CHARACTERIZATION OF FLUORIDE GLASSES FOR SINGLE-MODE OPTICAL FIBERS WITH LARGE REFRACTIVE-INDEX DIFFERENCE

In order to obtain fluoride glass optical fibers with large refractive index difference between the core and the cladding, refractive indice s and viscosities of PbF2-doped core glasses and HfF4-incorporated cla dding glasses were systematically investigated. From the point of view of viscosity matching, it was found that the 9 mol% PbF2-doped core g lass containing 14 mol% NaF was the most adequate choice in combinatio n with the 43 mol% HfF4-incorporated cladding glass containing 22 mol% NaF. Using a casting method, single-mode fluoride glass fibers with r elative refractive index difference of 2.9% were successfully fabricat ed.