PERFORMANCE IMPROVEMENT IN OPTICAL-FIBER FEEDERS FOR MICROCELLULAR MOBILE RADIO SYSTEMS

This paper reports performance improvement in an optical fiber feeder for microcellular mobile radio systems. A low noise optical receiver u sing a transformer resonant circuit is described. With this receiver, CNR degradation due to receiver noise is suppressed to less than 0.9 d B. Furthermore, two novel techniques, the use of a multiple-LD transmi tter and automatic LD input level control, are proposed. The multiple- LD transmitter increases transmitter output power and reduces the tran smitter noise. With a dual-LD transmitter, it is possible to increase the optical loss margin by 3.1 dB, which corresponds to transmission l ength expansion of 6.2 km, or to improve the received CNR by 2.8 dB, w hich enables communication range expansion. Automatic LD input level c ontrol, which optimizes LD input level according to the received radio power, can expand the actual dynamic range of the up link.