Installation Guide Manual

Rockwell Automation Publication CNET-IN001C-EN-P - October 2011 27
Chapter 2
Topology and Signal Considerations
Develop a Plan
Fiber-optic links in a ControlNet network system can do the following:
• Increase network length beyond that supported by coax
• Provide immunity to EMI
• Provide better electrical isolation than standard coax cable
Fiber is strongly recommended to avoid lighting problems when connecting
equipment in different buildings together.
You can create point-to-point, star, and ring configurations. Up to four fiber
modules, with two fiber ports each, can be directly plugged to a repeater adapter.
Multiple repeater adapters can be used to increase the number of fiber or
coax connections.
Each port needs two fiber connections, one for receiving and another for
transmitting signals. The basic configuration connects two coax segments
point-to-point by two repeater adapters and two fiber repeater modules, as
illustrated in Figure 9
.
Topic Page
Develop a Plan 27
Redundant Media 28
Topology Considerations 29
Coax Segment Constraints 30
Fiber Segment Constraints 31
Select a Module Type Based on Distance Requirements 31
Estimate Cable Lengths 33
Determine Attenuation Levels 35
Determine Propagation Delay 38