Second-Order Optical Differentiator Based on a Mechanically-Induced LPFG with a Single pi-Shift

摘要

An all-optical second-order temporal differentiator based on a mechanically-induced long-period fiber grating (MI-LPFG) with a single π-shift is demonstrated. The MI-LPFG is created by pressing a fiber between two periodically grooved plates with a π-shift located at the 3/4 length from the input end of LPFG. The coupling coefficient (κ) can be adjusted through changing the pressure applied on the fiber. The experimental results show that the transfer function of the proposed MI-LPFG can be adjusted to be close to the ideal transfer function of a second-order differentiator. The differential performance of the designed differentiator to a Gaussian pulse is also analyzed.