A Laser Driver Chip For Fast Establishment Of Up-current Laser Emission Power

The 21 st century is an era of rapid development of information transmission.Optical fiber communication system has become an important carrier of information transmission.Its various technologies are approaching maturity.Only the backwardness of access network technology restricts the domestic communication level.PON(Passive Optical Net)has become an important way to solve the backward technology of access network.Whether the laser can start quickly during the photoelectric conversion in access network technology is related to the network transmission speed and bandwidth utilization efficiency.The driver chip which can quickly set up the bias current to speed up the laser startup is the key to increase the network data transmission and bandwidth utilization.Therefore,it is important to study the fast and stable laser driver chip.This paper uses 0.25?m CMOS technology,designed a laser driver chip which can be applied to the GPON-ONU scene to quickly establish bias current during circuit start-up,can solve the problem that the GNC2800 chip cannot be used in high-speed communication scenarios because of the slow time of setting up the bias current.It consists of three modules: current comparator module,digital circuit module and analog-to-analog converter module: current comparator module uses twoterminal Wilson current source input structure,differential structure output,which can speed up the comparison time and improve the comparison accuracy.The digital circuit module uses a fast start algorithm,which can realize the dichotomy search mode and fine-tuning mode,guaranteeing that the search time is less than 400 ns.Even if the output power of the laser decreases due to temperature or aging,the digital circuit module can establish the specified bias current quickly and stabilize the output of the laser at the same time.The digital-to-analog converter module uses a piecewise 8-bit current rudder structure,the high six bits use thermometer codes,and the low two bits use binary codes.The converter includes decoding circuit,latch circuit,band gap reference circuit,bias circuit and current source array,etc.It has high output accuracy and anti-interference.The design circuit is simulated by EDA tool.The results show that the laser driver chip designed in this paper can establish a stable start-up bias current within 400 ns at 10 MHz.The simulation results of three modules inside the chip show that each module has normal functions,good performance,meets the design requirements,and can be used in GPON-ONU scenarios.