光學前端系統(tǒng)參考設計

　　此參考設計可實現(xiàn)并測量完整的120 mhz高帶寬光學前端;這種前端由高速跨阻放大器、全差動放大器和高速160位議員ADC（具有JESD204B接口）組成。設計中提供了相應的硬件和軟件，用于評估該系統(tǒng)對于隨附激光驅動器和二極管產生的高速光脈沖的響應性能，適合具有光時域反射（OTDR））的應用。

　　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-? resistor.