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

• Different modes can be transmitted with equal differential delay. • The number of excited modes and the length of the few-mode fiber can be varied. • There is no need to de-multiplex modes and readjust the power and time delay of modes. We propose a reconfigurable and tunable few-mode fiber-based microwave photonic filter. LP 01 mode and LP 11 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. LP 01 mode, LP 11 mode and LP 21 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 LP 01 mode, LP 11 mode and LP 21 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.