OTDR Set-Up - Testing Range

All OTDRs regardless of brand have four basic setup requirement i.e. the OTDR user is required to key in these four basic data parameters into OTDR in order to get good and accurate fiber trace analysis.

The required data parameters are :-

1. Testing Range 
2. Pulse Width - Refer Article HERE
3. Index of Refraction - Refer Article HERE
4. Averaging Time - Refer Article HERE

Fiber Optics Testing Range or Distance of Fiber Optics to Test

Many OTDRs have automatic length detection functions unless the end-user knows the approximate fiber distance then testing range can be set manually.
The following diagrams provide OTDR traces in accordance to OTDR testing range settings.

Too Short Testing Range

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• Assuming the fiber optics approximate distance is 1000 meter. 
• The OTDR testing range is set to 500 meter .
• The OTDR image / tracse  only show half of the distance thus provide inaccurate testing results.

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Too Long Distance Range

• Assuming the fiber optics approximate distance is 1000 meter. 
• The OTDR testing range is set to 5000 meter .
• The OTDR image / trace shown is compressed into a scale of 1:5 thus giving smaller OTDR traces which can lead into inaccurate measured values.

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Good Distance Range

• Assuming the fiber optics approximate distance is 1000 meter. 
• The OTDR testing range is set to 1500 meter - 2000 meter .
• The OTDR image / traces shown is a good OTDR chart thus measured values.

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Rule of Thumb The OTDR Testing Range must always be at least 25% greater than fiber optics under testing.