A popular approach to stabilize the output intensity is to first convert the photodiode current to voltage. This voltage can then be read by a microcontroller, where logic can be programmed to adjust the current supplied to the laser diode. SLDs, however, are prone to pathological drifts, such as temperature variations and mode-hopping, that can. Automatic power control (APC) in laser drive systems is designed for a stable and efficient laser operation by continuously regulating optical output power of the laser. In this experiment, we will develop an understanding of how a laser diodes optical power and wavelength can be varied by controlling its temperature and operating current.