Easy access cable - installation of distribution frame/box (example)

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Fiber optic systems in multifamily buildings (or MDUs - Multi-Dwelling Units) are becoming increasingly popular. They are installed by telecoms and other operators in existing buildings in order to provide a new range and quality of services. In many countries, including Poland, they are required in new buildings by current building regulations. So far, fiber optic systems have been the domain of metropolitan networks, and they have been deployed by large companies specializing in this field. In comparison, FTTH (Fiber To The Home) systems are normally installed in parallel with low-current networks typically implemented in each facility (television, LAN, fire alarm, intercom , CCTV monitoring, alarm system). All the systems are often installed by one contractor, so the installation companies should acquire both some theoretical knowledge and practical skills in optical technology.

Below there is an example of terminating FTTH network based on the so-called easy access cable. Currently, the use of easy access cables is the optimal solution for installing fiber-optic cabling in buildings.

Easy access cables are always terminated in optical distribution frames or boxes. In general, the number of fibers in the cable results from the number of end users (usually it is the same as the number of independent units/apartments). In the case of larger buildings, it requires application of large wall or rack-mount frames. The latter usually have the possibility of adding next splice trays/cassettes and adapters. The example shows the implementation of the L7824 24-fiber cable and the L5224 fiber optic box.

View of the L5224 fiber optic box, installed in a RACK cabinet, and the L7824 distribution cable. Before entering the box, it is necessary to prepare the cable end, i.e. to remove the outer jacket over a length suitable for distribution of the fibers inside the box, taking into account the layout of the fibers on the trays and ease of operations. It is also advisable to hold a spare length of the cable in front of the inlet opening. One should keep in mind that the trays can be taken out for future operations, so there is a need for compromise between the "comfort" and "minimum" length of the fibers inside the box. One should avoid to run any bare fibers outside the box.
The jacket of the cable can be easily taken off after incision made with special scissors L5904. Further, the jacket can be torn along the reinforcing fibers.

The L7824 cable has 24 fibers which should be divided into groups according to the amount of adapters installed on the trays. In the case of the L5224 box, each tray can accommodate 12 adapters. The fibers in the cable are marked with 12 colors plus additional black marker - each color is available with and without this marker. Thus, the fibers have been divided into 2 groups - with and without the black marker.

One of the cassettes mounted in the box, holding 12 SC/APC L4222 adapters

and spare lengths of 12 fibers (on the upper tray)

Each cassette is normally equipped with tray for placing fusion splices protected with sleeves. In the case of mechanical splices, it must be replaced by a different element that can accommodate the appropriate number of the larger splices.

The lower tray in the cassette is used to protect spare lengths of pigtail fibers that are to be spliced with the fibers of the easy access cable. In case of installations based on easy access cables, the dedicated single-mode pigtail set is L3560 with corresponding colors of the fibers. One end of each pigtail (connector) is plugged into the adapter, the second (fiber) is led to the upper tray of the cassette.

Terminating the end of a fiber optic cable with multiple fibers, the installer should pay attention to the appropriate order of the fibers spliced in the distribution frame or installation box. There are several standards addressing that issue, and although there are not general regulations, consistency in this field allows to avoid problems in the event of network maintenance or expansion. Installing optical cabling, it is worth to implement one of the European standards or the proprietary solutions used by cable manufacturers or large telecommunications operators. The table below shows the most common standards for the layout of fibers in optical distribution frames/boxes. A fixed sequence should be used both in the case of welding and connecting the fibers to adapters.

The most popular color sequences used in distribution frames/boxes

The upper tray with splices between the fibers of the easy access cable and those of the pigtails

Before welding, it is highly important to cut the fibers so that they can be properly arranged on the tray

The first pair of the fibers (red color) spliced with the Ultimode FAST MS-1 L5550 mechanical splice. Likewise, there should be spliced the next pairs of fibers with the same colors.