| 摘要 |
This invention relates to photonic amplifiers, e.g. fibre amplifiers, which are specially suitable for use in long distance telecommunications optical linkages. The amplifier includes an optical transmitt er, which is adapted to provide to the output of the amplifier a default signal which is digitally modulated and the digital modulati on includes the identity of the amplifier. The default fault condition is constituted when the traffic signals fall below a preset leve l, e.g. in the case of a cable break when the signal falls to zero. In a preferred embodiment, the traffic signals are modulated with a control tone which is used to control the AGC's of the telecommunications link. In this system, the default condition is constit uted when the level of control tone falls below a predetermined level, and the default signals also contain control tone, so that subsequent amplifiers are held out of default state.
|
