128-GS/s 1-to-4 SiGe Analog Demultiplexer with 36-GHz Bandwidth for 6-bit Data Converters

Coherent optical transceivers cover multiple wavelengths to meet the growing request for ultra-wideband data links, e.g. from ultra-high definition video-on-demand. However, costs increase with the number of wavelengths per channel, so that higher baud rates are used to reduce the receiver's complexity, while simultaneously increasing electrical bandwidth requirements. Especially sampling rate and analog input bandwidth between photodiode and data converters need to be improved. For that purpose, we present a 4-way time-interleaving analog demultiplexer in one of the most advanced SiGe-BiCMOS technologies to date, operating at the highest reported sampling rate of 128 GS/s. The total harmonic distortion of -37 to -22 dB indicates an accuracy of 5.9-3.3 ENOB
_THD
across the entire 36-GHz bandwidth of the sampled signal path and the signal-to-noise ratio of 28 dB at 2 GHz enables 4.4 ENOB
_SNR
. Each of the sampling front end's four output paths can drive a 32-GS/s 6-bit analog-to-digital converter that can be connected to commercially available 32-Gbit/s digital interfaces. Combining an ultra-high symbol rate with medium accuracy allows for a data rate beyond 1 Tbit/s per wavelength with dual polarization and quadrature amplitude modulation in a cost-efficient coherent optical receiver.