Optical-fiber Technology

Optical-fiber Technology - Architecture

Specification of FITL architecture

FTTC is an effective solution due to its price for a group of dwellings and residential areas. In this case the optical fiber reaches a street cabinet resistant to changeable weather conditions, near the road, often installed in places of termination of former copper track mains. This allows for usage of the already existing copper subscriber�s links and cable mains for further connection to subscribers. It is worth mentioning that the band rendered available for the user and, ipso facto, the multimedia services range depend on the length and quality of the copper wires and the applied transmission technique in the given section (ex. HDSL, SDSL, ADSL). There is also an emergency power supply installed in the street cabinets (accumulators), which allow for a few-hours� worth of work after the power supply disappears from the power net. An advantage of FTTC is the fact that the cost of such a solution is divided between many subscribers, As a consequence, the tariffs can remain low, which leads to quick spread of the services.

FTTB is a perfect architecture for providing advanced multimedia services for subscribers in a dwelling with numerous apartments, ex. office buildings, hotels, business centers and industry plants. Its likeliness with FTTC lies in the fact that the final connection to the users is made through the copper strand and costs of the installation and maintenance of the network is divided between many users. The difference is that the distribution network ends in the building, usually in the cellar or in the preservation channel. This makes configuration and realization of subscribers` terminals easier in the internal, dwelling telecommunication infrastructure. It also protects these devices from the influence of weather conditions and unauthorized access. Climatic conditions inside a building are more stable and easier to control. On the other hand, however, introduction of the device into a building requires individual talks with administrator of each object in which the ONU is to be mounted. If the constructed network covers premises administered by a company, a housing association, the task is relatively easy. In other case, the issue of choosing a location, talks with individual administrators and owners of the dwelling may considerably delay preparation of the investment and increase the costs.

FTTH consists in running a separate optical fiber to each subscribe`s house (ONU/NT group is mounted directly at the user`s). It is a final solution of network access, which guarantees a full width of the optical fiber for each user. In consequence, it is a more flexible solution due to its transmission band which basically provides the subscriber with an unlimited range of services which are there to be rendered. It is, however, the most expensive solution as it requires construction of a totally new infrastructure of the access network and, in consequence, it so hitherto most rarely used. At the moment and probably in near future, such a network structure will not be very attractive for housing users. It must be therefore noted that FTTH is a configuration for the future.

An optical fiber is a purely glass quartz fiber transmission medium made from silicon dioxide, it has a circular cross-section in which the light is closed by being encircled with opaque cladding of centrally situated core. For light rays with frequency in range proximal to IR, the light reflection coefficient is greater in the coat than in the core, which results in total internal ray reflection and leading it along the fiber`s axis.

Optical fiber consists of:

(1) the core - quartz glass SiO2 doped with GeO2,
(2) the cladding - pure quartz glass SiO2,
(3) the primary covering - acrylic covering (CPC) with an external colorful layer hardened in UV.

See also: Optical-fiber Technology Optical-fiber Technology - modes