An optical fibre probe

A fibre optic probe has a probe tip 86 with a smooth face in which lies the extremity of three optical fibers and an axially extending key 94 adapted to ride on a ramp to, and mate with, a notch (48, Fig. 5) to prevent relative rotation between the tip and a side arm. The probe includes the three optical fibers, and a collar 56, the collar including a pair of camming slots 60 circumferentially spaced 180{ for co-operation with the (50, Fig. 5) of a receptor, each of the slots including a first portion (62, Fig 5) angularly related to the axis of the collar to on rotation in a first direction drive the ears towards the collar and a second portion (64, Fig. 5) angularly related to the axis to on rotation drive on the side arm ears away from the collar, and a pair of longitudinally extending grooves 58 for co-operating with the ears to allow their movement into the slots 60. The probe further includes spring support means (74, Fig. 8) and spring means 102 biasing the tip away from the collar. A junction of three plastics optical fibres in also disclosed.