In this study, four-tone small signal analysis is performed for non-linear optoelectronic feedback laser diode system. In the analysis, after expanding the Volterra power series up to second-order, the second kernel (Z2) for the output intermodulation distortion (IMD) analysis is performed. The components which are 1. (ω0+ω1), (ω0- ω1) 2. (ω0+ω2), (ω0-ω2), 3. (ω0+ω 3), (ω0-ω3) and 4. (ω0+ω4), (ω0- ω4) among the alternative IMD frequencies are selected for the analysis. The amplitudes of the selected IMD frequency components are analysed depending on the time delay constant (t0) and the feedback gain constant (K). The critical frequencies (coherence collapse, chaos), and the critical feedback values are also determined.