Design Considerations and Experiments on Long-Distance Transmission for Digital Terrestrial Broadcasting Waves Using Optical Fibers

Numerous TV relay stations are required for digital terrestrial broadcasting services in mountainous regions and these are expensive to construct. To reduce their cost, we propose a system that can retransmit UHFband terrestrial digital TV signals (OFDM signals: nine channels) sent via long-distance (340km) optical-fiber networks. Weverified its exceptional performance through experiments. This system uses an LD direct optical modulator to reduce the construction costs and has a high equivalent C/N of about 40dB and very low distortion, which are traditionally considered to be very difficult to achievewith direct modulation. We attained these by adopting an optimum design to acquire a high C/N and wavelength dispersion compensation to transmit the OFDM signals.