Abstract

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_in,1(λ₁). P_in,3(λ₃) and P_in,2(λ₂)) are injected in SOAi and SOA₂ respectively. In this configuration, a negative feedback controls the evolution of the SOAs gains. In the absence of P_in,3 and the presence of a low power P_in,1 the P_in,2 signal profits from the high SOA₂ gain G₂ allowing to saturate the SOA₁ gain G₁. By increasing P_in,1 the SOA₁ output optical power injected in the SOA₂ becomes enough to saturate the gain G₂. This reduction in G₂ can induce an increase in Gi if the total injected power, coming from SOA₂ and from the increase in P_in,1, decreases. Figure 1 shows the evolution of the SOA, ₂ gains versus the input optical power P_in,1(/-i) and in the presence of P_in,2(λ₂) = -15 dBm. For high G₂ (I₂ = 280 inA), Gi presents a positive variation for P_in,1 , range - 23 dBm < P_in,l < -14 dBm, while G₂ decreases strongly beyond P_in,1 ,>-23 dBm. This positive slope disappears for low G₂ (I₂ = 150 inA). In this case, the G₂ reduction which occurs with high P_IM , power (P_in,1 =-13 dBm) is not sufficient to drop off the total injected power and the SOAi starts to saturate.

© 2007 IEEE