As emerging technologies like 5G, the Internet of Things (IoT), and cloud computing develop at a fast pace, there is a steady rise in bandwidth demand. To keep up with this demand, Passive Optical Network (PON) technologies are advancing as well. Currently, the primary PON technologies in use include GPON, XGS-PON, and NG-PON2; meanwhile, OTDR (Optical Time Domain Reflectometer) serves as a tool for diagnosing network faults and carrying out maintenance work. By leveraging 4CH WDM (Four-Channel Wavelength Division Multiplexing) technology, these various technologies can coexist on a single fiber—this not only boosts the network’s bandwidth but also improves its flexibility.