CDR-integrated Sn-Ag-Cu-solder reflow-capable miniature 28-Gb/s ? 4-channel optical modules

We report the design and transmission characteristics of clock-data-recovery (CDR)-integrated 28-Gb/s × 4-channel parallel-optical modules for QSFP28 AOCs. The module keeps the same package size with the 28-Gb/s × 4-channel module that we reported in a previous work. The CDR circuitry was integrated to the new module. Owing to the CDR functionality, we achieved a link total jitter margin of >0.4 U.I. when operating at a bit stream of 28-Gb/s, 2³¹-1 PRBS. A degraded electrical signal at the TX input can be compensated by the CDR circuitry to fully meet the specification of CEI-28G-VSR, where the total jitter margin was improved from 0.06 U.I. to 0.42 U.I. successfully together with remarkably low power dissipation of 390 mW/lane.