You can check attenuation with an OTDR or a power meter. A power meter checks the light at the start and end of the fiber. It's measured in decibels per kilometer (dB/km), and it determines how far a signal can travel before it becomes too weak to read. A standard single-mode fiber operating at 1550 nm loses. When it comes to testing fiber optic cables, an Optical Time-Domain Reflectometer (OTDR) is an essential tool. It provides an in-depth analysis of the fiber network, helping technicians identify faults and issues like attenuation.