Reduction of multi-core fiber preform geometric distortion

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 collapsing the cylinder onto the plurality of core rods and forming the preform,
• wherein a gap (g) between the peripheral core rods and the peripheral holes is maintained during the step of creating the plurality of peripheral core holes in the range of about 0.2 to 4 mm.

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 collapsing the cylinder onto the plurality of core rods and forming the preform, wherein an average radial temperature gradient is maintained between about 0.5 to 4° K/mm at a plane where collapse between the core rods and the cylinder starts.