Consider the exhibit.

The exhibit shows a diagram of a network with two nodes, Node A and Node B, connected by a fiber span. The diagram also shows the power readings at different points of the span. The calculated span loss from Node A to Node B is the difference between the output power at Node A and the input power at Node B. According to the diagram, the output power at Node A is +3.5 dBm and the input power at Node B is -4.5 dBm. Therefore, the span loss from Node A to Node B is 3.5 - (-4.5) = 8.0 dB.