To assess the quality, performance, and characteristics of laser diodes, manufacturers often perform exhaustive testing which requires electro-optical, spectral and spatial characterization of the laser output. It explains why testing is essential at various stages, from development and manufacturing quality control to the burn-in process for eliminating. It is often necessary to quantitatively assess the quality, performance, and characteristics of laser diodes. This is done through performing a series of experiments and obtaining certain significant parameters from which we can determine how well the laser diode is performing. Usually, a “laser diode module” is a combination of a laser diode and a photo detector (PD). A laser diode's output is dependent on its injection current and temperature.