As data center architectures scale to 800G (8x100G) and 1.6T (8x200G) per port, signal degradation across host traces makes traditional passive loopback testing insufficient. High-frequency 112Gbps and 224Gbps PAM4 signaling suffers severe insertion loss over PCB traces, requiring Active Loopback Modules (ALB) with integrated Digital Signal Processors (DSP) or Retimers to perform equalization, retiming, and link training.
In this generation, Active Loopbacks, Host Compliance Boards (HCB), and Module Compliance Boards (MCB) serve as essential tools to validate high-loss host channels, firmware state machines, and thermal limits before deploying production optics.