For longer runs, mark the cable at one-meter or one-foot intervals as you unspool it and count the marks. 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. You can measure cable length using a tape measure for accessible runs, but for cables already installed in walls, conduits, or buried underground, electronic methods are faster and far more accurate. Several methods exist, ranging from simple approximations to highly accurate techniques used in manufacturing and installation. Two. An Optical Time Domain Reflectometer (OTDR) sends light pulses through a fibre optic cable. These pulses travel down the fibre and reflect when they encounter inconsistencies, like breaks, splices, or bends. Fiber installations are increasingly required to have fiber length measurements to comply with bid requirements.
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