FOA Certified Fiber Optic Specialist, Splicing (CFOS S) Practice Exam

Testing attenuation in a fiber optic link is about quantifying how much signal is lost as light travels through the fiber, including losses at connectors and splices. The instrument that directly provides this quantitative loss is the optical power meter. By pairing a stable light source at the transmitter with a power meter at the receiving end, you can determine the insertion loss in decibels (dB) from the ratio of input to output power. In practical use, you may make a reference measurement at one end and then measure at the other to compute the exact loss along the link. An OTDR can show where losses occur along the fiber by analyzing backscattered light, and can estimate attenuation per segment, but its primary role is locating faults and characterizing the fiber, not giving a straightforward insertion-loss value. A visual fault locator injects visible light to help visually locate breaks or high-loss areas but does not provide a numeric attenuation measurement. An optical spectrum analyzer examines the spectral distribution of light, not the overall attenuation of the fiber link.