Design of High-Speed Mixed-Signal Circuits in 65 nm and 28 nm CMOS Technology for Optical Transmitters with Data Rates beyond 100 Gbit/s per

摘要

High-speed DACs that have sufficient resolution as well as application specific digital signal processors (DSP) are key components for optical transmitter modules that support data rates beyond 100 Gbit/s per optical wavelength channel. To reach such large data rates higher order modulation formats (i.e. n-fold QAM) have to be applied. The high order modulation can be combined with multi tone techniques (i.e. OFDM) to optimally use the available optical bandwidth. Advanced CMOS technologies allow for the integration of the digital signal processor on a single ASIC as ??System-on-Chip?? (SoC). Thus the optical transmitter may be implemented in a compact and cost-efficient way. The DACs and their interface to the DSP are designed as full-custom mixed-signal integrated circuits with extensive analog circuitry. The DSP may be implemented in a semi-automated way based on VHDL/Verilog and a standard cell library. This paper presents the design of an optical OFDM Tx IC in 65 nm CMOS technology. The IC supports data rates far beyond 100 Gbit/s per optical wavelength channel and the optimal use of the available SNR in the OFDM subchannels by means of two 32 GS/s 8 bit DACs and a standard-cell based DSP. Further the design of a 100 GS/s 8 bit DAC in 28 nm CMOS technology is presented. The DAC features an integrated memory to output cyclical symbol sequences and a hardware prototype of the DAC is already available.