A key performance parameter for both copper and fiber applications, insertion loss is measured in decibels (dB). It is typically a positive number that is calculated by comparing the input power of the signal at the source to the output power at the far end. This reduction of signal, also called attenuation, is directly related to the length of a cable—the. 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. Note: Remember that we are measuring in dB, so less power is a more negative number. Is that right? Well the real problem is that to understand this you need to understand logarithms and that's Algebra II*, way beyond fourth grade addition and subtraction. You see dB is defined as a logarithmic function: With logarithms.
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