APPLICATION NOTE 3795

HFAN-09.2.0: Thermistor Compensation for Temperature-Induced Slope Efficiency Variations in PON Burst-Mode Laser Drivers


Abstract: The optical network terminal (ONT) in any passive optical network (PON) system requires a burst-mode laser diode driver. This laser driver must be capable of quickly turning on a laser diode, modulating the laser to send a burst of data, and then quickly shutting down to allow another user to transmit. Since the ONT may be mounted on the outside of a building, it must be capable of robust operation over the full -40 to +85 °C temperature range. There are several integrated circuit burst-mode laser drivers commercially available today. In most cases these burst-mode laser drivers include very effective closed-loop temperature compensation for variations in laser diode threshold current caused by temperature and aging. Unfortunately they generally do not include internal methods for changing their output modulation current to compensate for temperature induced variations in laser diode slope efficiency.