Glass fibers of alkali disilicate composition were prepared under defined and systematically varied nozzle drawing conditions. Optical birefringence, ‘frozen-in’ apparent stress optical constant, density changes relative to the bulk glass and the expansion and shrinking behaviour during heating and annealing were examined. The optical properties indicate a marked cross-linking of the chain structure. The shrinking behaviour of the fibers shows an anomaly which seems to be typical of alkali disilicate glass fibers. Results add to earlier investigations on silicate glass fibers between the metasilicate range and silica glass fibers along the series xSiO2(1 − x)R2O. The structural alterations due to the variation of the ratio network former/network modifier are discussed over the large range of the nearly ideal three-dimensionally connected network structure of the silica glass fibers and of the nearly ideal one-dimensionally connected chain-ring-like structure of the meta-silicate glass fibers.