Light scattering from unclad fibers: ray theory.

Information contained in the position of the peaks of backscattered light intensity from an unclad fiber, with laser light incident at right angles to the fiber axis, is utilized to determine the parameter b/lambda (b = fiber radius, lambda free space wavelength). For known laser wavelength the fiber diameter can thus be determined. The theory is based on an approximate ray analysis and is compared with the results of the exact wave theory. Good agreement is obtained. The accuracy of this procedure may vary between 1% and 10%.