The fiber length in fiber optic cables is always longer than the cable length primarily because the optical fibers inside the cable are not laid straight, they are helically twisted or loosely spaced with some slack inside the protective loose tubes. While many of these cables are still being made and the excess length of fiber over jacket length is a function of the diameter of the core (larger core/bigger. Also, since the tube was following a helix around a central anti-buckling member, the overall fiber path was longer than the cable length. In the past, the usual procedure was to twist together a loose fiber optic cable with a small amount of excess length in the tube. As the components like fiber, connectors, splices, LED or laser sources, detectors and receivers are being developed, testing confirms their performance specifications and helps. The Optical Time Domain Reflectometer (OTDR) is useful for testing the integrity of fiber optic cables. It can verify splice loss, measure length and find faults. Later, comparisons can be made.
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