The installation of optical cables inside sewer ducts is basically a trenchless technique.
Optical cable installation in sewer ducts presents many advantages compared with traditional trench
installation techniques, such as: less time for cable laying, not limited by weather conditions,
increased protection of cable against damage, no traffic disruption, no noise pollution, no
excavation, no damage to road surfaces and underground installations, no heavy equipment, no
inconvenience to businesses or to citizens.
In general, there are two categories of sewers: man-accessible and non-man-accessible sewers.
The definition of whether a sewer is man-accessible or not depends not only on national regulations,
but also on the individual regulations of different sewer network operators.
Usually, non-man-accessible sewers have diameters between 200 mm and 700 mm.
Installation in non-man-accessible sewers is carried out with the help of robots. In man-accessible
sewers, both robot-assisted and manual installation of cables is feasible.
Basically, there are three different methods to install optical cables into sewer ducts:
a) Special armoured optical cables, designed to be directly installed at the bottom of the
sewers;
b) Self-supporting optical cables, designed to be directly suspended at the top part of sewers;
c) Traditional optical cables or micro-cables, designed to be installed in protective ducts
which have to be installed before the cable installation.
NOTE 1 – The most important optical cable structures and related performances suitable for these kinds of
installation techniques are described in [ITU-T L.78].
NOTE 2 – The sewer optical cables and/or related infrastructure should be designed and manufactured for an
expected operating lifetime of at least 15 years. It should be possible to install or remove the cable to/from
the sewer throughout the operation lifetime. The materials in the sewer optical cable and/or the related
infrastructure shall not present a health hazard within its intended use.