We propose a wavelength-converting optical-space switch in a Mach-Zehnder interferometer based on the semiconductor optical amplifier (SOA), and its pulse characteristics in the time domain are investigated theoretically. The cross phase modulation and the gating function in the SOA are utilized for a wavelength converter and optical space switch. The output pulse shape of the switch is varied for different injection current patterns, current levels, and probe power levels. To reduce the switching time, exponential current injection into the SOA is preferred to the cw current. The influences of the probe power and bias current of the wavelength converter on the switching characteristic are investigated, including the dynamics of the wavelength converter.