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

OTDRs map a fiber by sending a light pulse and watching the light that is scattered back. By measuring when that backscattered light returns, you can determine how far away events are along the fiber. The change in backscatter level over distance tells you how much loss occurs along the fiber (attenuation per kilometer), and sharp spikes in the trace indicate strong reflections from connectors, splices, or faults. What you can’t get from a standard OTDR is the fiber’s bandwidth—the data-carrying capacity or the dispersion characteristics that limit how fast you can transmit information. Bandwidth depends on the signal, modulation, and dispersion properties of the fiber and system, not on the backscattered trace the OTDR records. To assess bandwidth you’d perform transmission tests or dispersion measurements with other instruments, not an OTDR trace.