Tunable microwave photonic filters based on stimulated Brillouin scattering for radio over fiber applications

In the field of microwave photonics, there is an increasing demand for Microwave Photonic Filters (MPFs) capable of meeting the rigorous requirements of high-performance communication systems, especially those utilizing Radio over Fiber (RoF) technology. Traditional electronic filters encounter significant limitations in bandwidth, power consumption, and speed critical challenges as communication systems advance towards higher frequencies and broader bandwidths. The core issue addressed in this study is the development of a tunable MPF that overcomes these limitations by leveraging the Stimulated Brillouin Scattering (SBS) effect. SBS-based MPFs offer several advantages, including low threshold, high gain, and broad tunability, which are crucial for modern RoF applications. However, existing SBS-based MPFs often suffer from complex tuning mechanisms and susceptibility to environmental factors, hindering their practical implementation. This research aims to resolve these issues by designing a SBS-based MPF with a simplified tuning mechanism and enhanced stability, making it more suitable for real-world applications. The study focuses on optimizing the design to achieve a wide tuning range while maintaining stable performance under varying operational conditions. By addressing these challenges, the proposed MPF is expected to significantly advance microwave photonic signal processing capabilities in high-frequency and high-bandwidth systems. The study presents an MPF designed for high-performance flexible filtering, based on a Brillouin laser resonator using a Cascaded Ring Fabry-P & eacute;rot CR-FP configuration. The resonator includes a 100 m main cavity to reduce the Brillouin gain bandwidth and an additional 30 m cavity for single-frequency operation by side-mode suppression. The optical modulation signal interacts with the Brillouin gain spectrum to enable stable tuning of the filter passband by changing the wavelength in which SBS pump light is generated. Simulation experiments, conducted using OptiSystem software and supported by a mathematical model derived from the fundamental equations of the topic, show that the MPF can be continuously tuned in 0-20 GHz with an out-of-band average rejection rate of approximately 17.6 dB.