| Summary: | Much interest has recently been expressed in investigating the basic PIN (a diode with a wide, lightly doped between a p-type semiconductor and an n-type semiconductor region). And the more complex, expensive (about 4x the cost of the PIN) and voltage-hungry APD receiver(a highly sensitive semiconductor device that utilizes the photoelectric effect to convert light to electricity. It supplies a builtin first stage of gain through avalanche multiplication.) performances, mainly due to the on-going and high-pressured commercial demands for cost-cutting in systems incorporating these ultra-fast receivers. APD photodetectors have been shown as the better candidate for long haul communications, due to their internal gain availability. In the PIN photodiode, thermal noise plays the dominant role in the performance of the receiver. In the APD, both the thermal and shot noise is significant. In this report, a performance comparison of the conventional PIN photodiode with the Avalanche Photodiode (APD) in an optical communication system is presented. The effects of bandwidth, gain, extinction ratio, shot noise and thermal noise are compared and studied in detail. It was shown that the Q factor produced by each detector is heavily affected by the thermal noise in the PIN device, and by both the thermal and shot noise in the APD. It was also found that the APDs gain plays a significant role, and the shot noise has to be carefully dealt with. Additionally, the relationship of receiver sensitivity with thermal and shot noise was investigated and compared.
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