Thermal variations of the aperture of step-index optical fibers have been studied by measuring the transmitted power when a laser beam is launched with a variable incidence. For not too-long fibers only the rays launched with the higher incidence are affected. The variations of their transmittance have been accurately related to the refractive-index ones. Silicone clad silica fibers are sensitive to temperature because the silicone index varies much more the the silica index. On the contrary, due to a compensation phenomenon between index variations of core and cladding materials, PMMA core fibers have apertures that are nearly insensitive to temperature.
© 1988 Optical Society of America
J. Dugas, M. Sotom, E. Douhe, L. Martin, and P. Destruel, "Accurate determination of the thermal variation of the aperture of step-index optical fibers," Appl. Opt. 27, 4822-4825 (1988)