Testing Loss

There are two methods that are used to measure loss, which we call "single-ended loss" and "double-ended loss". Single-ended loss uses only the launch cable, while double-ended loss uses a receive cable attached to the meter also. Single-ended loss is measured by mating the cable you want to test to the reference launch cable and measuring the power out the far end with the meter. When you do this you measure 1. the loss of the connector mated to the launch cable and 2. the loss of any fiber, splices or other connectors in the cable you are testing. This method is described in FOTP-171 and is shown in the drawing. Reverse the cable to test the connector on the other end. In a double-ended loss test, you attach the cable to test between two reference cables, one attached to the source and one to the meter. This way, you measure two connectors' loses, one on each end, plus the loss of all the cable or cables in between. This is the method specified in OFSTP-14, the test for loss in an installed cable plant.