Use the formula below to calculate insertion loss in dB from measured input and output power values. This. Insertion loss is measured by comparing signal power (or sound level) before and after it passes through a component or system, then expressing the difference in decibels (dB). The core process is the same across fiber optics, RF electronics, and acoustics: establish a baseline reference without. Considering that lower insertion loss means less investment in DWDM network deployment, this post will illustrate a simple method on how to test and calculate the insertion loss of DWDM Mux Demux and make an insertion loss value comparison for 40CH DWDM Mux Demux in the market, which will help you. Excess loss in dB is determined by the ratio of the total input power to the total output power: P port1 is the input power at port 1 and P port2 +P port3 is the total output power from Ports 2 and 3. All powers are expressed in mW.