F A S T – Fibre Access by Sewer Tubes
1. The concept
With the FAST Fiber optic installation system, fiber optic networks can be realized in cities quickly, inexpensively and reliably. Existing sewer channels are used as a basis carrying the fiber optic network, thus construction work and related problems and difficulties are avoided.
FAST provides the installation of fiber optic cables in non-walk-in and walk-in sewer pipes. It implements a system of empty tubes, so that the replacement of fiber optic cables is possible to any time. Custom designed installation parts permit network branches and liaisons in the sewers.
Below, the essential characteristics of the systems are summarized.
2. FAST in non-walk-in sewer pipes
FAST Fiber optic networks can be installed in non-accessible sewer pipes from DN 200 (200 mm) to DN 700, independent from the sewage pipe material.
For this purpose, a special robot was developed for conducting and fixing the FAST-conduits in non-accessible pipes.
For fixing the conduits, so-called FAST-inner mounting rings are used. These are rings are made of V4A steel, that are mounted inside the sewer pipes at a distance of about 1.5 meters to 5 meters by the robot. The rings are are kept under constant tension with a spring package, so that they sit tightly on the inner wall of the tube.
The mounting rings carry clips in which the FAST-cable tubes are clipped by the robot. In that way, the tubes are fixed to the inner wall of the sewage pipe without the need for damaging the wall by drilling.
Following a networks requirements, the mounting rings can carry up to 9 FAST-tubes – for pipes from DN 450. For sewage pipes DN 300 to DN 400 a maximum of 7 FAST tubes, for sewer pipes DN 200 and DN 250 3 FAST-tubes can be carried.
The realization of the FAST system in non-walk-in pipes is consisting of the following steps:
Having defined that water routes to be used, these are inspectedin order to check whether the selected sewer pipes are suitable.
- The actual installation begins with an accurate examination by the FAST-Robots. During the examination, inlets and pipe sockets are tracked as well. The data obtained is stored in a central database and a mounting ring installation plan is being created, which defines the location and orientation of mounting rings.
- The mounting rings are set by the FAST-Robots.
- FAST cable tubes are fed into the sewer pipes and clipped into the mounting rings by the FAST-Robots.
- After installation is completed, FAST fiber optic cables are fed into the FAST-tubes.
3. FAST in walk-in sewer channels
The FAST installation system can also be used in walk-in sewer channels, meaning sewage pipes from DN 800 (800 mm in diameter are counted) and larger.
Instead of the 360 ° wide mounting ring, partial mounting rings are used. They are V4A-metal bands of a few centimeters in length, carrying clips as the full mounting rings. They are attached with of wedge bolt and nuts to the channel wall at a distance of about 1.5 meters – 5 meters. For the wedge a blind hole is drilled, which is easily possible for a pipe wall thickness of DN 800 and more.
The realization of the FAST system in walk-in pipes is consisting of the following steps:
- Having defined that water routes to be used, these are inspectedin order to check whether the selected sewer pipes are suitable.
- mounting clamps are set manually.
- FAST conduits are fed into the sewer pipes and manually pressed into the corresponding clips on the mounting clamps.
- After installation is completed, the FAST fiber optic cable in laid into the conduits.
4. FAST empty conduits and FAST fiber optic cables
FAST empty conduits are spirally corrugated and have an outside diameter of 11.5 mm and 15.5 mm depending on the variant. They are made of V4A stainless steel. The dimensions of the FAST-conduits was chosen to achieve a slight reduction in cross section of the sewage pipes. They protect the FAST fiber optic cable against rodent bites and give the fiber optic cable system the necessary mechanical protection.
For entry into various FAST conduits, different fiber optic cables are available.
In FAST conduits with 11.5 mm diameter, fiber optic cables with up to 144 fibers can be laid. FAST conduits with an external diameter of 15.5 mm increase the number of fibers to 216. Detailed cable specifications can be provided upon request.
Sewer pipes are used for branching of the fiber optic cable system, to install the connection for the fiber optic cable and to exit from the sewage network.
For safe and reliable transfer in the sewers specific FAST shaft mounting parts are required. These provide the mechanical protection of the cable system and ensure the required bending radii of the FAST fiber optic cable.
6. FAST fiber optic coupling sleeves
In the sewers, special FAST Fiber Optic coupling sleeves may be fitted with single-circuit and / or single-element management. Thus, the fiber optic network is very flexible, expandable and reliable. When working in the FAST Fiber Optic coupling sleeves, already switched connections are not impacted. The sleeve can be taken from the sewage pit for splice and measurement work.
7. Oversize containers
Besides adding extra length of cable for fiber optic coupling FAST Oversize containers include the ability to reserve length of the fiber optic cable. This demand can be used for the installation of additional fiber optic coupling for network branches and customer connections on the same site or elsewhere.
8. Home connection
A core drilling is placed in the sewer channel. From there, a HDPE pipe (usually 50 mm diameter) is laid to the building. The core hole is sealed against the HDPE pipe. Similarly, in the HDPE pipe, a seal is fitted to seal the tube against the cable.