Optical fibers play an important role in modern technologies. They are largely used both in industrial and civil applications: telecommunications, defense and aerospace, test and measurement, automotive, chemical, and specifically in medical applications [1-4]. We describe here two methods for optical fiber characterization - the far field method and the near field method. The far-field method gives information about the modal distribution of propagation light an optical fiber, and provides a technique for determining the numerical aperture of optical fiber, and allows identification of the conditions in which a stationary mode distribution has been formed. The near-field technique is a method for determination of the refractive index profile in an optical fiber. Both far-field and near-field methods are used for characterization of optical fibers [4], which is needed in development of various applications, specifically in development of biochemical and medical fiber optic sensors. Fig. 1. Experimental set-up for characterization of far-field distribution in an optical fiber. We show that, besides standard applications, the far-field technique can be applied for development of fiber sensors for registration of physical and biochemical parameters.