High-Speed Photodetectors: Bit Error Rate and Eye Diagrams

This lecture introduces the concepts of bit error rate (BER) and eye diagrams in high-speed photodetectors. It begins with the definition of BER as the probability of incorrectly identifying bits during transmission. The instructor explains the ideal BER, which is influenced by optical shot noise, and discusses the necessary number of photons required to achieve specific BER levels. The lecture then transitions to real receiver sensitivity, highlighting the impact of Gaussian noise on performance. The Q parameter is introduced as a measure of signal quality, linking it to the BER through error functions. The instructor also covers the analysis of eye diagrams, which visually represent signal integrity and can indicate issues such as jitter and signal degradation. The importance of maintaining an open eye diagram for effective transmission is emphasized, along with practical examples of eye diagrams at various data rates. Overall, the lecture provides a comprehensive overview of the factors affecting the performance of high-speed optical communication systems.