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On Sunday, September 8, 2019 11:42 PM, jim bell <jdb10987@yahoo.com> wrote:
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Silica fiber, being solid, has vastly less variation in the density of mass through the length of the fiber. So, I wouldn't expect that Rayleigh scattering is a major component of optical fiber loss, except if you are considering short wavelengths and considering Si-29 content as the source of that scattering.
i am finding this subject quite fascinating. here's a paper on thermal conductivity in single isotope germanium crystals which makes me wonder about the effect on light permeability...
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Isotopic disorder greatly decreases the thermal conductivityK(T) of dielectric single crystals if they are structurally perfect and sufficiently pure chemically. This effectwas predicted by Pomeranchuk1in 1942. The effect of isotopes on the thermal conduc-tivity of ordinary~non quantum! crystals has been studied experimentally for Ge,2LiF,3and recently for synthetic diamond.4The thermal conductivity of diamond enriched to99.9%12C is 50% higher than the thermal conductivity of natural diamond, where the12C content is equal to 98.9%, and at room temperature it is the highest of all known materials. Geballe and Hull2found that the thermal conductivity of germanium enriched to96%74Ge is approximately three times higher at the maximum than that of germanium with the natural isotopic composition. This increase in the thermal conductivity agrees qualitatively with the theory of Ref. 5, though it is much lower than the expected 15-foldincrease calculated on the basis of the 15-fold decrease in the mean-squared deviation in the mass of the isotopes.
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