Аналіз однорідності розподілу щільності потужності на виході багатомодового оптичного волокна

Abstract

The influence of the bending radius of a multimode optical fiber with a step-index refractive profile on the spatial distribution of laser radiation power density at the fiber output was investigated. For the experiment, a thermally stabilized laser module based on three laser diodes with a wavelength of 1064 nm and a radiation coupling system for a 200/240/375 μm multimode optical fiber were developed. The investigations were carried out for both straight fiber configuration and bent fiber configurations with diameters ranging 30 to 70 mm. It was established that fiber bending causes intermodal energy exchange and modification of the modal composition of radiation, which manifests itself in the equalization of the spatial intensity profile. It was shown that the optimal bending diameter for the investigated fiber is 40–50 mm, at which a compromise between the uniformity of the power density distribution and the preservation of output radiation power is achieved. It was also found that the angular conditions of radiation coupling and the asymmetry of the fiber end faces significantly affect the shape of the output profile; however, fiber bending reduces the sensitivity of the system to these factors due to modal mixing.