CH4, N2O, CO2 (including 13CO2/12CO2), H2O vapor (and its isotopologue HDO) in the atmospheric column will be presented and discussed.
In this work, two experimental methods are proposed to quantify the contributions of the different light scattering mechanisms to the total attenuation of each guided-mode of two weakly-coupled FMF presenting different index profiles. The first approach is based on the analysis of the angular distribution of the light scattered by each mode of the two fibers whereas the second technique is based on bidirectional OTDR measurements also performed for each mode of the two fibers at different wavelengths. Some preliminary examples are reported and discussed for the fundamental mode and one higher order mode guided in a step-index and a trapezoidal index profile few-mode fiber.
Hybrid optical fibers, i.e. optical fibers that combine, in the same structure, glass with crystal, metal, polymer or a second type of glass, open access to a wide range of optical properties or optical functions not accessible to common single-glass-made optical fibers. Silicon-core fibers are one type of hybrid fibers that have been intensively studied since 2006 with the aim to take benefit of the mid-infrared transparency of silicon or to implement opto-electrical functions in the optical fiber itself. Some of the unique optical properties of these semiconductor-core fibers have been demonstrated but it is admitted that optical losses are still today a drag on the rise of performances and hence devote specific attention. Post-processing based on laser or thermal annealing can be applied on the as-drawn fibers to improve core crystallinity and then reduce optical losses. However, such processing techniques have been demonstrated on centimeter-long fibers only. In the present paper, we demonstrate as-drawn silicon-core fiber with loss level below 0.2 dB/cm on the 1250-1650nm wavelength range, this fiber being continuously manufactured over length exceeding one hundred of meters. Several fibers have been fabricated from a rod-in-stack approach and different core dimensions ranging from about 0.8 to 3.4 μm have been successively realized and extensive characterizations (XRD, micro-Raman spectroscopy, TEM and ToF-SIMS analysis) have been conducted on the 3.4 μm core fiber. The crystalline state of the core, the absence of oxygen contamination and the optical transmission from 1.1 to 4 μm will be presented.
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