slipped over one fiber this tubing is an optional item which may be used to given mechanical protection to the finished joint particularly at the regions where the two fibers emerge from the glass sleeve the sleeve is typically between 1 2 cm and 1 cm in length and the heat shrinkable tubing 7 typically about 1 cm longer than the sleeve so that after the joint has been made and the tubing slipped over the sleeve it will extend a short distance beyond each end of the sleeve the bore of the sleeve does not have to be a tight fit over the bare fibers but is a clearance fit that is large enough for the fiber ends to be readily inserted by hand to this end it is convenient to employ sleeving that has a larger bore than is required to soften a short length and to draw it out or partially collapse it forming a necked portion of appropriate size not shown the central region of this necked portion is then parted from the remainder to provide a sleeve with slightly flared ends if a sleeve is cut from parallel walled sleeving having a bore of the appropriate size the bore may be slightly flared at both ends by enlarging the ends with the tip.