SBS-Based Tunable Microwave Photonic Notch Filter and Amplifier Simultaneously With Enhanced Gain, Bandwidth, and Polarization Control up to 50 GHz

Stimulated Brillouin scattering (SBS)-based filters can provide high gain, narrow bandwidth, and wideband tunability, which are critical to modern radio frequency (RF) systems. However, it is important to optimize all performance parameters to obtain stable response over wideband along with high gain. We present a novel SBS-based tunable microwave photonic notch filter and amplifier (TMWPNFA) configuration that can perform notch filtering, selective amplification, or both simultaneously by exploiting additional Brillouin gain modes and using both SBS stokes and antistokes in single-mode fiber. The TMWPNFA amplification and notch suppression are shown for maximum of 50 GHz in radio domain, which is the highest reported tunability to our knowledge. The TMWPNFA exhibits high gain of
$\simeq 35$
dB by employing RF amplifier (RFA). The TMWPNFA achieves SBS gains from 24 to 4 dB over the range. The suppression achieved by TMWPNFA ranges from 12 to 3 dB. We demonstrated the SBS pump’s RF mixing approach for increasing the −3 dB bandwidth of TMWPNFA to 35 MHz, resulting in greater separation of the amplification and suppression bands. The TMWPNFA phase noise distortion caused by SBS is measured to be less than −8.6 dBc/Hz at 125 kHz spacing. The filter achieved sharp −3 dB bandwidth of 20 MHz and
$Q$
factor of 200–2500. The degree of polarization of the SBS pump is shown to be the source of 6 dB gain control. It is shown that additional sound modes produced by SBS, separated by approximately two times bandwidth of SBS, can be used for notch filtering while simultaneously achieving selective amplification. The proposed 50 GHz TMWPNFA would provide unique benefits for satellite, aerospace, and beyond communication technologies.