Design considerations for PPM PIN-BJT receivers

Considers the design of a common-collector-cascode PPM PIN-BJT receiver. An expression is derived for the optimum first stage collector current, Iˆ_c1, that minimises the noise spectral density whilst employing a first order noise whitening filter. It is shown that, due to the occurrence of wrong slot errors which are inherent to this modulation format, this does not necessarily give the optimum receiver sensitivity. Sensitivity calculations show that, when operating at a bit-rate of 50 Mbit/s and a wavelength of 1.3 μm, this PPM PIN-BJT system can offer a sensitivity improvement of 6 dB when compared to a commercially available PCM transimpedance PIN-BJT receiver