An experimental study on Raman spectrum of liquid-core optical fiber

Abstract

The Raman spectra intensity can be enhanced in liquid core optical fiber (LCOF) .The total Raman power emitted by the LCOF is a function of the following parameters: LCOF length, LCOF loss coefficients at the laser and Raman wavelengths, the concentration of analyte and input laser power. The attenuation of the light in CS 2 is small in the range from 1400nm to1700nm. We dissolved liquid CCL 4 into CS 2 and got different solutions of different concentrations. When the analyte concentration was changed, the analyte molecules and the numerical aperture of the LCOF were also changed, so there is an optimum concentration at which the maximum Raman spectrum can be obtained. Our experiment result is in good agreement with the calculated results. Backward Raman scattering is superior to forward Raman scattering in our experiment. Raman intensity first increases to a maximum with fiber length, then decrease because the fiber attenuation becomes dominant. Therefore, there exists the optimum fiber length. In our experiment, we find that higher Raman intensity can be obtained when the fiber length is 2m. The Raman intensity becomes powerful when the input pump power becomes larger. Raman linewidth becomes narrow when the concentration decreased. Our experiment also approves it.