Insertion loss, or the loss of signal that happens along the length of a fiber optic link, is expressed in dBs and should always be a positive number. But it can be negative (which isn't a good thing). "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. By MARK MULLINS, Fluke Networks -- The confusion between positive return loss and negative reflectance means that you may see manufacturers specify a negative value for return loss when they really meant reflectance. You see dB is defined as a logarithmic function: With logarithms, if the ratio of measured power to reference power is greater than 1, e. This is always measured in dB (decibels) and will be displayed as a negative number. The closer the number is to zero, the higher the reflectance (meaning a poor connection). We will look at some of these to.
