A.M. carrier transmission method - uses signals which are modulated on bunched signal channels and transmitted through optical fibres

摘要

Pulse frequency modulation is used for transmission of analogue signals. A voltage controlled oscillator is used in the transmitter which has limited output amplitude, and which is connected to the light producing device at the end of the glass fibre line. The pulse frequency modulated signal is reconverted by the light receiver and is applied to a phase controlled loop consisting of connected in cascade phase shifter, low-pass filter and a voltage controlled oscillator. The pulse frequency modulated signal is applied to one input of a phase comparator and the voltage controlled oscillator output is applied to its other input; the low-pass filter output signal is the demodulated frequency modulated signal.