Siemens SIMATIC NET PROFIBUS - Manual (Page 456)

Installation and Startup
5-6
PROFIBUS Optical Bus Terminal (OBT)
C79000-G8976-C122-02
Connecting the Optical Cables
A B C D
Figure 5-4 View of the Module from Below with the Optical Channels CH2 and CH3
A = CH2, optical receiver
B = CH2, optical sender
C = CH3, optical receiver
D = CH3, optical sender
S Connect the individual PROFIBUS OBTs using a duplex FO cable, fitted with
two pairs of simplex connectors.
S
Make sure that in each case an optical input is connected to an optical output
(crossover).
S Make sure that there is reliable strain relief for the FO cable and do not bend
the cable beyond the minimum bending radius.
S Close unused FO sockets with the plastic plugs provided. Extraneous light,
particularly when it is extremely bright can cause disturbances on the
PROFIBUS network.
S Remember the minimum and maximum length of the FO cable and the
permitted fiber types specified in Table 1 and in the technical specifications.
S
You should also make sure that no dust can enter the optical components. Dust
in optical components can make them unusable.
S The fibers of the cable must be flush with the front surface of the connector.