Variations in fiber-cladding diameter on a nanometer scale were measured along millimeter to centimeter lengths by use of whispering-gallery modes (WGMs) in the elastic scattering of the fiber. The fiber was side coupled with a wavelength-tunable Gaussian beam. The scattered light was imaged ≈1:1 onto a multichannel photodiode array detector. Based on the WGM wavelength shifts along the fiber, the taper of the fiber cladding's diameter was measured on a nanometer/millimeter scale. The fiber's surface roughness amplitude (in nanometers) and granular size (≈100 µm) along centimeter-length fibers could also be revealed by use of higher- Q resonances.
© 2001 Optical Society of America
(060.2300) Fiber optics and optical communications : Fiber measurements
Andrew W. Poon, Richard K. Chang, and Dipak Q. Chowdhury, "Measurement of fiber-cladding diameter uniformity by use of whispering-gallery modes: nanometer resolution in diameter variations along millimeter to centimeter lengths," Opt. Lett. 26, 1867-1869 (2001)