IBM 8265, Руководство по подготовке площадки

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Chapter 4. Planning for Fiber Connections
27
Planning Cabling Distances
This section describes how to plan the cabling distance between two ports (or
between a port and a user device) in a fiber network. To ensure that a link will be valid
for data transmission, collect the following information:
•
Type and length of fiber cable
•
Type and number of connectors used
•
Type and number of splices used
•
Type and number of patch panels used
•
Number of jumper cables used
•
Modal dispersion of the fiber (MHz/Km) when using multimode fiber cable.
Once you have the necessary information, you can plan the cabling distance between
ports (or a port and a device) by following these steps:
1. Determine the optical power budget for the port and cable size using the tables
given in Chapter 7. “Planning for Media Modules”.
2. Verify that the overall power loss in the link due to connectors, splices, cable type,
patch panels, and jumper cables is less than the optical power budget.
These steps are described in the following sections.
Notes:
1. The distances achievable depend not only on the fiber diameter, but also on the
modal dispersion of the fiber given by the fiber manufacturer, as shown in the
example in Table 19.
For other modal dispersion values, use a linear interpolation. For example, for a
50/125 micron fiber of 800MHz/Km, the range is:
2.1 + (3.1-2.1) * (800-600)/(1000-600) = 2.6 Km.
2. The (conservative) recommended distances between ports and transceivers are
as follows:
Multimode fiber
500 meters (1,640 ft) for 62.5/125 micron fiber
200 meters (656 ft) for 50/125 micron fiber
Singlemode fiber
15 km (9.32 miles)
If these distances are exceeded, you must carefully calculate the power loss
across the link to make sure that it does not exceed the total power budget.
Table 19. Modal Dispersion and Range
50/125 micron
diameter
62.5/125 micron
diameter
Modal Dispersion (MHz/Km) 600 1000 500 800
Range (Km) 2.1 3.1 2.0 2.9