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Wednesday, February 25, 2009

Nonlinear Effects in an OFDM-RoF Link

Nonlinear Effects in an OFDM-RoF Link

Abstract

Integration of orthogonal frequency division multiplexing (OFDM) and radio over fiber (RoF) technique emerged the possibility of cost-effective and high data rate ubiquitous wireless networks. As because OFDM is a combination of few subcarriers; resulting OFDM signal contains large peak to average power ratio (PAPR). The level of non-linear distortions largely depends on PAPR of an input signal led to a power amplifier (PA). RF power amplifier over a large dynamic range is also desired as high PAPR ratio reduces the power efficiency of the system. Hence, this work investigates the distortion effects of OFDM signals fed via an RF amplifier integrated with an RoF link employing electro absorption modulators (EAM) as a receiver for broadband in-building network applications. Firstly, adjacent channel power ratio (ACPR) (which estimates the degree of spectral re-growth due to the in-band and out-of-band interference resulting from distortion effects upon nonlinear amplification) is observed for the proposed system. Later, the dependence of PAPR and SFDR on the number of subcarriers of OFDM signals over RoF links integrated with an RF amplifier is examined. A complete analytical model of the OFDM-RoF system is also simulated and a closer agreement is reported for the distortion effects experienced in the system. To the best of knowledge, until now, the distortion effects of OFDM signals over RoF links integrated with an RF amplifier and EAM have not been reported with consideration of the distortion parameters as mentioned above. Therefore, this research will be helpful to determine design requirements for suitable picocell and microcell RoF applications in the future.

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