Frequency domain equalization of optical channel distortion in free-space optical wireless communications

Abstract

In digital communications, as an alternative to conventional time domain equalization (TEQ), frequency domain equalization (FEQ) has been of interest, in particular for OFDM. In any optical channels, such as in fiber optic transmission or free-space optical communications (FSO), there can be channel dispersion, causing intersymbol interference (ISI). One feasible solution to this is FEQ of the distorted light signal by established theory of equalization. A new idea is presented that examines possibility of adaptive optical frequency-domain pulse shaping and equalization to remedy the optical channel dispersion problem in the light spectral domain.

Development of a Transient Magnetic Field Sensor Based on Digital Integration and Frequency Equalization

“…Analog equalization has the disadvantages of limited bandwidth, weak anti-interference ability, and lack of flexibility and is not suitable for the transmission of transient signals. Wei designed a digital amplitude-frequency equalizer to make the power amplifier fluctuate less than 1 dB in the 20-20 kHz [11], whereas Kavehrad [12] and Falconer [13] used digital equalization for OFDM to improve communication efficiency. In indoor visible light communication, Long used carrier-free amplitude-phase modulation with digital filtering and frequency equalization technology to reduce the complexity in the system [14].…”