Keysight Technologies 86120B, User Manual

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Performance Tests
Test 4. Optical Input Return Loss
Procedure: Option 022 instruments (angled contacting connectors)
1 Turn the source module’s output off.
2 Connect a single-mode patchcord between the source module’s optical output and the
return-loss module’s INPUT SOURCE connector.
3 Set the return-loss module’s wavelength to 1550 nm, and select an average time of 1
second.
4 Locate an HMS-10/HRL to FC/APC (angled FC) patchcord. Connect the HMS-10/
HRL end of the patchcord to the return-loss module’s OUTPUT connector.
Terminate the FC/APC end of the cable.
5 Zero the return-loss module.
6 Turn on the source module.
7 Remove the termination from the cable, and connect the FC/APC end of an FC/APC
to FC/PC cable to the free end of this cable. Leave the cable’s free end uncovered.
8 The return-loss module measures the reflection reference (14.6 dB return loss of the
patchcord’s FC/PC connector in air).
9 Disconnect the FC/APC to FC/PC cable.
10 Make a low-reflection termination in the HMS-10/HRL to FC/APC patchcord. Do
this by wrapping the cable 6 times around a 5 mm diameter mandrel.
11 The return-loss module measures the termination parameter.
12 Connect the HMS-10/HRL to FC/APC patchcord to the Keysight 86120B’s front
panel OPTICAL INPUT connector.
13 The lightwave multimeter measures the return loss. Compare this measurement with
the specification listed in
Chapter 7, “Specifications and Regulatory Information” .
FC/APC patchcord loss
The effect of having loss in the FC/APC patchcord 1 to 2 connector 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 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 displayed.