Driving modes of laser driver

The main function of laser driver is to enlarge high speed signal outputted by a multiplexer to drive the laser diode to work effectively.

Figure 1.The modulation modes of laser driver

Subsequent circuit of laser driver is light emitting device and there are two driving modes to drive it, as shown in the figure 1. One is directly working on laser diode. The main principle is to change the input current of laser diode and then the required optical digital signal is generated, which is called direct modulation. The generation and modulation of light wave are both completed in this method. It is easy to implement this driving mode and this node has simple equipment, low cost and wide bandwidth, etc.

The other diving mode is indirect modulation. Generally speaking, by using electro-optic crystal modulator, modulation in the external light source can be realized and the continuous wave of laser driver is modulated by transmission digital signal in the electro-optic crystal modulator. The advantage of external modulation is that it can reduce Chirp effect that is the maximum factor to block bit rate increase, so as to obtain higher bit rate and further transmission distance.

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