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Why do OTDR measurements use a dead-zone fiber?

While testing attenuation of an optical fiber using an OTDR (Optical Time Domain Reflectometer), it is preferred to use a dead-zone fiber connected to the Input/output port of OTDR. Some people call this dummy fiber or reference fiber. Why do we need to use a dead-zone fiber in OTDR measurements?

There will be a reflection peak at the beginning of launch end of OTDR. This happens at the connection point where the light meets another medium for propagation. The launched light gets stabilized after certain distance, say about 200 meters. If we include this peak in our attenuation calculation, it gives wrong value and hence must be avoided. The best way to eliminate the dead zone is to use a dead zone fiber. This fiber is also called dummy fiber or reference fiber (or some people wish to call it). In one sense, dead zone fiber eliminates unwanted noise from the attenuation measurement.