Siemens SIMATIC NET PROFIBUS - Manual (Page 249)

Testing PROFIBUS
A-9
PROFIBUS Networks SIMATIC NET
6GK1970-5CA20-0AA1 Release 2 05/2000
A.2.3 Optical Time Domain Reflectometer (OTDR)
If the attenuation measurement described above indicates that the total attenuation
of the fiber-optic link is too high, the causes and the location of the problem must
be established. In this case OTDR units are used (OTDR = Optical Time Domain
Reflectometer).
Figure A-3 Optical Time Domain Reflectometer (OTDR)
OTDRs exist for the wavelengths 850 nm and 1300 nm. This means that this
method can be used for both multimode and single-mode fiber-optic cables.