Choosing OTDR parameters
OTDR parameters need to be chosen wisely to match the measurement target. With the correct combination of set ups, the instrument can be used effectively and the user doesn't run risking to have overlooked faults or to have made wrong statements.
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Length of pulse
widths & detection
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Pulse widths affect dead zones and detectability
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Optical pulses sent by OTDR correspond to physical lengths (for instance 10ns is 1 meter long)
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As long as a pulse length is shorter than the distance between the first and the subsequent event, the subsequent event can be detected (Event Dead Zone)
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However, shorter pulse widths have less energy. The pulse can travel less and the OTDR effective dynamic is reduced
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Practically, a compromise between both parameters must be found
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Range and
Resolution
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Localization accuracy and measrurement capacity through chosen range & resolution
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The number of sampling points should be used carefully to achieve location information with proper accuracy during a optical link trouble shooting
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A higher resolution increases the measurement time for the same averaging
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Chosen range should cover the actual fiber length + 30% to ensure that no loss in physical resolution occurs
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The Corning OV1000 OTDR has a measurement mode that determines the necessary parameters automatically. Also the chosen range resolution is logically calculated to make ful use of the available dynamic and resolution...
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