Conectronica Revista Maganize industrial de electronica

The selection of the more appropriate optical fiber cable for an application makes specific is a more and more frequent task, as much for the departments of engineering like for the buyers of the different companies. Direct consequence of the increase of use of this means of transmission in all type of facilities this task has stopped being a work of specialists to become a more and more frequent assignment for the majority from the people in charge of these departments in all type of Companies. Next, we realised a route on the different indispensable requirements from the different components from an optical cable, as well as from the answers offered by the market and the keys for a correct identification of the supply.

He is more and more frequent the one that the people in charge of the purchase or installation of an optical cable are with definitions of the type of “Cable of `n' fibers multiway for outer interior/, antihumidity and antirodents”, or “Cable of `n' fibers monoway, dielectric and with non-flammable cover”. It is this sufficient one for an exact description of the necessary thing? What data are necessary to obtain a definition fit of the necessary thing? We review with a certain one details the structure of a cable of this type, thus to be able to give answer to these questions: Generic description of an optical fiber cable

The optical cables are formed by two basic components, each one of as it must suitably be selected based on the received specification, or of the work to develop: - The optical nucleus: Formed by the set of optical fibers, it conforms the system guide-waves responsible for the transmission of the data. Their characteristics will come defined by the nature from the network to install. It will define if one is a cable with fibers Monomodo, Multimodo or compound. - The protection elements: Its mission consists of protecting to the optical nucleus against the surroundings in which the cable will be located, and consists of several elements (Covered, armor, etc.) superposed in concentric layers from the optical nucleus. Based on its composition, the cable will be of interior, outside, to install in conduit, aerial, etc. The optical nucleus:

Types of fibers

Basically, the present optical fibers to the date in ours market is divided in two great groups, generally selected based on the application to develop: Optical fiber Monomodo: For needs of long distance or great bandwidth. It is totally defined by followed abbreviations SM of the corresponding norm, as for example one is in Table 1. The cables provided in formats standard by the different manufacturers usually are constructed with fibers of the type including in the first row of Table 1, reason why any other type will have specifically to be indicated. Optical fiber Multimodo: Used habitually in local networks (LAN), of monitoring or security. Its definition consists of three parts: - MM (Abbreviations corresponding to the MultiMode denomination) - Relation nucleus/coating (Normally 50/125 or 62,5/125) - Type of fiber: OM1, OM2 or OM3 according to Table 2. The safety nets (industrial control and video baseband) use fibers MM (types OM1 or OM2 indifferently), of 62.5/125 or 50/125 based on the distance requirements.

Fit construction. It consists of equipping individually to each fiber of a plastic protection extrusionada directly on her, until reaching a diameter of 900 µm. Staple fibres of Aramida or fiber glass are placed surrounding the fibers to secure the necessary tensile strenght. With this base the cable is constructed. Its main advantage is an optimal protection considerable antihumidity and a flexibility and mechanical resistance. Its main disadvantage is the difficulty to make cables of more than 24 fibers.  comfortable Construction: The individual fibers, conserving their outer diameter of 250 µm, are lodged, in number of up to 24, inside plastic tubes containing waterproof gel that acts like protective antihumidity. The cables type-r count on gel between the different tubes like additional protection. This method allows to the manufacture, using these tubes like basic element, of cables with great number of relatively reduced fibers (multi-barrel monotube up to 24 fibers and in future, up to 256 optical fibers) and outer diameters. The optical nucleus thus constituted is complemented with an element to equip it with tensile strenght (metallic or dielectric flexible rod like central element; or staple fibres of Aramida or located fiber glass peripherally). As inconvenient it is possible to indicate the possibility of lack of protection in front of the humidity in vertical sections, consequence of the fluidity of the gel, or the relative fragility in front of the breakage of individual fibers. Table 3 summarizes the main characteristics of both types of structures. The protection elements: The covers They are those parts of the cable, that, in contact with their surroundings, conform a barrier against possible aggressions of external agents. Constructed generally with different plastic materials, whose characteristics summary in Table 4, take the form from unique cover in called cables “of inner interior” and covers (next to the optical nucleus) and outside (in contact with means) separated by an armor. This double cover has as mission maintaining the protection of the nucleus in the case of the destruction of first; as it can happen in the case of attack of rodents or punched accidental.

The protection elements: The armors

Its mission, within the cable, consists of providing an additional protection against certain aggressions, as they can be the crushing, the attacks of the rodents, the fire, etc. They consist generally of elements (rods, staple fibres, braids or laminae) of steel, or located fiber glass between the two covers (if they exist) or under the outer cover in cables of this structure. The metallic armors, perhaps more effective like protection against the rodents, present/display the disadvantage of suppressing one of the advantages looked for in an optical fiber connection, their characteristic of dielectric connection. The dielectric armors usually are of several types: - Fiber glass Rods: very solid, they provide a high rigidity to the cable - Fiber glass Staple fibres: they maintain the flexibility, present/display a dissuasive effect in front of the rodents, but its effectiveness falls in the curves of the laying, by displacement. - Fiber glass Braid: It adds to the previous advantages (dielectricidad and dissuasive effect) a permanent protection, and in some cables (as type CDAD of OPTRAL) constitutes a barrier in front of the fire. Once taken in account the previous considerations, it is an important point to analyze: How move all these characteristics to the denomination of optical fiber cables, for a fast and easy identification?

The identification of optical fiber cables

Table 5 describes the composition of the optical cable of it go to inside, allowing its easy identification. Thus, for example, a cable type J-K (ZN) H12G50/125OM3 would correspond with: - J: Cable of interior. - - K: Fit structure. - ZN: Elements of traction nonmetalists. - H: Cover LSZH (Zero halogenous). - 12:12 fibers. - G: Multimodo. - 50/125 OM3. Another form to denominate cables of comfortable structure, used by the majority of the present agents in the market, usually is its description, of it go to inside, using symbols of the type of: - P: Polythene - T: Thermoplastic material LSZH - D: FV: Fiber glass - S: Steel - E: Tobacconist - - R: Stuffed - -1: Monotubo Thus, a cable type PESP-R 8 xs SM would be a watertight cable with stuffed double, comfortable structure, with double covered with EP and steel armor, of 8 optical fibers SM. The cables of fit structure, used generally in applications LAN and of security, usually use denominations related to their generic application. Thus, he is habitual that we find in these identifying cases like CDI (Cable of distribution of interior) or CDAD (Armed Cable of Distribution Dielectric). It is essential, to resist his construction with the necessary requirements, resorting to the corresponding technical description. Conclusion Had it counts previously exposed, when defining or to locate an optical fiber cable for a concrete application, does not seem to be sufficient with mentioning the generic application (by ex. “inner/outer” or “antirroedores-antihumedad”), but is precise to identify the different components from its structure (optical nucleus, cover or cover, armor) thus to be able to be safe to use the suitable material and to obtain the looked for results. Generally, a lack of uniformity in the compared elements can arrive at confusion. We see an example: - A cable with “metallic armor and cover for outside, of 24 optical fibers MM 50/125” can correspond with:  a cable type SP-124x50 OM1: steel monocover, armor, monotube, 8 fibers of 50/125 OM1 (apt nm leaves Gigabit to 1300)  a cable of type PESP-R 24 xs 50 OM3: Covered cable of double, steel armor, multi-barrel of 50/125 OM3 (apt for 10 Giga to 300 M.s)  A cable type CDAM 24 xs 50 OM2: Cable of structure fit, double steel fiber braid cover, armor, 24 fibers 50/125 OM2 (apt for Gigabit to 850 nm). Evidently, the prices will not be the same, but the benefits either, and the risk of committing error exists.

For this reason, it seems logical to deduce, that for the correct identification of an optical cable it is precise to successfully obtain the following data:

- Optical Nucleus: Type and number of fibers, type of structure (Comfortable or fit), type of traction element (central or peripheral Element).

- Covers: Number (Simple or double) and type (Generally EP or LSZH. Special cases PUR or NBR).

- Armors: Dielectric (Rods, staple fibres or prance) or metallic (indented steel Plate or prances).

- Generally: Mechanical characteristics required by the project, or type of installation. (Tensile strenght, radio of curvature, etc.). Once located these data, we will know and be able to compare the cable between the alternative presents.