
A Background to Return Loss Measurement
Getting Started with Return Loss
Agilent 81610A/11A/12A/13A/14A Return Loss Module, Fifth Edition
41
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
, with the measurement patchcord, as used in
Measure Return Loss” on page 31
. This is caused by differences in
reflections from the front panel connector and also differences in the
backscatter level of the fibers.
3
5HI
F
1
0
5HI
5
5HI
0
UHI
0
SDUD
---------------
3
SDUD
+
=
(5)
3
'87
F
1
0
'87
5
'87
0
'87
0
SDUD
---------------
3
SDUD
+
=
(6)
3
5HI
0
5HI
0
SDUD
---------------
3
SDUD
–
F
1
0
5HI
5
5HI
=
(7)
3
'87
0
'87
0
SDUD
---------------
3
SDUD
–
F
1
0
'87
5
'87
=
(8)
5
'87
0
5HI
0
'87
---------------
P
'87
0
'87
0
SDUD
---------------
3
SDUD
–
P
5HI
0
5HI
0
SDUD
---------------
3
SDUD
–
--------------------------------------------------------
5
5HI
=
(9)
5/
'87
10
5
'87
log
–
=
10
0
5HI
0
'87
---------------
P
'87
0
'87
0
SDUD
---------------
3
SDUD
–
P
5HI
0
5HI
0
SDUD
---------------
3
SDUD
–
-------------------------------------------------------- 10
5
5HI
log
–
log
–
=
(10)
5/
5HI
10
5
5HI
log
–
=
(11)
Содержание 81610A
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