Direct Modulation Laser Driving Circuit for High-speed Optoelectronic Interconnection

Abstract

The invention belongs to the technical field of chip design, and relates to a direct modulation laser driving circuit for high-speed optoelectronic interconnection, comprising: a first matching resistor, a second matching resistor, a transistor M1 and a transistor M2; when the transistor M1 is closed, and the transistor M2 is off When on, the drive current of the laser diode is I 1 ; When the transistor M2 is closed and the transistor M1 is open, the driving current of the laser diode is I 1 +I 2 , for: modulation. The application provides impedance matching through matching resistors on both sides of the laser diode, suppresses the reflection of high-speed signals, and improves signal quality; controls the switches of a pair of high-speed CMOS transistors through high-speed differential input signals to obtain different driving currents, thereby obtaining rapidly changing Optical signal, realize modulation of optical signal.

Description

technical field [0001] The invention belongs to the technical field of chip design, and relates to a direct modulation laser drive circuit for high-speed optoelectronic interconnection, in particular to a direct modulation laser drive circuit for high-speed optoelectronic interconnection based on CMOS technology. Background technique [0002] The technical scheme of the prior art one related to the present invention is briefly described as follows: [0003] figure 1 It is a schematic diagram of the structure of a DC-coupled drive circuit. The output of the drive circuit is connected to the cathode and anode of the laser diode LD through two resistors. The cathode of the laser diode LD is directly biased to the power supply, and a current source is connected to the anode to control the DC current. The bias current and the modulation current of the laser diode LD are determined by the tail current of the transistor in the left drive circuit. The structure of the DC-coupled d...

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Problems solved by technology

[0005] The problem with the DC-coupled drive circuit is that it is difficult to achieve a high modulation current when the laser diode needs to be driven at a relatively high rate; for example: when the power supply voltage is V DD , for a data rate of 25Gbit / s, the maximum modulation time for the current to rise from the bias to the peak value is 20ps, and the modulation current I mod is 60mA, the equivalent resistance R of the laser diode D is 20 ohms (including the packaging resistance), assuming that the waveform is symmetrical, the equivalent resistance R of the laser diode D The instantaneous voltage change across V L As shown in formula (1),

[0013] Compared with the DC-coupled drive circuit, the design margin of the AC-coupled drive circuit structure is larger, but it introduces additional capacitance and inductance. For high-speed paths, it may cause signal distortion, so the requirements for circuit matching are higher.

In addition, the coupling capacitor in the structure of the AC coupling drive circuit will have a certain impact on the jitter of the system, and its capacitance value needs to be set large enough to reduce the above impact, but at the same time it will have an impact on the bandwidth of the AC coupling drive circuit , the above factors should be fully considered in the design, which increases the difficulty of the design

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