On investigations of refractive indices and birefringence of fiber using duplicate and non-duplicate micro-interferograms of double refracting interferometer.

The formula of refractive index of fiber considering the refraction has been reviewed. This formula is used to investigate the effect of refraction on the accuracy of refractive index calculations with different simulated micro-interferograms of duplicate interference fringes with different fringe shifts order. Also a more accurate formula to calculate the birefringence from the non-duplicate interference fringes has been derived and tested to calculate the birefringence of simulated and experiment micro-interferogram. The presented micro-interferograms were automatically analyzed and the contour lines of the bright fringes were determined using Fourier transform technique. A prepared software program takes the contour line of the fringes and automatically calculate the refractive index, the radius, and the birefringence of fiber. A good result was obtained in case of using immersion liquid matches between the parallel and perpendicular refractive indices of fiber. Formula of refractive index of fiber considering the refraction has been reviewed. The refraction effect on the accuracy of refractive index calculations was presented. More accurate Formula to calculate the birefringence of fiber was derived. Automatic fringe analysis was done for duplicate and non-duplicate fringes. The contour line of the fringe used directly to calculate the birefringence of fiber.