Cable type
Minimum bend radius
Network Cat 5/6 (Unshielded)
1.75 in (4.44 cm)
Network Cat 5/6 (Shielded)
3.5 in (8.90 cm)
Coaxial (50W)
1.2 in (3 cm)
Coaxial (75W)
1.7 in (4.31 cm)
R1 InfiniBand - at connector
4.6 in (11.68 cm)
R2 InfiniBand - away from connector
2.6 in (6.60 cm)
• Power cable: Minimum bend radius prevents disconnection from power socket and possible arcing
under high-voltage conditions. When there is a high voltage or high current on the cable, sharp edges
or turns can cause puncturing of the cable jacket or arcing to equipment at local potential.
• Copper cable: Too sharp a radius will stress the center conductor, and may cause the cable outer
conductor to collapse or buckle. A sharp radius will cause impedance discontinuities at the bends
resulting in reflections and leads to signal degradation and circuit problems. An excessive bending of
cable can affect the geometry of the twists and increase the sensitivity to external noise and cause
stress on cable terminations.
• Fiber optic: Tighter bends may cause micro-bending of individual fibers that allow light to escape the
signal path, resulting in signal attenuation. More severe bends can break fiber strands completely,
resulting in signal loss.
General guidelines for cabling
• If not already applied by the factory, label all cables.
• Use the shortest possible cable between devices. Shorter cables reduce the possibility of signal
degradation over longer distances and are easier to route along the rear of the rack.
• Cables cannot have any obvious kinks, deformation, or damage to the connector housing or
sheathing. To prevent these issues, use extra care when unpacking, unwinding, routing, and storing
cables.
• To prevent mechanical damage or depositing contaminants from your hands, do not touch the ends of
the cable connectors.
• Before connecting a cable to a port, lay the cable in place to verify the length of the cable.
• Some data cables are prebent. Do not unbend or manipulate the cables.
• For components that must be movable while powered on, ensure that a full range of motion (frequently
called a service loop) is possible without cable interference or disconnection.
• Leave some slack in the cable (service loop). The slack provides room to remove and replace
components, allows for minor, inadvertent movement of the rack, and helps prevent the cables from
being bent to less than the minimum bend radius. The slack can be addressed by forming loops or
using a take-up spool as long as the minimum bend radius is maintained.
Guidelines for connecting, routing, and restraining cables
• When routing cables, always be sure that the cables are not in a position where they can be pinched
or crimped.
• When routing cables onto a management arm, secure the cables enough to prevent interference or
pinch areas during movement, yet not so tight as to cause binding.
More information
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