Comparison of some fiber optic configurations for measurement of luminescence and Raman scattering

Abstract
Measurements are made for a number of dual fiber optic configurations to determine their relative sensitivity using bare fibers and graded-refractive-index lenses. An analysis of the background fiber emission for a typical silica-on-silica fiber (Diaguide, 200-μm core) is presented, and the origin (core or cladding) for several prominent Raman peaks is determined. Also, a forward-scattering fiber geometry is introduced, and the dependence of sensitivity on the type of optical termination and fiber separation is determined.