All-optical logic OR gate based on cross gain modulation in Semiconductor Optical Amplifiers

摘要

Semiconductor Optical Amplifiers (SOAs) are very attractive components for optical communication systems. We have already shown that two-cascaded SOAs in a counterpropagating configuration (TC-SOA-CC) based on XGM is interesting for all-optical signal processing (Fig. 1) [1-3]. The contra-directional input signals P{sub}(in,1)(λ{sub}1), P{sub}(in,3)(λ{sub}3) and P{sub}(in,2)(λ{sub}2) are injected in SOA{sub}1 and SOA{sub}2 respectively. In this configuration, a negative feedback controls the evolution of the SOAs gains. In the absence of P{sub}(in,3) and the presence of a low power P{sub}(in,1), the P{sub}(in,2) signal profits from the high SOA{sub}2 gain G{sub}2 allowing to saturate the SOA{sub}1 gain G{sub}1. By increasing P{sub}(in,1), the SOA{sub}1 output optical power injected in the SOA{sub}2 becomes enough to saturate the gain G{sub}2. This reduction in G{sub}2 can induce an increase in G{sub}1 if the total injected power, coming from SOA{sub}2 and from the increase in P{sub}(in,1), decreases. Figure 1 shows the evolution of the SOA{sub}1,2 gains versus the input optical power P{sub}(in,1)(λ{sub}1) and in the presence of P{sub}(in,2)(λ{sub}2) = -15 dBm. For high G{sub}2 (I{sub}2 = 280 mA), G{sub}1 presents a positive variation for P{sub}(in,1) range - 23 dBm < P{sub}(in,1) < -14 dBm, while G{sub}2 decreases strongly beyond P{sub}(in,1)> -23 dBm. This positive slope disappears for low G{sub}2 (I{sub}2 = 150 mA). In this case, the G{sub}2 reduction which occurs with high P{sub}(in,1) power (P{sub}(in,1) = -13 dBm) is not sufficient to drop off the total injected power and the SOA{sub}1 starts to saturate.