REDUCTION OF OPTICAL-FIBER LINES IN FIBEROPTIC SCM TRANSMISSION FOR RADIO BASE STATIONS

To meet the increased number of radio base stations (BSs) in fiber-opt ic microcellular radio systems, less expensive fiber-optic transmissio n methods are now being studied. In this paper, we propose a novel opt ical transmission method for reducing optical fiber lines for an SCM ( sub-carrier multiplexing) optical transmission system between the BSs and mobile control center (MCC) in a mobile telephone system. In our m ethod the signals of three sectors are frequency converted and a frequ ency division multiplexed to one signal stream, which is then through- transmitted through one optical fiber. Using this technique with wavel ength division multiplexing (WDM), the number of optical fiber lines i s reduced to two for nine signals of three sectors. The optical link p erformance is discussed from the viewpoint of third-order distortion a nd carrier-to-noise ratio (CNR) for system design on the basis of the proposed new evaluation method. The results indicate the possibility o f achieving the same performance of the new system as in conventional systems by utilizing one newly developed semiconductor laser which tra nsmits the frequency multiplexed signal. (C) 1998 Scripta Technica.