Abstract: A method of assembling two optical fiber tube preforms end-to-end without negatively impacting the local glass chemistry at the joint. The ends of two tubes to be joined together are reverse-tapered by a grinding such that the outside portion of the tube walls extend further outward than the inner portions of the tube walls. Two tubes having such ends are briefly heated and brought together, and the reverse taper minimizes the size of the cross-sectional area of the tube portions to be joined. A minimal amount of heat that does not significantly impact the glass chemistry at the joint is applied to the outside of the tubes to effect a tack weld that joins the tubes. Once the tack weld is in place, additional heat in combination with a vacuum force can be applied to the tubes, which completes the sealing of the weld.