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6-8
Performance Tests
Test 4. Optical Input Return Loss
FC/APC patchcord loss
The effect of having loss in the FC/APC patchcord 1 to 2 connector pair is to under mea-
sure the return loss by twice the FC/APC patchcord 1 to 2 loss. For example, if this con-
nector 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 DUT 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.