Although orthogonal frequency-division multiplexing (OFDM) modulation technology in radio-frequency communication systems has the same principle as OFDM modulation technology in wireless laser-communication systems, there are also significant differences. For example, in an intensity modulation/direct detection (IM/DD) optical communication system, the receiving end can determine the intensity of the optical signal, but not the phase information. The channel condition of optical wireless communication (OWC)-OFDM is even worse, and the attenuation of a laser signal by the atmosphere is much greater than that of a radio-frequency signal. This chapter discusses the IM/DD-type OWC-OFDM system model.