FTTx Wiring Concerns – Deploying Optical Fiber Cables in Multi Dwelling Units

With service providers started offering high speed internet based quality services, the OSP contractors are busy in installing indoor fiber optic cables in apartments and office buildings. Multi dwelling apartments have typical problems that an OSP contractor shall be prepared to face.

Reduced space for riser cable installation comes at first. The vertical shaft space is always limited and not even sufficient for fiber optic cables. Manufacturers offering small diameter fiber optic riser cables will be encouraged to supply for such projects. Reduced diameter with high fiber density is one of the criteria to solve the space related issues.

Installing a joint box in the vertical shaft if branching is required is another headache. In such cases, single or dual fiber indoor cables can be directly connected from the fiber distribution hub or main distribution frame at the bottom of the apartment to the customer premise.

Skilled manpower to install sensitive optical fiber cables poses another issue for multi-dwelling wiring. Since the optical fibers are sensitive to bend and strain, trained technicians are required. Recently some manufacturers from East Asia have come up with fiber optic indoor cables with very low friction coefficient. These indoor cables will easily slide through conduits with existing communication cables. On many occasions, installing a separate conduit for new fiber optic indoor cables is not required.

The low friction indoor cable can be pushed through the conduits by virtually anybody who happened to have his first look at fiber optic cables just by opening the pack before installation! This is what the manufacturers tell about their low friction indoor cables. We have tested the performance of low friction indoor cables and compared it with conventional indoor cables at an exhibition and found extremely satisfied with new cables. In contrast to pulling installation methods, low friction fiber optic indoor cables are installed by pushing. This easy to install indoor cables will find their market in many developing and emerging markets for FTTH.

Another issue is the availability of suitable plug and play devices. The intermediate joint boxes and connectors shall be extremely user friendly in order to make the indoor installation a child game. One such easy to connect mechanical splice which is used for fast FTTH connection is Fujikura’s FAST Connectors.

The customers in a multi-dwelling apartment are unpredictable in their demand for high bandwidth requirements. The indoor fiber optic cables shall be so easy to install as and when customers ask for a connection. After applying for connection, customers do not have the patience to wait as they apply for upgrading bandwidth when it is extremely felt by them – quite natural.

Multi Dwelling apartment

Multi-dwelling units have multiple bends that are small and sharp. FTTH cables will be designed to meet these bending requirements. FTTH cables with ITU-T G.657A complying fibers will have a minimum bending radius of 15 mm and ITU-T G.657B complying fibers will have a minimum bending radius of 7.5mm.

This will meet the house wiring conditions. Corning’s Clear-Curve and Draka’s Bendbright bend insensitive optical fibers are industry leaders in FTTH applications. Fujikura’s ITU-T G.657 complying fibers are also well employed in many multi-dwelling apartments in middle east Asia and Southeast Asian countries apart from Japan. OSP contractors shall analyze the performance versus the cost factors to decide on the economy of FTTH installation.

ITU-T G.657A fibers have good backward compatibility with G.652 fibers. Bend insensitive fibers will meet ITU-T G.652D – Low water peak fiber specifications also. Therefore backward compatibility is not an issue. But OSP contractor shall confirm as some optical fibers have differences in the mode field diameter range.

ITU-T has a broad range of mode field diameter with tolerance. Optical fiber manufacturers comply with ITU-T specification for Bend insensitive fiber’s mode field diameter, but may not necessarily compatible with the optical fibers used in the existing next works or backbone networks. This will create high splice loss problems, even though it is a small effect.

Installers shall ensure that the Optical fiber cable used for the riser area shall meet the fire ratings as per NESC specifications. Low smoke zero halogen materials are employed to protect the indoor cables. In case of fire, many casualties happen due to smoke generated from the cables installed in the buildings. The fire-resistant sheathed indoor cables have to be passed in the vertical flame test as per IEC standards.

The most important concern is the cost of FTTx cable. FTTx cables are blamed for their high investment cost. The economically viable solution shall be searched while retaining the high quality of optical fiber cables. Low cost at the cost of quality will not be a practical solution. Fortunately, we have many worlds reputed manufacturers for Drop, Riser, Plenum, and other types of Indoor cables used for FTTx applications.

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