Figure 1. (a) Ring-modulator-based QPSK transmitter using the AIM Photonics PDK. (b) Schematic for simulating transmitter in a back-to-back configuration with a coherent receiver.
The OptSim Circuit topology of Figure 1(b) depicts the test schematic connecting this transmitter to a QPSK receiver in a back-to-back configuration. The coherent receiver consists of a 90˚ hybrid with local oscillator and balanced receiver, to recover the original transmitted in-phase and quadrature signals.
Figure 2 depicts the QPSK constellation diagram at the output of the transmitter. Figure 3(a) shows the transmitted and received in-phase signals, while Figure 3(b) shows the corresponding quadrature signals. As can be seen, the receiver is able to recover the transmitted signals.
Finally, if you have PhoeniX Software’s OptoDesigner installed and have loaded PDAFlow Libraries into OptSim Circuit, including the PhoeniX version of the AIM Photonics PDK, then you can generate a layout for the transmitter. To do so, use the Generate PDAFlow Netlist from the Utilities menu. This will produce an SPT file in the project directory, which can be loaded into OptoDesigner. Figure 4 shows the corresponding layout.