| 摘要 |
In the transmission of digital signals via optical fibres (3) which have a considerable chromatic dispersion at the wavelength used, the length of the transmission link is very limited if the digital signal to be transmitted is converted into an optical signal by means of intensity modulation. If a frequency modulation (also called FSK = frequency shift keying) is used instead of the intensity modulation, the length of the link which can be bridged can be greatly increased but a suitable optical receiver is needed at the receiving end. According to the invention, a simple optical receiver (4) is used which is not sensitive to frequency modulation but to intensity modulation. This is possible because, due to the chromatic dispersion of the optical fibre (3) and resultant differences in transit time of signal components of different wavelengths ( lambda 0, lambda 1), the initial frequency modulation becomes an intensity variation in the course of the transmission via the optical fibre (3), the course of which variation contains the digital signal to be transmitted. <IMAGE> |
