100 dB Microwave Photonic Filter for Communications and RF Sensing Applications

This paper presents a microwave photonic filter with an in-band to out-of-band rejection ratio of 100 dB. The filter exhibits an electromagnetically induced transparency-like response, and harnesses stimulated Brillouin scattering (SBS). The filter is implemented using a single laser system to ensure stability and utilizes an SBS pump power of only 13 dBm. The demonstrated EIT filter is realized by superimposing a strong anti-Stokes resonance with a weak Stokes resonance on a phase-modulated analog photonic link. This incorporates RF interferometry and advanced phase manipulation to achieve the desired outcomes. The resulting amplitude response results in phase enhancement, leading to an adjustable delay response. The impact of this response on a 100 ns pulse is demonstrated. Moreover, the filter exhibits potential for various applications, such as switching and digital modulation, by transmitting quadrature amplitude modulation (QAM) through the filter. The feasibility of instantaneously sensing RF frequencies is validated as a proof of concept.