A NEW FREQUENCY SWITCHING IM3 REDUCTION METHOD IN FIBEROPTIC MICROCELLULAR SYSTEM

Fiber-optic microcellular system has been studied actively as an excel lent system for solving the equipment cost problems in microcellular s ystems. However, the occurrence of intermodulation distortion (IMD) ar ising from the nonlinearity of the laser diode used for E/O conversion which degrades the transmission quality is a serious problem in this system. In this paper, we propose a new frequency switching/IM3 reduct ion method, which dynamically reassigns the carrier frequencies to min imize the carrier to IMD power ratio under the hostile environment wit h time-varying received carrier strength, and analyze the performance improvements by the proposed method. The improvements obtained both fo r the worst value of the overall CNR and for the overall CNR in a spec ific user are numerically made clear. It is also shown that if the int erval between frequency reassignings is set less than one second, a su fficient improvement in the overall CNR is achievable.