Four-tone small signal analysis was performed for a nonlinear optoelectronic feedback laser diode system. In the analysis, Volterra power series up to second-order opening, the second kernel for the output intermodulation distortion (IMD) analysis was performed. The components of the alternative IMD frequency were selected for analysis. These are the four IMD frequency components. The variation of IMD frequency component amplitudes was investigated under various values of delay-time (to) and the feedback gain constant (K). The feedback values and the critical frequencies, at which the coherence collapse or chaos occur, were also determined.