Fig. 3: Microwave-photonic notch filter frequency tunability.
From: Narrowband microwave-photonic notch filters using Brillouin-based signal transduction in silicon
a Schematic illustration of the experimental setup used to tune the notch frequency. The input RF signal is modulated using a phase modulator (PM). An optical local oscillator (LO) tone is synthesized using an intensity modulator (IM) and an optical bandpass filter (BPF). VOA variable optical attenuator, ODL optical delay line, EDFA erbium-doped fiber amplifier, PC polarization controller, DeMod phase demodulation (bandpass filtering), RFSA RF spectrum analyzer. b Aggregated data from four measurements demonstrating the tunability of the filter notch frequency over a wide range. For each measurement, the LO was set and the input signal swept a 1 GHz span around the notch frequency. The insets show a magnified view (6 MHz span) of the filter stop-band at each LO setting, demonstrating ∼40 dB extinction. c Experimental demonstration of high-resolution filtering. The input RF signal consists of three tones, separated in frequency by 5 MHz (left panel). By tuning the notch filter to the frequency indicated by the red arrow (middle and right panels), one of the tones can be suppressed without affecting the other tones.
