Insertion loss, also known as attenuation, is the loss of optical power that occurs when light passes through a fiber optic connector. It is caused by factors such as misalignment, air gaps, and imperfections in the connector components. In the test report for a fiber cable, you may often see some data related to fiber insertion loss (IL) and return loss (RL), but do you know what insertion loss and return loss actually mean? How do the values of IL and RL impact the quality of the fiber cable? Are higher values better, or lower. Fiber loss, also called fiber optic attenuation or attenuation loss, refers to the loss of signal between input and output. Losses can be divided into intrinsic and. Guidelines On What Loss To Expect When Testing Fiber Optic Cables To be able to judge whether a fiber optic cable plant is good, one does a insertion loss test with a light source and power meter and compares that to an estimate of what is a reasonable loss for that cable plant. What Is Insertion Loss and Return Loss for Fiber Connectors? What Is Insertion Loss? In telecommunications, insertion loss refers to the loss of signal. Losses in the optical fiber can be categorified into intrinsic optical fiber losses and extrinsic optical fiber loss depending on whether the loss is caused by intrinsic fiber characteristics or operating conditions. Intrinsic Optical Fiber Losses comprise of absorption loss, dispersion loss and.