A novel method is presented for the measurement of optical fibers with diameters of 10-120 μm. The method is based on the detection of resonances in the intensity of dye laser light backscattered from a fiber in the far-field when tuning the wavelength. It has been experimentally confirmed that not only a thick (-120 μm) communication fiber produces Fabry--Perot resonances, but a thin (-13 μm) doubly-clad imaging fiber as well. The obtained accuracy is better than ± 0,1 μm. Also, the basic features of the WIRE GAUGE instrument based on laser beam scanning are shortly outlined.
"Diameter Measurement Of Optical Fibers And Wires By Laser", Proc. SPIE 0398, Industrial Applications of Laser Technology, (26 October 1983); doi: 10.1117/12.935387; https://doi.org/10.1117/12.935387