Analysis of effective power budget in optical bus and star networks using erbium-doped fiber amplifiers

Passive optical bus networks have been considered to be inferior to star networks because of their poorer power-loss characteristics, which means that they can support fewer stations than a star. This paper studies the use of erbium-doped fiber optical amplifiers (EDFAs) in bus and star networks. We determine the number of stations that can be supported with and without amplifiers in a single folded bus, a double bus, and a star. For a typical case, when only one station on the bus is allowed to transmit at a time, as is the case in a time-division multiplexed network, the number of stations that can be supported with amplifiers is of the order of several thousands. However, this number drops to less than a thousand when all stations are allowed to transmit simultaneously on different channels in a wavelength-division multiplexed network, because of amplifier gain saturation. In the former case, the bus has the potential to outperform the star, but in the latter case, the star topology is still better.