This method is intended to measure the cladding diameter and noncircularity of optical fibers.

This method is intended to be used on Class IV single-mode fibers. Although other fiber classes may be measured by this method, details of the applicability have yet to be determined.

In this method, the motion of one or more components of a white light Michelson interferometer is measured precisely, using a second (monochromatic) interferometer. This motion can be related to the fiber's cladding diameter.

The main advantages of this method are a) high precision, b) no reliance on surface contacts or edge definition, and c) measurement of fiber diameter relative to a wavelength of light. Because of c), the insmment could, at least in principle, be internally calibrated.

This method is intended for laboratory use, with possible use for the creation of transfer standards. In the current implementation, the equipment and procedures are not recommended for routine production or field measurements.