Two primary methods dominate insertion loss testing: direct testing using a light source and power meter and indirect testing using Optical Time Domain Reflectometry (OTDR). What Is Fiber Insertion Loss Detection? Fiber insertion loss detection includes intra-site fiber insertion loss detection and inter-site fiber insertion loss detection. Detection position: Detects the contamination of the near-end. To test the loss of a signal in a fiber optic link in a way that mimics the way the link transmits data, we use an insertion loss test. Some examples: A fiber connector, a mechanical splice or a fusion splice may be used to connect two fibers, instead of having a single continuous fiber. In reality, it is a symptom indicator of underlying.