Agilent Technologies 8166B User Guide

Return Loss Measurement A Background to Return Loss Measurement
176 Agilent 8163A/B, 8164A/B, and 8166A/B User’s Guide, Fourth Edition
If we substitute equation 3 into equations 2 and 4, this gives us the
following two equations:
If we subtract P
para
from equations 5 and 6, this gives us the following
equations:
If we divide equation 8 by equation 7, this gives us the following
equations:
Thus we can use the equation below to calculate return loss:
The return loss of the reference reflection is given by:
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 161, with the measurement patchcord, as used in “How to
Measure Return Loss” on page 166. This is caused by differences in
reflections from the front panel connector and also differences in the
backscatter level of the fibers.
P
Ref
c
1
M
Ref
R
Ref
M
ref
M
para
----- ----------
P
para
+=
(5)
P
DUT
c
1
M
DUT
R
DUT
M
DUT
M
para
------- --------
P
para
+=
(6)
P
Ref
M
Ref
M
para
--------- ------
P
para
– c
1
M
Ref
R
Ref
=
(7)
P
DUT
M
DUT
M
para
----- ----------
P
para
– c
1
M
DUT
R
DUT
=
(8)
R
DUT
M
Ref
M
DUT
-------- -------
P
DUT
M
DUT
M
para
-------- -------
P
para
–
P
Ref
M
Ref
M
para
------- --------
P
para
–
-------- ------------------------------------------------
R
Ref
=
(9)
RL
DUT
10 R
DUT
log–=
10
M
Ref
M
DUT
--------- ------
P
DUT
M
DUT
M
para
--------- ------
P
para
–
P
Ref
M
Ref
M
para
-------- -------
P
para
–
--------- -----------------------------------------------
10 R
Ref
log–log–=
(10)
RL
Ref
10 R
Ref
log–=
(11)

Agilent Technologies 8166B Specifications

General

Brand	Agilent Technologies
Model	8166B
Category	Measuring Instruments
Language	English