Distortion analysis of a stimulated Brillouin scattering-based microwave photonic bandpass filter

The signal distortions of the microwave photonic bandpass filter based on stimulated Brillouin scattering is presented in this paper for the first time. We assume that modulated signal pulse propagates through a continuous-wave-pumped Brillouin fiber gain medium, where the carrier angular frequency of the pulse is tuned so that it´s near to Stokes resonance. The decibel gain and broadening factor of signal pulse are studied in the small-signal and gain-saturation region. Simulation results show that saturation effect of Brillouin microwave photonic filter restricts the linearity performance of relevant filter. In the small-signal region, both signal decibel gain and broadening factor increase linearly with increasing gain coefficient. In the gain-saturation region, both signal decibel gain and broadening factor decrease with increasing gain coefficient, and the pulse even achieves a compression. The signal decibel gain and the broadening factor are constant for a low pulse peak power and are reduced at a high peak power because of gain saturation. Longer pulses obtain both larger signal decibel gain and less broadening factor in pump-undepletion region, thus they are suitable for filtering processing of this type of stimulated Brillouin scattering-based microwave photonic bandpass filter.