Fluorophosphate cladding glasses for fluoride glass fibers

Fluorophosphate glasses have been investigated in NaPO3-ZnF2-PbF2-BaF2 systems. Stable glass-forming areas were determined when NaPO3 content was 30, 40 and 50 mol%. Glass characteristic temperatures, refractive index and thermal expansion coefficient were measured. Large variations are observed for n(D) and T-g depending on lead fluoride concentration. Anionic oxygen also increases n(D) and T-g values but decreases thermal expansion. The application of these glasses as cladding materials for fluorozirconate, fluoroindate and cadmium fluorochloride glasses is discussed. Good chemical compatibility between a fluoroindate core glass and a fluorophosphate cladding glass was observed by thermal analysis.