This paper presents a potential FM double modulation technique for subcarrier optical transmission in order to improve the input dynamic range. The proposed theory of FM double modulation is presented. The BER performance and input dynamic range are shown theoretically and experimentally compared with conventional direct intensity modulation. It was found that the dynamic range could be experimentally improved by 20dB compared with the conventional method by using FM double modulation. The proposed technique achieved an input dynamic range of 60 dB even when using a commercial Fabri-Perot LD.

This paper describes a fiber-optic microcell radio system with a spectral delivery switch to meet traffic demands. Optical link performance is discussed from the view points of link loss and noise figure aimed at system design. The theoretical carrier-to-noise ratio (CNR) performance is shown as a function of the input electrical power of the laser and the received optical power. Improvement of dynamic range defined by both CNR and intermodulation distortion is proposed by using the frequency modulation (FM) technique. The experimental results using the proposed technique indicate that the performance is much better than that of conventional methods. Moreover, economical diversity planning delivery methods over fibers are presented. This strategy will provide more cost effective and flexible networks.