Nondestructive determination of refractive index profile of an optical fiber: backward light scattering method.

A new nondestructive technique is presented for determining the refractive index profile of an optical fiber from its backscattered pattern arising from a normally incident laser beam to the fiber axis. The proposed method requires no sample preparation or index matching liquid. The principle of the method is to construct a deflection function from the measured pattern. The index profile can then be determined by the inversion of an Abel integral equation. Good agreement is obtained between the index profile determined by this technique and that measured by the near-field scanning technique.