RADIO OVER FIBER SYSTEMS: EFFECT OF LASER AND RF OSCILLATOR PHASE NOISES ON THE PERFORMANCE OF QAM SYSTEMS

Abstract

The Radio over Fiber systems have of late emerged as the most promising solution for distribution of the radio signals between the base station (BS) and the mobile switching center(MSC) owing to its low cost, reduced complexity at the BS, centralized signal processing and high mobility combined with the high fiber bandwidth low loss over the fiber. However since the fiber channel is prone to the dispersive effects, any signal launched along the fiber will, due to the dispersive nature of the fiber, have phase noise added to it. This phase noise will affect the performance of the channel and will degrade the Carrier to Noise Ratio (CNR) and hence the Bit error Rate (BER) of the signal launched in the fiber. The phase noises arise due to the finite spectral widths of the laser diode and the RF oscillator. Further the most promising modulation scheme for the sub carrier modulation (SCM) transmission over the fiber is Qaudrature Amplitude Modulation (QAM) due to its high spectral and pow...