Fig. 1: Operation scheme of a PPER-based microwave-photonic notch-filter.
From: Narrowband microwave-photonic notch filters using Brillouin-based signal transduction in silicon
a Operation scheme of the notch filter. The signal is split into two paths, one of which is bandpass filtered. By combining the two signals out of phase, a notch filter frequency response is obtained. b Schematic illustration of the experimental setup used to demonstrate PPER-based notch filtering. The input RF tone is modulated onto an optical carrier using an intensity modulator (IM). The optical signal is split into two paths: One path is bandpass filtered using a PPER-based filter (shaded region), and the second path is controlled using an optical delay line (ODL) to achieve signal cancellation at the detector. VOA: variable optical attenuator, EDFA: erbium-doped fiber amplifier, PC: polarization controller, DeMod: phase demodulation (bandpass filtering), RFSA: RF spectrum analyzer. c Optical spectrum at different stages of the signal path: (I) Wideband RF signal modulated on an optical carrier. (II) The acoustic response (blue) transduces a narrow spectral band. (III) The resulting narrowband phase modulation. (IV) At the detector, the wideband intensity-modulated signal (red) is combined with the bandpass-filtered signal (orange).
