Instruction Manual

5
RIO network system with optical fiber repeaters topology
Earthing recommendations
When using optical fiber repeater 490NRP95400, either to extend total RIO network length, or to improve RIO immunity to
EMC disturbances, NRP chassis must be connected to Ground, through dedicated screw. RIO cable shield must be set to
specify the NRP relationship to chassis ground. Jumper switch is shipped in neutral position, it must be placed either in
position 1, when NRP acts as a drop on CRP side (cable shield is isolated from chassis ground by a capacitor), or in
position 2, when NRP acts as a head on CRA side (cable shield is connected directly to chassis ground).
Note: The NRP repeater RIO port has the same electrical specifications & restriction as the CRP Head processor.
Design precautions for optical fiber repeaters
• The NRP operates either from a 110/220VAC or from a 24VDC line power. When using the 24VDC power port, a
dedicated 24VDC power source should be used with EMI low emission, to avoid injecting interferences on RIO
network. Do not use this source to power any other equipment of the cabinet.
• Minimum bending radii specified for fiber cables must not be exceeded, for example when routing fiber cables into
plastic trunking/tube. Plan for extra fiber length on main cable to prevent damages for mechanical constraints; use
patch cords to connect the NRP fiber ports to the main fiber cable.
• Unused NRP fiber ports or fiber cables should be protected from dust – use dedicated caps.
• The RIO network must be powered off before installing or replacing an optical fiber repeater.
• Do not look at the ends of optical fiber cable under magnification while a transmit signal is present on the cable –
severe eye damage may result. Use white light only.
CAUTION
EYE DAMAGE
Do not look at the ends of optical fiber cable under magnification while a transmit signal is present on the cable.
Use white light only.
Failure to follow these instructions can result in injury or equipment damage.
Attenuation & jitter considerations in a optical path
As with coaxial cable, on an optical fiber link, splices, cables and connections determine the attenuation. The allowable
attenuation or Power Loss budget for the NRP repeaters to work correctly is 11.0dB for a 62.5/125µm multimode, graded
index fiber, rated at 3.5dB/km attenuation at 820nm. This budget already includes the loss of the two ST-type connectors
which connect at the two repeaters and also a system margin of 3dB.
dB loss = FCA x Length + (Number of additional connectors x CA) + (Number of splices x SA)
Where:
• FCA = the optical fiber cable attenuation per kilometer
• CA = connector attenuation
• SA = fiber splice attenuation
The maximum number of repeater in a network is five, but this number may be reduced by the RIO system total pulse-
width distortion or jitter. The total allowable jitter equals 130ns for a RIO fiber network. The Jitter effects from fiber links
separated by a coaxial cable segment are cumulative
For a 62.5/125µm multimode, graded index fiber, jitter contribution is 5.0ns/km. For each NRP repeater, the optic-to-optic
jitter contribution is 10ns and the electrical-to-optic jitter contribution is 40ns (transmit and receive).
Maximum number of repeaters =
ns10
ns40kmjitterlengthcablefiberns200 −×− )/(
Note: For other types of fiber and to know how to select optical fiber cable, see RIO Cable System planning & installation
guide (890USE10100) or Optical Fiber Repeaters User’s Guide (GM-FIBR-OPT).