Abstract: A fibre optic terminal (1) for use with a bi-directional optic fibre (6) including an optical receiver (2) positioned in the path of light (8) emitted from an end (5) of the optical fibre to receive the light, and an optical emitter (4) arranged to emit light (7) from a position adjacent the optical receiver onto the end of the optical fibre, the position being in the path of light emitted from the end of the optical fibre so that substantially all of the light emitted from the optical emitter is incident on the end of the optical fibre, and the area from which the optical emitter emits light being small relative to the light receiving area of the optical receiver so that substantially all of the light emitted from the end of the optical fibre is received by the optical receiver.

Abstract: A data transmission system including a transmitting station (13 to 15 and T) wherein three-state signals representing data are converted to two-state signals so that the data can be transmitted via a transmission line adapted to transmit only two-state signals such as a fibre optic transmission line.

Abstract: A multi-access fiber optic communication system in which each terminal of the system is directly connected with n other terminals of the system via point-to-point transmitting and receiving links and each terminal of the system includes regenerating means whereby a signal received by that terminal is re-transmitted to the other n terminals. The signals are pulse signals and the regenerating means are arranged to re-transmit a received pulse in response to the leading edge of a received pulse.

Abstract: A method and apparatus for testing a ferruled termination of a fibre optic cable by illuminating the active optical area of the cable at the end of the cable remote from the termination and successively measuring through a series of apertures of different area aligned with the ferrule the light energy output from said termination. The apertures may be provided by a series of apertures in a plate or may be provided by a shutter having an opening which may be discretely set to each of the apertures.