Analog processing-based coherent optical receiver for 16-QAM signals with 12.5 GBd baud rate

Several terabytes of data get generated and transferred through the Internet everyday. With bandwidth-intensive on-line applications such as video, music, and voice the demand for higher data rate increases. The ever-increasing data rate demand will be supported by multilevel signaling over fiber-optic links in the backplane. Traditional coherent optical links use the power hungry ADC+DSP approach at the receiver side for mitigating the distortions caused by the system non-idealities. A significant amount of power consumption can be reduced if the received signals are processed in the analog domain itself. This paper presents a 12.5GBd 16-QAM analog processing-based coherent receiver, that has been designed and simulated using 130nm BiCMOS technology. The receiver uses radius directed equalization and Costas loop based carrier phase recovery and compensation. Simulations indicate that the receiver is capable of mitigating a dispersion of up to 160 ps/nm and a frequency offset of up to 10 MHz. For a transmission over 10 km-long fiber the receiver gives an output error vector magnitude of 23.2% when the laser linewidth is 200 kHz. The receiver is projected to consume ~3.5W of power.