The Active Optical Cable (AOC), especially parallel multi-lane cables using QSFP+ modules, is one of the most important devices used by high-speed interconnects, such as InfiniBand. Accurate cable testing is necessary for ensuring that these AOCs have reliable data transmissions and interoperability. This application note explains how to evaluate the QSFP+ type AOC for 56G-IB-FDR, which consists of four 14-Gbps parallel lanes.