InArmor CST Corrugated Steel Tape (CST)

Direct buried cable used in rural and urban construction when aerial and conduit space is unavailable.


Central strength member: FRP


Water-swellable yarns


Optical fiber


Dry loose tube


Water-swellable tape


Corrugated steel tape armor


Polymer jacket




Water-swellable yarns

Excellent rodent resistance

The most popular design

Cost-effective design

Reduced weight and size

Increased tightness due to application of water-swellable tape

InArmor CST is a cost-effective and one of the most popular designs. It is a multi-tube cable with corrugated steel tape as an anti-rodent armoring. Apart from an excellent rodent resistance, this cable is also UV-resistant, so it features multi-purpose outdoor installation: from direct buried to duct and aerial lashed. Even though it has a reduced weight and size, it provides increased tightness due to application of water-swellable tape.

Typically, this cable consists of a stranded core with a central strength member (FRP) and dry loose tubes with optical fibers. The stranded core is fixed by water-swellable yarns. A water-swellable tape is laid over loose tubes. An armor of corrugated steel tape is laid over the water-swellable tape.

InArmor CST’s maximum rated design tension can reach up to 607 lb but it may be produced with even higher MRDT up to 1.124 lb. It has a wide range of operating temperatures from -40°F to +158°F and installation temperatures from -22°F to +158°F (operating temperature range can be increased on request).

Check how this direct buried fiber optic cable can be deployed in FTTH system.

Maximum rated design tension (MRDT) 607 lb (2.7 kN)
Crush 126 lb/in (0.22 kN/cm)
Fiber count, up to 72 (6x12) 96 (8x12) 144 (12x12)
Cable diameter, in 0.476 0.539 0.681
Cable weight, lb/ft 0.088 0.109 0.162
Minimum bending radius, in 7.2 8.1 10.2
Operating temperature -40°F ... +158°F
Installation temperature -22°F ... +158°F
Transportation and storage temperature -58°F ... +158°F
Minimum bending radius 15 x cable diameter
Design life 25 years

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