➀ 52.7% of failures in 200G FR4 modules are due to 50G PAM4 DFB laser power degradation or absence. ➁ PCBA failures significantly increased to 24.8%, likely due to high-speed HDI board and dense soldering processes. ➂ 15.9% of failures are attributed to gold wire bonding in the Rx section. ➃ In 400G FR4 modules, EML is used instead of DFB, resulting in lower failure rates at 13.4%, with PCBA emerging as the primary failure point.