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6-10 Test 4. Optical Input Return Loss
FC/APC patchcord loss
The effect of having loss in the FC/APC patchcord 1-to-2 con-
nector pair is to under measure the return loss by twice the FC/
APC patchcord 1-to-2 loss. For example, if this connector pair
loss is 0.5 dB, then the actual return loss caused by the 14.6 dB
Fresnel reflection is 15.6 dB, but we enter 14.6 dB as an R
value. Then, if the device under test return loss is exactly 40 dB
below that of the 14.6 Fresnel reflection, the optical return loss
module will display 53.6 dB because the 0.5 dB connector pair
loss (seen twice) is removed. In reality, the return loss is
54.6 dB (exactly 40 dB below 14.6 dB), better than that dis-
played.
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