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We propose two mode optical fibers (TMFs) with minimally low differential modal delay (DMD) slope which are suitable for wavelength division multiplexing and multiple input multiple output (MIMO) combined transmission system. We designed and fabricated three different kinds of TMF, nearly zero-DMD (zTMF), positive-DMD (pTMF) and negative-DMD (nTMF) with a graded index core and a depressed inner cladding. We confirmed that the fabricated zTMF has DMD of below 15 ps/km in the C band and the fabricated pTMF and nTMF have the same degree of effective areas. We also confirmed that a DMD compensation line with a length of 100 km composed of pTMF and nTMF can successfully achieve the best properties of low DMD in the C + L band and low mode conversion.

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Silver plates were exposed to an urban atmosphere for one month to investigate the corrosion products formed in the early stages. After the exposure experiments, the corrosion products on the silver plates were characterized using x-ray techniques, including x-ray diffraction (XRD) and x-ray fl uorescence analysis (XRF). The XRD patterns of the corrosion products on silver revealed that both silver chloride (AgCl) and silver sulfi de (Ag 2 S) formed. The diffraction peaks originating from AgCl were much stronger than those of Ag 2 S; therefore, AgCl was predominant in the corrosion products observed on the outdoor-exposed silver. The chlorine that formed the AgCl originated primarily from sea-salt aerosols. The seasonal differences in the AgCl intensities in the XRD pattern could be observed. However, there was almost no difference in the Ag 2 S intensities. This was due to the low sea-salt concentrations and relative humidity during winter. Only Ag 2 S formed on the indoor-exposed silver. The absence of AgCl peaks in the XRD patterns indicated that the sea-salt concentrations were quite low in the indoor exposure site. Silver was found to be sensitive to the chloride in sea-salt aerosol and reduced sulfurous gases.KEY WORDS: atmospheric corrosion, silver, urban atmosphere, x-ray diffraction, x-ray fl uorescence analysis