referring now also to the drawing , an optical fibre cable 1 terminates and is secured in an axial bore of ferrule 2 . the optical fibre cable consists of an outer sheath 1b which terminates in a rear portion of the ferrule 2 , and an optical fibre 1a . the optical fibre 1a extends forwardly from the rear portion 2a of the ferrule and terminates in the plane of the end face 4 of the ferrule 2 . the optical fibre is rigidly located in the bore of the ferrule 2 by means of a hard setting compound 3 , for example epoxy - resin or light curable dental adhesive . the forward portion 2b of the ferrule 2 ending in the end plane 4 is bounded by a surface 6 which , when machined , provides the cylindrical locating surface of the ferrule . to machine the outer cylindrical surface 6 the ferrule 2 is mounted on a precision lathe , schematically illustrated as having a chuck 8 , four jaws ( of which only two , 7a and 7b , are shown ) and a hollow head spindle 9 . the head spindle 9 is chosen to have an internal diameter large enough to permit the ferrule to be passed through the spindle for mounting in the chuck 8 . with the ferrule 2 mounted in the chuck 8 , the optical fibre cable 1 passes through the hollow head spindle 9 to a former , or reel , 10 onto which the remaining length of the optical fibre is wound . the former 10 is mounted so as to rotate in synchronism with the spindle 9 . a light source 13 is provided adjacent to end 11 of the optical fibre , the end 11 being the end of the fibre 1a remote from the ferrule 2 . the axis about which to machine the surface 6 for it to be concentric with the end 5 of the fibre 1a , is found by shining light into the end 11 of the fibre . the light is transmitted by the fibre , more particularly by the core of the fibre , and emerges as a beam of light at the end 5 of the fibre 1a . the chuck 8 , and hence the ferrule 2 , are then rotated . any offset of the fibre end 5 from the axis of rotation of the chuck 8 is detected , conveniently by means of a microscope ( not shown ) by viewing in the direction of the arrow 14 . with offset , the light emerging from the fibre end of 5 traces out a circle whose centre lies on the axis of rotation . by suitably adjusting the jaws the ferrule 2 is moved across the chuck 8 until rotation of the chuck 8 results in a stationary point of light emerging from the fibre end 5 . it will be readily appreciated that in this position ferrule 2 now rotates about an axis which coincides with the fibre end 5 . a grinding or cutting tool 12 , when brought into contact with the surface 6 of the ferrule will , on rotation of the chuck 8 , effect machining of the surface 6 concentrically with the optical fibre end 5 . in order to facilitate observation , electronic imaging techniques may be employed for observation of the light beam emerging from the fibre . it should be noted here that in practice a jaw arrangement as illustrated in the drawing will frequently prove insufficiently precise to permit exact positioning of the ferrule 2 and recourse to clamping arrangements such as , for example , collets , may be necessary . however , including in the drawing the details of a practical precision lathe arrangement , employing for example , collets rather than moveable jaws , is considered to detract from the principles of the present invention which the drawing is intended to illustrate . the ferrule 2 itself , illustrated in the drawing as a straight sided cylinder , will , in practice , often include flanges , stops and the like , for example , to limit insertion of the ferrule into a socket ( not shown ). connector ferrules made in accordance with the invention have been found to provide sufficiently accurate concentricity for use with monomode fibres , and have been successfully employed in optical fibre connectors of the kind described in u . s . patent application ser . no . 555 , 077 , &# 34 ; connectors &# 34 ;, filed nov . 25th , 1983 .