April 2003 - No-Dig International

Much is made of the term 'trenchless' technology but it has become accepted that in most cases some degree of 'excavation' is required with several 'No-Dig' methods. However in comparison with traditional trenching techniques the degree of excavation is minimal. Much has also been made over the past few years of the 'last mile' installation sector, particularly in the provision of fibre optic cables to the customer.

In an effort to combine the advantages of minimum excavation and the needs of the last mile contractor, U.K.-based TeraSpan Networks Ltd has introduced its patent-pending 'Trenchless Fibre Technique' which reduces the often seen 'narrow' trench with a simple slot of between 50 and 150 mm depth depending on the local existing infrastructure and situation.

The slot is produced on the required line using a standard cutting wheel unit as often seen cutting the edge/guide slots for full trench works. Into this slot the special fibre cable or cables are stacked depending on the fibre density required. The slot then has a foam backing rod placed on top of the cables after which the slot is back filled with a grout material to surface. The cables used are specially designed TeraSpan Micro-Cables. Junction box points are created at 25 to 50 m intervals by using wider and deeper slots. Cable loops are placed vertically into these junction points. New connections are made at the junction points.

The advantages claimed for this system include: fast deployment; minimal impact on the surrounding infrastructure and environment; minimal disruption to traffic and pedestrians; and it is a cost effective alternative to full trenching.