Switchable Microwave Photonic Filter Between Low-Pass and High-Pass Responses

A novel and simple microwave photonic filter (MPF) is proposed and experimentally demonstrated. The MPF can be switched between low-pass and high-pass frequency responses. The MPF is realized by using an electro-optic phase modulator (EOPM) and two cascaded tunable optical bandpass filters (TOBFs). One TOBF (TOBF1) is used to change the modulation format of the phase modulated signal and, consequently, switch the MPF between low-pass and high-pass frequency responses. The other TOBF (TOBF2) is used to adjust the cutoff frequencies of the low-pass and the high-pass frequency responses. In the experiment, a switchable MPF from 0 to 40 GHz is demonstrated. By changing the center wavelength of TOBF2, the cutoff frequencies of the low-pass and the high-pass frequencies are continuously changed from 2.9 to 20.1 GHz and from 15.4 to 31.2 GHz, respectively.