An Optical Time-Domain Reflectometer (OTDR) is a device used to analyze optical fibers. It sends pulses of light into the fiber and measures the light that is reflected back. This helps identify faults, splices, and connectors along the fiber, making it essential for maintaining and troubleshooting fiber optic networks. OTDRs are commonly used in telecommunications and data networks to ensure optimal performance. By providing detailed information about the fiber's condition, they help technicians locate issues quickly and accurately. This technology is crucial for ensuring reliable communication in systems that rely on fiber optics.