A 28Gb/s transceiver with chirp-managed EDC for DML systems

Directly modulated lasers (DMLs) are widely employed in medium-reach optical links owing to their simplicity and cost effectiveness. However, the chirp phenomenon under direct modulation limits the reach (2–10km) in a standard single-mode fiber (SMF). Although diverse optical-domain chirp-management techniques have been studied [1], excessive cost and installation difficulties have limited their widespread use. Therefore, external modulation schemes are predominant in applications requiring extended-reach, despite their high cost and power dissipation. Recently, an electronic dispersion compensation (EDC) IC has been reported to compensate for the chirp-induced dispersion (adiabatic chirp) of a 6Gb/s DML [2,3]. However, such a technique cannot be applied to high-speed (>10Gb/s) DML applications since spectral broadening caused by transient chirp dominates in high-speed links. In this paper, an adaptive EDC-based CDR IC compensating for both adiabatic and transient chirp in DMLs is proposed to help extend the reach of both 10Gb/s and 28Gb/s optical links.