| 摘要 |
A supervising transmitting and receiving circuit for an optical transmission system having a plurality of optical repeaters, each of which includes a pair of up and down side repeating circuits using respective optical amplifiers inserted in an optical transmission link having up and down side optical fibre channels for a two way communication. The circuit comprises a sine wave oscillator 25 producing a carrier, circuit 36 generating pulses which have a width narrower than a time of an optical signal travelling through the spacing between said repeaters, and a period longer than a going and returning delay time of an optical signal travelling the overall length of said optical transmission system, a gate circuit 37 for modulating the amplitude of said carrier by said pulse signal and outputting a pulse modulated signal, a transmission light source 28 for transmitting a communication signal as a trunk channel signal, an optical amplitude modulator 29 for amplitude-modulating said trunk channel signal with said pulse modulated signal to produce a supervisory signal and sending said supervisory signal to an up side optical fibre channel, a photo-detector 30 for converting a returned optical signal into an electric signal, said returned optical signal returned by a group of parallel supervising loopback circuits Aa - An through a down side optical fibre channel, a band pass filter 38 for eliminating noise of said electric signal and an oscilloscope 39 for displaying said electric signals passed through said band pass filter. <IMAGE>
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