Multiple and Reconfigurable Microwave Photonic Filter With Out-of-Band Interference Cancellation

A multiple and reconfigurable microwave photonic filter based on a dual-drive Mach-Zehnder modulator (DDMZM) and a polarization-maintaining phase-shifted fiber Bragg grating (PM-PSFBG) with low birefringence is proposed and experimentally demonstrated. The two modulated signals along the fast and slow axes of the PM-PSFBG can be summed at one port and subtracted at the other port. As the DDMZM is biased for an equivalent phase modulator (e-PM), a traditional dual-passband filter is obtained at the summed port. Meanwhile, a performance-improved single-passband (SPB) filter is obtained at the subtracted port due to the out-of-band interference cancellation. The out-of-band rejection is greatly improved by 15 dB compared to the conventional SPB filter. As the DDMZM is biased for a single-sideband (SSB) modulator, a dual-notch filter and a complementary SPB filter with a rejection ratio of about 15 dB are simultaneously achieved at the two ports, respectively.