SECTION 3: TRACE ANALYSIS
12
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.
The trace information (located below the trace) will show the distance and
relative power (in dB) at the point where each cursor is placed, as well as the
total link distance and end-to-end link loss.
In this example, the total link length is
, and the end-to-end link
loss is
.
red
green
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.
The trace information (located below the trace) will show the distance and
relative power (in dB) at the point where each cursor is placed, as well as the
loss and distance of the section of fiber being analyzed.
In this example, the section of fiber being analyzed has
of loss, and is
.
Using this information, dB per kilometer can also be calculated, which can be
compared to the fiber manufacturer attenuation specification. To determine
dB/km:
1.76 dB / 7.040 km = 0.25 dB/km
n the example shown here, the attenuation measurement also includes the loss through the connector located near the red
cursor.
red
green
1.76 dB
7040 meters
I
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
