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In this work, we develop a relatively simple and reliable technique to mitigate the effect of modal dispersion of standard, 1 mm step-index plastic optical fiber (SI-POF). We focus on decreasing the modal dispersion by reducing the effective numerical aperture (NA) of the fiber link. The technique involves a spatial mode filter that is constructed by using a commercially available polycarbonate capillary tube having a refractive index of 1.59, with inner and outer diameters of 1 mm and 2 mm, respectively. The capillary tube holds two pieces of 1 mm SI-POF, one comes from the transmitter and the other shorter one connects to the receiver. The two fibers are aligned by the tube and separated by an air gap. Increasing the gap width inside the tube effectively reduces the NA of the fiber link. We experimentally demonstrated an error-free 1 Gb/s over 30 m of SI-POF. The simplicity, reliability, robustness, and low cost make this technique an ideal candidate for dispersion mitigation in short range telecommunication networks.
Adviser: Lim Nguyen