An apparatus for preparing a preform cone having desired shape and dimensions, including diameter is provided, wherein said apparatus comprises a box type structure having a coupling means suitably provided on the inner side of upper face for holding one end of the core rod of the soot preform which is required to be subjected to step of cone preparation; a grinding or cutting means suitably provided on the inner side of one of the faces of the box type structure for grinding or cutting the preform end to produce preform cone of desired shape and dimensions including diameter; a suction means suitably provided on inner side of one of the faces of the box type structure for immediate removal of soot particles produced during grinding or cutting of the preform end to produce the preform cone of desired shape and dimensions; and an adjustable rotating means suitably connectable to grinding or cutting means to have simultaneous control of rotation speed and position of the grinding or cutting means with respect to preform end wherein the preform cone is being prepared. A process for preparation of preform cone of desired shape and dimensions including diameter, and soot preform prepared by said process and optical fiber prepared from said soot preform are also provided.