Rockwell Automation 1786-series ControlNet Fiber Media Planning and Installation Guide - Manual (Page 36)

36 Rockwell Automation Publication CNET-IN001C-EN-P - October 2011
Chapter 2 Topology and Signal Considerations
You can also affect the power budget by the quality of the connectors and fiber
cable you choose. If you use a high-quality connector and fiber cable, you will be
able to stretch your power budgets. Higher-quality connectors and cable can
withstand a broader range of temperatures and distances.
In most situations you will not have to determine the attenuation levels for
short-distance fiber cable. The cable comes pre-terminated with connectors with
the proper length of cable to be used under the maximum attenuation levels. If
you modify the cables with splices then you must calculate the attenuation levels.
Figure 12 is an example of determining the maximum distance between two fiber
repeaters. These are measured path losses, not theoretical. If the system
attenuation exceeds the power budget, you will need to add additional repeaters.
Figure 12 - Maximum Distance Between Two Repeater Modules
Step 1: Total your loss budget
With the type of fiber module selected, how much total loss (dB) can
you have?
4.2 dB on the 1786-RPFS module
Step 2: Subtract loss for connectors
Select connectors. You need to account for at least two connectors per
fiber cable segment.
Loss per connector x 2 connectors (1 at each end)
2 (1.5 dB) = 3 dB
31505-M
Connector 1 = Fiber Connector
(Each Fiber Connector is 1.5 dB)
Fiber Cable 1 = Short Distance
Fiber Cable Measured @ .1 dB)
Connector 1 + Fiber Cable 1 + Connector 2 = Total Attenuation
1.5 + .1 + 1.5 = 3.1 dB
Connector 2 = Fiber Connector
(Each Fiber Connector is 1.5 dB