Scattering Characteristics of Over 3 km Long Adiabatic Tapered Single Mode Fiber

An Ultra-long adiabatic tapered single mode fiber (UATSMF) is proposed for the Rayleigh back-scattering enhancement and nonlinear suppression. Its Rayleigh back-scattering is enhanced by increasing its the back-scattering coefficient without additional loss. Its nonlinearity is suppressed by nonuniform Brillouin frequency shift along UATSMF. A 3.44 km long UATSMF with a radius distribution from 4.5 μm to 3.2 μm is drawn and demonstrates its Rayleigh back-scattering enhanced by 0.24 dB and Brillouin frequency shift changed by 0.0242 GHz to increase the SBS threshold by 0.23 dB. The experimental results are consistent with the theoretical analysis. The further improvement on Rayleigh back-scattering enhancement and nonlinear suppression is also discussed by optimizing the refractive index of UATSMF. The results could be used as a reference for the improvement of signal noise ratio and nonlinear performance of Rayleigh back-scattering based optical fiber sensing.