NONCONTACT CALIBRATION OF OPTICAL-FIBER CLADDING DIAMETER USING EXACTSCATTERING-THEORY

A new, contactless and nondestructive method for measuring the diamete r of an optical fiber is described which has 10 nm sensitivity. In thi s method, polarized laser light is backscattered from the fiber, perpe ndicular to its axis. The measured intensity shows excellent agreement with calculations from an exact scattering theory, and reveals both t he 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 sensit ivity of this method leads to an absolute calibration accuracy of 10 n m of the fiber diameter.