Loss measurements on laser-dye-doped and undoped unclad plastic optical fibers

We present side induced fluorescence (SIF) results on laser dye doped unclad plastic optical fibers. The SIF data can be used to obtain optical loss spectra for the low loss region of the absorption tail of the laser dye that has been doped into the fiber. Dyes which have been examined include derivatives of rhodamine and pyromethene. SIF deduced loss results in combination with cutback loss measurements on undoped fibers suggest that the electronic absorption of the laser dye dominates the loss far (> 200 nm) from the peak of the dye absorption (the order of 0.5 cm-1 at 750 nm). Loss measurements of unclad undoped fibers suggest that loss is dominated by scattering and defect mechanisms. In fact these losses are quite high compared to literature measurements of analogous clad fibers. Thus intrinsic loss of the polymer (PMMA in most cases) is minor compared to scattering and defect losses when dealing with unclad fibers. We also present the fit of our dye-doped fiber loss data to homogeneous and inhomogeneous broadening equations and show that broadening is dominated by inhomogeneous mechanisms as is expected.