Fast-Locking Burst-Mode Clock and Data Recovery for Parallel VCSEL-Based Optical Link Receivers

Abstract

A burst-mode clock-and-data-recovery (CDR) system for a multi-channel vertical-cavity surface-emitting laser (VCSEL)-based non-return-to-zero (NRZ) optical link’s quarter-rate receivers is presented, that utilizes proxy timing recovery for fast turn-on time. The proxy timing recovery scheme takes advantage of correlated data jitter over parallel optical lanes typically deployed in a data center. Rapid timing recovery of the burst-mode channel is enabled by incrementing/decrementing its phase rotator (PR) control code during idle periods using phase updates from an always-active channel in the link. This work also presents circuit-design techniques to reduce power dissipation during idle times while still enabling fast turn-on time. Simulated in 65 nm CMOS technology, the proposed CDR consumes only 19.5 mW per channel while operating at 10 Gbps/ch and 0.58 mW during its idle-state. Simulation results are presented for the turn-on time with the proposed technique and compared against the turn-on time of a conventional receiver. The proposed technique allows the CDR to lock within 26 unit intervals (UIs) from when it is powered on irrespective of a 1000 ppm frequency offset between the incoming data and the CDR’s reference clock. The complete CDR of each channel occupies an area of 0.045 mm2. The proposed scheme introduces only 1.3 % of area and 2.6 % of on-state power overhead while reducing idle-time power dissipation by 97 %.

Keywords

• Burst-mode
• clock and data recovery (CDR)
• energy efficiency
• injection locked oscillator (ILO)
• optical link
• power-proportional