Abstract: The invention relates to a plug connection for a mobile optical multi-thread plug part (2, 3) which comprises various adaptive means. The adaptive section (PA1) of the first adaptive means (6, 8) is longer than the adaptive section (PA2) of the second adaptive means (7, 9) in relation to the longitudinal axis thereof. The adaptive means (6, 7, 8, 9) are embodied in such a manner that initially the first adaptive means (6, 8) and then the second adaptive means (7, 9), after surpassing an insertion path, can be impinged upon by associated guiding means of the plug part, when the plug part (2, 3) is inserted.

Abstract: Device for measuring the concentricity of the core 21 of an optical fiber 19 relative to a reference axis 22, comprising a means for determining the position of the intersection of the reference axis 22 with an optical face 23 on the end of the optical fiber 19, a means 17 for injecting light into the core 21 of the optical fiber 19, an objective 30 and a means 4 for observing, in a plane 5 conjugate with the optical face 23, the light emitted by the core 21 of the optical fiber 19, characterized in that the objective 30 has a numerical aperture sin ? smaller than the numerical aperture sin ? of the optical fiber to be measured.