Laser is a kind of light source components. In actually,
drive circuit refers to modulation circuit of light source device, which plays a role of converting digital signal to optical pulse signal and then sending to fibers. This part is the core of optical transmitter, which decides many important technical parameters.
As shown in figure 1, the main function of laser drive circuit is to provide appropriate bias and modulation current for laser diodes, which can make laser work normally. Thereinto, the bias current is constant and it can make laser diodes always work in linear region above the threshold current; the modulated current is constantly changing and with the change of the input voltage waveform, it can do the synchronous switch operation. The threshold current and the slope efficiency of semiconductor laser are closely related to its structure, fabrication process, manufacturing materials and working temperature. Ideally, laser bias current should change with the threshold current in the same direction. The modulation current will reversely change with the change of slope efficiency.
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