PRODUCTION OF POROUS GLASS BASE MATERIAL

PURPOSE:To enhance the yield of a porous glass base material, by controlling the following relative velocity in case of relatively transferring both a freely rotary rodlike base material and a production means of fine glass particles along the direction of the axial center line of the rodlike base material and forming the porous glass base material on the outer periphery of the rodlike base material. CONSTITUTION:While blowing fine glass particles produced via a production means of the fine glass particles by vapor phase chemical reaction at high temp. on the outer periphery of a rodlike base material rotating with the axial center line in the lengthwise direction as a center, these rodlike base material and the production means of the fine glass particles are relatively transferred along the direction of the axial center line of the rodlike base material and thereby the fine glass particles are deposited in the lengthwise direction and the diametrical parallel of the outer periphery of the rodlike base material and the layer of the fine glass particles is grown. In the above-mentioned method, the relative transferring velocity of the rodlike base material and the production means of the fine glass particles in case of forming the end part of a porous glass base material in the lengthwise direction is made slower than the relative transferring velocity in case of forming the intermediate part thereof in the lengthwise direction.