An electronic dispersion compensation transceiver for 10- and 28-Gb/s directly modulated lasers-based optical links

This paper presents an electronic dispersion compensation (EDC) transceiver to encompass extended reach of both 10- and 28-Gb/s directly modulated lasers (DMLs). In DML-based links, direct modulation of laser diodes induces power-dependent frequency chirp on the generated optical signals, which causes severe chromatic dispersion as well as pattern dependence on the received signal after optical fiber transmission. Such time-varying nature of the dispersion makes conventional equalization methods ineffective for compensation. The proposed EDC-based clock and data recovery (CDR) IC overcomes the chirp-induced dispersion via a linear equalizer followed by a double-sampling decision feedback equalizer (DFE) at the receiver and a pattern-dependent pulse shaping filter at the transmitter. The chirp-managed EDC improves the receiver sensitivity at a bit error rate (BER) of 10^-6 by 1.3 dB in a 3-km link using a DML at a modulation rate of 28 Gb/s, where transient chirp is dominant, and by more than 7 dB in a 105-km link at 10 Gb/s, where adiabatic chirp is dominant. The chip prototype is fabricated in a 40-nm CMOS process and packaged in a flip-chip ball grid array (BGA). The single-chip IC containing dual-lane transceivers and a global clock generator (CG) occupies an active area of 2.8 mm². The test chip consumes 236 mW, wherein a single-lane transceiver consumes 105.5 mW and a global CG consumes 25 mW from a 0.9-V supply at 28 Gb/s.