Testing With Tdrs And Otdrs; Testing With Tdrs; Testing With Otdrs - Cisco 10000 Series Troubleshooting Manual

Testing with TDRs and OTDRs

Test fiber-optic cable both before installation (on-the-reel testing) and after installation. Continuity
testing of the fiber requires either a visible light source or a reflectometer. Light sources capable of
providing light at the three predominant wavelengths, 850 nanometers (nm), 1300 nm, and 1550 nm, are
used with power meters that can measure the same wavelengths and test attenuation and return loss in
the fiber.
Testing with TDRs and OTDRs
This section describes time domain reflectometers (TDRs) and optical time domain reflectometers
(OTDRs), which are typically used to detect cable defects.

Testing with TDRs

Use time domain reflectometers to test for the following cable defects:
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A TDR works by "bouncing" a signal off the end of the cable. Open circuits, short circuits and other
problems reflect the signal back at different amplitudes, depending on the problem.
A TDR measures:
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Some TDRs can also calculate the propagation rate based on a configured cable length.

Testing with OTDRs

Use optical time domain reflectometers to:
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An OTDR can be used to identify the "signature" of a particular installation, noting attenuation and
splice losses. This baseline measurement can then be compared with future signatures if you suspect a
problem in the system.
Cisco 10000 Series Router Troubleshooting Guide
B-2
Open and short circuits
Crimps, kinks, and sharp bends
Impedance mismatches
Other defects
Amount of time it takes for the signal to reflect
Physical distance to a fault in the cable
Length of a cable
Locate fiber breaks
Measure attenuation
Measure the length of a fiber
Measure splice or connector losses
Appendix B Recommended Tools and Test Equipment
OL-0439-02