Improper use or interpretation of OTDR test results can result in wasted time, materials and money. Estimates indicated contractors lose as much as $100,000 annually due to improperly reading OTDR test results. OTDRs are often used to create a "picture" of a fiber optic cable when it is first installed so later comparisons can be made to help with troubleshooting network problems. OTDRs send pulses of light into optical fibers at varying pulse widths. Then, they measure the small amounts of reflected light that are sent back from faults in the fibers. The device then determines the size and distance of the faults, and defines them as losses or changes in the cable’s light-carrying capacity.

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