Measurement of Optical Fiber Refractive Index Distribution Based on White Light Scanning Interferometry

A method for measuring the refractive index distribution of optical fibers is presented,which uses the white light scanning interference technology and builds the same structure on the reference mirror as the optical fiber sample to overcome the limitation of the short white light coherence length,optimizes the optical path and improves the contrast between the interference fringes. For white light interference signals, Morlet wavelet which has Gaussian distribution like envelope of white light interference fringes is used as the mother wavelet of wavelet transform for fitting processing,and the relative height between the fiber and the matching fluid with known refractive index is obtained. The refractive index distribution of optical fiber can be obtained by calculation,and fitting the obtained data with the classical function of the refractive index distribution of the fiber core,the coefficients of determination of the multi-mode fiber and singlemode fiber are 0.997 2 and 0.996 4 respectively. Finally,the experimental results are compared with the official parameters,and the error is 0.01%,which shows that this method has a high precision and can be used to measure the refractive index of optical fiber.