光学前端系统参考设计

　　此参考设计可实现并测量完整的120 mhz高带宽光学前端;这种前端由高速跨阻放大器、全差动放大器和高速160位议员ADC（具有JESD204B接口）组成。设计中提供了相应的硬件和软件，用于评估该系统对于随附激光驱动器和二极管产生的高速光脉冲的响应性能，适合具有光时域反射（OTDR））的应用。

　　A high-speed laser driver pulses the laser diode that transmits an optical pulse through the fiber. The optical attenuator controls the strength of the optical pulse incident on the photo-diode without changing the operating point of the laser diode or its driver. A high-speed photodiode placed in close proximity to the transimpedance amplifier converts the optical energy into an output current. The transimpedance amplifier converts the current into a pseudo-differential output voltage. The subsequent fully differential amplifier （FDA） stage converts the signal to a fully differential signal and level-shifts the output commonmode to match the ADC. The FDA drives the ADC through a doubly terminated 50-Ω resistor.