Reconfigurable and tunable few-mode fiber-based microwave photonic filter

Abstract

We propose a reconfigurable and tunable few-mode fiber-based microwave photonic filter. LP01 mode and LP11 mode are simultaneously excited by a few-mode long-period fiber grating. The free spectral range of the two-tap microwave photonic filter varies with the length of the few-mode fiber. LP01 mode, LP11 mode and LP21 mode are simultaneously excited by cascading different few-mode long-period fiber gratings and reflected at the same wavelength by different few-mode fiber Bragg gratings, which allows LP01 mode, LP11 mode and LP21 mode to be transmitted with equal differential delay. The free spectral range of the three-tap microwave photonic filter varies with the length of the few-mode fiber. A reconfigurable and tunable few-mode fiber-based microwave photonic filter can be implemented by changing the number of excited modes and the length of the few-mode fiber.