Mode-coupling and single-mode excitation characteristics of multimode fibers with ultra-short optical pulses

摘要

Multimode(MM) optical fihers can transmit high energy and can be easily used for connection and splicing because of its large core diameter. However - due to microbending-induced mode coupling the multimode fibers exhibit a speckle pattern at the output of the MM fiber. In this paper, single-mode excitation of step-index and graded-index multimode fibers with light sources with short temporal coherence lengths is demonstrated using a Ti:sapphire laser with wavelength the of 790 nm and 836 nm and pulse widths of 60～90 fs. The mode-coupling coefficients and launching efficiencies are determined experimentally from diffraction half-angle of the output pattern exiting from the MM fiber and single-mode(SM) excitation in the presence of mode-coupling is discussed for the MM fibers.