Rockwell Automation SA3100 Fiber-Optic Cabling-Distributed Pwr System - Manual (Page 16)

3-2 Fiber-Optic Cabling
The main requirement for reliable fiber-optic link operation is that the total system loss
must be less than the power budget. Use the following equations to calculate the
losses present in the system:
Power Budget Calculation
• Cable Loss = Total Cable Length x Cable Attenuation
(3.5dB/Km)
• Connector Loss = # of Connector Pairs x Connector Attenuation
(0.6dB)
• Total Loss = Cable Loss + Connector Loss
Using the example in figure 3.1:
Since 2.3dB (total loss) is less than 2.6dB (power budget), the system will work as
designed.
3.2 Installation Planning
Use the following procedure to design a fiber-optic link that will achieve maximum
signal isolation and cable protection in a specific environment with minimal fiber-optic
cable usage.
You will need to select the tools and personnel that are required for fiber-optic cable
assembly and installation. Unless you have in-house expertise with fiber-optic cable
assemblies and installation, we recommend that you contact an experienced
contractor for making up and installing fiber-optic cables.
Step 1. Identify the actual location of the UDC module and the PMI(s) using an
equipment floor plan.
Step 2. Identify the tentative fiber-optic cable route. Route the cables to allow easy
access in the future.
Step 3. Identify the environmental conditions (temperature, humidity, hazardous
chemicals) along the route.
Step 4. Determine how to bypass physical obstructions (walkways, heat sources,
furnaces, caustic chemicals) along the route.
Step 5. Determine the best type of fiber-optic cable installation (conduit, raceway,
wiring tray). Refer to R/E 704201-80 in your system documentation for the
appropriate method.
Step 6. Calculate the total length of the fiber-optic cable.
Step 7. Calculate the optical power budget as described in section 3.1.
• Cable Loss = Total Cable Length x Cable Attenuation
1.1dB (.309Km) 3.5dB/Km
• Connector Loss = # of Connector Pairs x Connector Attenuation
1.2dB 2 additional pairs 0.6dB
• Total Loss = Cable Loss + Connector Loss
2.3 dB 1.1dB 1.2 dB