The modulation characteristics of wafer-fused long-wavelength vertical-cavity surface-emitting lasers (VCSELs) for multichannel microwave-band analog signal transmission were investigated within a large-signal behavioral model based on a commercial microwave electronic computer-aided design (E-CAD) tool. To enhance the fitting precision, a step-by-step extraction procedure is implemented numerically, optimizing at each step no more than five parameters. The simulation and experimental results of intermodulation distortions are in perfect agreement.