Theoretical and Experimental Study of a Numerical Aperture for Multimode PCS Fiber Optics Using an Imaging Technique

We study theoretically and experimentally the properties of numerical aperture (N_A) of multimode graded-index plastic core silica (PCS) fibers by using an image technique. A He-Ne laser at wavelength 632.8 nm and output power 1 mW is used as the transmitter light source. The output beam images and intensity profiles of an optical fiber are investigated by using an imaging technique. The laser beam profiles captured by a sensitive digital Nikon camera are processed and analyzed by using a Gaussian intensity distribution in a 2D graph. A MathCAD 14 program is used for converting the image of the laser output beam into data. The theoretical and experimental values of the numerical aperture for the used optical fiber in this study are found to be 0.5 and 0.4924, respectively. The theoretical value of V-number is also calculated to be approximately 2482.