Observing cross-sectional images of various optical fibers using low coherence transformed laser light

When the laser light of high optical coherence is launched into various optical fibers, such as a single-mode fiber, a multimode fiber, and a polarization-maintaining fiber, the observed optical patterns exhibit fragmented speckles due to the field interference of higher-order modes. Hence, the coherent laser light imaging system cannot be exploited to observe high-quality fiber crosssectional images. By putting a rotating diffuser directly on the laser beam, the original coherent speckled light spots at the fiber output endfaces could be smeared out efficiently and easily. Using the low coherence transformed laser light, we can thus obtain uniform fiber cross-sectional images and clear information for the tiny index structures in the specialty optical fibers.