Fiber optic hybrid coherence multiplexed/subcarrier multiplexing (CM/SCM) system for microcellular mobile communications

On the down link for fiber optic microcell systems, the combination of subcarrier multiplexing and coherence multiplexing (CM/SCM) systems is presented. In this hybrid scheme, since each optical channel is modulated by M microwave subcarriers, the bandwidth allocation is very flexible. Moreover, the same microwave subcarrier frequency may be used among the different optical channels, because the optical channels are uncorrelated each other. We derive the received carrier-to-noise ratio (CNR) characteristics of CM/SCM system with an optical amplifier as the preamplifier or in-line amplifier for the optical down link from the central station to the base stations. The CM/SCM system performance is compared with those of coherent SCM (CSCM) and CM systems from the viewpoint of the maximum number of base stations to be admitted