In this paper we demonstrate the application of two microscopic imaging techniques, Raman Fluorescence Intensity Confocal Optical Microscopy and Nano-Secondary Ion Mass Spectroscopy (NanoSIMS), to the determination of the relative erbium ion distribution in optical fibers. We also employ Quantitative Phase Microscopy (QPM) for the acquisition of the refractive index profile of one of the investigated samples. As well as being able to acquire two dimensional profiles of the relative erbium ion distribution, these methods can also provide valuable information on a submicron level regarding physical and optogeometric parameters of the examined samples.