Effects of the Weak Absorption Tail on the Transmission Loss of Ge-Sb-Se Optical Fibers

Selenide glass optical fibers were fabricated for Ge30Sb10Se58S2 and Ge20Sb10Se70 glasses. Their transmission loss has been measured and compared with the theoretical attenuation loss that was calculated taking into account the electronic transition absorption, Rayleigh scattering, and multiphonon absorption. A low attenuation loss of the Ge20Sb10Se70 glass composition in 1.2–1.7 μm range has been expected due to its high optical band gap energy compared with the Ge30Sb10Se58S2 glass. However, the measured attenuation loss of the Ge30Sb10Se58S2 glass fiber was ∼13 dB/m at 1.5 μm while Ge20Sb10Se70 glass showed ∼82 dB/m. An enhanced weak absorption tail due to the localized states of the Ge20Sb10Se70 glass was responsible for this behavior. Structural defects are related to the localized states and discussed for the present glass compositions.