This distinguishes between two very different fault categories carried in a transceiver-fault trap: a checksum-failed value points to a problem reading the optic's own EEPROM identification data, often a bad or counterfeit module, while an optical-fault value points to an actual signal-path problem, so the admin's next troubleshooting step differs sharply depending on which value this reports. For example, chksumFailed on a newly-inserted third-party transceiver would suggest the module itself may be defective or unsupported, whereas opticalFault on a long-installed, previously-working optic would point toward a developing hardware failure in that specific unit.