TOA KIKAI KOGYO Co.,Ltd.

A new installation technology using spiral airflow to control turbulence has been enabled optical fibers and cables to be installed in conduits 6 �| 150 mm in diameter over distances much longer than achieved with conventional systems. With this new system, a 2 mm optical fiber has been successfully blown through a 1500 meter, 6 mm diameter tube coiled in a drum. In the process of laying a 12 mm optical cable, a 10 mm pulling rope was passed through a 1200 meter, 80 mm diameter conduit. The spiral generator constructed with a single device, or combination of devices, each consisting of a conical cylinder with an annular slit, produces a highly focussed, stable airflow which increases the drag force on the fiber and reduces scraping against the conduit, enabling installation over long distances.

Application for multiple cable installation over long distance.

Multiple cable installation technology should be developed from the viewpoint of more effectively utilizing existing conduits. A conventional multiple installation system, which can only install additional cables over a maximum 250 meters, is not satisfactory for installing cables through a long conduit. Using the new spiral airflow technology, cables have been installed in existing conduit 1200 meters long.

The conventional cable installation method using compressed air involves four steps:

1. Purging water and mud.
2. Blowing a lead rope.
3. Installing a pulling rope.
4. Installing a cable with the pulling rope.

There are several drawbacks of this conventional method. In step (1) the water and mud cannot be purged completely, thus the installation process is rarely smooth. To accomplish step (2) , a pig(or parachute) is attached to the end of the lead rope and blown through the conduit (with the nozzle sealed at its entrance) by a large quantity of compressed air. Unfortunately, this process limits the installation distances, often causes the rope to violently fly out of the conduit due to the extremely high air pressure developing in the sealed conduit and may cause the lead rope to entangle with the existing cables making additional installation impossible.

With the new spiral flow installation nozzle as shown in Figure, water and mud are purged completely, the pulling rope can be installed without a lead rope(thus eliminating step(2),above), and the pulling rope does not become entangled with the existing cables.