An optical time domain reflectometer also known as an OTDR is a test instrument that measures the attenuation (the reduction in power of the light signal as it is transmitted) of optical signals passing through a fiber optic cable.

Why would you use an OTDR?

The OTDR essentially performs an analysis of a light pulse with an attached detector and displays the results in numerical format, allowing the user to assess the state of an optical fiber. Typically, an OTDR will also determine when there is insufficient light coming back from a connection that might indicate damage to the fiber. OTDRs can be used to test for:

• Continuity in fiber optic cables
• Checking for any defects and faults in a cable
• Analysing how long it takes light to travel from one end of a cable to another