In this paper, we present a simple time-domain traveling-wave dynamic model for the simulation of wavelength tunable three-section slotted Fabry-Perot (3s-SFP) semiconductor lasers. The longitudinal spatial hole burning, the nonlinear gain compression, and the refractive index changes with carrier density are included in this model. The slot structure is characterized by using the boundary conditions of the optical fields propagating through the slot facets. For the first time, the tuning mechanism of the 3s-SFP laser is studied in detail by using the proposed model. Characteristics of the 3s-SFP laser including the lasing wavelength, the side-mode suppression ratio, the output spectrum, and the wavelength switching dynamics are simulated. The potential of increasing the tuning range of the 3s-SFP laser is also discussed by optimizing design parameters of the device. Virtual digital infinite-impulse response bandpass filters with different central wavelengths are developed to examine the mode power of different channels during wavelength switching events. Switching times of approximately 2-5 ns are demonstrated theoretically. Good agreements have been found between the simulation results and the experimental measurements. © 1995-2012 IEEE.