Mode field evolution in 1 550 nm single-mode tapered fiber

According to the theory of optical fiber transmission mode, combined with the structure of single-mode tapered fiber, the paper uses finite difference beam propagation method (FD-BPM) to simulate the transmission of fiber mode at 1 550 nm wavelength, and analyzes the influence of the mode in cladding on the mode in fiber core. The results show that, because of the existence of cladding mode, with the reduction of cladding mode number and the change of the constraint state of mode field in fiber core, the mode field distribution within different regions of tapered fiber core changes significantly, and the root-mean-square(RMS) widths of mode field within different regions have different degrees of ups and downs. The distribution of mode field energy is obtained by using numerical method and the existence of cladding mode is found to slower the reduction of mode field energy.