Equivalent circuit model for multi-electrode semiconductor optical amplifiers and analysis of inline photodetection in bidirectional transmissions

A rate equation model for static and dynamic behavior for bidirectional transmission in a multisection semiconductor optical amplifier (SOA) is presented. The rate equations for each section have been implemented on an electrical simulator. Here, we have used the model to study the inline photodetection in presence of bidirectional transmission. Small signal photodetection response in presence of co- and contrapropagating signals is given. The photodetection crosstalk expression in bidirectional transmission has also been reported. Simultaneous bidirectional photodetection experiments using a three-electrode SOA show good agreement between measured crosstalk and simulated results obtained by harmonic balance method. A photodetection response nearly free of crosstalk has been obtained for certain operating conditions due to the cross gain modulation between contrapropagating signals.