Bandstop-to-Bandpass Microwave Photonic Filter Using a Phase-Shifted Fiber Bragg Grating

A bandstop-to-bandpass microwave photonic filter (MPF) using a phase-shifted fiber Bragg grating (PS-FBG) and a dual-drive Mach-Zehnder modulator (DD-MZM) is proposed and experimentally demonstrated. The PS-FBG has an ultra-narrow notch in the reflection band. The DD-MZM is employed to generate a phase-modulated or a quasi-single-sideband (QSSB) optical signal by controlling the bias voltage. By applying the phase-modulated or QSSB signal to the PS-FBG to suppress one sideband, a bandpass or a bandstop MPF is implemented. The MPF can be continuously tuned from bandstop to bandpass or vice versa by controlling the bias voltage applied to the DD-MZM. The frequency tuning can be simply done by tuning the wavelength of the optical carrier. The proposed MPF is experimentally evaluated. Continuous tuning from a bandstop to bandpass filter with a bandstop rejection as high as 60 dB and frequency tuning with a frequency tunable range as large as 10 GHz are demonstrated.