Practice
In the 21st century the cable jetting technique is used worldwide, from small optical telecom cables (1.8 mm diameter) in small microducts (3 mm internal diameter) up to large copper telecom cables (35 mm diameter) in large ducts (50 mm internal diameter). Jetting is done with a pressure of the compressed air in the order of 10 bar. With the jetting technique distances per blow of 3.5 km have been reached, while spliceless links of 12 km have been reached by placing jetting equipment in tandem. It is possible to install 12 km in one day with one small crew.
In mid 1990s the technique was also developed to install multiple smaller microducts, bundles, into a larger duct in one installation. This is called multi-ducting, microduct cabling, or bundle blowing. Each can hold a cable.
Another capability is to install a single cable or a bundle of small ducts into an occupied duct. The most cost driving activity of installing a network is the need for civil works. Thus, re-using ducts occupied with one cable, leaving some space, is a tempting and often possible and cost effective alternative.
Read more about this topic: Cable Jetting
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