10E: Bi-directional Attenuation
Using Two Sources & Meters, or Two Simple LTS

Written by Bruce Roberson 97-03. © Kingfisher International

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This method is convenient and accurate for any link. It makes very little difference if a source and meter, or an integrated LTS (Loss Test Set) is used.


The actual method of operation is the same as Example 1, except that:

For example AP1, AP2 are the readings from one meter, and BP1, BP2 are the readings from the other.
Averaged link insertion loss in linear units = (AP1+BP1-AP2-BP2)/2 where all measurements are in linear units
[If you use meters with a reference facility, the calculation becomes:
Averaged link loss in linear units = (link loss measured by meter A + link loss measured by meter B)/2 ]

Note that use of this technique eliminates calibration accuracy as an issue, leaving only meter linearity and short term source stability as instrument limiting factors.

In this situation ‘Autotest’ type features can result in better measurement confidence, lower skill requirements and twice the productivity for dual wavelength measurements.

Fiber Optic Test Method


Conectorised Link Connectorised link
Fiber Optic Test Cord Patch Cord
Fiber test through connector Through adaptor
multimode madrel wrapping Source, incl. mandrel wrap if multimode
Fiberoptic meter Meter
Fiber Optic DUT DUT Device Under Test (system being tested)

[instructions on use of the relative mode are in italics]