A 22-Gb/s Time-Interleaved Low-Power Optical Receiver With a Two-Bit Integrating Front End

This article presents the implementation of a novel 22-Gb/s energy-efficient optoelectronic receiver architecture in 65-nm CMOS for short-reach optical communication. The receiver incorporates four sub receivers with a two-bit integrating resettable front-end in each sub receiver. The inputs to two of the four sub receivers are optically delayed by one bit and two complementary quarter-rate clock phases are used to completely recover the data. The two-bit integrating low-bandwidth front end replaces the full-bandwidth transimpedance amplifier used in conventional optoelectronic receivers, resulting in improved energy efficiency. The low-bandwidth operation is enabled by using a capacitor at the input and by amplifying the two-bit integrated voltage with low-bandwidth voltage gain stages that require a bandwidth of only 35% of the operating data rate. The receiver performs a 1:4 demultiplexing operation by only using two quarter-rate clock phases instead of the four phases that are conventionally used in a quarter-rate clocking system. This clocking scheme reduces complexity while maintaining the same timing margin of the quarter-rate systems. This two-clock phase system is enabled by optical delay lines and splitters. The receiver is experimentally validated with a 1550-nm photodetector array wire bonded to the four inputs. The electronic part of the receiver achieves error-free transmission (BER <; 10 ^-12 ) at 22 Gb/s with an energy efficiency of 1.43 pJ/bit and an average sensitivity of -7.8 dBm (or -6.2 dBm optically modulated amplitude) with a 1.09-V supply.