Switchable Microwave Photonic Filter Based on a Multi-Wavelength Fiber Laser

In this paper, a switchable microwave photonic filter (MPF) based on multi-wavelength erbium-doped fiber laser incorporating a reflective fiber Mach-Zehnder interferometer (FMZI) and dispersive medium is proposed and experimentally demonstrated. The reflective FMZI acts as the wavelength selective element in the fiber laser, and by adjusting the polarization controller (PC) in the reflective FMZI, the wavelength spacing of the transmission spectrum of the reflective FMZI can be switched between from Δλ to Δλ/2. In this way, the time delay realized by the dispersive medium will be changed from ΔT to ΔT/2, so the FSR of the MPF will be switched from one time of FSR to twice of that. In our experiment, an MPF with an extinction ratio of larger than 20 dB, FSR of 2.7 GHz has been implemented, and by adjusting the PCs the FSR of the MPF has been switched to half of the FSR (1.34 GHz), and extinction ratio of up to 10 dB has been achieved.