Stimulated Brillouin Scattering Enhanced Fibers for Narrow-Band Filtering by Tailoring Brillouin Gain Spectrum

A novel highly nonlinear optical fiber with enhanced stimulated Brillouin scattering for narrow-band filtering is proposed. Herein, we initially discuss the tailoring of the Brillouin gain spectrum in germanium and fluorine co-doped single cladding fibers. By adjusting the fiber structure and the doping concentration, the excitation of optical and acoustic modes, as well as coupling efficiency between them, can be manipulated properly. Then a double cladding structure is introduced in order to mitigate the accompanying undesired four-wave mixing effect. The simulation results show that the Brillouin gain spectrum of the proposed fiber is composed of single peak, corresponding to the fundamental optical mode and fundamental acoustic mode. The Brillouin gain efficiency is ∼2.45 m −1 ·W −1 , and the bandwidth is ∼17 MHz. Finally, the experimental and simulated frequency responses of the narrow-band optical filter utilizing the proposed fiber are in good agreement.