Systems and techniques for splicing together optical fiber ribbon cables having different core-to-core spacings

A system forms, at an end of a multifiber ribbon cable, a multifiber ribbon cable segment having an enlarged core-to-core spacing. A UV-transparent mold is mounted on top of a chassis. The mold defines a plurality of individual fiber channels corresponding to individual fibers of the existing multifiber ribbon cable and having a spacing equal to that of the enlarged core-to-core spacing. Each individual fiber channel passes through the internal cavity. The assembled mold further includes an injection system for receiving light curable, flowable material from the reservoir and pumping system and feeding it into the internal cavity, and at least one vent for allowing air to escape from the internal cavity as the light-curable, flowable material is fed into the internal cavity. The injected material is cured by exposure to a curing light.