Production process for porous glass preform

摘要

A method for producing a porous preform comprising measuring the surface temperature distribution at the end of the core soot preform, and (1) maintaining the surface temperature Tc at the center point on the end of the core soot preform in the range of 500 to 1000° C., and preferably in the range of 600 to 950° C.; and maintaining the difference Tm-Tc between the maximum surface temperature Tm at the end of the core soot preform and the surface temperature Tc at the center point on the end of the core soot preform in the range of 5 to 45° C.; and/or (2) maintaining the ratio R of the area in which the surface temperature at the end of the core soot preform is higher than the surface temperature Tc at the center point on the end of the core soot preform in the range of 5 to 30%.