3Com 510M-FBP, 5102M-FBP 10BASE-FB Module Configurations, Fiber Backbone, Fiber-to-the-Desk

10BASE-FB Module Configurations

The theoretical maximum diameter of an all fiber Ethernet network is limited to 4.2 km as defined by the 51.2 μsec slottime that is specified for the round trip delay budget set by the IEEE 802.3 CSMA/CD protocol. (Thus, point-to-point link distances are limited to a maximum of 4.2 km.) This section describes how to define total network size based on the limits of IEEE 802.3 collision detection.

This section describes the following scenarios:

❑Fiber Backbone, Fiber-to-the-Desk

❑Fiber Backbone, Unshielded Twisted Pair-to-the-Desk

❑Fiber Backbone, Coaxial Connection

Fiber Backbone, Fiber-to-the-Desk

When designing an all-fiber network (Figure 2-5), keep the following rules in mind:

1.Limit the longest path from one fiber optic transceiver to another to 4.2 km (2.6 miles).

2.Each 10BASE-FB Module in a serial path between two transceivers reduces the maximum cable distance between the transceivers by

190 meters (623 feet). The equivalence is:

❑ 140 meters for signals that externally enter a 10BASE-FB Module port

❑50 meters for signals that internally enter a 10BASE-FB Module from the concentrator backplane

For simplicity, use 190 meters per 10BASE-FB Module in the path when calculating fiber equivalent distances.

Designing and Expanding the Network 2 - 17