8.1 A 6Gb/s transceiver with a nonlinear electronic dispersion compensator for directly modulated distributed-feedback lasers

The directly modulated distributed-feedback laser (DML) is widely employed in medium-reach optical links due to its cost effectiveness. However, DMLs are not appropriate for use in fiber links longer than 20km at 6Gb/s or equivalent, because the SNR penalty increases abruptly due to excessive chromatic dispersion caused by frequency chirp. Therefore externally modulated lasers (EMLs), which are more costly, have been a natural choice for applications requiring extended reach. In this paper, a clock and data recovery (CDR) IC that compensates for chromatic dispersion caused by the frequency chirp of the DML is presented. The CDR with EDC is fabricated in a 90nm CMOS process, and the test-chip consumes 226mW at 6Gb/s.