The effect of defocus blur on a spatial OFDM optical wireless communication system

Imperfect focusing of the receiver can be an important impairment in MIMO optical wireless systems using imaging receivers. This paper investigates the effect of defocus blur on an optical wireless system using spatial orthogonal frequency division multiplexing (OFDM). It is shown that when defocus blur is the only impairment, and when transmitter and receiver are perfectly aligned, the defocus blur causes the received constellation points to be attenuated. Simulation results show that the signal-to-noise ratio (SNR) penalty caused by defocus blur is less for a system using spatial asymmetrically clipped optical OFDM than for one using spatial DC biased optical OFDM.