SSBI Mitigation in A-RF-Tone-Based VSSB-OFDM System With a Frequency-Domain Volterra Series Equalizer

The analog domain generated radio frequency-tone (A-RF-tone)-based virtual single sideband (VSSB) direct detection (DD) optical orthogonal frequency division multiplexing (OFDM) scheme is employed to eliminate the residual RF-tone image and substantially improve the signal quality after digital-to-analog converter. The VSSB signal is generated by electrically combining the baseband OFDM signals with sinusoidal waves without a frequency guard band to maximize the electrical and optical spectral efficiencies. The input-output relationship of the VSSB DD-OFDM system is represented and modeled as a second-order nonlinear kernel function by using the theory of Volterra series for the first time. The theory of Volterra inverse for the nonlinear system is introduced to analyze and mitigate subcarriers-to-subcarriers beating interference. In this paper, we further compare and analyze the inherent relationship between the iteration interference cancellation technique and Volterra postinverse equalizer, and that between symbol predistortion algorithm and Volterra preinverse equalizer. The analysis results show that the iteration interference cancellation technique can be considered as a second-order Volterra postinverse equalizer with iterative decision feedback, and symbol predistortion algorithm as a special designed second-order Volterra preinverse equalizer with iteration and step size control.