Fictive temperature measurement of single-mode optical-fiber core and cladding

The fictive temperatures of single-mode optical-fiber core, along with its inner and outer cladding, were measured using an infrared (IR) reflection method on the fiber cross-sectional surface. To allow for usage of a larger IR beam size than the diameter of the fiber core, the cross-sectional area of the fiber was increased by slicing the fiber at an oblique angle, along approximately 3 degrees off the fiber axis direction. The magnitude of the fictive temperature was estimated from the IR peak wavenumber-fictive temperature relation obtained for bulk glasses with the same compositions. The observed fictive temperature was in the range of 1150 similar to 1300 degreesC for the core, 1450 similar to 1550 degreesC for the inner cladding, and 1620 similar to 1660 degreesC for the outer cladding and exhibited good correlation with the fiber cooling rate.