Fluke OF-500 OptiFiber, Technical Reference Handbook

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OF-500 OptiFiber Certifying OTDR
Technical Reference Handbook
2-10
Changing the Index of Refraction
The index of refraction is the ratio of the speed of light in
a vacuum to the speed of light in a fiber. The tester uses
the index of refraction to determine fiber length.
You can change the index of refraction on the Cable tab
in Setup.
When MANUAL CABLE SETTINGS on the Cable tab is
disabled, the tester uses the n values specified in the
selected fiber type.
When MANUAL CABLE SETTINGS is enabled, the tester
uses the n values you enter.
The n values defined in the fiber types are suitable for
most applications. Minor differences between the tester's
n and a fiber's actual n usually do not make enough
difference in length to fail a fiber.
You may want to change the index of refraction if
•
The customer wants you to use a specific n value for
the job.
•
The cable's fibers are longer than its jacket, and you
need to precisely locate a point on the cable (such as
a fault). In this case, adjust n until the measured
length matches a known length of fiber.
Increasing n decreases measured length.
Note
If you try to enter a value outside the valid
range for n, the tester shows
N/A for the value.
The valid range is 1.1 to 1.71 inclusive.
To use the default n values specified in the selected fiber
type, set
MANUAL CABLE SETTINGS to Disabled .