Writing technology for long-period fiber grating

Transmission spectrum characteristics of long-period fibre grating(LPFG) were theoretically analysed by using coupled-mode theory.Based on Matlab software simulation,the relationships between the transmission spectrum characteristics of long-period fibre grating and parameters of fibre grating have been deeply studied.The available approach for controlling the transmission spectrum characteristics of LPFG by adjusting parameter of LPFG has been proposed.With precise stepping motor and high-frequency CO_2 laser,combined with common communication single-mode fibre exposure,LPFG is written step by step symmetrically by focused high-frequency CO_2 laser pulses.By this mean,refractive index of fibre core can be modulated periodically,long-period fibre grating can be prepared successfully.