LUIS CARLOS DÍAZ DÍAZ, Bucaramanga, Colombia

INTRODUCTION

To navigate for the world net of nets, Internet, they are not only needed a computer. Recently a service allows to be connected Internet through the optic fiber.

Origin and Evolution

The History of the communication for the optic fiber is relatively short. In 1977, he/she settled a test system in England; two years later, took place already important quantities of orders of this material.
Before, in 1959, as derivation of the studies in physics focused to the optics, he/she was discovered a new use of the light, to which was denominated ray laser that was applied to the telecommunications with the purpose of that the messages were transmitted to unusual speeds and with wide covering.

However this use of the laser was very limited because the conduits and appropriate channels didn't exist to make the electromagnetic waves caused by the rain of photons originated in the source denominated laser to travel.
It was then when the scientists and technicians specialized in optics directed their efforts to the production of a duct or channel, well-known today like the optic fiber.

In 1966 the proposal arose of using an optic guide for the communication.
This form of using the light like portadora of information can explain to herself in the following way: It is an electromagnetic wave of the same nature in fact that the radio waves, with the only difference that the longitude of the waves is of the order of micrometers instead of meters or centimeters.

What Optic Fiber it is

Before explaining directly that it is the optic fiber, it is convenient to stand out certain basic aspects of optics. The light moves to the speed of the light in the hole, however, when he/she spreads for any other means, the speed is smaller. This way, when the light passes of spreading for a certain means to spread for other certain half, its speed changes, also suffering reflection effects (the light bounces in the change of half, as the light reflected in the glasses) and of refraction (the light, besides changing the I modulate of its speed, it changes propagation address, for that reason we see a tablespoon like bent when it is in a glass of water, the address of where he/she comes us the light in the part that is to the air it is not the same one that the one that is put in the water).

This leaves better form in the drawing that he/she appears to our right.
Depending on the speed with which the light spreads in a means or material, he/she is assigned an Index of Refraction "n", a deduced number of dividing the speed of the light in the hole among the speed of the light in this means. The reflection effects and refraction that are given between two in the frontier means depend on their Indexes of Refraction. The most important law that I will use in this article is the following one for the refraction:

This formula tells us that the index of refraction of the first means, for the breast of the angle with which impacts the light in the second means, is similar to the index of the second means for the breast of the angle with which comes out spread the light in the second means. And this so that it serves?, is the only thing that interests us here of this law that given two means with index n and n', if the sheaf of light impacts with a bigger angle that a certain angle limit (that is determined with the previous equation) the you make he was always reflected between both in the separation surface means. This way you can guide the light in a such controlled way and like leave in the drawing of below (that represents in a schematic way as it is the optic fiber).

As you leave in the drawing, we have an encircling material with index n and an interior material with index n'. So that it is possible to guide the light for the cable. The Optic Fiber consists therefore, in a cable of this type in the one that the materials are much more economic that the conventional of copper in telephony, in fact they are material optic much slighter (optic fiber, tells it the name), and the cables are also much finer, so many can go more cables in the space where before alone a copper cable went.

Concept of Optic Fiber

The circuits of optic fiber are glass filaments (made up of natural glasses) or plastic (artificial glasses), of the thickness of a hair (between 10 and 300 microns). they Take messages in form of faces of light that pass really through them of an end to other, where he/she wants that the filament goes (including curved and corners) without interruption.
The optic fibers now can be used as the conventional copper wires, so much in small autonomous atmospheres (such as systems of prosecution of data of airplanes), like in big geographical nets (as the systems of long urban lines maintained by phone companies).

The principle on that the transmission of light is based by the fiber is the total internal reflection; the light that travels for the center or nucleus of the fiber impacts on the external surface with a bigger angle that the critical angle, so that all the light is reflected without losses toward the interior of the fiber. This way, the light can be transmitted at long distance being reflected thousands of times. To avoid losses for dispersion of due light to sludges of the surface of the fiber, the nucleus of the optic fiber is recovered by a glass layer with a much smaller refraction index; the reflections take place in the surface that separates the glass fiber and the recubrimiento.

Production of the Optic Fiber

The images here show like the fiber monomodo is manufactured. Each stage of production this cultured one for a short filmed sequence.

The first stage consists on the assembling of a tube and of a bar of cylindrical glass mounted concentrically. He/she warms the everything to assure the homogeneity of the glass bar.

A bar of glass of a longitude of 1 m and of a diameter of 10 cm he/she allows to obtain for stretching a fiber monomodo of a longitude of around 150 km.

The bar this way obtained it will be installed vertically in a tower located in the first floor and heated by the ramps to gas.
The glass will stretch out and "to strain" in address of the root to be wound on a reel.

The thickness of the fiber is measured (~10um) to dominate the speed of the motor of the winder, in order to assure a constant diameter.

Each fiber reel makes the object of a control of quality made to the microscope. Then he will wrap up the glass with a protection lining (~230 um) and to assemble the fibers to obtain the final cable to an or several strands.

Of what are the Optic Fibers made?

Most of the optic fibers are made of sand or silica, matter prevails abundant in comparison with the copper. with some kilograms of glass they can be manufactured 43 kilometers of optic fiber approximately. The two essential constituents of the optic fibers are the nucleus and the lining. The nucleus is the most internal part in the fiber and it is the one that guides the light.

It consists on an or several thin strands of glass or of plastic with diameter of 50 to 125 microns, the lining is the part that surrounds and it protects to the nucleus.

The nucleus group and lining is in turn surrounded by a lining or case of plastic or other materials that preserve him against the humidity, the squashing, the rodents, and other risks of the environment.

How does the Optic Fiber work?

In a transmission system for optic fiber a transmitter that takes charge of transforming the electromagnetic waves in optic energy exists or in luminous, for he/she is considered it the active component of this process. Once the luminous sign is transmitted by the minuscule fibers, in another end of the circuit he/she is a third component to which is denominated detecting optic or receiving whose mission consists in transforming the luminous sign in electromagnetic energy, similar to the original sign.

The basic system of transmission is composed in this order, of entrance sign, amplifier, source of light, optic corrector, line of optic fiber (first tract), connect, line of optic fiber (second tract), optic corrector, receiver, amplifier and exit sign.

In summary, one can say that this communication process, the optic fiber works like half of transportation of the luminous sign, generated by the transmitter of LED'S (issuing diodes of light) and laser.
The issuing diodes of light and the diodes laser are appropriate sources for the transmission by means of optic fiber, because their exit you can control quickly by means of a polarization current. Also their small size, their brightness, wave longitude and the first floor necessary voltage to manage them are characteristic attractive.

Which are the implicit devices in this process?

The main blocks of a connection of communications of optic fiber are: transmitter, receiver and fiber guide. The transmitter consists of an analogical or digital interface, a voltage converter to current, a source of light and an adapter of source of light to fiber. The fiber guide is a pure ultra glass or a plastic cable. The receiver includes a device detecting connector of fiber to light, a detecting picture, a current converter to voltage a voltage amplifier and an analogical or digital interface In a transmitter of optic fiber the source of light you can modulate for a similar or digital sign.

Coupling impedances and limiting the width of the sign or in pulses digitales.El voltage converter to current serves as electric interface between the entrance circuits and the source of light.

The source of light can be an issuing diode of light LED or a diode of injection laser ILD, the quantity of emitted light is proportional to the excitement current, therefore the converter voltage to current transforms the voltage of the entrance sign into a current that is used to direct the source of light. The source connection to fiber is a mechanical interface whose function is to couple the source of light to the cable.

The optic fiber consists of a nucleus of glass fiber or plastic, a cover and a layer protector. The joining device of the fiber detector to light is also a mechanical acoplador.

The detector of light is generally a diode PIN or an APD (avalanche fotodiodo). Both transform the energy of light into current. In consequence, an average converter is required to voltage that transforms the changes in the current from the detector to voltage changes in the exit sign.

COMPONENTS AND TYPES OF OPTIC FIBER

Components of the Optic Fiber

The Nucleus: In silica, fused quartz or plastic - in which the optic waves spread. Diameter: 50 or 62,5 um for the fiber multimodo and 9um for the fiber monomodo.

The Optic Case: Generally of the same materials that the nucleus but with preservatives that confine the optic waves in the nucleus.

The protection lining: in general this manufactured in plastic and it assures the mechanical protection of the fiber.

Types of Optic Fiber:

Fiber Monomodo: 

Potentially, this it is the fiber that he/she offers the biggest capacity of transport of information. He/she has a band in passing of the order of the 100 GHz/km. The biggest flows are gotten with this fiber, but it is also the most complex of implanting. The drawing shows that they can only be transmitted the rays that have a trajectory that follows the axis of the fiber, for what the name has been won of "monomodo" (propagation way, or on the way to the luminous, only sheaf). they are fibers that have the diameter of the nucleus in the same order of magnitude that the longitude of wave of the optic signs that you/they transmit, that is to say, of unos 5 to 8 m m.

If the nucleus is constituted of a material whose refraction index is very different to that of the cover, then it is spoken of fibers monomodo of staggered index. The high flows that can be reached constitute the main advantage of the fibers monomodo, since their small dimensions imply a delicate handling and they involve connection difficulties that still restrain bad.

Fiber Multimodo of Index Gradiante Gradual: 

The fibers multimodo of index of gradual gradient have a band in passing that it arrives up to the 500MHz for kilometer. Their principle is based in that the refraction index inside the nucleus is not only and it falls when he/she moves of the nucleus toward the cover. The luminous rays are focused toward the axis of the fiber, like one can see in the drawing. These fibers allow to reduce the dispersion among the different propagation ways through the nucleus of the fiber.
The fiber multimodo of index of gradual gradient of size 62,5/125 m (diameter of the núcleo/diámetro of the cover) it is normalized, but they can be other types of fibers:

Multimodo of index staggered 100/140 mm.

Multimodo of index of gradient gradual 50/125 mm.

Fiber Multimodo of staggered index:

The fibers multimodo of staggered index are manufactured with the help of glass, with an attenuation of 30 dB/km, or plastic, with an attenuation of 100 dB/km. they Have a band in passing that it arrives until the 40 MHz for kilometer. In these fibers, the nucleus is constituted by an uniform material whose refraction index is clearly superior to of the cover which surrounds it. The step from the nucleus until the cover bears a brutal variation of the index therefore, of there its name of staggered index.

What type of connectors does it use?

With the Optic Fiber you can use Acopladores and Connectors:

Acopladores:

An acoplador is basically the necessary mechanical transition to be able to give continuity to the step of light of the end conectorizado from a cable of optic fiber to another. They can also be provided type acopladores "Hybrid" that allow to couple two designs different from connector, one of each side, conditioned to the coincidence of the profile of the refined one.

Connectors:

1. - the connector is recommended 568SC because this it maintains the polarity. The position corresponding to the two connectors of the 568SC in their adapter, they are denominated like TO and B. This help to maintain the correct polarity in the system of having wired and it allows to the adapter to implement guessed right inverse polarity of couples among the connectors.

2. - systems with connectors BFOC/2.5 and adapters (Type ST) installed they can continue being used in current and future platforms.

Identification: Connectors and adapting Multimodo are represented by the color ivory Connectors and adapting Monomodo they are represented by the blue color.

For the termination of an optic fiber it is necessary to use connectors or to connect Pigtails (armed cables with connector) by means of coalition. For the case of conectorización they are different types of connectors depending the use and used l normative World cup and their characteristics.

ST connector of Fiber for Monomodo or Multimodo with habitual use in Nets of Data and teams of local Networking in form Multimodo.

CHARACTERISTIC OF THE OPTIC FIBER

General characteristics:

More resistant coverings:

The special cover is directly extruida to high pressure on the same nucleus of the cable, being in that the internal surface of the covered with the cable has helical edge that you/they make sure with the subcables.

The cover contains 25 more material% that the conventional covers.

The resistance to the water, mushrooms and emissions ultra violet; the resistant cover; buffer of 900 µm; optic fibers proven under 100 kpsi; and extended environmental operation; they contribute to a bigger dependability during the time of life.

In cables of tube ample fillers of gel, the gel inside the cover settles leaving channels that allow that the water migre toward the termination points. The water can accumulate in small pools in the holes, and when the delicate optic fiber is exposed, the useful life is clipped by the harmful effects of the water in contact. they combat the intrusion of humidity with multiple protection layers around the optic fiber. The result is a humid specially ambient bigger life useful, bigger dependability.

The new advances in anti-inflammable protection make the risk that you/they suppose the old facilities of Optic Fiber that contained covered with inflammable material to diminish and I stuff of gel that is also inflammable.

These materials cannot fulfill the requirements of the installation norms, they present an additional risk, and they can also create an expensive and difficult challenge in the restoration after a fire. With the new advances in this field and in the design of these cables these risks are eliminated and it is fulfilled the installation norms.
Packed of high density:

With the maximum number of fibers in the smallest possible diameter a quicker and easier installation is gotten, where the cable should face sharp cuffs and narrow spaces. You has ended up getting a cable with 72 fibers of construction dense súper whose diameter is 50 smaller% to that of the conventional cables.

Technical characteristics:

The fiber is a means of transmission of analogical or digital information. The electromagnetic waves travel in the space to the speed of the light.

Basically, the optic fiber is composed by a cylindrical region, for which the propagation, denominated nucleus is made and of an external area to the nucleus and coaxial with him, completely necessary so that the propagation mechanism takes place, and that it is denominated cover or lining.

The capacity of transmission of information that has an optic fiber depends on three fundamental characteristics:
to) Of the geometric design of the fiber.
b) Of the properties of the materials employees in their elaboration. (I design optic)
c) Of the ghastly width of the source of used light. As much as adult is this width, minor it will be the capacity of transmission of information of that fiber.

It presents more reduced dimensions that the means preexistentes. A cable of 10 fibers has an approximate diameter of 8 or 10 mm. and it provides the same or more information that a coaxial of 10 tubes.
The weight of the cable of optic fibers is very inferior to that of the metallic cables, redounding in its installation easiness.
The silica has a wide operation margin regarding temperature, because he/she is founded at 600C. The F.O. it presents an uniform operation from -550 C to +125C without degradation of their characteristics.

Mechanical characteristics:

The F.O. as willing resistant element inside a cable formed by aggregation of several of them, he/she doesn't have appropriate characteristics of traction that allow their direct use.
On the other hand, in most of the cases the facilities are to the bleakness or in aggressive atmospheres that can affect to the nucleus.

The investigation on component optoelectrónicos and optic fibers have brought I get a sensitive increase of the quality of operation of the systems. It is necessary to prepare of covered and protection of quality able to protect to the fiber. To reach such an objective it is necessary to keep in mind their sensibility to the bend and microcurvatura, the mechanical resistance and the aging characteristics.

The microcurvaturas and tensions are determined by means of the rehearsals of:

Tension: when he/she stretches out or it contracts the cable forces they can be caused that they surpass the percentage of elasticity of the optic fiber and break or form microcurvaturas.

Compression: it is the traverse effort.

Impact: it owes himself mainly to the protection of the optic cable.

Enrollamiento: it always exists a limit for the bend angle but, the existence of the lining prevents him to be surpassed.

Torsion: it is the lateral effort and of traction.

Thermal limitations: these limitations differ grade on high as it is fibers carried out starting from the glass or starting from synthetic materials.

Another objective is to minimize the additional losses had wired and the variations of the attenuation with the temperature. Such you differ they should to designs sometimes calculated to improve other properties, as the mechanical resistance, the connection quality, the filler coefficient (number of fibers for mm2) or the production cost.

ADVANTAGES AND DISADVANTAGES OF THE OPTIC FIBER.

APPLICATIONS OF THE OPTIC FIBER

Internet

The connection service to Internet for optic fiber, demolishes the biggest limitation in the ciberespacio: their infuriating slowness. The purpose of the following article is to describe the action mechanism, the advantages and its disadvantages.
To navigate for the world net of nets, Internet, a computer, a modem and some programs are not only needed, but also a great dose of patience. The ciberespacio is a slow world until the I despair. An user can spend several minutes waiting to that it is loaded a page or several hours trying to go down a program from the Net to his PC.

This is due to that the phone lines, the means that uses most of the 50 million users to be connected Internet, was not created to transport videos, graphic, texts and all the other elements that travel from a side to another in the Net.

But the phone lines are not the only road toward the ciberespacio. Recently a service allows to be connected Internet through the optic fiber.

The optic fiber makes possible to navigate for Internet to a speed of two million bps.

Nets
The optic fiber is used more and more in the communication, because the waves of light have a high frequency and the capacity of a sign to transport information it increases with the frequency. In the nets of communications laser systems are used with optic fiber. Today many fiber nets work for communication at long distance that you/they provide transcontinental and transoceanic connections.

An advantage of the systems of optic fiber is the great distance that a sign can travel before needing a repeater to recover its intensity. At the present time, the repeaters of optic fiber are separated about 100 kms to each other, in front of approximately 1,5 km in the electric systems. The recently developed amplifiers of optic fiber can still increase more this distance.

Another more and more extended application of the optic fiber is the nets of local area. On the contrary that the communications of long distance, these systems connect to a series of local subscribers with teams centralized as computers (computers) or printers. This system increases the yield of the teams and it allows the incorporation easily to the net of new users. The development of new component electroópticos and of integrated optics it will increase even more the capacity of the fiber systems.

Net of local area or LAN, group of computers that can share data, applications and resources (for example printers). The computers of a net of local area (LAN, Local Area Network) they are separated by distances of until some few kilometers, and they usually use in offices or campus university students. A LAN allows the quick and effective transfer of information in the breast of a group of users and it reduces the costs of exploitation.

Other connected computer resources are the nets of wide area (WAN, Wide Area Network) or the particular switchboards (PBX). The WAN is similar to the LAN, but they connect computers separated by more distances to each other, located in different places of a country or in different countries; they use specialized and expensive physical team and they lease the services of communications. The PBX provides continuous computer connections for the transfer of specialized data as phone transmissions, but they are not appropriate to emit and to receive the picks of data of short duration used by most of the computer applications.

The public communication nets are divided in different levels; according to the operation, to the transmission capacity, as well as to the reach that you/they define. For example, if he/she is approaching from the exterior toward the interior of a great city, one has the intercity net and net provicional firstly, next the lines lingering aportadoras of traffic of lower capacity coming from far away areas (rural net), toward the center the urban net and finally subscriber's lines. The parameters dictated by the practice are the transmission tract that is possible to cover and the specific binary speed as well as the adapted type of optic fiber, that is to say, cables with fibers monomodo or multimodo.

Telephony
With reason of the normalization of existent interfaces, he/she has the transmission systems for optic fiber for the levels of the net of public telecommunications in a wide application, contrarily for systems of subscriber's net (subscriber's line), there is a series of considerations above all.

For the connection of a telephone it is totally enough with the existent copper drivers. In fact with the installation of the services in wide band as the videoconference, the videotelefonía, etc, the optic fiber will become indispensable for the subscriber. With the BIGFON (integrated urban net of telecommunications in wide band for optic fiber) wide experiences have been gathered in this aspect. According to the elaborated strategy, the services of wide band later on will be enlarged with the services of radio distribution and of television in a net of telecommunications integrated in wide band (IBFN).

Other applications

The optic fibers are also used in a wide variety of sensors that you/they go from thermometers to gyroscopes. Its application potential in this field hardly has limits, because the light transmitted through the fibers is sensitive to numerous environmental changes, among them the pressure, the sound waves and the deformation, besides the heat and the movement. The fibers can be specially useful when the electric effects could make that a conventional cable was useless, imprecise or even dangerous. Fibers have also been developed that transmit rays laser of high power to cut and to drill materials.

The simplest application in the optic fibers is the transmission of light to places that would be difficult to illuminate otherwise, as the cavity perforated by the turbine of a dentist. They can also be used to transmit images; in this case faces of several thousands of very fine fibers are used, located exactly one beside the other one and optically polished in their ends. Each point of the image projected on an end of the sheaf reproduces in the other end, with what the image is reconstructed that can be observed through a magnifying glass. The transmission of images is used a lot in medical instruments to examine the interior of the human body and to make surgery with laser, in reproduction systems by means of facsimile and phototypesetting, in computer graphics or computer and in many other applications.

SuperCable: it is a transnational company of services of telecommunications in voice, video and it dates that he/she has offered television for cable in Venezuela from beginning of the years 90. With their technology of transmission of data in optic fiber, digital communications and compression of data, it is in capacity of intruding in the vast market of the telecommunications.

The entirety of the net of SuperCable is made of optic fiber that allows the transmission of wide band. The sector of wide Band of Motorola, company leader at global level in integral solutions of communications and absorbed solutions, is the technological partner of Supercable in the development of its television system for cable, the one that will be transformed in a package of interactive services in next years. The agreement includes the implementation of a platform of interactive digital cable in Bogotá and in Caracas.

Motorola technological partner of Supercable

The announcement has wakened up the interest of the sector of business of television he/she pays in the region. Supercable began operations in Ecuador, then he/she settled last year in Venezuela and the the shareholders of the company they took the determination of participating at level panregional. The first step is the launching in the Colombian market with plans of adding another country this year. They installed their main house in the south of The Florida, in United States.

COMPARISON WITH OTHER MEANS OF COMMUNICATION

Comparison with the coaxial cables

Communications for Satellite vs Optic Fiber

It is more economic the F.O. for distances short and high traffic volumes, for example, for a route of 2000 ctos., the satellite is not profitable in front of the solution of the cable of fibers until a longitude of the same similar to about 2500 kms.
The quality of the sign for cable is for much higher that for satellite, because in the geoestacionarios, located in orbits of about 36,000 kms. of height, and the next retard to 500 mseg. it introduces echo in the transmission, while in the cables this it is located below the 100 mseg admitted by the CCITT. The inclusion of suppressive of echo urges the installation, it diminishes the reliability and subtraction the quality when cutting the sentence beginnings.

The satellite adapts to the digital technology, although the advantages in this field are not so evident in the analogical one, when being required a bigger band width in that and to be this a critical factor in the design of the satellite.

PERSONAL OPINIONS

In our opinion the F.O. alone it is advisable for Companies and it doesn't stop small users due to their high cost, not alone the installation cost but also for that of the quotas, also always these to expense that there is a line of F.O. near your house since if it is not the installation it is not this way feasible.

Definitively, the small consumers will wait to that the science advances a little but in this field and be accessible for all, alone then we will be able to benefit of the advantages that he/she offers us this technology.