Installation guide

Planning and Designing RIO Cable System
58
890 USE 101 00 October 2006
Maximum Number of Repeaters and Jitter Considerations
Overview Due to the cumulative effects of reactive components, the maximum number of
repeaters in a linear network is five. This number may be reduced by the system’s
total pulse width distortion, or jitter. The table below shows jitter contributed by
recommended fiber optic cables.
Fiber repeater jitter effect is analogous to tap loss in coaxial cable networks. The
fiber to fiber jitter contribution is 10 ns and can be compared to tap insertion loss.
The fiber to coaxial cable jitter contribution is 20 ns and comparable to tap drop loss.
in the diagram above, jitter contribution is 50 ns from point A to point B. The following
represents individual jitter contributions as shown in the diagram:
z 20 ns for Repeater 1 from the coax connection (A) to the fiber cable
z 10 ns for Repeater 2 from its fiber cable input to its fiber cable output
z 20 ns for Repeater 3 from its fiber cable input to the coax connection (B)
Jitter contribution as measured from the coax input on Repeater 1, point A to the
coax connection at Repeater 2, point C is 40 ns. In both repeaters, the coax and fiber
interfaces contribute 20 ns to jitter.
The total allowable jitter in a fiber network is 130 ns. Jitter effects from fiber links
separated by a coaxial cable segment are cumulative. Using the diagram above and
presuming the fiber cable contribution to be 5 ns, total jitter from point A to point B
is 55 ns. If this network was duplicated and separated by a coaxial cable segment,
then the total fiber network jitter contribution would be 110 ns between the RIO head
and the last drop.
Core Diameter Jitter
50/125 μm 3.0 ns/km
62.5/125 μm 5.0 ns/km
100/140 μm 7.5 ns/km
(B)
Coax TrunkCoax Trunk
(C)(A)
Coax from RIO Head
Repeater 1 Repeater 2 Repeater 3
This document provided by Barr-Thorp Electric Co., Inc. 800-473-9123 www.barr-thorp.com