Optical power abnormalities often indicate deeper issues such as fiber degradation, connector contamination, excessive attenuation, or equipment malfunction. First, the transmission class of the optical module fault investigation and solution method This type of optical module failure mainly includes port not UP, port status is UP but do not receive or send messages, port frequently up or down and CRC error. However, during installation and daily operation, various issues may arise. Therefore, understanding common optical module. The article Digital Diagnostic Function (DDM) For Optical Modules describes that DDM function can be used for real-time monitoring and fault location of the module's working status, in which the optical module's transmitting optical power and receiving optical power are the key parameters for. Digital Diagnostic Monitoring (DDM), also called Digital Optical Monitoring (DOM), is one of those small features that saves hours in the field. Built into modern SFP/SFP+/ SFP28 /QSFP family modules and standardized by SFF-8472, DDM/DOM exposes real-time values for the module's temperature, supply. To maintain stability, most SFP, SFP+, SFP28, and QSFP modules provide two key diagnostic indicators: TX Fault and RX LOS. These signals help engineers quickly identify optical issues, prevent link failures, and maintain reliable network uptime.