Eigen-Mode Expansion Analysis of Mode Propagation in Tapered Single Mode Fiber

In this paper the mode evolution and interaction in single mode tapered fiber was investigated. The eigen-mode expansion technique was used to calculate the mode coupling and interaction along the length of the taper. In this simulation, the taper was symmetrically excited and the excited modes along the tapered fiber are observed to be the LP_0n (HE_0n) modes. The interference of these modes forms self-imaging along the length of the taper waist. The amplitude and beat-length of these interference patterns are dependent on the excitation coefficient and the effective index difference between the LP₀₁ and LP₀₂ modes.