A simple refractive index measurement method for step-index fiber based on radial displacement optical power scan

In this paper, a novel method for measuring the refractive index of single-mode step-index fiber based on radial displacement optical power scan is proposed. The radial displacement optical power curves of different fibers have different bending degrees and a r parameter is used to characterize the bending degree of the radial displacement optical power curve. The r-n polynomial formulas of different core diameters are obtained via beam propagation method, which are used for the calculation of the fiber refractive index. As proof of principle, two commercial single-mode step-index fibers were measured experimentally. Simulation results reveal that the refractive index measurement error is within & PLUSMN;0.0003. The measurement formulas of optical fiber refractive index are given by simulation and the measuring range is 6.0 to 10 & mu;m with an interval of 0.5 & mu;m. This method has the advantages of low cost, convenient operation, and can be used under laboratory conditions.