Connectorized nano-engineered optical fibers and method for forming them are disclosed. The methods include heating a mid-span bare fiber portion of the nano-engineered fiber to substantially collapse the airlines therein so as to form a substantially airline-free portion. The fiber is then inserted into a ferrule channel so that the fiber end protrudes beyond the ferrule end face, but with the substantially airline-free portion positioned at the ferrule end face. The fiber is then cleaved at or near the ferrule end face in the substantially airline-free portion, and the new fiber end face polished to create a solid fiber end face that coincides with the ferrule end face. The methods result in relatively small changes to the mode field diameter (MFD) and/or to the outer cladding diameter.