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Fiber optic cable loss measurement results may be negative

A negative insertion loss indicates a problem, one of which is often improper reference setting. For example, if a reference cable is dirty when setting the zero reference, and then cleaned before testing, the insertion loss could show a gain and potentially be indicated with a. 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. 3 (), at the end of the Fiber Autotest, if there is a negative loss of more than -0. 09 dB, a warning will be given. "How can I get a negative loss? Isn't that a gainer?" The principle causes of negative loss readings are: The following articles include a step to verify your Test. Insertion loss is usually shortened to IL, and the unit of measurement for insertion loss is dBm. Insertion loss is the signal power loss caused by inserting devices (such as fiber connectors, fiber jumpers, couplers, etc.