| 摘要 |
An optical amplifier or transmitter which is shut down for a preset time when the absence of an input signal is detected. The optical amplifier comprises a doped fibre 274, a pumping light source 278, interception detection means 268,270 for detecting that inputting of the signal light to said doped fibre is intercepted, a photo detector 284 for detecting the intensity of light outputted, automatic level control means 288 for supplying a controlling electric current to said pumping light source 278 so that the output level of said photo detector 284 may be fixed, and shutting down means 266 for intercepting the input to the doped fibre 274 for a predetermined period of time in response to an output signal from said interception detection means 268,270. This prevents an optical surge. The transmitter is constructed similarly. Embodiments that intercept the output are also disclosed. |
