Noncontact calibration of optical fiber cladding diameter using exact scattering theory

A new, contactless and nondestructive method for measuring the diameter of an optical fiber is described which has 10 nm sensitivity. In this method, polarized laser light is backscattered from the fiber, perpendicular to its axis. The measured intensity shows excellent agreement with calculations from an exact scattering theory, and reveals both the refractive index and diameter of the fiber. The high sensitivity of this method results from the intrinsic interferometric properties of the fiber itself, and depends on the wavelength of the coherent light source only. If the fiber's circumference is circular, the high sensitivity of this method leads to an absolute calibration accuracy of 10 nm of the fiber diameter.>