How do you measure attenuation in fiber? You can check attenuation with an OTDR or a power meter. The OTDR sends a light pulse and shows where the loss is. This loss can be caused by a multitude of factors, ranging from intrinsic material properties to environmental conditions. The losses are typically categorized. Fiber optic loss, also known as optical attenuation, refers to the light loss between the transmitter and receiver. In summary, fiber optic loss is. This article provides a practical, engineering-oriented explanation of fiber optic loss, focusing on how it affects network performance, how it should be measured and evaluated, and how it can be effectively controlled through better splicing and design practices. Insertion Loss (IL) is defined as the total decrease in power between the input and output terminal of the Device Under Test (DUT).