New materials for fiber optics based on KBF4-BPO4-LiF and KBF4-BPO4 glasses are present. Transition of fluor-ion from BF4 groups to phosphorous were investigated. New glasses have refractive index lower than 1.430. With these glasses construction of fiber tip was offered. This new tip has a mechanical resistance 2 - 3 larger than polymer analogs, is efficient at LNT and may collect a set of 500 W laser without being destroyed. Corrosion degree of SiO2-glass on several fluor-containing melts was determined under some conditions. These melts appear corrosion activity as under as above the melt.