| 摘要 |
A data transmission system uses a single optical fibre highway (4) for data transmission on a bi-directional basis. The two directions of transmission are separated on a bi- directional basis, and each terminal only has one light detector (7), which is so coupled to the highway via optical couplers (2, 3, 1) that it can receive light from either direction. The central circuitry (8) of the terminal is also connected to a light source (6), which supplies light for an outgoing message to both directions. The timings are such that messages can pass simultaneously in both directions through the highway, being interlaced in time when arriving at each terminal's receiver. Each message traversing the system is regeneratively repeated at each station via which it travels. Two of the couplers (2, 3) are also connected via a low-loss bypass (10) which is normally disabled, but is rendered effective when the terminal fails, so that continuity is maintained. In a second version of the system, separate light sources are provided for the two directions of transmission and continuity is maintained if a terminal fails via an attenuator between that terminal's optical couplers. <IMAGE>
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