Influence of primary polymer coatings on low-temperature optical losses in fiber waveguides

An investigation of the temperature dependence of the additional optical losses in fiber waveguides prepared by the chemical vapor deposition method revealed for the first time that crystallization at temperatures below – 40 °C of a soft silicone coating increased the losses strongly. This effect had not been observed earlier because of the slow rate of crystallization of the silicone elastometer in the temperature range from – 40 °C to – 60 °C and because of the limited duration of low-temperature laboratory tests of fiber waveguides. The use of a noncrystallizing silicone elastomer ensured that in practice there was no increase in the optical losses in the fiber waveguides as a result of cooling down to – 60 °C.