| 摘要 |
There is described an optical free-space signalling system for signalling between a distribution node and a plurality of remote terminals. Each of the remote terminals includes a light source, a lens system for directing light emitted by the light source to the distribution node, and a detector which detects a modulated light beam from the distribution node and generates an electrical signal which varies in dependence upon data conveyed by the modulated light beam. The distribution node comprises a main receiver for receiving data to be transmitted to the plurality of remote terminals, and a plurality of separate modulator units. Each modulator unit has a housing which supports a retro-reflector which reflects light received from a corresponding remote terminal back to the corresponding remote terminal, and a modulator which modulates the reflected light in accordance with received data to form the modulated light beam. By using plural modulator units, the functionality of each individual modulator unit can be simplified. |
