Uncertainty of the Sagnac interferometer-based measurement of the modal birefringence of polarization maintaining optical fibers

Presented is an analysis of the expanded uncertainty of an indirect measurement of modal birefringence of polarization maintaining fibers, based on the Sagnac interferometer and an optical spectrum analyzer. By using this method it is easy to achieve an expanded measurement uncertainty considerably lower than 1%, at a confidence level of 0.95, in measurements of fibers, whose birefringence is independent of the wavelength, as well as fibers, whose birefringence depends on the wavelength, including birefringent photonic crystal fibers (PCF). Guidelines are given, on how to minimize the measurement uncertainty of modal birefringence of these groups of birefringent fibers.