OTDR MODE
TEST PROCEDURES
OTDR MODE
By placing the cursors at the beginning and ending points of the fiber trace, the distance
between the cursors will show a close approximation of the total length of the optical fiber
link, as well as a close approximation of the total fiber link loss.
CURSOR PLACEMENT
Proper cursor placement is necessary to determine the end to end length and link loss of
an optical fiber link. Refer to the diagram at right when placing cursors for fiber length
measurement.
The
cursor should be placed directly before the first reflective event, before the
slope of the line begins to spike.
The
cursor should be placed directly before the last event, before the slope of
the line begins to spike.
Cursor information is located below the trace.
and
cursor information shows
the distance to the cursor, and the
information shows the distance and relative power
(in dB) between the
and
cursors.
With cursors placed as shown at right, the
length number is the approximate end-to-
end length of the fiber link, and the
dB number is the approximate dB loss of the link
(not including the loss of the far end patch panel.)
In this example, the total link length is
, and the end-to-end link loss (not including the far end patch panel) is
.
NOTE: use this length as the length to enter during CERT mode
red
green
Red
red
green
green
blue
blue
blue
24718 meters
7.43 dB
FIBER LENGTH MEASUREMENT/LINK LOSS
The fiber attenuation, or loss, for a certain section of an optical fiber link can be determined
by placing the cursors at the beginning and end points of the segment of fiber under test.
CURSOR PLACEMENT
Proper cursor placement is necessary to determine the attenuation of a certain segment of
fiber.
The
cursor should be placed at the beginning of the section of fiber under test.
The
cursor should be placed at the end of the section of fiber under test.
Cursor information is located below the trace.
and
cursor information shows
the distance to the cursor, and the
information shows the distance and relative power
(in dB) between the
and
cursors.
With cursors placed as shown at right, the
length number is the length of fiber
between the cursors, and the
dB number is the dB loss of the fiber between the
cursors.
In this example, the section of fiber being analyzed has
of loss, and is
.
Using this information, attenuation of fiber (dB per kilometer) can also be calculated, which can then be compared to the fiber
manufacturer attenuation specification. To determine dB/km:
1.76 dB / 7.040 km = 0.25 dB/km
red
green
Red
red
green
green
blue
blue
blue
1.76 dB
7040
meters
FIBER ATTENUATION MEASUREMENT
1m
24719m
24718m
RFL dB
-81.00
24718
dB
7.43
7.43
L m
Fiber #
CURSOR
LOCK
ZOOM
TEST
ENTER
AUTO
1550nm
4086m
11126m
24718m
RFL dB
-34.26
7040
dB
1.76
7.43
L m
Fiber #
CURSOR
LOCK
ZOOM
TEST
ENTER
AUTO
1550nm
