An optical receiver for hybrid SCM video distribution systems that distribute AM, QAM (quadrature amplitude modulation) and FM TV signals simultaneously is investigated. We propose a novel receiver configuration called the Frequency Division type Receiver (FDR) with consists of a photo detector, filter, and multiple preamplifiers. The receiver is compared with existing receivers in terms of optical sensitivity, distortion characteristics, and configuration simplicity. We clarify that the newly developed FDR type receiver is most suitable for hybrid SCM video distribution systems.

This paper describes the impact of EDFAs on AM/FM FDM subcarrier multiplexing (SCM) all-fiber video distribution (AFVD) systems. As AM/FM hybrid system using EDFAs which can simultaneously distribute 11 AM-TV channels and 50 FM-TV channels is proposed and discussed. 4-stage amplifier-branch transmission experiments are introduced. The construction and performance of a newly designed 50 channel FM tuner are also presented.

Fiber loss fluctuations due to manual handling are sometimes inevitable when it comes to touching cable connection points during maintenance and operational activities. These fluctuations cause momentary input optical power changes and give raise to bit errors in receivers. This phenomenon is a serious problem for fiber optic subscriber systems in which cable construction and maintenance frequently take place. Measures to counter this degradation have to be considered to realize stable transmission characteristics. As a result of this consideration, the loss fluctuation tolerance of digital optical receivers has been investigated for fiber optic subscriber transmission systems. From the viewpoint of design and adjustment, the most effective method to solve the fluctuation problem is to adopt d.c. balanced transmission line coding. A receiver having an optimum low cutoff frequency for this type of coding performs well against fiber loss fluctuations without adjustment for special operational conditions.