Ideal Networks Serie 33-960 Cable tester, cable tester 33-960-3 User Manual

OTDR

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Setting the Acquisition Parameters

You can set parameters such as IOR (group index), backscatter, and helix 
factor. You can also enable or disable the first connector check.

Setting the IOR, Backscatter, and Helix Factor

Your unit contains default IOR (group index), backscatter, and helix factor 
values that you can modify if they do not suit your testing needs. You 
should set the IOR (group index), backscatter, and helix factor before 
performing tests in order to apply them to all newly acquired traces.

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The index of refraction (IOR) (also known as group index) is used to 
convert time-of-flight to distance. Having the proper IOR is crucial for 
all OTDR measurements associated with distance (event position, 
attenuation, total length, etc.). IOR is provided by the cable or fiber 
manufacturer.

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The (Rayleigh) backscatter value represents the amount of backscatter 
in a particular fiber. The backscatter is used in the calculation of ORL 
and reflectance, and it can usually be obtained from the cable 
manufacturer.

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The helix factor takes into account the difference between the length 
of the cable and the length of the fiber inside the cable; it does not vary 
with wavelengths.

The length of the OTDR distance axis is always equivalent to the 
physical length of the cable (not the fiber).