Refractive index retrieving of polarization maintaining optical fibers

In this paper, the cross-section images, of two different types of polarization maintaining (PM) optical fibers, are
employed to estimate the optical phase variation due to transverse optical rays passing through these optical
fibers. An adaptive algorithm is proposed to recognize the different areas constituting the PM optical fibers crosssections.
These areas are scanned by a transverse beam to calculate the optical paths for given values of refractive
indices. Consequently, the optical phases across the PM optical fibers could be recovered. PM optical
fiber is immersed in a matching fluid and set in the object arm of Mach-Zehnder interferometer. The produced
interferograms are analyzed to extract the optical phases caused by the PM optical fibers. The estimated optical
phases could be optimized to be in good coincidence with experimentally extracted ones. This has been achieved
through changing of the PM optical fibers refractive indices to retrieve the correct values. The correct refractive
indices values are confirmed by getting the best fit between the estimated and the extracted optical phases. The
presented approach is a promising one because it provides a quite direct and accurate information about refractive
index, birefringence and beat length of PM optical fibers comparing with different techniques handle the
same task.