Installation guide

RIO Network Hardware Components
890 USE 101 00 October 2006 71
Selecting Fiber Optic Cable
Overview If you are using 490NRP954 Fiber Optic Repeaters in your RIO network, there are
several parameters you need to consider, among them cable attenuation and cable
bandwidth. Parameters are specified by the cable manufacturer and are based on:
z The wavelength of the optical signal—820 nm in the RIO optical link
z The cable index—use graded-index cable only
z The fiber size—50/125 μm, 62.5/125 μm, or 100/140 μm
For most optical cable links, the use of 62.5/125 μm cable is recommended because
of its relatively low loss and signal distortion. In applications where high optical
power is required—e.g., to support additional optical devices such as splitters or star
couplers—the 100/140 μm cable should be used (see Attenuation Considerations in
an Optical Path, p. 56 for more details on design considerations).
Many cable vendors offer multiple choices for a variety of code ratings:
z From the variety of cables—e.g., AMP or Belden offerings—select the one that
meets the demands of your application. Wherever possible, Modicon
recommends that a multiconductor cable be considered, since it is inexpensive;
it provides a backup in case a cable gets cut in the process of pulling it; and you
will always find uses for the extra path(s), be it for voice, video, other
communications, and/or other control applications.
z Most 62.5/125 μm cables are rated at 3.5 dB loss per km. With a multiconductor
cable, all the pairs usually come with an attenuation specification as measured,
which may be significantly less than 3.5 dB/km.
This document provided by Barr-Thorp Electric Co., Inc. 800-473-9123 www.barr-thorp.com