Waveguide connectors and methods of forming the same include heating a polymer waveguide having one or more waveguide cores and alignment features to a first temperature. A ferrule having alignment features is heated to the first temperature, the ferrule having a different coefficient of thermal expansion from the polymer waveguide. The alignment features of the polymer waveguide align with the alignment features of the ferrule when the polymer waveguide and the ferrule are heated to the first temperature. The polymer waveguide is positioned on the ferrule without a waveguide backfilm. The alignment features of the polymer waveguide are bonded to the corresponding alignment features of the ferrule.