Ultra-low-LO-Power Optical Coherent Receiver on Silicon

A silicon photonic coherent receiver is proposed and demonstrated by introducing balanced Ge/Si avalanche photodiodes (APDs), which have a primary responsivity of 0.84 A/W and a maximum gain of ~289 for ~30 dBm input optical power. The present APD-based silicon photonic coherent receiver works well for 25 Gbaud Quadrature Phase-Shift Keying (QPSK) signals even with low LO optical power of ~11 dBm, enabling high-sensitivity data-receiving of the QPSK signals with a low optical power of ~22 dBm without any equalization.