An optical transmitter that outputs an optical signal with a pulse amplitude modulation (PAM) configuration is disclosed. The optical transmitter includes a light-generating device and a driver. The light-generating device has non-linearity in a transfer characteristic between the electrical driving signal and the optical signal. The driver includes a PAM signal generator, a level controller, and an output driver. The PAM signal generator receives the input electrical signal and outputs a PAM signal. The level controller adjusts the electrical levels of the PAM signal based on the non-linear transfer characteristic of the light-generating device, where the electrical levels set the optical levels of the optical signal with preset ratios. The output driver generates the driving signal by superposing the electrical levels adjusted by the level controller with the PAM signal provided from the PAM signal generator.