The static and dynamic multiplication factor in avalanche photodiode optical receivers

By applying two different methods we analyze the nonlinear network which determines the multiplication factor M (t) of an avalanche photodiode (APD) in an optical receiver. For the special time dependence of incident light power we give numerical results and approximate analytic expressions for the dc and ac component of the multiplication factor M. We then discuss amplification fluctuations in analogue optical receivers for both constant current and constant voltage biasing of the APD. A constant current biased APD amplifies temperature and signal independently, if the received mean optical power is constant (PPM, FM). In case of modulation schemes with signal dependent mean optical power (PFM, IM), a constant voltage biasing is more suited, although an AGC circuit is required now in order to compensate for the temperature-dependent amplification.