Rockwell Automation 1786-series ControlNet Fiber Media Planning and Installation Guide - Manual (Page 38)

38 Rockwell Automation Publication CNET-IN001C-EN-P - October 2011
Chapter 2 Topology and Signal Considerations
Attenuation Levels for Long-distance Fiber Segments
The power loss budget for the long-distance fiber repeater
(catalog number 1786-RPFRL) is 15 dB. The maximum amount of attenuation
between the two fiber repeaters shall not exceed 15 dB. This power
loss budget includes the entire bulkhead/fusion splice.
Attenuation Levels for an Extra-long Fiber Segment
The power loss budget for the extra-long distance fiber repeater
(catalog number 1786-RPFRXL) is 10.5 dB. The maximum amount of
attenuation between the two fiber repeaters shall not exceed 10.5 dB. This power
loss budget includes the entire bulkhead/fusion splice.
Determine Propagation
Delay The ControlNet network maximum propagation delay specification refers to the
worst-case signal delay between any two nodes on a network. You need to figure
out the worst-case scenario based on distances and the number of repeaters
through which the signal has to travel.
Network delays include the delays through coax and fiber media, coax repeaters,
repeater adapters, and fiber modules.
In order for a network to operate, the sum of the network’s delays must be equal
to or less than the maximum propagation delay of 121 μs. The total network
allowable delay each way is 121 μs.
Table 6 - Delay Values for ControlNet Network Media
ControlNet Network Items Delay Values
1786-RPCD 100 ns
1786-RPA/B 901 ns
1786-RPFS 94 ns
1786-RPFRL/B 420 ns
1786-RPFRXL/B 420 ns
1786-RPFM 153 ns
Coax cable 4.17 ns/meter
62.5/125 micron fiber 5.01 ns/meter
200 micron fiber
9/125 micron fiber