The reading on the meter (in dB) is the total loss of the link including connectors and splices. Compare this against your link budget calculation — if the measured loss exceeds the budget, you have a problem somewhere in the path. The text on the cable starts with the Corning product name "Corning Rocket Ribbon (TM) Optical Cable," date of manufacture "01/2022" and a serial number. This is followed by the essential. An optical power meter measures the strength of light traveling through a fiber optic cable, giving you a reading in dBm (decibels relative to one milliwatt). Many bulk cable spools come pre-printed with sequential footage markings on the jacket, so you can simply read the numbers at each end and subtract to find the length of a pulled section.