Silicon photonic integrated circuits for coherent communications

Coherent communications is transmitting an optical signal with an advanced format down an optical fiber and receiving it with an optical coherent receiver. An optical coherent receiver interferes the incoming signal with a local continuous-wave laser in a dual-polarization, dual-quadrature 90° hybrid with balanced photodiode pairs. The primary advantages of coherent communications are high spectral efficiency, high sensitivity, and digital compensation of transmission impairments.