| 摘要 |
To transmit analog modulated signals via an optical transmission fibre (such as AM-modulated TV signals via a local optical network), it is important that the noise is minimal. External modulation of the laser signal (a) is therefore preceded by filtering out the noise signal at least in the frequency range of the modulation signal (m), with the result that the modulated signal (c) is free of noise. The occurrence of distortion as a consequence of external modulation by means of, for example, a Mach-Zehnder modulator is compensated for by adding the harmonics normally introduced by such a modulator to the modulation signal in phase opposition. <IMAGE> |
