Optical fiber

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A bundle of optical fibers

http://en.wikipedia.org/wiki/Optical_fiber

 

A TOSLINK fiber optic audio cable being illuminated on one end

An optical fiber (or fibre) is a glass or plastic fiber that carries light along its length. Fiber optics is the overlap of applied science and engineering concerned with the design and application of optical fibers. Optical fibers are widely used in fiber-optic communications, which permits transmission over longer distances and at higher bandwidths (data rates) than other forms of communications. Fibers are used instead of metal wires because signals travel along them with less loss, and they are also immune to electromagnetic interference. Fibers are also used for illumination, and are wrapped in bundles so they can be used to carry images, thus allowing viewing in tight spaces. Specially designed fibers are used for a variety of other applications, including sensors and fiber lasers.

Light is kept in the core of the optical fiber by total internal reflection. This causes the fiber to act as a waveguide. Fibers which support many propagation paths or transverse modes are called multi-mode fibers (MMF), while those which can only support a single mode are called single-mode fibers (SMF). Multi-mode fibers generally have a larger core diameter, and are used for short-distance communication links and for applications where high power must be transmitted. Single-mode fibers are used for most communication links longer than 550 metres (1,800 ft).

Joining lengths of optical fiber is more complex than joining electrical wire or cable. The ends of the fibers must be carefully cleaved, and then spliced together either mechanically or by fusing them together with an electric arc. Special connectors are used to make removable connections.

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[edit] History

Daniel Colladon first described this "light fountain" or "light pipe" in an 1842 article entitled On the reflections of a ray of light inside a parabolic liquid stream. This particular illustration comes from a later article by Colladon, in 1884.

Fiber optics, though used extensively in the modern world, is a fairly simple and old technology. Guiding of light by refraction, the principle that makes fiber optics possible, was first demonstrated by Daniel Colladon and Jacques Babinet in Paris in the early 1840s. John Tyndall included a demonstration of it in his public lectures in London a dozen years later.[1] Tyndall also wrote about the property of total internal reflection in an introductory book about the nature of light in 1870: "When the light passes from air into water, the refracted ray is bent towards the perpendicular... When the ray passes from water to air it is bent from the perpendicular... If the angle which the ray in water encloses with the perpendicular to the surface be greater than 48 degrees, the ray will not quit the water at all: it will be totally reflected at the surface.... The angle which marks the limit where total reflexion begins is called the limiting angle of the medium. For water this angle is 48°27', for flint glass it is 38°41', while for diamond it is 23°42'."[2][3]

Practical applications, such as close internal illumination during dentistry, appeared early in the twentieth century. Image transmission through tubes was demonstrated independently by the radio experimenter Clarence Hansell and the television pioneer John Logie Baird in the 1920s. The principle was first used for internal medical examinations by Heinrich Lamm in the following decade. In 1952, physicist Narinder Singh Kapany conducted experiments that led to the invention of optical fiber. Modern optical fibers, where the glass fiber is coated with a transparent cladding to offer a more suitable refractive index, appeared later in the decade.[1] Development then focused on fiber bundles for image transmission. The first fiber optic semi-flexible gastroscope was patented by Basil Hirschowitz, C. Wilbur Peters, and Lawrence E. Curtiss, researchers at the University of Michigan, in 1956. In the process of developing the gastroscope, Curtiss produced the first glass-clad fibers; previous optical fibers had relied on air or impractical oils and waxes as the low-index cladding material. A variety of other image transmission applications soon followed.

Jun-ichi Nishizawa, a Japanese scientist at Tohoku University, was the first to propose the use of optical fibers for communications in 1963.[4] Nishizawa invented other technologies that contributed to the development of optical fiber communications as well.[5] Nishizawa invented the graded-index optical fiber in 1964 as a channel for transmitting light from semiconductor lasers over long distances with low loss.[6]

In 1965, Charles K. Kao and George A. Hockham of the British company Standard Telephones and Cables (STC) were the first to promote the idea that the attenuation in optical fibers could be reduced below 20 decibels per kilometer (dB/km), allowing fibers to be a practical medium for communication.[7] They proposed that the attenuation in fibers available at the time was caused by impurities, which could be removed, rather than fundamental physical effects such as scattering. The crucial attenuation level of 20 dB/km was first achieved in 1970, by researchers Robert D. Maurer, Donald Keck, Peter C. Schultz, and Frank Zimar working for American glass maker Corning Glass Works, now Corning Incorporated. They demonstrated a fiber with 17 dB/km attenuation by doping silica glass with titanium. A few years later they produced a fiber with only 4 dB/km attenuation using germanium dioxide as the core dopant. Such low attenuations ushered in optical fiber telecommunications and enabled the Internet. In 1981, General Electric produced fused quartz ingots that could be drawn into fiber optic strands 25 miles (40 km) long.[8]

Attenuations in modern optical cables are far less than those in electrical copper cables, leading to long-haul fiber connections with repeater distances of 70–150 kilometres (43–93 mi). The erbium-doped fiber amplifier, which reduced the cost of long-distance fiber systems by reducing or even in many cases eliminating the need for optical-electrical-optical repeaters, was co-developed by teams led by David N. Payne of the University of Southampton, and Emmanuel Desurvire at Bell Laboratories in 1986. The more robust optical fiber commonly used today utilizes glass for both core and sheath and is therefore less prone to aging processes. It was invented by Gerhard Bernsee in 1973 of Schott Glass in Germany.[9]

In 1991, the emerging field of photonic crystals led to the development of photonic-crystal fiber[10] which guides light by means of diffraction from a periodic structure, rather than total internal reflection. The first photonic crystal fibers became commercially available in 2000.[11] Photonic crystal fibers can be designed to carry higher power than conventional fiber, and their wavelength dependent properties can be manipulated to improve their performance in certain applications.

[edit] Applications

[edit] Optical fiber communication

Main article: Fiber-optic communication

Optical fiber can be used as a medium for telecommunication and networking because it is flexible and can be bundled as cables. It is especially advantageous for long-distance communications, because light propagates through the fiber with little attenuation compared to electrical cables. This allows long distances to be spanned with few repeaters. Additionally, the per-channel light signals propagating in the fiber can be modulated at rates as high as 111 gigabits per second,[12] although 10 or 40 Gb/s is typical in deployed systems.[citation needed] Each fiber can carry many independent channels, each using a different wavelength of light (wavelength-division multiplexing (WDM)). The net data rate (data rate without overhead bytes) per fiber is the per-channel data rate reduced by the FEC overhead, multiplied by the number of channels (usually up to eighty in commercial dense WDM systems as of 2008[update]).

Over short distances, such as networking within a building, fiber saves space in cable ducts because a single fiber can carry much more data than a single electrical cable.[vague] Fiber is also immune to electrical interference; there is no cross-talk between signals in different cables and no pickup of environmental noise. Non-armored fiber cables do not conduct electricity, which makes fiber a good solution for protecting communications equipment located in high voltage environments such as power generation facilities, or metal communication structures prone to lightning strikes. They can also be used in environments where explosive fumes are present, without danger of ignition. Wiretapping is more difficult compared to electrical connections, and there are concentric dual core fibers that are said to be tap-proof.

Although fibers can be made out of transparent plastic, glass, or a combination of the two, the fibers used in long-distance telecommunications applications are always glass, because of the lower optical attenuation. Both multi-mode and single-mode fibers are used in communications, with multi-mode fiber used mostly for short distances, up to 550 m (600 yards), and single-mode fiber used for longer distance links. Because of the tighter tolerances required to couple light into and between single-mode fibers (core diameter about 10 micrometers), single-mode transmitters, receivers, amplifiers and other components are generally more expensive than multi-mode components.

Examples of applications are TOSLINK, Fiber distributed data interface, Synchronous optical networking.[jargon]

[edit] Fiber optic sensors

Main article: Fiber optic sensor

Fibers have many uses in remote sensing. In some applications, the sensor is itself an optical fiber. In other cases, fiber is used to connect a non-fiberoptic sensor to a measurement system. Depending on the application, fiber may be used because of its small size, or the fact that no electrical power is needed at the remote location, or because many sensors can be multiplexed along the length of a fiber by using different wavelengths of light for each sensor, or by sensing the time delay as light passes along the fiber through each sensor. Time delay can be determined using a device such as an optical time-domain reflectometer.

Optical fibers can be used as sensors to measure strain, temperature, pressure and other quantities by modifying a fiber so that the quantity to be measured modulates the intensity, phase, polarization, wavelength or transit time of light in the fiber. Sensors that vary the intensity of light are the simplest, since only a simple source and detector are required. A particularly useful feature of such fiber optic sensors is that they can, if required, provide distributed sensing over distances of up to one meter.

Extrinsic fiber optic sensors use an optical fiber cable, normally a multi-mode one, to transmit modulated light from either a non-fiber optical sensor, or an electronic sensor connected to an optical transmitter. A major benefit of extrinsic sensors is their ability to reach places which are otherwise inaccessible. An example is the measurement of temperature inside aircraft jet engines by using a fiber to transmit radiation into a radiation pyrometer located outside the engine. Extrinsic sensors can also be used in the same way to measure the internal temperature of electrical transformers, where the extreme electromagnetic fields present make other measurement techniques impossible. Extrinsic sensors are used to measure vibration, rotation, displacement, velocity, acceleration, torque, and twisting.

[edit] Other uses of optical fibers

A frisbee illuminated by fiber optics

Fibers are widely used in illumination applications. They are used as light guides in medical and other applications where bright light needs to be shone on a target without a clear line-of-sight path. In some buildings, optical fibers are used to route sunlight from the roof to other parts of the building (see non-imaging optics). Optical fiber illumination is also used for decorative applications, including signs, art, and artificial Christmas trees. Swarovski boutiques use optical fibers to illuminate their crystal showcases from many different angles while only employing one light source. Optical fiber is an intrinsic part of the light-transmitting concrete building product, LiTraCon.

Optical fiber is also used in imaging optics. A coherent bundle of fibers is used, sometimes along with lenses, for a long, thin imaging device called an endoscope, which is used to view objects through a small hole. Medical endoscopes are used for minimally invasive exploratory or surgical procedures (endoscopy). Industrial endoscopes (see fiberscope or borescope) are used for inspecting anything hard to reach, such as jet engine interiors.

In spectroscopy, optical fiber bundles are used to transmit light from a spectrometer to a substance which cannot be placed inside the spectrometer itself, in order to analyze its composition. A spectrometer analyzes substances by bouncing light off of and through them. By using fibers, a spectrometer can be used to study objects that are too large to fit inside, or gasses, or reactions which occur in pressure vessels.[13][14][15]

An optical fiber doped with certain rare-earth elements such as erbium can be used as the gain medium of a laser or optical amplifier. Rare-earth doped optical fibers can be used to provide signal amplification by splicing a short section of doped fiber into a regular (undoped) optical fiber line. The doped fiber is optically pumped with a second laser wavelength that is coupled into the line in addition to the signal wave. Both wavelengths of light are transmitted through the doped fiber, which transfers energy from the second pump wavelength to the signal wave. The process that causes the amplification is stimulated emission.

Optical fibers doped with a wavelength shifter are used to collect scintillation light in physics experiments.

Optical fiber can be used to supply a low level of power (around one watt) to electronics situated in a difficult electrical environment. Examples of this are electronics in high-powered antenna elements and measurement devices used in high voltage transmission equipment.

[edit] Principle of operation

An optical fiber is a cylindrical dielectric waveguide that transmits light along its axis, by the process of total internal reflection. The fiber consists of a core surrounded by a cladding layer. To confine the optical signal in the core, the refractive index of the core must be greater than that of the cladding. The boundary between the core and cladding may either be abrupt, in step-index fiber, or gradual, in graded-index fiber.

[edit] Index of refraction

Main article: Refractive index

The index of refraction is a way of measuring the speed of light in a material. Light travels fastest in a vacuum, such as outer space. The actual speed of light in a vacuum is about 300 million meters (186 thousand miles) per second. Index of refraction is calculated by dividing the speed of light in a vacuum by the speed of light in some other medium. The index of refraction of a vacuum is therefore 1, by definition. The typical value for the cladding of an optical fiber is 1.46. The core value is typically 1.48. The larger the index of refraction, the slower light travels in that medium. From this information, a good rule of thumb is that signal using optical fiber for communication will travel at around 200 million meters per second. Or to put it another way, to travel 1000 kilometres in fiber, the signal will take 5 milliseconds to propagate. Thus a phone call carried by fiber between Sydney and New York, a 12000 kilometre distance, means that there is an absolute minimum delay of 60 milliseconds (or around 1/16th of a second) between when one caller speaks to when the other hears. (Of course the fiber in this case will probably travel a longer route, and there will be additional delays due to communication equipment switching and the process of encoding and decoding the voice onto the fiber).

[edit] Total internal reflection

Main article: Total internal reflection

When light traveling in a dense medium hits a boundary at a steep angle (larger than the "critical angle" for the boundary), the light will be completely reflected. This effect is used in optical fibers to confine light in the core. Light travels along the fiber bouncing back and forth off of the boundary. Because the light must strike the boundary with an angle greater than the critical angle, only light that enters the fiber within a certain range of angles can travel down the fiber without leaking out. This range of angles is called the acceptance cone of the fiber. The size of this acceptance cone is a function of the refractive index difference between the fiber's core and cladding.

In simpler terms, there is a maximum angle from the fiber axis at which light may enter the fiber so that it will propagate, or travel, in the core of the fiber. The sine of this maximum angle is the numerical aperture (NA) of the fiber. Fiber with a larger NA requires less precision to splice and work with than fiber with a smaller NA. Single-mode fiber has a small NA.

[edit] Multi-mode fiber

The propagation of light through a multi-mode optical fiber.

A laser bouncing down an acrylic rod, illustrating the total internal reflection of light in a multi-mode optical fiber.

Main article: Multi-mode optical fiber

Fiber with large core diameter (greater than 10 micrometers) may be analyzed by geometric optics. Such fiber is called multi-mode fiber, from the electromagnetic analysis (see below). In a step-index multi-mode fiber, rays of light are guided along the fiber core by total internal reflection. Rays that meet the core-cladding boundary at a high angle (measured relative to a line normal to the boundary), greater than the critical angle for this boundary, are completely reflected. The critical angle (minimum angle for total internal reflection) is determined by the difference in index of refraction between the core and cladding materials. Rays that meet the boundary at a low angle are refracted from the core into the cladding, and do not convey light and hence information along the fiber. The critical angle determines the acceptance angle of the fiber, often reported as a numerical aperture. A high numerical aperture allows light to propagate down the fiber in rays both close to the axis and at various angles, allowing efficient coupling of light into the fiber. However, this high numerical aperture increases the amount of dispersion as rays at different angles have different path lengths and therefore take different times to traverse the fiber. A low numerical aperture may therefore be desirable.

Optical fiber types.

In graded-index fiber, the index of refraction in the core decreases continuously between the axis and the cladding. This causes light rays to bend smoothly as they approach the cladding, rather than reflecting abruptly from the core-cladding boundary. The resulting curved paths reduce multi-path dispersion because high angle rays pass more through the lower-index periphery of the core, rather than the high-index center. The index profile is chosen to minimize the difference in axial propagation speeds of the various rays in the fiber. This ideal index profile is very close to a parabolic relationship between the index and the distance from the axis.

[edit] Single-mode fiber

The structure of a typical single-mode fiber.
1. Core: 8 µm diameter
2. Cladding: 125 µm dia.
3. Buffer: 250 µm dia.
4. Jacket: 400 µm dia.

Main article: Single-mode optical fiber

Fiber with a core diameter less than about ten times the wavelength of the propagating light cannot be modeled using geometric optics. Instead, it must be analyzed as an electromagnetic structure, by solution of Maxwell's equations as reduced to the electromagnetic wave equation. The electromagnetic analysis may also be required to understand behaviors such as speckle that occur when coherent light propagates in multi-mode fiber. As an optical waveguide, the fiber supports one or more confined transverse modes by which light can propagate along the fiber. Fiber supporting only one mode is called single-mode or mono-mode fiber. The behavior of larger-core multi-mode fiber can also be modeled using the wave equation, which shows that such fiber supports more than one mode of propagation (hence the name). The results of such modeling of multi-mode fiber approximately agree with the predictions of geometric optics, if the fiber core is large enough to support more than a few modes.

The waveguide analysis shows that the light energy in the fiber is not completely confined in the core. Instead, especially in single-mode fibers, a significant fraction of the energy in the bound mode travels in the cladding as an evanescent wave.

The most common type of single-mode fiber has a core diameter of 8–10 micrometers and is designed for use in the near infrared. The mode structure depends on the wavelength of the light used, so that this fiber actually supports a small number of additional modes at visible wavelengths. Multi-mode fiber, by comparison, is manufactured with core diameters as small as 50 micrometers and as large as hundreds of micrometres. The normalized frequency V for this fiber should be less than the first zero of the Bessel function J0 (approximately 2.405).

[edit] Special-purpose fiber

Some special-purpose optical fiber is constructed with a non-cylindrical core and/or cladding layer, usually with an elliptical or rectangular cross-section. These include polarization-maintaining fiber and fiber designed to suppress whispering gallery mode propagation.

Photonic crystal fiber is made with a regular pattern of index variation (often in the form of cylindrical holes that run along the length of the fiber). Such fiber uses diffraction effects instead of or in addition to total internal reflection, to confine light to the fiber's core. The properties of the fiber can be tailored to a wide variety of applications.

[edit] Mechanisms of attenuation

Light attenuation by ZBLAN and silica fibers

Main article: Transparent materials

Attenuation in fiber optics, also known as transmission loss, is the reduction in intensity of the light beam (or signal) with respect to distance travelled through a transmission medium. Attenuation coefficients in fiber optics usually use units of dB/km through the medium due to the relatively high quality of transparency of modern optical transmission media. The medium is typically usually a fiber of silica glass that confines the incident light beam to the inside. Attenuation is an important factor limiting the transmission of a digital signal across large distances. Thus, much research has gone into both limiting the attenuation and maximizing the amplification of the optical signal. Empirical research has shown that attenuation in optical fiber is caused primarily by both scattering and absorption.

[edit] Light scattering

Specular reflection

Diffuse reflection

The propagation of light through the core an optical fiber is based on total internal reflection of the lightwave. Rough and irregular surfaces, even at the molecular level, can cause light rays to be reflected in random directions. This is called diffuse reflection or scattering, and it is typically characterized by wide variety of reflection angles.

Light scattering depends on the wavelength of the light being scattered. Thus, limits to spatial scales of visibility arise, depending on the frequency of the incident lightwave and the physical dimension (or spatial scale) of the scattering center, which is typically in the form of some specific microstructural feature. Since visible light has a wavelength of the order of one micron (one millionth of a meter) scattering centers will have dimensions on a similar spatial scale.

Thus, attenuation results from the incoherent scattering of light at internal surfaces and interfaces. In (poly)crystalline materials such as metals and ceramics, in addition to pores, most of the internal surfaces or interfaces are in the form of grain boundaries that separate tiny regions of crystalline order. It has recently been shown that when the size of the scattering center (or grain boundary) is reduced below the size of the wavelength of the light being scattered, the scattering no longer occurs to any significant extent. This phenomenon has given rise to the production of transparent ceramic materials.

Similarly, the scattering of light in optical quality glass fiber is caused by molecular level irregularities (compositional fluctuations) in the glass structure. Indeed, one emerging school of thought is that a glass is simply the limiting case of a polycrystalline solid. Within this framework, "domains" exhibiting various degrees of short-range order become the building blocks of both metals and alloys, as well as glasses and ceramics. Distributed both between and within these domains are micro-structural defects which will provide the most ideal locations for the occurrence of light scattering. This same phenomenon is seen as one of the limiting factors in the transparency of IR missile domes.[16]

At high optical powers, scattering can also be caused by nonlinear optical processes in the fiber.[17][18]

See also: Physics of glass

[edit] UV-Vis-IR absorption

In addition to light scattering, attenuation or signal loss can also occur due to selective absorption of specific wavelengths, in a manner similar to that responsible for the appearance of color. Primary material considerations include both electrons and molecules as follows:

1) At the electronic level, it depends on whether the electron orbitals are spaced (or "quantized") such that they can absorb a quantum of light (or photon) of a specific wavelength or frequency in the ultraviolet (UV) or visible ranges. This is what gives rise to color.

2) At the atomic or molecular level, it depends on the frequencies of atomic or molecular vibrations or chemical bonds, how close-packed its atoms or molecules are, and whether or not the atoms or molecules exhibit long-range order. These factors will determine the capacity of the material transmitting longer wavelengths in the infrared (IR), far IR, radio and microwave ranges.

The design of any optically transparent device requires the selection of materials based upon knowledge of its properties and limitations. The lattice absorption characteristics observed at the lower frequency regions (mid IR to far-infrared wavelength range) define the long-wavelength transparency limit of the material. They are the result of the interactive coupling between the motions of thermally induced vibrations of the constituent atoms and molecules of the solid lattice and the incident light wave radiation. Hence, all materials are bounded by limiting regions of absorption caused by atomic and molecular vibrations (bond-stretching)in the far-infrared (>10 µm).

Normal modes of vibration in a crystalline solid.

Thus, multi-phonon absorption occurs when two or more phonons simultaneously interact to produce electric dipole moments with which the incident radiation may couple. These dipoles can absorb energy from the incident radiation, reaching a maximum coupling with the radiation when the frequency is equal to the fundamental vibrational mode of the molecular dipole (e.g. Si-O bond) in the far-infrared, or one of its harmonics.

The selective absorption of infrared (IR) light by a particular material occurs because the selected frequency of the light wave matches the frequency (or an integral multiple of the frequency) at which the particles of that material vibrate. Since different atoms and molecules have different natural frequencies of vibration, they will selectively absorb different frequencies (or portions of the spectrum) of infrared (IR) light.

Reflection and transmission of light waves occur because the frequencies of the light waves do not match the natural resonant frequencies of vibration of the objects. When IR light of these frequencies strike an object, the energy is either reflected or transmitted.

[edit] Manufacturing

[edit] Materials

Glass optical fibers are almost always made from silica, but some other materials, such as fluorozirconate, fluoroaluminate, and chalcogenide glasses, are used for longer-wavelength infrared applications. Like other glasses, these glasses have a refractive index of about 1.5. Typically the difference between core and cladding is less than one percent.

Plastic optical fibers (POF) are commonly step-index multi-mode fibers with a core diameter of 0.5 millimeters or larger. POF typically have higher attenuation co-efficients than glass fibers, 1 dB/m or higher, and this high attenuation limits the range of POF-based systems.

[edit] Silica

Tetrahedral structural unit of silica (SiO2).

The amorphous structure of glassy silica (SiO2). No long-range order is present, however there is local ordering with respect to the tetrahedral arrangement of oxygen (O) atoms around the silicon (Si) atoms.

Silica exhibits fairly good optical transmission over a wide range of wavelengths. In the near-infrared (near IR) portion of the spectrum, particularly around 1.5 μm, silica can have extremely low absorption and scattering losses of the order of 0.2 dB/km. A high transparency in the 1.4-μm region is achieved by maintaining a low concentration of hydroxyl groups (OH). Alternatively, a high OH concentration is better for transmission in the ultraviolet (UV) region.

Silica can be drawn into fibers at reasonably high temperatures, and has a fairly broad glass transformation range. One other advantage is that fusion splicing and cleaving of silica fibers is relatively effective. Silica fiber also has high mechanical strength against both pulling and even bending, provided that the fiber is not too thick and that the surfaces have been well prepared during processing. Even simple cleaving (breaking) of the ends of the fiber can provide nicely flat surfaces with acceptable optical quality. Silica is also relatively chemically inert. In particular, it is not hygroscopic (does not absorb water).

Silica glass can be doped with various materials. One purpose of doping is to raise the refractive index (e.g. with Germanium dioxide (GeO2) or Aluminium oxide (Al2O3)) or to lower it (e.g. with fluorine or Boron trioxide (B2O3)). Doping is also possible with laser-active ions (for example, rare earth-doped fibers) in order to obtain active fibers to be used, for example, in fiber amplifiers or laser applications. Both the fiber core and cladding are typically doped, so that the entire assembly (core and cladding) is effectively the same compound (e.g. an aluminosilicate, germanosilicate, phosphosilicate or borosilicate glass).

Particularly for active fibers, pure silica is usually not a very suitable host glass, because it exhibits a low solubility for rare earth ions. This can lead to quenching effects due to clustering of dopant ions. Aluminosilicates are much more effective in this respect.

Silica fiber also exhibits a high threshold for optical damage. This property ensures a low tendency for laser-induced breakdown. This is important for fiber amplifiers when utilized for the amplification of short pulses.

Because of these properties silica fibers are the material of choice in many optical applications, such as communications (except for very short distances with plastic optical fiber), fiber lasers, fiber amplifiers, and fiber-optic sensors. The large efforts which have been put forth in the development of various types of silica fibers have further increased the performance of such fibers over other materials. [19] [20] [21] [22] [23] [24] [25] [26] [27]

[edit] Fluorides

Fluoride glass is a class of non-oxide optical quality glasses composed of fluorides of various metals. Due to their low viscosity, it is very difficult to completely avoid crystallization while processing it through the glass transition (or drawing the fiber from the melt). Thus, although heavy metal fluoride glasses (HMFG) exhibit very low optical attenuation, they are not only difficult to manufacture, but are quite fragile, and have poor resistance to moisture and other environmental attacks. Their best attribute is that they lack the absorption band associated with the hydroxyl (OH) group (3200–3600 cm−1), which is present in nearly all oxide-based glasses.

An example of a heavy metal fluoride glass is the ZBLAN glass group, composed of zirconium, barium, lanthanum, aluminum, and sodium fluorides. Their main technological application is as optical waveguides in both planar and fiber form. They are advantageous especially in the mid-infrared (2000–5000 nm) range.

HMFG's were initially slated for optical fiber applications, because the intrinsic losses of a mid-IR fiber could in principle be lower than those of silica fibers, which are transparent only up to about 2 μm. However, such low losses were never realized in practice, and the fragility and high cost of fluoride fibers made them less than ideal as primary candidates. Later, the utility of fluoride fibers for various other applications was discovered. These include mid-IR spectroscopy, fiber-optic sensors, thermometry, and imaging. Also, fluoride fibers can be used to for guided lightwave transmission in media such as YAG (yttria-alumina garnet) lasers at 2.9 μm, as required for medical applications (e.g. ophthalmology and dentistry). [28] [29]

[edit] Phosphates

The P4O10 cagelike structure—the basic building block for phosphate glass.

Phosphate glass constitutes a class of optical glasses composed of metaphosphates of various metals. Instead of the SiO4 tetrahedra observed in silicate glasses, the building block for this glass former is Phosphorus pentoxide (P2O5), which crystallizes in at least four different forms. The most familiar polymorph (see figure) comprises molecules of P4O10.

Phosphate glasses can be advantageous over silica glasses for optical fibers with a high concentration of doping rare earth ions. A mix of fluoride glass and phosphate glass is fluorophosphate glass. [30] [31]

[edit] Chalcogenides

The chalcogens—the elements in group 16 of the periodic table — particularly sulphur (S), selenium (Se) and tellurium (Te) — react with more electropositive elements, such as silver, to form chalcogenides. These are extremly versatile compounds, in that they can be crystalline or amorphous, metallic or semiconducting, and conductors of ions or electrons.

[edit] Process

Illustration of the modified chemical vapor deposition (inside) process

Standard optical fibers are made by first constructing a large-diameter preform, with a carefully controlled refractive index profile, and then pulling the preform to form the long, thin optical fiber. The preform is commonly made by three chemical vapor deposition methods: inside vapor deposition, outside vapor deposition, and vapor axial deposition.[32]

With inside vapor deposition, the preform starts as a hollow glass tube approximately 40 centimetres (16 in) long, which is placed horizontally and rotated slowly on a lathe. Gases such as silicon tetrachloride (SiCl4) or germanium tetrachloride (GeCl4) are injected with oxygen in the end of the tube. The gases are then heated by means of an external hydrogen burner, bringing the temperature of the gas up to 1900 K (1600 °C, 3000 °F), where the tetrachlorides react with oxygen to produce silica or germania (germanium dioxide) particles. When the reaction conditions are chosen to allow this reaction to occur in the gas phase throughout the tube volume, in contrast to earlier techniques where the reaction occurred only on the glass surface, this technique is called modified chemical vapor deposition.

The oxide particles then agglomerate to form large particle chains, which subsequently deposit on the walls of the tube as soot. The deposition is due to the large difference in temperature between the gas core and the wall causing the gas to push the particles outwards (this is known as thermophoresis). The torch is then traversed up and down the length of the tube to deposit the material evenly. After the torch has reached the end of the tube, it is then brought back to the beginning of the tube and the deposited particles are then melted to form a solid layer. This process is repeated until a sufficient amount of material has been deposited. For each layer the composition can be modified by varying the gas composition, resulting in precise control of the finished fiber's optical properties.

In outside vapor deposition or vapor axial deposition, the glass is formed by flame hydrolysis, a reaction in which silicon tetrachloride and germanium tetrachloride are oxidized by reaction with water (H2O) in an oxyhydrogen flame. In outside vapor deposition the glass is deposited onto a solid rod, which is removed before further processing. In vapor axial deposition, a short seed rod is used, and a porous preform, whose length is not limited by the size of the source rod, is built up on its end. The porous preform is consolidated into a transparent, solid preform by heating to about 1800 K (1500 °C, 2800 °F).

The preform, however constructed, is then placed in a device known as a drawing tower, where the preform tip is heated and the optic fiber is pulled out as a string. By measuring the resultant fiber width, the tension on the fiber can be controlled to maintain the fiber thickness.

[edit] Practical issues

[edit] Optical fiber cables

An optical fiber cable

Main article: Optical fiber cable

In practical fibers, the cladding is usually coated with a tough resin buffer layer, which may be further surrounded by a jacket layer, usually plastic. These layers add strength to the fiber but do not contribute to its optical wave guide properties. Rigid fiber assemblies sometimes put light-absorbing ("dark") glass between the fibers, to prevent light that leaks out of one fiber from entering another. This reduces cross-talk between the fibers, or reduces flare in fiber bundle imaging applications.[33][34]

Modern cables come in a wide variety of sheathings and armor, designed for applications such as direct burial in trenches, high voltage isolation, dual use as power lines,[35][not in citation given] installation in conduit, lashing to aerial telephone poles, submarine installation, and insertion in paved streets. The cost of small fiber-count pole-mounted cables has greatly decreased due to the high Japanese and South Korean demand for fiber to the home (FTTH) installations.

Fiber cable can be very flexible, but traditional fiber's loss increases greatly if the fiber is bent with a radius smaller than around 30 mm. This creates a problem when the cable is bent around corners or wound around a spool, making FTTX installations more complicated. "Bendable fibers", targeted towards easier installation in home environments, have been standardized as ITU-T G.657. This type of fiber can be bent with a radius as low as 7.5 mm without adverse impact. Even more bendable fibers have been developed.[36] Bendable fiber may also be resistant to fiber hacking, in which the signal in a fiber is surreptitiously monitored by bending the fiber and detecting the leakage.[37]

[edit] Termination and splicing

ST connectors on multi-mode fiber.

Optical fibers are connected to terminal equipment by optical fiber connectors. These connectors are usually of a standard type such as FC, SC, ST, LC, or MTRJ.

Optical fibers may be connected to each other by connectors or by splicing, that is, joining two fibers together to form a continuous optical waveguide. The generally accepted splicing method is arc fusion splicing, which melts the fiber ends together with an electric arc. For quicker fastening jobs, a "mechanical splice" is used.

Fusion splicing is done with a specialized instrument that typically operates as follows: The two cable ends are fastened inside a splice enclosure that will protect the splices, and the fiber ends are stripped of their protective polymer coating (as well as the more sturdy outer jacket, if present). The ends are cleaved (cut) with a precision cleaver to make them perpendicular, and are placed into special holders in the splicer. The splice is usually inspected via a magnified viewing screen to check the cleaves before and after the splice. The splicer uses small motors to align the end faces together, and emits a small spark between electrodes at the gap to burn off dust and moisture. Then the splicer generates a larger spark that raises the temperature above the melting point of the glass, fusing the ends together permanently. The location and energy of the spark is carefully controlled so that the molten core and cladding don't mix, and this minimizes optical loss. A splice loss estimate is measured by the splicer, by directing light through the cladding on one side and measuring the light leaking from the cladding on the other side. A splice loss under 0.1 dB is typical. The complexity of this process makes fiber splicing much more difficult than splicing copper wire.

Mechanical fiber splices are designed to be quicker and easier to install, but there is still the need for stripping, careful cleaning and precision cleaving. The fiber ends are aligned and held together by a precision-made sleeve, often using a clear index-matching gel that enhances the transmission of light across the joint. Such joints typically have higher optical loss and are less robust than fusion splices, especially if the gel is used. All splicing techniques involve the use of an enclosure into which the splice is placed for protection afterward.

Fibers are terminated in connectors so that the fiber end is held at the end face precisely and securely. A fiber-optic connector is basically a rigid cylindrical barrel surrounded by a sleeve that holds the barrel in its mating socket. The mating mechanism can be "push and click", "turn and latch" ("bayonet"), or screw-in (threaded). A typical connector is installed by preparing the fiber end and inserting it into the rear of the connector body. Quick-set adhesive is usually used so the fiber is held securely, and a strain relief is secured to the rear. Once the adhesive has set, the fiber's end is polished to a mirror finish. Various polish profiles are used, depending on the type of fiber and the application. For single-mode fiber, the fiber ends are typically polished with a slight curvature, such that when the connectors are mated the fibers touch only at their cores. This is known as a "physical contact" (PC) polish. The curved surface may be polished at an angle, to make an "angled physical contact" (APC) connection. Such connections have higher loss than PC connections, but greatly reduced back reflection, because light that reflects from the angled surface leaks out of the fiber core; the resulting loss in signal strength is known as gap loss. APC fiber ends have low back reflection even when disconnected.

[edit] Free-space coupling

It often becomes necessary to align an optical fiber with another optical fiber or an optical device such as a light-emitting diode, a laser diode, or an optoelectronic device such as a modulator. This can involve either carefully aligning the fiber and placing it in contact with the device to which it is to couple, or can use a lens to allow coupling over an air gap. In some cases the end of the fiber is polished into a curved form that is designed to allow it to act as a lens.

In a laboratory environment, the fiber end is usually aligned to the device or other fiber with a fiber launch system that uses a microscope objective lens to focus the light down to a fine point. A precision translation stage (micro-positioning table) is used to move the lens, fiber, or device to allow the coupling efficiency to be optimized.

[edit] Fiber fuse

At high optical intensities, above 2 megawatts per square centimeter, when a fiber is subjected to a shock or is otherwise suddenly damaged, a fiber fuse can occur. The reflection from the damage vaporizes the fiber immediately before the break, and this new defect remains reflective so that the damage propagates back toward the transmitter at 1–3 meters per second (4−11 km/h, 2–8 mph).[38][39] The open fiber control system, which ensures laser eye safety in the event of a broken fiber, can also effectively halt propagation of the fiber fuse.[40] In situations, such as undersea cables, where high power levels might be used without the need for open fiber control, a "fiber fuse" protection device at the transmitter can break the circuit to prevent any damage.

[edit] See also

Electronics portal

[edit] Notes

  1. ^ a b Bates, Regis J (2001). Optical Switching and Networking Handbook. New York: McGraw-Hill. p. 10. ISBN 007137356X. 
  2. ^ Tyndall, John (1870). "Total Reflexion". Notes about Light. http://www.archive.org/details/notesofcourseofn00tyndrich. 
  3. ^ Tyndall, John (1873). "Six Lectures on Light". http://www.archive.org/details/sixlecturesonlig00tynduoft. 
  4. ^ Nishizawa, Jun-ichi; Suto, Ken (2004). "Terahertz wave generation and light amplification using Raman effect". in Bhat, K. N.; DasGupta, Amitava. Physics of semiconductor devices. New Delhi, India: Narosa Publishing House. p. 27. ISBN 8173195676. http://books.google.com/books?id=2NTpSnfhResC&pg=PA27&lpg=PA27&dq=Jun-ichi+Nishizawa+proposal+on+use+of+optical+fiber&source=bl&ots=iufv_Gmp98&sig=eqBUDA5OOfotJGSajaExFFf1cvA&hl=en&ei=aznYSf_DB4OoM9mO6PQO&sa=X&oi=book_result&ct=result&resnum=1#PPA27,M1. 
  5. ^ "New Medal Honors Japanese Microelectrics Industry Leader". Institute of Electrical and Electronics Engineers. http://www.ieee.org/portal/site/tionline/menuitem.130a3558587d56e8fb2275875bac26c8/index.jsp?&pName=institute_level1_article&TheCat=1003&article=tionline/legacy/inst2003/jun03/6w.nishizawa.xml&;jsessionid=SthNJY1YrB9lTcqQpQct4J2tWnvTl2PbJwyYcp10ys3xQpQ1LC2p!-437537516!-618147781. 
  6. ^ "Optical Fiber". Sendai New. http://www.city.sendai.jp/soumu/kouhou/s-new-e6/page01.html. Retrieved April 5, 2009. 
  7. ^ Hecht, Jeff (1999). City of Light, The Story of Fiber Optics. New York: Oxford University Press. p. 114. ISBN 0195108183. 
  8. ^ "1971-1985 Continuing the Tradition". GE Innovation Timeline. General Electric Company. http://www.ge.com/innovation/timeline/index.html. Retrieved 2008-10-22. 
  9. ^ "Light conducting fibers of quartz glass". FreePatentsOnline.com. http://www.freepatentsonline.com/3966300.html. 
  10. ^ Russell, Philip (2003). "Photonic Crystal Fibers". Science 299 (5605): 358. doi:10.1126/science.1079280. PMID 12532007. 
  11. ^ "The History of Crystal Fibre A/S". Crystal Fiber A/S. http://www.crystal-fibre.com/. Retrieved 2008-10-22. 
  12. ^ M. S. Alfiad, et al. (2008). "111 Gb/s POLMUX-RZ-DQPSK Transmission over 1140 km of SSMF with 10.7 Gb/s NRZ-OOK Neighbours". Proceedings ECOC 2008: pp. ??? Mo.4.E.2. 
  13. ^ Al Mosheky, Zaid; Melling, Peter J. ; Thomson, Mary A. (June 2001). "In situ real-time monitoring of a fermentation reaction using a fiber-optic FT-IR probe" (pdf). Spectroscopy. http://www.remspec.com/pdfs/SP5619.pdf. 
  14. ^ Melling, Peter; Thomson, Mary (October 2002). "Reaction monitoring in small reactors and tight spaces" (pdf). American Laboratory News. http://www.remspec.com/pdfs/amlab1002.pdf. 
  15. ^ Melling, Peter J.; Thomson, Mary (2002). "Fiber-optic probes for mid-infrared spectrometry". in Chalmers, John M.; Griffiths, Peter R. (eds.) (pdf). Handbook of Vibrational Spectroscopy. Wiley. http://www.remspec.com/pdfs/2703_o.pdf. 
  16. ^ Archibald, P.S. and Bennett, H.E., Scattering from infrared missile domes, Opt. Engr., Vol. 17, p.647 (1978)
  17. ^ Smith, R.G., Optical power handling capacity of low loss optical fibers as determined by stimulated Raman and Brillouin scattering, Appl. Opt., Vol. 11, p. 2489 (1972)
  18. ^ Paschotta, Rüdiger. "Brillouin Scattering". Encyclopedia of Laser Physics and Technology. RP Photonics. http://www.rp-photonics.com/brillouin_scattering.html. 
  19. ^ Glasesmenn, G. S., Advancements in Mechanical Strength and Reliability of Optical Fibers, Proc. SPIE, Vol. CR73, p. 1 (1999)
  20. ^ Boulos, E.N., Ed., Glass and Optical Materials I: Fracture and Strength, Glass Structure and Processing, Modeling and Computer Simulation (American Ceramic Society, Columbus, 1994)
  21. ^ Kurkjian, C.R., Strength of Inorganic Glass, (Plenum Press, New York, 1985); Mechanical Stability of Oxide Glasses, J. Non-Cryst. Solids, Vol. 102, p. 71 (1988); Strength and Elasticity of Glasses, Glass '89, Proc. XV Int'l. Congress on Glass, Leningrad 327 (1989); Kurkjian, C.R., et al., Strength and fatigue of silica optical fibers, J. Lightwave Tech., Vol. 7, p. 1360 (1989); Strength, Degradation and Coating of Silica Lightguides, J. Am. Ceram. Soc., Vol. 76, p. 1106 (1993); Critical Issues in the Mechanical Reliability of Lightguide Fibers, in Reliability of Photonics Materials and Structures, Suhir, E., Fukuda, M., Kurkijan, C.R., Eds., Proc. Mat. Res. Soc., Vol. 531, p. 39 (1998); Strength variations in silica fibers, Proc. SPIE, Vol. 3848, p. 77 (1999); Mechanical Strength and Reliability of Glass Fibers, Ch. 24 in Specialty Optical Fibers Handbook (Elsevier, Inc., 2007)
  22. ^ Bradt, R.C. and Tressler, R.E., Eds., Fractography of Fiberglass (Plenum Press, New York, 1994)
  23. ^ Gupta, P.K., Strength of Glass Fibers, in Fiber Fracture, Elices, M. and Llorca, J., Eds., p. 128 (Elsevier Science Ltd., 2002)
  24. ^ Skontorp, A. Nonlinear mechanical properties of silica-based optical fibers, Proc. SPIE, Vol. 4073, p. 278 (2000)
  25. ^ Thomas, W.F., An investigation of the factors likely to affect the strength and properties of glass fibers, Phys. Chem. Glasses, Vol. 1, p. 4 (1960)
  26. ^ Proctor, B.A., et al., The strength of fused silica, Proc. Roy. Soc., Vol. A297, p. 534 (1967)
  27. ^ Bartenev, G.M., The stucture and strength of glass fibers, J. Non-Cryst. Sol., Vol. 1, p. 69 (1968); The structure and strength of glass fibers of different chemical composition, Mat. Sci. Engr., Vol. 4, p. 22 (1969); Structure and Mechanical Properties of Inorganic Glasses, (Walters-Noordhoff, 1970)
  28. ^ Tran, D., et al., Heavy metal fluoride glasses and fibers: A review, J. Lightwave Technology, Vol. 2, p. 566 (1984)
  29. ^ Nee, S.F., et al., Optical and surface properties of oxyfluoride glasses, Proc. SPIE, Vol. 4102, p. 122 (2000); Characterization of optical constants for transparent materials, in Properties and Characteristics of Optical Glass, Ed. A.J. Marker III, Proc. SPIE, Vol. 979, p. 62 (1988)
  30. ^ Karabulut, M., et al., Mechanical and Structural Properties of Phosphate Glasses, J. Non-Cryst. Solids, Vol. 288, p. 8 , (2001)
  31. ^ Kirkjian, C.R., Mechanical properties of phosphate glasses, J. Non-Cryst. Solids, Vol. 263, p. 207 (2000)
  32. ^ Gowar, John (1993). Optical Communication Systems (2d ed.). Hempstead, UK: Prentice-Hall. p. 209. ISBN 0136387276. 
  33. ^ "Light collection and propagation". National Instruments' Developer Zone. National Instruments Corporation. http://zone.ni.com/devzone/cda/ph/p/id/129#toc2. Retrieved 2007-03-19. 
  34. ^ Hecht, Jeff (2002). Understanding Fiber Optics (4th ed.). Prentice Hall. ISBN 0-13-027828-9. 
  35. ^ "Screening report for Alaska rural energy plan" (pdf). Alaska Division of Community and Regional Affairs. Archived from the original on May 8, 2006. http://web.archive.org/web/20060508191931/http://www.dced.state.ak.us/dca/AEIS/PDF_Files/AIDEA_Energy_Screening.pdf. Retrieved April 11, 2006. 
  36. ^ Corning Incorporated (2007-07-23). "Corning announces breakthrough optical fiber technology". Press release. http://www.corning.com/media_center/press_releases/2007/2007072301.aspx. Retrieved 2007-12-09. 
  37. ^ Olzak, Tom (2007-05-03). "Protect your network against fiber hacks". Techrepublic. CNET. http://blogs.techrepublic.com.com/security/?p=222. Retrieved 2007-12-10. 
  38. ^ Atkins, R. M.; Simpkins, P. G.; Yablon, A. D. (2003). "Track of a fiber fuse: a Rayleigh instability in optical waveguides". Optics Letters 28 (12): 974–976. doi:10.1364/OL.28.000974. http://ol.osa.org/abstract.cfm?id=72607. 
  39. ^ Hitz, Breck (August 2003). "Origin of 'fiber fuse' is revealed". Photonics Spectra. http://www.photonics.com/content/spectra/2003/August/tech/79825.aspx. Retrieved 2008-07-05. 
  40. ^ Seo, Koji; et al. (October 2003). "Evaluation of high-power endurance in optical fiber links". Furukawa Review (no. 24): 17–22. ISSN 1348-1797. http://www.furukawa.co.jp/review/fr024/fr24_04.pdf. Retrieved 2008-07-05. 

[edit] References

[edit] External links

Last update 25th June 2009

 

FIBRE - FTTH

ARCEP defines the terms of optical fibre rollouts to stimulate investment 

Paris, 22 June 2009

Deploying new ultra high-speed digital networks nationwide constitutes a major challenge for France, from both an economic and societal standpoint and in terms of regional development.

On the fixed network front, the momentum in the broadband market in France and the willingness of several operators to invest in a new fibre-to-the-home (FTTH) local loop is helping to create a unique environment in Europe, which is particularly propitious to nationwide ultra broadband rollouts.

This involves deploying new infrastructure with potentially unlimited and symmetrical bitrates and which will be used for decades to come.

This major shift in technology must not, however, result in creation of a new monopoly over the local loop.

The issues raised by nationwide fibre rollouts require an ambitious and coordinated approach, of which ARCEP is an essential component.

·         Reminder of existing regulatory provisions

Ultra-fast broadband regulation contains two points:

·         Regulation of France Telecom civil engineering (ducts)

Stipulated in mid-2008 as part of the market analysis performed by the Authority, it allows alternative operators to deploy their optical fibre networks under the same conditions as France Telecom, keeping in mind that civil engineering accounts for between 50% and 80% of the cost of deploying an optical fibre local loop;

·         Regulation of the last segment of the optical fibre network (closest to subscribers, inside buildings and up to the shared access point).

The legal framework was defined in summer 2008 by the Law on modernising the economy (LME) which:

- instils the principle of having operators share the last segment of the networks, thus reducing the amount of work that needs to be done on the private property while also limiting the dangers of a local monopoly forming in the buildings;

- stipulates that the shared access point will be located outside the boundaries of the public property, except in cases defined by ARCEP.

·         ARCEP’s draft legal framework submitted today to public consultation

To kick-start this coordinated approach, investments in very densely populated areas need to be freed up as quickly as possible. The goal is to enable each operator to develop its strategy according to its technological choices.

The Authority is not seeking to impose any given technology but rather, on the contrary, to encourage their coexistence – which itself constitutes a opportunity for the still nascent ultra-fast broadband market, on both the innovation and competition fronts.

To achieve this, the draft legal framework produced by ARCEP specifies the following points:

- Very densely populated areas

These are areas with a concentrated population where it is economically possible for several operators to deploy their own infrastructure, in this case optical fibre networks, in the vicinity of customer premises.

148 municipalities are concerned at this point, representing 5.16 million households (more than half of which are outside the metropolitan Paris area), including 3 million which can be served immediately.

·         Cases where the shared access point can be located inside the private property

ARCEP has today defined the exceptions to the principle stipulated in the law of having the network share point located outside the boundaries of the private property. These exceptions are confined to very densely populated areas only, where the deployment of several dense networks is possible. The shared access point can be located on private property in two cases:

- buildings connected to visitable sewers (as is the case in Paris), regardless of the size of the building;

- buildings with 12 or more units: this threshold, which enables large enough economies of scale, was approved by the majority of players and is compatible with operators’ technological choices.

- A technologically neutral framework for deploying optical fibre in buildings

In a bid to ensure a neutral approach to operators’ technical-economic choices, ARCEP proposes:

- the optional installation of additional dedicated fibre: any operator may request that the building operator (i.e. the operator appointed by the property owner to outfit the building with optical fibre) install an additional dedicated fibre on its behalf for each unit, in exchange for pre-financing its installation and co-financing of the initial investment;

- installation of a cross-connection point: all operators are guaranteed the option of having a cross-connection apparatus installed on its behalf, at the shared access point, for instance.

This provision does not impose a multi-fibre standard but gives operators the ability to exercise that option.

It has a positive impact on the competition dynamic and offers a guarantee for the future without creating excessive restrictions for operators. First, it involves a modest additional cost compared to a single fibre architecture and, second, it stimulates investment in outfitting buildings with fibre by encouraging shared costs, hence shared risks.

From a consumer standpoint, installing additional fibre will make it easier for them to switch operators (without losing their service) and to subscribe to different operators’ services. For property co-owners and residents, this option should limit service calls in the long run, particularly at the shared access point located inside of buildings.

·         ARCEP publishes a new version of the sample agreement that property owners can sign immediately

After a series of talks with players from the real estate sector (co-op boards, property managers, trustees, property co-owners, landlord and consumer association representatives) and the leading operators (France Telecom, Free, Numéricâble and SFR), an updated version of the sample agreement produced by ARCEP in 2008 has been published.

This document achieved full consensus. Operators’ signature of this sample agreement guarantees property owners the installation of fibre in their building under satisfactory terms and conditions, provided the building operator complies with the regulation defined by ARCEP.

·         Procedure that is currently underway expected to result in the official adoption of decisions in the autumn

ARCEP is submitting several documents to public consultation today:

- draft decision on the location of the shared access point;

- draft decision on the terms of access;

- draft recommendations on the practical implementation of these terms.

The Authority will consult with the competition authority, the Consultative Committee for Electronic Communication Networks and Services, CCRSCE (Commission consultative des réseaux et services de communications électroniques) and the European Commission on these drafts. The decisions will then be submitted to the Minister responsible for electronic communications for endorsement.

These decisions are thus expected to come into effect in autumn 2009.

·         ARCEP continues its work on ultra fast broadband solutions

Outside of very densely populated areas, the implementation of a system of infrastructure sharing higher up in the network is a more complicated matter, and one that requires greater cooperation between the players.

A second stage of work has now begun under the aegis of ARCEP, which involves close collaboration between operators, local authorities and the Caisse des dépôts et consignations – the purpose being to specify the methods for deploying operators’ networks or public-initiative networks in less densely populated areas.

This new work will be based on the efforts of technical groups that will perform a new series of trials.

Optical fiber connector

From Wikipedia, the free encyclopedia

  (Redirected from Optical Fiber Connector)

Jump to: navigation, search

An optical fiber connector terminates the end of an optical fiber, and enables quicker connection and disconnection than splicing. The connectors mechanically couple and align the cores of fibers so that light can pass. Most optical fiber connectors are spring-loaded: The fiber endfaces of the two connectors are pressed together, resulting in a direct glass to glass or plastic to plastic, respectively, contact, avoiding any glass to air or plastic to air interfaces, which would result in higher connector losses.
A variety of optical fiber connectors are available. The main differences among types of connectors are dimensions and methods of mechanical coupling. Generally, organizations will standardize on one kind of connector, depending on what equipment they commonly use, or per type of fiber (one for multimode, one for singlemode). In datacom and telecom applications nowadays small form factor connectors (e.g. LC) and multi-fiber connectors e.g. MTP) are replacing the traditional connectors (e.g. SC), mainly to pack more connectors on the overcrowded faceplate, and thus reducing the footprint of the systems.

Contents

[hide]

[edit] Types

LC connector

SC connector

ST connector

MT-RJ connector

MIC (FDDI) connector

FC connector

TOSLINK connector

Fiber connector types

Short name  ↓

Long form  ↓

Coupling type  ↓

Ferrule diameter  ↓

Standard  ↓

Typical applications  ↓

Avio (Avim)

 

Screw

 

 

Aerospace and avionics

ADT-UNI

 

Screw

2.5 mm

 

Measurement equipment

Biconic

 

Screw

2.5 mm

 

Obsolete

D4

 

Screw

 

 

Telecom in the 1970s and 1980s, obsolete

Deutsch 1000

 

Screw

 

 

Telecom, obsolete

DIN (LSA)

 

Screw

 

IEC 61754-3

Telecom in Germany in 1990s; measurement equipment; obsolete

DMI

 

Clip

2.5 mm

 

Printed circuit boards

E-2000 (AKA LSH)

 

Snap, with light and dust-cap

2.5 mm

IEC 61754-15

Telecom, DWDM systems;

ESCON

Enterprise Systems Connection

Snap (duplex)

2.5 mm

 

IBM mainframe computers and peripherals

F-3000

 

Snap, with light and dust-cap

1.25 mm

IEC 61754-20

Fiber To The Home (LC Compatible)

FC

Ferrule Connector

Screw

2.5 mm

IEC 61754-13

Datacom, telecom, measurement equipment, single mode lasers; becoming less common

Fibergate

 

Snap, with dust-cap

1.25 mm

 

Backplane connector

FSMA

 

Screw

3.175 mm

IEC 60874-2

Datacom, telecom, test & measurment

LC

Lucent Connector or
Local Connector
[citation needed]

Snap

1.25 mm

IEC 61754-20

High-density connections, SFP transceivers

LX-5

 

Snap, with light- and dust-cap

 

IEC 61754-23

High-density connections; rarely used

MIC

Media Interface Connector

Snap

2.5 mm

 

Fiber distributed data interface (FDDI)

MPO / MTP

Multi-Fibre Push On

Snap (multiplex push-pull coupling)

2.5×6.4 mm [1]

IEC-61754-7; EIA/TIA-604-5 (FOCIS 5)

SM or MM multi-fiber ribbon. Same ferrule as MT, but more easily reconnectable.[1] Used for indoor cabling and device interconnections. MTP is a brand name for an improved connector, which intermates with MPO.[2]

MT

Mechanical Transfer

Snap (multiplex)

2.5×6.4 mm

 

Pre-terminated cable assemblies; outdoor applications[1]

MT-RJ

Mechanical Transfer Registered Jack

Snap (duplex)

2.45×4.4 mm

IEC 61754-18

Duplex multimode connections

MU

 

Snap

1.25 mm

IEC 61754-6

Common in Japan

NEC D4

 

Screw

 

 

Common in Japan telecom in 1980s

Opti-Jack

 

Snap (duplex)

 

 

 

OPTIMATE

 

Screw

 

 

Plastic fiber, obsolete

SC

Subscriber Connector or
Standard Connector or
Siemon Connector
[citation needed]

Snap (push-pull coupling)

2.5 mm

IEC 61754-4

Datacom and telcom; extremely common

SMA 905

Sub Miniature A

Screw

typ. 3.14 mm

 

Industrial lasers, military; telecom multimode

SMA 906

Sub Miniature A

Screw

Stepped; typ. 0.118", then .089"[citation needed]

 

Industrial lasers, military; telecom multimode

SMC

Sub Miniature C

Snap

2.5 mm

 

 

ST / BFOC

Straight Tip / Bayonet Fiber Optic Connector

Bayonet

2.5 mm

IEC 61754-2

Multimode, rarely singlemode; APC not possible

TOSLINK

Toshiba Link

Snap

 

 

Digital audio

VF-45

 

Snap

 

 

Datacom

V-PIN

V-System

Snap (Duplex) Push-pull coupling

 

 

Industrial and electric utility networking; multimode 200 μm, 400 μm, 1 mm, 2.2 mm fibers

[edit] Notes

[edit] Mnemonics

[edit] Analysis

[edit] See also

[edit] References

  1. ^ a b c Shimoji, Naoko; Yamakawa, Jun; Shiino, Masato (1999). "Development of Mini-MPO Connector". Furukawa Review (18): 92. http://www.furukawa.co.jp/review/fr018/fr18_16.pdf. 
  2. ^ "Frequently asked questions". US Conec. http://www.usconec.com/pages/faq/faqfrm.html. Retrieved 12 Feb 2009. 
  3. ^ Hayes, Jim (2005). "Connector Identifier". The Fiber Optic Association — Tech Topics. http://www.thefoa.org/tech/connID.htm. Retrieved Feb. 6, 2009. 
  4. ^ Sezerman, Omur; Best, Garland (December 1997). "Accurate alignment preserves polarization". Laser Focus World. http://www.laserfocusworld.com/display_article/31401/12/none/none/News/Accurate-alignment-preserves-polarization. Retrieved March 12, 2009. 
  5. ^ "Polarization maintaining fiber patchcords and connectors" (pdf). OZ Optics. http://www.ozoptics.com/ALLNEW_PDF/DTS0071.pdf. Retrieved Feb. 6, 2009.