Process of making multi-core fiber preform by integrating core rods and cladding cylinder

A process for manufacturing a multicore optical fiber preform having a center longitudinal axis, a plurality of core rods each being positioned in a respective core hole and extending along the longitudinal axis, and a common cladding covering each of the plurality of core rods, the process comprising the steps of:

• providing a cylinder which will form the cladding of the preform, the cylinder optionally having a center core hole;
• creating a plurality of peripheral core holes in the cylinder extending along the longitudinal axis;
• inserting each of a plurality of core rods into a respective peripheral core hole of the cylinder;
• and
• heating the cylinder with the plurality of core rods inserted in the respective core holes by exposing the cylinder and core rods to a heating element, thereby integrating the plurality of core rods and the cylinder and forming the preform,
• wherein the position error of the core holes with respect to the diameter of the preform is no larger than 0.6%.