A tunable and dispersion-insensitive microwave photonic filter

A tunable and dispersion-insensitive two-tap microwave photonic filter (MPF) with a complex coefficient is proposed and demonstrated. By simply adjusting a polarization controller (PC) in one tap, the filter can be tuned over the entire free spectral range (FSR) while keeping the shape of the filter unchanged. Because the two taps are both single-sideband (SSB) modulated, the filter has high tolerance to fiber dispersion. The transmission response of a system with 25- or 40-km single-mode fiber (SMF) was measured and compared with an MPF with one double sideband (DSB) modulation tap. The proposed MPF shows much better performance for long-distance fiber transmission.