Mode converter based on the long-period fiber gratings written by the electric arc discharge method

In this paper, we designed and fabricated a few-mode fiber (FMF) for writing a long-period fiber grating (LPFG) mode converter to improve its conversion efficiency. First, we used finite element method to simulate the relationship between the period of LPFG and the resonant wavelength. Subsequently, we used the arc discharge method to write LPFGs in FMFs (FMF-LPFGs), and systematically analyzed the relationship between the period numbers and the resonant wavelength. The experimental results showed that the LPFG mode converter could effectively realize the mode conversion from LP₀₁ to LP₁₁ at 1310nm, with a conversion efficiency exceeding 90%. This addresses the gap in the performance of LPFG mode converters at the 1310nm wavelength. The LPFG proposed in this paper demonstrates excellent mode conversion capabilities, providing a solid foundation for its applications in the fields of laser technology, fiber optic communications, and sensing.