A Background to Return Loss Measurement Return Loss Measurement
Agilent 8163A/B, 8164A/B & 8166A/B Mainframes, Sixth Edition 195
Calculating the Front Panel Delta
The Front Panel Delta is the change in loss variation that is caused by
replacing the reference cable, as used in “Reflectance Calibration” on
page 180, with the measurement patchcord, as used in “How to Measure
Return Loss” on page 184. This is caused by differences in reflections from
the front panel connector and also differences in the backscatter level of
the fibers.
To measure the front panel delta you must measure the power transmitted
through the reference cable, “Measuring the Power Transmitted Through
the Reflection Reference” on page 190, and the power transmitted through
the measurement cable, see “Measuring the Power Transmitted Through
the Measurement Patchcord” on page 191. The system may be
represented by Figure 117 :
Figure 117 Generalization of a Return Loss Measurement
The transmitted power, (E), is directly proportional P
src
.
That is:
The constant a is a multiplier giving the proportion of power that the light
source emits that is measured by the power meter.
The constants a
Ref
and a
Meas
apply to the setups described in “Measuring
the Power Transmitted Through the Reflection Reference” on page 190
and in “Measuring the Power Transmitted Through the Measurement
Patchcord” on page 191 respectively.
This gives the following two equations:
Power Meter
E
Agilent 81610A
Reflection Reference
P
src
EaP
src
=
(12)
E
Ref
a
Ref
P
src
=
(13)
E
Meas
a
Meas
P
src
=
(14)
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