• Design and implementation of photodiode-based receiver systems for a 1574 nm eye-safe lidar

      Yue, Jia (2004-08)
      In this thesis we present the design, implementation and testing of a photodiode-based receiver systems for a 1574 nm eye-safe lidar. The specific goal of this thesis was to precisely and accurately convert and amplify nW optical signals into robust mV voltage signals. The receiver system incorporates both analog and digital circuitry and a software-based digital processing system. Four analog circuits were constructed and tested using both PIN diodes and APDs, and two high-speed commercial op amps. A single high-speed digital processing system was tested with each of the analog circuits. The analog circuitry was found to be the fundamental limitation on the performance of the system with the receiver bandwidth limited to -6 MHz for the PIN-based systems and -14 MHz for the APD-based systems. Inherent oscillations in the analog circuits were successfully removed using digital filtering techniques in the software-based digital processing systems. Furthermore, the APD-based systems had less rms noise than the PIN-based systems. The lidar receiver system could support measurements with a maximum resolution of 10 m and a range of up to 40 km.