APC Design Of 2.5Gb/s Burst Mode Laser Driver For 10G PON

Due to the development of optical communication technology,the domestic backbone network has achieved digitization,broadband and fiberization.The establishment of high-speed and high-data capacity transmission systems has led to the continuous improvement of optical fiber communication systems,and the progress and upgrade of optical fiber subscriber access network technologies.The mismatch has largely limited the use of Internet features.As a solution to the access network,PON(Passive Optical Network)is accepted by global optical communication manufacturers.Its uplink non-burst mode and burst module are related to bandwidth utilization and network transmission rate,so a high-performance laser driver is introduced.It is significant to operate in asymmetric burst mode and non-burst mode.For burst mode drivers,the APC-Automatic Power Control must be selected because the power adjustment must be achieved in the very short time that the initial burst signal arrives,and the system must be stable before the burst signal arrives.Normal data transfer.High-power lasers must use large semiconductor devices and therefore have high input capacitance,which makes the design of high-speed laser drivers difficult.The laser output power determines the maximum allowable attenuation in the fiber and the sensitivity required by the receiver.For the shortcomings of power control related circuits,the paper uses SMIC 0.18um technology to design a 2.5G bps laser driver for 10G PON with digital average automatic power circuit.Ensure that the laser driver has a large output power,select the laser diode as the light source,and design the laser driver in burst mode according to its characteristics.The driver core circuit consists of a polarity inversion circuit,a burst enable circuit,and a modulation/bias circuit that provides bias current,bias voltage,and internal power conversion.The laser is a current-controlled light-emitting device.When the driving current is greater than the threshold current,the laser diode will work.The threshold current varies with temperature and lifetime.To ensure the stable output power of the laser driver in burst mode,an automatic power control circuit(APC)is designed.In the average automatic power module circuit,the fast start algorithm is selected,including coarse adjustment(ramp mode adjustment and binary adjustment)and fine adjustment to reduce the burst open time of the circuit,which is less than 5 ns.Because the temperature and device aging make the bias current not stable in the circuit,the programmable circuit compensates for changes in the laser characteristics,and the external current source is adjusted to compensate for the effects of temperature and device aging.When the burst signal is turned off,the automatic power control circuit can accurately maintain the bias current.A 10-bit R2R DAC(Digital to Analog Converter)is designed at the APC output.When the next burst signal arrives,it can be quickly Establish a stable APC loop.The Cadence spectre software and professional software were used to simulate the burst mode circuit structure introduced in this paper.The maximum rate is 2.5G bit/s,the modulation current is 100mA,the bias current is 80mA,the eye pattern is good,and the burst enable is coming.The system responds quickly,the average automatic power remains within the dynamic range of the design value,and the high-low temperature test of the optical module of the optical chip burst mode laser driver is designed,and the data meets the requirements to meet the design requirements.