Analog signal transmission over optical waveguides

The paper discusses some of the possibilities existing at the present for using an optical communication system for transmission of analog signals, such as a phase-alternating line TV signal, over short distances around 5 km. On the transmission end, the best device at present is a GaAlAs semiconductor in the form of a light-emitting diode at 820 nm. On the receiving end, photodiodes with or without cascade effect are available. When the ratio of the available transmission bandwidth to the signal bandwidth is small, phase or frequency modulation is recommended, and for the case of TV signals, frequency modulation is preferred over phase modulation. For higher transmission to signal bandwidth ratios, pulse modulation methods are suitable. An experimental PAL-TV transmission circuit containing 10 fibers for a length of 2.1 km with frequency modulation has demonstrated that transmission up to about 5 km without relay amplifier is possible.