A combined model of the transmission-line laser model (TLLM) and the digital filter approach is developed to simulate the shuttering characteristic of a semiconductor optical amplifier (SOA), which is integrated with a sampled grating distributed Bragg reflector (SGDBR) laser, to create a so called SOA-SGDBR laser. The SOA section acts as a shutter to blank the laser output during wavelength switching events. Simulated results show that the turn-on edge of the SOA blanking process will oscillate when the facet reflection of SOA is relatively high. This phenomenon is also observed by experiments.