Gain-flattened two-segment SOA for WDM optical communication systems

We present the design and characteristics of a two-segment semiconductor optical amplifier (SOA), whose segment lengths and bias current ratio are optimized for application to in-line amplification of 8 WDM channels in the C-band of optical communication. We show that the gain flatness and noise figure can be improved by tailoring the longitudinal carrier density profile. The differential gain among the channels is also reduced due to the contrasting gain and transmission spectra of the two gain segments. Numerical simulation of the amplifier characteristics is carried out by using a well-established model, available in the literature, for the conventional SOA. For an input channel power of −40 dBm, with a bias current of 100 mA to the two-segment SOA, a channel gain of 21.5 dB with a gain flatness of 1.3 dB and a noise figure of 7.9 dB is obtained.