Fibre for City of Cape Town broadband

March 14th, 2014, Published in Articles: EngineerIT

 

Social demands for increased municipal services have created the need for faster and improved communications to cater for increased capacity in the network. The choice for upgrading the City of Cape Town system was to change over from the conventional fibre optic (FO) cable interconnecting method, to a blown fibre optic (BFO) cable.

One of the features of the project was the use of locally manufactured thermoplastic components and engineering expertise. The project started in 2007, when a decision was made by city engineers to use BFO instead of a conventional fibre optic cable.

Fig. 1: Broadband blown fibre optic interconnecting system design.

Fig. 1: Broadband blown fibre optic interconnecting system design.

After the initial design requirement meetings, a site meeting was held to determine if the proposed system configuration from Tank Industries would meet the fitment requirements of the “Rocha” manhole design. A simulated Rocha manhole was created in the company’s test laboratory, and fitted with blown fibre optic cables.

The prototype design proposal was for a 96 fibre “core closure” and a 24 fibre “access closure” (Fig. 1) interconnected to a R&M ODF and an R&M patch panel distribution unit respectively. Following a few design changes, two samples were manufactured for testing.

Fig. 2: Dome closure configurations.

Fig. 2: Dome closure configurations.

Fig. 3: Core enclosure 144 fibres.

Fig. 3: Core enclosure 144 fibres.

Fig. 4: Access closure.

Fig. 4: Access closure.

The 144 FO core closure is the main feed for the system. It is a moulded dome shaped outer shell with a moulded base housing a 144 FO organiser management system. Fibre splices are protected by way of silicone heat-shrinkable tubes with a stainless steel rod inserted between the tubes for mechanical strength. These are supported in FO splice protector holders. A moulded swing clamp with an O-ring holds and seals the two substructures together. Two oval ports and six PMA polyamide conduits are sealed into the base for FO cable entry and exit.

The 48 FO access closure is manufactured to the same design as the FO core closure. The core closure has a direct FO tube to FO tray system where as the access closure has a tubeless fibre management system, which allows for easy distribution of fibres between the trays, and controlled distribution of fibres to the clients. Fibre optic coil boxes are utilised to store all excess FO cables.

Other accessories include LC-APC pigtails, adaptors and patch cords for installation into the various switching centres. Five switch centres have been built by the city, the main centres at Gallows Hill, Athlone, Parow and Bellville, all in the Western Cape.

Performance testing for configuration, fitment and interchangeability was carried out in a Rochla manhole at Blackheath, Cape Town. The system met all the specifications and customer requirements. Environmental testing was carried out in the Tank Industries Laboratory in Retreat, Cape Town

Contact Eric Martinsich, Tank Industries, Tel 021 700-4380, eric.martinsich@tank.co.za

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