Topologies

LightPointe's optical wireless products, based on the latest in FSO technology, are designed and engineered to work in any network topology, including point-to-point, mesh, point-to-multipoint, and ring with spurs. This simple approach provides Enterprises and Mobile Carriers the ability to easily build and extend networks that deliver fiber-optic speeds for customers. FSO-based products enable cost-effective deployment and the highest throughput with same-day connections possible from roof-to-roof, roof-to-window and window-to-window — all without tearing up streets
and sidewalks.

Light scattering

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 of the glass, can cause light rays to be reflected in many random directions. We refer to this type of reflection as “diffuse reflection”, and it is typically characterized by wide variety of reflection angles. Most of the objects that you see with the naked eye are visible due to diffuse reflection. Another term commonly used for this type of reflection is “light scattering”. Light scattering from the surfaces of objects is our primary mechanism of physical observation. ^{[16] [17]}

Specular Reflection

Diffuse Reflection

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 microstuctural 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 limting case of a polycrystalline solid. Within this framework, "domains" exhibiting various degress 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 microstructural 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 tranparency of IR missile domes

Multi-mode 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.

Other uses of optical fibers

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.

Fiber optic sensors

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.

Optical fiber 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

History

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, 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 50–80 kilometres (31–50 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.

Optical fiber

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.

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).^[25][26] 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.^[27] 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.

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.

Termination and splicing

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.

Optical fiber cables

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.^[20][21]

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,^{[22][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.^[23] 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

Process of opti fiber

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.^[19]

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.

Manufacturing

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.

Commercialization:

LightPointe is not the only U.S. provider of FSO equipment, but it does have a product line, a product development plan, customers, partners for field testing, adequate funding, a multinational presence, and a reasonably strong intellectual property position with multiple patents. A direct descendant of BMDO SBIR-sponsored technology is now commercially available for beta trials. This is a 2.5Gb/s capacity FlightSpectrum™ product operating with multibeams and RF out-of-band management at the 1550nm wavelength over a distance of up to 1000 meters. The company anticipates the general release of this product in the first quarter of 2002.

The current Flight™ product line features three models (FlightLite™, FlightPath™, and FlightSpectrum) and two networking tools (FlightManager™ and FlightNavigator™) that enable LightPointe to meet customer demands for communication equipment directly and also indirectly through service providers (who have their own networks and customers). The capacity offered ranges from 10Mb/s up to 1.25Gb/s, operating at 850nm wavelength and lower power. The company is beginning to introduce the higher powered 1550nm wavelength lasers. All of these products operate at layer one and accommodate any protocol, connect to existing network equipment, and require no licensing. Costs vary depending upon transmitter power and management software, but the range runs anywhere from $5,000 to $50,000 per pair of transceiver units. The company is aggressively pricing its FlightLite 1550 product, providing 155Mb/s over a distance of up to 500 meters, for $8000. This compares favorably with the cost of laying fiber-optic cable, which in U.S. metropolitan areas can run between $100,000 to $200,000 per kilometer.

Of the work directly funded by BMDO regarding the use of a RF backup hybrid system, LightPointe has one patent pending.

In the year 2000, Lightpointe obtained more than $1 million in revenue from the sale of FSO products and services. For the year 2001, it anticipates a much higher total revenue figure, but below $10 million. Existing customers include Rockefeller Group Telecommunications Services, Inc.; The Smithsonian Institution; Barclays Bank; Dain Rauscher; and New School University. The company also has established working relationships with more than one dozen carriers located in 31 nations for the purpose of field- and beta- testing new equipment and obtaining lifecycle information on existing equipment.

In September 2000, LightPointe received $12 million in venture capital funding from Sevin Rosen Funds, Ampersand Ventures, and Telecom Partners. In January 2001, LightPointe obtained $6.5 additional working capital and debt financing from Silicon Valley Bank and GATX Ventures Inc. Later in 2001, first-round venture capital firms, Cisco Systems, Inc., and Corning Innovation Ventures invested an additional $33 million.

In general, LightPointe intends to capture a significant share of the international FSO market by emphasizing its ability to meet different customer needs. It can provide a range of capacity and price accordingly; it can supply service quickly (within days); and because its equipment requires no permanent infrastructure, the company can enter into leasing arrangements with service providers. LightPointe’s business strategy relies heavily on the continuing evolution of telecommunications to all-optical configurations (avoiding or eliminating electro-optic conversion).

Technology Description:

LightPointe’s patented technology uses a combination of adaptive power control techniques, active tracking systems, spatial diversity for both transmitters and receiving lenses, microwave radio frequency out-of-band management, higher powered lasers operating at 1550nm wavelength, and protocol-independent physical-layer (layer one) equipment. For carrier-grade reliability (one bad bit out of every ten billion carried) at a data transfer rate of OC-48 (2.5Gb/s) through dry air, one kilometer is the current maximum distance between LightPointe transceivers. If an active tracking system is employed, that range might be doubled. A newer version currently undergoing “beta testing” will transmit four separate wavelengths that could provide either four OC-48 signals or the capacity of one OC-192 (10 Gb/s).

LightPointe’s solution to problems of scintillation (atmospheric turbulence) and Mie scattering (dense fog) is an approach called “spatial diversity”. A transceiver actually houses three laser transmitters separated by approximately 200mm. By sending three beams simultaneously, it is highly probable that at least one will get through unperturbed. Likewise, the use of multiple, spatially separated, large-aperture receiving lenses also reduces problems associated with scintillation.

FSO: Optical or Wireless?

Speed of fiber — flexibility of wireless.
Optical wireless, based on FSO-technology, is an outdoor wireless product category that provides the speed of fiber, with the flexibility of wireless. It enables optical transmission at speeds of up to 1.25 Gbps and, in the future, is capable of speeds of 10 Gbps using WDM. This is not possible with any fixed wireless or RF technology. Optical wireless also eliminates the need to buy expensive spectrum (it requires no FCC or municipal license approvals worldwide), which further distinguishes it from fixed wireless technologies. Moreover, FSO technology’s narrow beam transmission is typically two meters versus 20 meters and more for traditional, even newer radio-based technologies such as millimeter-wave radio. Optical wireless products' similarities with conventional wired optical solutions enable the seamless integration of access networks with optical core networks and helps to realize the vision of an
all-optical network.

How it Works

FSO technology is surprisingly simple. It's based on connectivity between FSO-based optical wireless units, each consisting of an optical transceiver with a transmitter and a receiver to provide full-duplex (bi-directional) capability. Each optical wireless unit uses an optical source, plus a lens or telescope that transmits light through the atmosphere to another lens receiving the information. At this point, the receiving lens or telescope connects to a high-sensitivity receiver via
optical fiber.

This FSO technology approach has a number of advantages:

• Requires no RF spectrum licensing.
• Is easily upgradeable, and its open interfaces support equipment from a variety of vendors, which helps enterprises and service providers protect their investment in embedded telecommunications infrastructures.
• Requires no security software upgrades.
• Is immune to radio frequency interference or saturation.
• Can be deployed behind windows, eliminating the need for costly rooftop rights.

History

Originally developed by the military and NASA, FSO has been used for more than three decades in various forms to provide fast communication links in remote locations. LightPointe has extensive experience in this area: its chief scientists were in the labs developing prototype FSO systems in Germany in the late 1960s, even before the advent of fiber-optic cable. To view a copy of the original FSO white paper in German, published in Berlin, Germany, in the journal Nachrichtentechnik, in June 1968 by Dr. Erhard Kube, LightPointe's Chief Scientist and widely regarded as the "father of FSO technologyWhile fiber-optic communications gained worldwide acceptance in the telecommunications industry, FSO communications is still considered relatively new. FSO technology enables bandwidth transmission capabilities that are similar to fiber optics, using similar optical transmitters and receivers and even enabling WDM-like technologies to operate through free space.

The Technology at the Heart of Optical Wireless

Imagine a technology that offers full-duplex Gigabit Ethernet throughput. A technology that can be installed license-free worldwide, can be installed in less than a day. A technology that offers a fast, high ROI.

That technology is free-space optics (FSO).

This line-of-sight technology approach uses invisible beams of light to provide optical bandwidth connections. It's capable of sending up to 1.25 Gbps of data, voice, and video communications simultaneously through the air — enabling fiber-optic connectivity without requiring physical fiber-optic cable. It enables optical communications at the speed of light. And it forms the basis of a new category of products — optical wireless products from LightPointe, the recognized leader in outdoor wireless bridging communications.

This site is intended to provide valuable background and resource information on FSO technology. Whether you're a student, an engineer, account manager, partner, or customer, this site provides the FSO insight you may require. And for providing high-speed connections, across Enterprises and between cell-site towers, it is the best technology available.FSO is a line-of-sight technology that uses invisible beams of light to provide optical bandwidth connections that can send and receive voice, video, and data information. Today, FSO technology — the foundation of LightPointe's optical wireless offerings — has enabled the development of a new category of outdoor wireless products that can transmit voice, data, and video at bandwidths up to 1.25 Gbps. This optical connectivity doesn't require expensive fiber-optic cable or securing spectrum licenses for radio frequency (RF) solutions. FSO technology requires light. The use of light is a simple concept similar to optical transmissions using fiber-optic cables; the only difference is the medium. Light travels through air faster than it does through glass, so it is fair to classify FSO technology as optical communications at the speed of light.

Hardwares for Aerial Fiber Optic cable installation

Hardwares for Aerial Fiber Optic cable installation

Because of the different types of fiber optic dead-ends and tangent assemblies available, it is necessary to select the proper one for the cable design and route. In order to select the proper product the installer must know the following:

• nominal outside diameter of the cable
• degree of offset from one pole to the next
• maximum cable tension under loaded conditions

When ordering dead-ends, it is important to ensure that all other necessary pole hardware is ordered. These items include:

• thimble clevis
• eye nuts
• extension links (to maintain cable minimum bend radius)

Determine the proper attachment location of the cable on the poles. Mark the location of the attachment point on the cable with a wrap of tape.

Drill the appropriate holes in wooden poles or apply band attachments to concrete or metal poles and mount supporting hardware accordingly.

Refer to the manufacturer’s recommended procedures for installation.

For those applications where the cable may be subjected to wind-induced vibrations, special dampeners can be used to minimize these effects.

Tyco Telecommunications - Company Information Tyco Telecommunications, a business unit of Tyco Electronics and an industry pioneer in undersea communi

Tyco Telecommunications - Company Information

Tyco Telecommunications, a business unit of Tyco Electronics and an industry pioneer in undersea communications technology and marine services, is a leading global supplier for today's undersea communications requirements.

Drawing on its heritage of technical innovation and industry recognized performance, the company delivers the most reliable, high-quality solutions to organizations with undersea communications needs vital to their core mission. In more than five decades of operation, Tyco Telecommunications has designed, manufactured, and installed more than 80 undersea fiber optic systems around the world.

Tyco Telecommunications’ global presence, backed by industry leading research and development laboratories, manufacturing facilities, installation and maintenance ships, depots, and management team work together to implement integrated solutions and network upgrades, with unsurpassed reliability, that support the needs of telecommunications, internet providers, offshore and science customers worldwide.

Duraline - Company Information

Duraline - Company Information

Dura-Line is a leading manufacturer and supplier of pre-lubricated HDPE ducts and microducts specially developed to house and protect fiber optic infrastructure in FTTx networks.

Duraline Corporation was founded in 1971 at Middlesboro, Tennessee as a manufacturer and supplier of HDPE water pipes. In 1981 it was invited by American Telephone & Telegraph Company to supply a duct for the protective installation of fiber optic cables throughout the length and breadth of America. It thus became the first company to manufacture HDPE telecom ducts.

The company pioneered and developed the patented Silicore® co-extruded solid polymer inner lining. The Silicore® lined ducts are the world’s first ducts co-extruded with a super slick permanent lining.

The US fiber optic industry grew rapidly in the mid-1980s. During this time, Duraline developed several products and created a highly respected technical service group, which enabled it to become the industry leader.

Today Duraline Corporation is one of the world’s larger suppliers of a diversified range of high density polyethylene (HDPE) pipe, duct and conduit products. These products serve the needs of the Telecommunications, Cable Television, Electric Power, Water and Natural Gas Industries in applications as diverse as conveyance of fiber optic, co-axial and electric power cables, and water and natural gas.

Duraline serves its customers from manufacturing and distribution facilities located around the world. It has sold Silicore® ducts to over 1500 customers and has a customer base in more than 120 countries. Duraline has manufacturing facilities in USA, Mexico, Czech Republic and India.

Fusion Splicing of Optical Fibers

It is the most widely used method for splicing optical fibre. There are a number of fusion welding machines manufactured by different companies, some of them are fully automatic and controlled by a microprocessor and some are partly automatic and manually controlled. In some cases, the fibre ends & the fusion process can be seen on a TV monitor screen.

The process can be sub-divided into the following three steps:

(a) Axial alignment.
(b) Prefusion
(c) Actual fusion welding.

In some of the machines the axial alignment is done manually by manipulating a number of knobs and is observed with the help of a high power microscope. This is normally followed in case of multimode fibre. In some modern machines, pre-aligned, V-grooves are provided & finer adjustment is done, if necessary. For single mode fibre, other techniques are followed. The best one is fully automatic core alignment method which is used now a days.

After aligning is done, the ends of the fibres are fire polished by an electric are and this method is called pre-fusion. During this process, the fibre ends are kept separated at a distance, after this they are brought closer and the process is called as fibre end feeding. This feeding process is continued during actual fusion by electric arc to prevent a reduced section at the point of welding.

The process of prefusion, fibre ends feed and actual fusion are critical to a good weld and are automatically controlled by the fusion machine. The fusion time of single mode fibre is less than that of multimode fibre.

Geometrical parameters of an Optical fiber

Geometrical parameters of an Optical fiber

Core

The central region of an optical fiber through which most of the optical power is transmitted. It is characterized by a refractive index, which is higher than that of the surrounding cladding. The core diameter is often determined by the near field measurement technique.

Cladding
The layer of dielectric material surrounding the core.

Cladding Mode Stripper
A device that encourages the conversion of cladding modes to radiation modes.

Cladding Surface Centre
For a cross section of an optical fiber, it is the position of the circle which best fits the focus of the cladding surface in the given cross section.

The best fit method has to be specified.

Cladding Surface Diameter
The diameter of the circle defining the cladding centre.

For normally circular fiber, the cladding surface diameter in any orientation of the cross section is the largest distance across the cladding

Non-Circularity of the Cladding Surface
The difference between the maximum cladding surface diameter Dmax and minimum cladding surface diameter D min ( with respect to the common cladding surface centre) divided by the nominal cladding diameter D.

Bandwidth in optical fiber

The value numerically equal to the lowest frequency at which the magnitude of the base band transfer function of optical fiber decreases to a specified fraction generally to –3dB optical (-6dB electrical) of the zero frequency value.

The band width of an optical fiber is limited by several mechanisms, mainly by chromatic dispersion. Fiber band width is usually characterized in the time-domain as pulse broadening or more technically as dispersion.

Mode Field Diameter-MFD, Cut-off wavelength and Zero Dispersion Slope

Mode Field Diameter - MFD

The mode field is the single mode field distribution giving rise to a spatial intensity distribution in the fiber. Mode field diameter is the diameter of energy path in an optical fiber. This parameter is one of the important parameter in a single mode optical fiber. Mode field diameter is measured by using Variable apertures method.

Cut off Wavelength

The cutoff wave length is the wave length greater than which the ratio between the total power including higher order modes and the fundamental mode power has decreased to less than a specified value, the modes being substantially uniformly excited.

1. By definition the specified value is chosen as 0.1 dB for a substantially straight 2 meter length of fiber including one single loop of radius 140 mm.

2. The cut off wave length defined in ITU-T recommendation is generally different from the theoretical cutoff wave length that can be computed from index profile of the fiber.

Zero dispersion slope: - The slope of the chromatic dispersion coefficient versus wave length curve at the zero dispersion wave length.

Zero dispersion wavelength: - The wavelength at which the chromatic dispersion vanishes is called Zero dispersion wavelength. This parameter is measured along with other chromatic dispersion characteristics of an optical fiber.

This Home is Fiber Connected – FTTH council badge says

Here is a encouraging and helpful work from FTTH council for the public. Fiber-to-the-Home Council announced that there are 34 telecom service providers approved for the council's network certification program in the effort's first two years as on 30th July 2008. FTTH Council certification is intended to help the public customers identify which providers are offering 100% fiber-optic connections for delivering next-generation video, Internet, and voice services.

This is a great idea implemented by FTTH council and must be appreciated. The certification allows certified providers to display a badge stating "This Home is Fiber Connected" at the subscriber premise, and to use the image on the badge in promoting their services. By using the image the subscribers are ensured that an installation done by the providers meets the FTTH Council's standard for running fiber-optic cable all the way to the boundary of the home.

Mr. Joe Savage is the president of FTTH council North America. He explained the achievements of the council during the last years in providing quality service to the public. FTTH council offers this program to ensure that there is no confusion, and that broadband and video subscribers know that they are getting the quality and bandwidth capabilities that are present only when fiber is run all the way to the home. The phenomenal growth from zero to 34 companies in two years shows how quickly FTTH is growing as a consumer technology in the North America.

The growing popularity of fiber to the home, along with the high performance and service quality widely associated with direct fiber connections, have prompted some providers that are still using copper in their last mile to claim that they deliver service over what they call a "fiber network”.

It is well known to everybody now that competing video or Internet service providers would want to associate their products with optical fiber. But consumers do not get the benefits of a 100% fiber network unless the fiber-optic cable goes all the way to the home. This is the reason why FTTH council came up with the certification program and the fiber-connected badge.

Though there are hundreds of providers in the United states offering fiber to the home to at least some of their subscribers, the FTTH Council certified networks connect to an estimated three quarters of all fiber-connected homes in the country The number of home connected through fiber is now estimated to be between 3 and 4 million households. Verizon became the first company to receive FTTH Council network certification and authorization to use the badge in 2006.

With fibers connected to home, the subscribers are ensured of faster data rates and more robust video services such as high definition and video on demand. Not limited to the above advantages only exactly, but consumers are also future-proofed for the next-generation of Internet services and applications, which are projected to consume many times the bandwidth as today's applications.

Below is the list of 34 FTTH Council certified providers:

Alpine Communications (Elkader, IA)
ATMC (Shallotte, NC)
Broadband Associates (Granite Bay, CA)
Burlington Telecom (Burlington, VT)
City of Wilson (Wilson, NC)
City Of Windom (Windom, MN)
Columbus Telephone Co. (Columbus, KS)
Connexion Technologies (Cary, NC)
CTC Telecom, Inc. (Cambridge, ID)
Elim Valley Development (St George, UT)
Embarq Corp. (Overland Park, KS)
Gainesville Regional Utilities (Gainesville, FL)
Genext, LLC (Wenatchee, WA)
GVTC (New Braunfels, TX)
Hancock Telecom (Greenfield, IN)
Home Telephone Co. (Moncks Corner, SC)
Horry Telephone Cooperative, Inc. (Conway, SC)
Jackson Energy Authority (Jackson, TN)
LBH, LLC (Sulphur, LA)
LightNex Communications (Billings, MT)
Molalla Communications Co. (Molalla, OR)
Morristown Utility System (Morristown, TN)
Moundville Telephone Co., Inc. (Moundville, AL)
NanoFibre Networks Inc. (Radium Hot Springs, BC, Canada)
NCW-Online (Wenatchee, WA)
Optical Entertainment Network, Inc. (Houston, TX)
Reedsburg Utility Commission (Reedsburg, WI)
T² Communications (Holland, MI)
UTOPIA (West Valley City, UT)
Verizon Services Corp. (Basking Ridge, NY)
West Wisconsin Telcom Cooperative (Downsville, WI)
WestelFiber (Boise, ID)
Xittel Telecommunications Inc. (Trois Rivieres, QC)
Zoomy Communications (Glenwood Springs, CO).

FTTH overtakes DSL and CATV in Japan

Mainly NTT’s plan to achieve the 20 million subscriber target by 2011 has boosted the deployment of FTTH cables in Japan. Along with NTT, it was KDDI which announced 1 Gbps transmission to the Japanese homes. The continued investments by Japans two largest fixedline operators NTT DoCoMo and KDDI into fibre to the home (FTTH) through network deployments has helped Japan to have more number of FTTH subscribers than digital subscriber lines (DSL).

At the end of June 2008, as per official records, out of the 29.342mn broadband subscribers, FTTH accounted for 45%, compared to DSL which was 42%, cable television (CATV) (13%) and fixed wireless access (FWA) (0.04%). FTTH has more advantages as opposed to traditional copper wires is that it allows operators to deliver data rich content through broadband, digital TV and telephone services with greater speed and efficiency between the telephone exchange and the home.

The licensing of WiMAX in telecom sector is expected to aid future growth in the market, although some industry insiders are skeptical of its ability to bring about change, largely as mobile broadband services are widely accessed in Japan. It will add further dimensions to the competition in the broadband market.

At the end of June 2008, the number of mobile subscribers in the market reached 108.2mn, of which there were 91.221mn 3G subscribers. Given the level of maturity in the market, growth is slowing, with operators shutting down their 2G networks in favor of generating greater activity over 3G. KDDI became the first to announce the closure of its TuKa brand, while NTT DoCoMo and Softbank Mobile are expected to follow suit. By the end of our forecast period in 2012, 3G penetration rates will have reached in excess of 100%.

The maturity of Japan’s telecom market has enabled the country to retain a strong standing in almost all telecom growth ratings. The worsening economic climate, forecast to grow by just 1% in 2008, could have a downward impact on the spending patterns of Japanese consumers and their attitude towards the mobile market. This may already have been realized with fewer subscribers looking to acquire new handsets. Japan is not alone in this regard, however, with Singapore Telecommunications and the Philippines Long Distance Telephone Company (PLDT) announcing concerns that they could be hit by the overall economic slowdown.

Optical Fiber and Preform Manufacturing Process

One advance bail we may like to take is for preparing this article we have referred some articles of some European fiber drawing tower manufacturers. Utilization of optical fibers in the field of communication has already been playing a predominant role over other long distance transmission media like coaxial cables microwave etc.

When put in simple words, an optical fiber is a thin cylindrical glass rod. Optical fibers are dielectric. Optical fibers consists of core and cladding having different refractive indices for total internal reflection of light so as the light to propagate through the optical fiber.

There are two steps involved in the manufacturing process of low loss optical fiber. Preform fabrication and Fiber drawing process from preform. Preform fabrication and Fiber drawing from performs are carried out at Optical fiber manufacturing plant.

The most commonly employed methods for optical fiber preform fabrication can be broadly categorized into the following types:

Inside Vapor Deposition Method ( IVD)

Out side Vapor Phase Oxidation (OVPO)

Inside vapor deposition method is further categorized as shown below:

Modified Chemical Vapor Deposition Method - MCVD

Plasma Chemical Vapor Deposition - PCVD

Plasma Enhanced MCVD - PMCVD

The outside vapor phase oxidation method is further categorized as shown below:

Outside Vapor Deposition Method - OVD

Vapor Axial Deposition Method – VAD

In all vapor deposition processes mentioned above, high purity glass to which different doping elements such as Germanium, Phosphorous, Boron, Fluorine etc. are added. This doping is done to modify the refractive indices. This refractive index difference is the basic characteristic of light propagation through an optical fiber. Generally, Germanium and Phosphorous are used to increase the refractive index of Silica. Boron and Fluorine are used to reduce the refractive index.

Basic raw materials used for making perform are in the form of halides, such as SiCl4, GeCl4, POCl3 etc. These are liquids. BCL3, SF6 etc. are vapors. These raw materials of Optical fiber will be converted into vapor phase. By converting into vapor phase, transition metal impurities like Ferrous, Nickel, Cobalt etc. will left un-vaporized. This happens because of the large difference in vapor pressure between the halides and the transitional metal impurities.

The raw material vapors are mixed with oxygen to form the reactant vapor stream. Reactant generation control of composition and transport is done with a vapor delivery system. Carrier gas will be bubbled through the liquid raw materials in order to convert them to vapor by the vapor delivery system. This output is transported to the heat zone where the reaction takes place in the heat zone of the tube and soot particles consisting of SiO2. GeO2, P2O5 etc. are formed which finally deposit on the inside glass surface.

The above is the procedure for making performs. The next process is drawing optical threads and applying coating over it in order to make them practically usable in the field.
A good fiber drawing process will ensure the following requirements.

* Draw optical fibers of desired diameter with very precise diameter control.

* Refractive index profile created at the preform stage should not be altered.

* The perform is made with a core-clad dimensional ratio. The fiber drawing should ensure the same ratio through the process of optical fiber drawing.

Optical characteristics should not be degraded during drawing and the suface quality shall be maintained ad high intrinsic tensile strength of glass shall be retained.

The perform is fed in to the high temperature furnace by a high precise feeding mechanism. The melted fiber is pulled by a capstan whose speed is automatically controlled by a fast response feed back loop from a scanning laser diameter guage to maintain an online optical fiber diameter value. The laser monitor gauge is capable of providing positional information which will be utilized to serve precision stepper motor driven X-Y slides on the perform feed to automatically maintain a fixed fiber line into the acrylate coating applicator.

As a current practice two protective coatings are applied on line by polymerization of concentrically applied liquid coating curable either UV radiation. Optical fiber Drawing tension is monitored as a function of time. The Optical fiber thus formed is reeled at low tension into fiber spools.

History of Fiber Optic Communications - a tribute to the great Inventors

It is good to start with ‘Once upon a time there lived Mr. Claude Chappe in France who invented the Optical semaphore telegraph. That was in 1790s. The history of Optical communication systems dates back to that period. Alexander Graham Bell developed the first optical telephone system in 1880. He named his new device suitably as Photophone.

Alexander Graham Bell became part of the history by inventing the telephone, which is his masterpiece invention. Alexander Graham Bell’s Photophone invention stayed as an experimental invention but could not realized. It took another 40 years till and England scientist Mr. John Logie Baird and US scientist Mr. Clarence W. Hansell brought up the idea of using arrays of hollow pipes or transparent rods to transmit images for television or facsimile systems in 1920s.

Abraham Van Heel from Netherlands and Harold H. Hopkins from Britain in 1945 separately wrote about imaging bundles. Both reported about the fibers, but with slightly different ideas. When Hopkins reported on imaging bundles of unclad fibers, Van Heel reported on simple bundles of clad fibers. Van Heel detailed about a bare fiber having transparent cladding with a lower refractive index. He said that this clad will protect the fiber reflection surface from outside distortion and greatly reduce interference between fibers, when put into operation together. Van Heel’s idea of a clad over the core of the fiber was more practical as we can see today’s optical fibers are manufactured with a doped silica core with a silica cladding.

Abraham Van Heel thus became the prominent contributor towards the new age optical fiber telecommunication.. Along with Brian O'Brien, Van Heel progressed towards the innovation of cladding fiber optic cables. Before Van Heel optical fibers developed were bare and lacked any form of cladding. If there is no cladding layer over the core of the fiber the total internal reflection occurs at the glass - air interface. Abraham Van Heel could correctly point to a bare fiber or glass or plastic with a transparent cladding of lower refractive index. This development of cladding of lower refractive index made the total internal reflection to happen inside the core path.

Glass cladded fibers having an attenuation of around 1 decibel (dB) per meter were developed by 1960. These fibers were used in medical imaging to observe the internal body parts etc., The attenuation of 1 decibel or dB is too high for communication purpose.

The credit of inventing the single mode fiber goes to Elias Snitzer of American Optical who could put forward the theory of a fiber with a small core. This core is too small that it could carry light with only one waveguide mode. This restriction of waveguide by limiting the core size of fiber was very crucial in the development of modern day telecommunication grade optical fibers in the sense that it suggested the geometrical relation of core and number of waveguides, but the attenuation was still high at 1 decibel per meter. Therefore, Snitzer's invention was more suitable for medical instruments that looked the inside parts of the human body. Telecommunication purpose fibers are required to carry optical signals longer distances and hence required an attenuation of less than 10 or 20 dB per kilometer. Copper cables had 20dB attenuation per kilometer. Optical fibers are useful if they can compete with copper.

Dr. Charles K. Kao identified the need for the 10 or 20 dB of light loss per kilometer for an optical fiber to be used for long distance telecommunication. Dr K. Kao put forward his theory in 1964. Dr. Kao successfully proved the need for a purer form of glass to help reduce light loss.

A team of communication researchers were experimenting with fused silica in Corning’s lab. Silica is a material capable of extreme purity with a high melting point and a low refractive index. Corning Glass researchers Robert Maurer, Donald Keck, and Peter Schultz invented fiber optic wire or optical waveguide fibers. This newly invented Optical fiber could carry 65,000 times more information than copper wire.

The Corning’s research team could solve the decibel loss problem pointed out by Dr. Kao. Corning could thus develop a single mode fiber, SMF with a loss of 17 dB/km at 633 nm. This they achieved by doping titanium into the core of the optical fiber.

Peter Schultz Robert, Maurer and Donald Keck invented germanium doped multimode fiber in 1972. This multimode fiber was with a loss of 4 dB per kilometer and much greater strength than titanium doped fiber., John MacChesney developed a modified chemical vapor deposition process, MCVD process for manufacturing the preform, the raw material of fiber, at Bell Labs in1973. With the invention of MCVD process, the commercial production of optical fiber started.

Our internet resources said, The General Telephone and Electronics tested and deployed the world's first live telephone traffic through a fiber-optic system running at 6 Mbps, at Long Beach, California In April 1977. Bell in May 1977, installed an optical telephone communication system in the downtown Chicago area, covering a distance of 2.4 kilometers. Each pair of optical fiber carried the equivalent of 672 voice channels and this was equivalent to a DS3 circuit.

Today optical fiber cables carry more than 80 percent of the long distance voice and data traffic all over the world. The fiber has virtually penetrated to every walks of the life. Looking back to the historical days, the efforts of the great people who made this mode of communication possible, has contributed to the fast modernization of the human civilizations around the world by revolutionizing the information technology.

Applications of Optical fibers and fiber optic related technologies

Today the fiber optic technology has reached to the houses in many advanced countries. The demand for optical fiber and related services has grown tremendously and applications of optical fiber are various. Uses of fiber optics in telecommunication applications itself are widely distributed. The use fiber optics ranges from global long distance telecom networks to local and desktop computers. Some of the remarkable application of fiber optics includes the transmission of voice, data, or video over distances of hundreds of kilometers. There are different types of designs for optical fiber cables for different applications.

Service providers and carriers use optical fiber to transmit plain old telephone service called POTS throughout the national networks. Applications of optical fibers are not limited to long distance data transmission. It also includes the transmission of video services and CATV.

Optical fibers are also used extensively deployed for transmission of data. Corporate houses and MNCs need safe and reliable systems to transfer their confidential data and financial information from their head office to the branches within the country and faraway countries. Optical fibers are the safest medium free from immediate tapping and leaking.

CATV, Cable television companies now a days use optical fiber to deliver the digital video and data services. The high bandwidth provided by optical fiber makes it the suitable medium for transmitting broadband signals such as high-definition television telecasts.

Automated toll-booths, smart highways with intelligent traffic lights, and other Intelligent transportation systems, changeable message signs etc are also beneficiaries of fiber optic technology based telemetry systems.

Biomedical industry is one of the major area of application for optical fibers. Optical fiber systems are used in most modern telemedicine devices for transmission of digital diagnostic images. Fiber optics is usable for military application and fiber has made applications in Automotive and other industrial applications.

To summarize, major application of fiber optics is long distance communication of data, voice, image and video even now. However, fiber optic applications are not limited to this field and thus scatters to medical field, CATV, traffic signaling, image processing, illumination and decoration industry to mention a few.

How the Optical fiber works? - Propagation of light and Total Internal Reflection

An optical fiber has a core and a cladding. The core diameter of a single mode fiber is approximately 9 micrometers. But more than the geometrical core, the Mode field diameter is important for an optical fiber for transmission. Mode field diameter is the diameter of the light travelling area inside the fiber. It includes core and some portion of the cladding too.

The core and the cladding have different refractive indices. This means the light travels at different speeds at core and cladding. This difference is very low, but is very important for the optical fiber to carry the light along its length. Due to this refractive index difference between the core and cladding, the light hits at the border of the core will return back and hit at the opposite border and again reflect back. This process of total reflection is called Total Internal Reflection. Total Internal Reflection or TIR is the basic principle on which an optical fiber works.

Core has slightly higher refractive index than the cladding. The light theories says, when light travels from a medium of higher refractive index to a medium of lower refractive index, the light reflect back. This total internal reflection is shown in the diagram.

If n1 is the refractive index of core and n2 is the refractive index of cladding, then n1>n2 is the condition for total internal reflection.

Some back reference to the velocity of light here will be useful to remember. The speed of light in vacuum is 300,000 km per second. If light travels through a medium at a speed of 200,000 km per second, the refractive index of the medium is 1.5. The calculation is as simple as this. The refractive index is calculated by dividing the speed of light in vacuum by the speed of light in the medium.

So, to put in the form of mathematical formula; Refractive index of a medium = Speed of light in vacuum/Speed of light in the medium.

Total internal reflection happened and the light travelled all the way along the fiber carrying our valuable Voice, data, video and image. How useful is this total internal reflection!

Glimmerglass - Intelligent Optical Switching solutions for Fiber Optic Communication

Glimmerglass develops and markets Intelligent Optical Switching solutions for the Telecommunications Industry and Government. Glimmerglass has shipped more than 40,000 optical cross connect ports to over 50 customers across Europe, Asia and North America.

The demand for video and streaming media services by service providers, national carriers and content providers are driving bandwidth demand. This has resulted in the exponential growth in Internet traffic. Service providers are looking for Intelligent Optical Switching to meet the ever growing requirement at today’s market and for the future solutions.

The solutions from Glimmerglass have the capability to Create, Monitor and protect fiber-optic light paths. Customers can utilize effectively the Glimmerglass solutions in five major application areas providing dramatic reductions in operational expenses, OPEX, and capital expenses, CAPEX, while increasing network capacity.

Glimmerglass identifies those five areas of major applications as given below;

Increasingly complex fiber plants and reduced OPEX budgets require innovative solutions. Using Glimmerglass Intelligent Optical Switches to manage light paths enables "lights out" data centers. In the New Optical Internet, Central Offices are becoming overloaded with fiber. Connected by high speed fiber-optic links to the rest of the Internet, they are the major aggregation and disaggregation points and, with the rapid growth of FTTx, the customer links are also increasingly fiber-based. Managing these external optical links is an increasing problem. Rapid growth in both the number and speeds of these links, combined with the need for increased reliability and flexibility, must be handled in a very cost-constrained environment.

Watch the video demonstration

Glimmerglass Intelligent Optical Switches add major flexibility in the management of light paths while enabling significant reductions in both OPEX and CAPEX. Visionary telecommunications carriers and researchers recognize that a hybrid of routers and optical switches provides the most efficient and highest capacity Internet backbone infrastructure.

One major European carrier has deployed Glimmerglass solutions to protect all wavelengths at the juncture of the undersea cable and the land-based fiber plant. Undersea fiber-optic cables provide the vast majority of the intercontinental bandwidth of the Internet. Remotely Creating, Monitoring and Protecting the light-paths on these fibers is increasingly important to the New Optical Internet. With the rapid growth in the amount of traffic carried on undersea cables, the outages seen in the past caused by cable breaks and equipment failures are no longer acceptable.

Peering Exchanges are the most data intensive sites in the world. AMS-IX, Europe's largest Internet Exchange, relies on Glimmerglass switches in the heart of its hybrid IP/ switched network to provide the ability to create new light paths on demand and to monitor and protect all high speed links.

An Internet Exchange is a meeting point for independent Internet Service Providers (ISPs) enabling them to exchange Internet traffic with each other, nationally and internationally. This exchange of traffic is known as “peering.” Since without peering, the Internet is nothing, network reliability at Internet Exchanges is of extreme importance. In addition, rapid growth of the Internet has resulted in Internet Exchanges seeing traffic double every year. This places a severe strain on both network architecture and planning.

Glimmerglass Intelligent Optical Switches provide the optimal monitoring environment for lawful intercept and other government applications.

Signals monitoring and analysis demand the highest possible optical signal quality over a wide range of conditions. The use of pure optics with no electrical conversions enables Glimmerglass Intelligent Optical Switches to deliver the best possible performance — independent of signal type. Glimmerglass solutions are non-blocking, deliver very low optical insertion loss (typical 1.7 dB), support a wide range of signals on single mode fiber (1260 nm–1630 nm) and operate with ultra low input power (-35 dBm).

What are the Advantages of Optical Fibers?

Every day we read news about new fiber optic projects coming up from many parts of the world. Fiber optic technology is relatively new in communication having around 30 years of developing experience ever since the first fiber optic link was installed in the US. What is the reason behind the use of fiber optics massively being deployed for telecommunication? While comparing with the existing copper communication cables, the optical fibers have many advantages. The advantages of fiber optic technology or more precisely the advantages of optical fibers over copper cables can be summarized as given below:

Expense: Low investment cost: Money matters to a great extent when it comes to the project cost. Fiber systems buying alone may be costly, but when the communication starts through the fiber, it dominates the cheapest option over copper. Fiber is the cheapest communication medium for long distance and short distance high bandwidth transmission. A fiber optic cable having only a single fiber can carry equivalent or more signals for several miles if compared with a 3000 pair copper cable. Long distances of optical cables are cheaper than equivalent lengths of copper wires. Several subscribers can be connected through a few fibers. Cable TV and internet service providers can transmit virtually unlimited bandwidth through optical fiber.

Small size: Let us say mini cables. Fiber optic cables are small in size. The diameter of an optical fiber generally used for telecommunication purpose is 0.25 millimeter. A single fiber cable developed for FTTH and other premise application can be around 2 to 3 millimeter. Fiber optic companies are engaged in further size reduction. Thinner cables makes the installation and handling of optical fibers easy and simple.

Information carrying capacity: Compare to copper cables the information carrying capacity of optical fibers are many times higher. An optical fiber can carry many terra bits of information. The optical supporting devices have to be developed to support optical fibers’ huge potential to carry information.

Low attenuation or light loss: Optical fibers have very low attenuation. This allows the optical fibers to carry the information for long distances with out the need for regenerating. The current single mode fiber cables installation practices requires a repeater typically after 80 kilometers. There are no equivalent comparison for copper cables!

Interference: Since the optical fibers carry light, there is no chance for interference. No cross-talk between different optical fibers. Copper cables are infamous for their cross talk and we all might have heard of other people’s sound in our telephone. This overhearing or cross-talk as known in the industry can be avoided by using optical fibers. Optical fiber communication offers clearer phone conversations or TV reception compared to copper cables.

Lightning resistance: Since optical fibers carry light, they are immune to electrical influences. Optical fiber communications are not affected by lightning. This should not be confused with the protection of metallic armored optical fiber cables from lightning. That is a different type of protection to the safety of optical fiber cables. As far as communication is concerned, optical fibers have high advantage over copper cables in lightning prone areas.

Digitized information: Optical fibers carry information in the digital form. Digital signals are used in computer networks.

Low weight: Optical fiber cables are extremely lightweight. Now a 96 fiber cable having a micro-duct structure weighs approximately 35 kg. A normal duct cable of 96 fibers will have approximately 110kg. The weight varies slightly among different manufacturers according to the design and application of fiber optic cable. But compared to the optical fiber volume and information carrying equivalency of copper cables, optical fiber cables with many advantages are at top that makes them far from comparison.

Flexibility: This is very important for handling and installation. Optical fiber cables are very flexible. Due to their small size and flexible nature of optical fibers, installation of fiber optic cable is easier. This saves in terms of installation cost.

The advantages of optical fibers do not end here. We might have missed many points and will update as when we get more information.

Demand for Optical fiber connectivity in Taiwan is on the top

Optical fiber has become the fastest growing access technologies in Taiwan. Taiwan has more than 800,000 Subscribers connected through Fiber optics by the end of June 2008. Much credits goes to the government and the construction sector.

In order to provide customers the best services, Taiwan telecommunications companies has taken initiatives to adopt broadband services using fiber-optic technology to replace traditional telephone lines and replacing Wi-Fi - Wireless Fidelity access points with WiMAX access. WIMAX access was designed for high-speed, high-capacity wireless data solutions.

Taiwan’s Ministry of Economic Affairs, MOEA’s Committee of Communications Industry Development has formed a Task force in collaboration with Fiber Broadband Operators in Taiwan, in order to promote the deployment and application of the fiber network. This task force will promote a Fiber Broadband Building - FBB labeling system.

With the constant promotion of Fiber optic technology to the home by the task force, the number of household users of fiber to the home (FTTH) and fiber to the building (FTTB) had increased by 37,239 on 172 construction projects in 18 cities or counties in Taiwan.

Construction companies are convinced by the task force tor the construction of optical fiber networks on their new building construction projects, with the budget for such networks amounting to an estimated NT$40 million. Driven by the contributions of the construction sector, fiber subscriptions surged sharply to 800,000 at the end of June 2008 from 200,000 at the end of 2006, representing a nationwide penetration rate of 17 percent in Taiwan.

Taiwan was ranked fourth in the FTTH and FTTB services penetration rate in the world in July 2008, a significant move up from seventh position last year.

Sterlite bagged order worth US$ 5.1 million for supply of 288F High count metal free fiber optic cables from BSNL

Sterlite will supply 288F high count Ribbon Fiber optic cables to BSNL, India’s public sector telecommunication operator. This is the first time in India, a company being awarded an order for supply of High count Metal free Ribbon optical fiber cables of more than 144F.BSNL has special design requirements for high count metal free optical fiber cables that will be used for access networking. Sterlite will supply high-density ribbon fiber optic cables to BSNL whose plan is to initially install these cables in 100 city locations across the country.

India’s BSNL buy High count ribbon cables of loose tube design. 12 fiber ribbons are placed in loose tubes color coded for easy identification. These loose tubes are stranded over a central strength member which is up-jacketed with polyethylene. Stranded core is sheathed with Polyethylene and further protected by Nylon-12 jacket against termite attacks.

288F high count metal free Ribbon optical fiber cables are manufactured with eight small intermittent fillers to give circularity to the stranded core. The loose tube outer diameter is 6.7mm which is quite high and cable weight is also higher compared to the current industry trends and practices. BSNL designs for higher count cables starts from 48 Fiber per cable. 48F, 96F, 144F, 288F and 576F cables are classified as High count cables by BSNL in India. A sample diagram of 144F High count Non-metallic Ribbon Optical fiber cable used by BSNL in India is shown below:

BSNL will use these high count ribbon fiber optic cables in their Pan-India broadband access network in order to enhance the efficiency of network roll-out. High count Ribbon fiber optic cables will provide an efficient way to achieve high fiber density, as well as to reduce the time required for installation per fiber. This will reduce installation time and cost.

The contract worth US$ 5.1 million or 24 Crores Indian rupees is considerably a big tender in Indian telecom scenario. Sterlite plans to cash out from the growth in demand for fiber cable from the domestic and global telecom and power sectors. To accelerate the growth, Sterlite is also scaling up its operations.

Sterlite will double its manufacturing capacity at its optical fiber facility to 12 million-km and is planning 3 fold increase in the manufacturing capacity at its fiber optic cables facility to six million-km.Recently, Sterlite, India’s leading optical fiber and telecom cables manufacturer, had bagged two contracts worth US$ 26 million or Indian Rs 107 crores from BSNL.

The first contract was for the supply of fiber optic cables that BSNL will install in 900 urban centers across India and the second was for copper telecom cables to develop basic telephone infrastructure in India’s rural areas.