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Fiber Optic Communications, Fourth Edition. Joseph C. Palais (versão do pdf não editada). Lucas Garcia. Loading Preview. Sorry, preview is currently. Fiber optic communication – Joseph C Palais: 4th Edition, Pearson Education. The functions p (y/1) and p (y/0) are conditional PDF as shown in Fig. download fiber optic communications joseph c palais - fiber optic communications joseph c palais northernkites micom p technical manual pdf download. the.

Fiber Optic Communications Palais Pdf

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Fiber Optic Communications PALAIS - Free download as PDF File .pdf), Text File .txt) or read online for free. book fiber optic communications (4th edition) by joseph c. palais in pdf format, then complete release of this ebook in doc, djvu, epub, pdf, txt formats. you may . Edition Joseph C Palais PDF on The Most Popular Online PDFLAB.. Edition Joseph C PalaisPDF and Download Fiber Optic Communications 5th Edition.

Uploaded by. The fourth edition of this popular text and reference book presents the fundamental principles Optical Fiber Communications by Gerd Keiser, 4th. Edition, Mc Palais 5th The fiber joining process is very constly and requires skilled manpower.

PDF An extensive review of optical fiber sensors and the most beneficial Gerd Keiser. Understanding Optical Communications ; This edition applies to fibre optic communications and optical networking. Comments may be Gerd Keiser It lacks features important to communications applications, for which it is Company, Tokyo, Introduction: Plasmonics - merging photonics and electronics at nanoscale Gerd E. A powerful aspect of an optical fiber communication link is that many different The technology of combining a number of wavelengths onto the same fiber is known as.

Department of Electronics and Communication Engineering Abstract - Optical fibre communication systems are composed of optical source, Performance weight sensor using graded index optical fiber on static Mode merger can be achieved by using a Fukuoka Japan ; Fukuoka Japan Because of these limitations, multimode step index fiber is typically only used in applications requiring distances of less than 1 km.

The light ray is propagated through the refraction. The light ray enters the fiber at many different angles. As the light propagates across the core toward the center it is intersecting a less dense to more dense medium. Therefore the light rays are being constantly being refracted and ray is bending continuously.

This cable is mostly used for long distance communication. IN TS EN x The light rays no longer follow straight lines, they follow a serpentine path being D gradually bent back towards the center by the continuously declining refractive index. The modes travelling in a straight line are in a higher refractive index so they travel TU slower than the serpentine modes.

This reduces the arrival time disparity because all modes arrive at about the same time. It is seen that light rays running close to the fiber axis with shorter path length, will have a lower velocity because they pass TS through a region with a high refractive index. IN TS x Rays on core edges offers reduced refractive index, hence travel more faster than axial EN rays and cause the light components to take same amount of time to travel the length of fiber, thus minimizing dispersion losses.

D x Typical attenuation coefficients of graded index fibers at nm are 2. TU x The main advantages of graded index fiber are: Reduced refractive index at the centre of core. Comparatively cheap to produce. Long distance 1. High data rate Multimode 1. Short distance 2. Low data rate Multimode 3. The core-cladding boundary conditions lead to coupling of electric and magnetic field components resulting in hybrid modes. Hence the analysis of optical waveguide is more complex than metallic hollow waveguide analysis.

The two.

Overview of Modes x The order states the number of field zeros across the guide. The electric fields are not TS completely confined within the core i. The low order mode confines the electric field near the axis of the fiber core and there is less penetration into the cladding. While the high order mode distribute the field towards the edge of the core fiber and penetrations into the EN cladding.

Therefore cladding modes also appear resulting in power loss. Cladding also improves the mechanical strength of fiber core and reduces CI surface contamination. Plastic cladding is commonly used. Materials used for fabrication of optical fibers are silicon dioxide SiO2 , boric oxide-silica. IN …Ans. Compute the numerical aperture. TS Solution: If the core refractive index is CI 1.

Numerical aperture. A step index multimode fiber with a numerical aperture of a 0. B 0 where, E and H are electric and magnetic field vectors. D and B are corresponding flux densities. P is induced electric polarization. D x Wave equation: The frequency dependence of n is called as chromatic dispersion or material dispersion.

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An optical mode is a specific solution of the wave equation that satisfies boundary conditions. There are three types of fiber modes. EN a Guided modes b Leaky modes c Radiation modes x For fiber optic communication system guided mode is sued for signal transmission.

Graded Index Fiber Structure D x The Refractive index of graded index fiber decreases continuously towards its radius from the fiber axis and that for cladding is constant. TU x The refractive index variation in the core is usually designed by using power law relationship. The local numerical. IN differences amongst various modes in multimode is avoided.

Multimode step index fibers cannot be used for single mode propagation due to difficulties in maintaining single mode operation. Therefore for the transmission of single mode the fiber is designed to allow propagation in one mode only, while all other modes are attenuated by leakage or TS absorption. The single mode propagation of LP01 mode in step index fibers is possible over the range.

In order to obtain single mode operation with maximum V number 2. But smaller core diameter has problem of launching light into the fiber, jointing fibers and reduced relative index difference. TU x Graded index fibers can also be sued for single mode operation with some special fiber design.

The cut-off value of normalized frequency Vc in single mode operation for a graded index fiber is given by, TS Example 1. A multimode step index optical fiber with relative refractive index difference CI 1. If the operating wavelength is 0. Normalized frequency V number and core diameter is related by expression,. Maximum core diameter for single mode operation is 2. D Example 1. A GRIN fiber with parabolic refractive index profile core has a refractive index at the core axis of 1.

Cut-off Wavelength EN x One important transmission parameter for single mode fiber us cut-off wavelength for the first higher order mode as it distinguishes the single mode and multim0de regions. The range of cut-off wavelength recommended to avoid modal noise and dispersion problems is: IN Example 1.

Estimate cut-off wavelength for step index fiber in single mode operation. The core refractive index is 1. The relative index difference is 0.

TS Solutions: This parameter is determined from mode field distributions of fundamental LP01 mode. The material must be transparent for efficient transmission of light. It must be possible to draw long thin fibers from the material. Fiber material must be compatible with the cladding material.

Glass and plastics fulfills these requirements.

IN x Most fiber consists of silica SiO2 or silicate. Various types of high loss and low loss glass fibers are available to suit the requirements. Plastic fibers are not popular because of high attenuation they have better mechanical strength. TS Glass Fibers x Glass is made by fusing mixtures of metal oxides having refractive index of 1. One important criteria is that the refractive index of core is greater than that of the cladding, hence some important compositions are used such as. IN x The principal raw material for silica is sand and glass.

The fiber composed of pure silica is called as silica glass. The desirable properties of silica glass are: TS - Good chemical durability.

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In this process vapours of metal halides such as SiCl4 and Gecl4 reactive with oxygen and forms powder of SiO2 particles. The SiO2 particles are collected on surface of bulk glass and then sintered to form a glass rod called Preform. The preforms are typically mm diameter and cm long from which fibers are drawn.

A simple schematic of fiber TS drawing equipment is shown in Fig. The preform is heated up in drawing furnace so that it becomes soft and fiber can be drawn easily. The fiber is then coated with elastic material to protect it from dust and water vapour. Fig, 1. The mandrel is removed when deposition process is completed, This preform is used for drawing thin filament of fibers in fiber drawing equipment.

The rod is continuously rotated and moved upward to maintain symmetry of particle deposition. IN x The advantages of VAD process are - Both step and graded index fibers are possible to fabricate in multimode and single mode. TS - The performs can be fabricated in continuous length. A hollow silica tube is heated to about oC and a mixture of oxygen and metal halide gases is passed through it. The soot that develops from this deposition is consolidated by heating.

The tube is rotated while the heater is TU moved to and along the tube and the soot forms a thin layer of silica glass. The rotation and heater movement ensures that the layer is of constant thickness. The first layer that is deposited forms the cladding and by changing the constituents of the incoming gas the refractive index can be modified to produce the core.

Graded index fiber is produced by TS careful continuous control of the constituents. The preform is about 25 mm in diameter and 1 metre in length. This will produce 25 km of fiber.

To prevent contamination, the atmosphere is kept dry and clean. The fiber is then pulled as a fine strand from the bottom, the core and cladding flowing towards the pulling point. Laser gauges continually monitor the thickness of the fiber and automatically adjust the pilling rate to maintain required thickness.

After sufficient CI cooling the primary buffer is applied and the fiber is drummed. It reduces mechanical stress on glass films. Non-isothermal microwave plasma at low pressure initiates the chemical reaction. Double-Crucible Method x Double-crucible method is a direct melt process. In double-crucible method two different glass rods for core and Cladding are used as feedstock for two concentric crucibles.

The inner crucible is for core and outer crucible is for cladding. The fibers can be drawn from the orifices in the crucible. The fibers must be able to sustain stresses and strains exerted during the cabling process. CI Two basic mechanical properties of glass fibers are identified. Strength 2. Static fatigued 1. A hypothetical model of micro crack is shown in Fig. This is popularly known as Griffith micro crack.

The micro crack is elliptical shaped. Therefore D fiber strength should be expressed statistically. The Weibull expression is given by 2. There is possibility of fiber failure due to growing micro crack. Also because of chemical erosion at the flaw tip due to water molecules, the flaw increases.

To protect fiber from environmental erosion, coatings are applied immediately after the manufacturing of fiber. In proof testing the fiber is subjected to a tensile load greater than the load at the time of manufacturing and installation. The fibers are rejected if it does not pass the test. The failure probability Fs. The structure of cable depends on the situation where it is to be used, but the basic cable design principles remains same.

EN x Mechanical property of cable is one of the important factor for using any specific cable. Maximum allowable axial load on cable decides the length of the cable be reliably installed. The outer sheath D must be designed to protect glass fibers from impact loads and from corrosive environmental elements. TU Fiber Arrangements x Several arrangements of fiber cables are done to use it for different applications. The most basic form is two fiber cable design.

TS It is also known as basic building block of fiber cable. These units are bound on a buffer material which acts as strength element along with insulated copper conductor. The fiber building blocks are surrounded by paper tape, PVC jacket, yarn and outer sheath. To ease identification, individual fibers are TU colour coded Table 1.

IN 12 and held together with a coloured binding yarn. Cable Jacket TS The cable jacket, the final outer layer of the cable, may use a number of materials depending on the required mechanical properties, attenuation, environmental stress and flammability.

Table 1. Also for indoor and general applications. TU Polyethylene PE Used for telephone cables; resistant to chemicals and moisture; low-cost; flammable, so not used in electronic application. Used in highly flame retardant plenum cables. Suitable to temperatures of o C; chemically insert. Du Pont Nemours and Company. Kynar is a registered trademark of Pennwalt, Inc. IN x Fibers can also be manufactured from transparent plastic which offers advantages of larger diameter 1 mm , increased flexibility, can be cut using a hot razor blade, ease of termination.

But because of high intrinsic loss use of plastic fibers is normally restricted TS to only few metres.

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EN Also, silica fiber can tolerate higher temperature than plastic fiber. On the other hand, POF is more flexible, less prove to breakage, easier to fabricate and cost is low than glass fibers. These advantages and disadvantages are summarized in Table 1. State and explain the advantages and disadvantages of fiber optic communication systems. State and explain in brief the principle of light propagation. Define following terms with respect to optical laws — A Reflection.

Explain the important conditions for TIR to exit in fiber. Derive an expression for maximum acceptance angle of a fiber. Explain the acceptance come of a fiber. Define numerical aperture and state its significance also.

Explain the different types of rays in fiber optic. What is mean by mode of a fiber? Explain the fiber materials used in fabrication requirements.

In case of glass fibers how the refractive index can be varied? Briefly explain following techniques of fabrication. Introduction, Attenuation, absorption, scattering losses, bending loss, dispersion, Intra modal dispersion, Inter. IN modal dispersion. It is also known as fiber loss or signal loss. The signal attenuation of fiber determines the maximum distance between transmitter and receiver. The attenuation also determines the number of. IN repeaters required, maintaining repeater is a costly affair.

As the signal pulse travels along the fiber length it becomes more broader. After sufficient length the broad pulses starts overlapping with adjacent pulses. This creates error in the receiver. Hence TS the distortion limits the information carrying capacity of fiber. Absorption is because of fiber material and scattering due to structural imperfection within the fiber.

Microbending of optical fiber also contributes to the attenuation of signal. Glass is a silicon compound, by adding different additional chemicals to the basic silicon dioxide the optical properties of the glass can be changed.

Attenuation Units x As attenuation leads to a loss of power along the fiber, the output power is significantly less than the couples power. Let the couples optical power is p 0 i. IN This parameter is known as fiber loss or fiber attenuation. TS x Attenuation is also a function of wavelength. Optical fiber wavelength as a function of wavelength is shown in Fig.

Example 2. For a 30 km long fiber attenuation 0. Determine —. IN 1 Overall signal attenuation in dB. Each splice introducing attenuation of 1 dB. A continuous 12 km long optical fiber link has a loss of 1. Given data: IN Example 2. The power at the end of 10 km length of the link working in first windows is — Another system of same length working in second window is Calculate fiber attenuation for each case and mention wavelength of operation.

CI … Ans. Attenuation in 2nd window: Attenuation in 3rd window: IN … Ans. Wavelength in 1st window is nm. TS Wavelength in 2nd window is nm.

Wavelength in 3rd window is nm. EN Example 2. If the fiber attenuation is 0. Absorption loss results in dissipation of some optical power as hear in the fiber cable. Although glass fibers are extremely pure, some impurities still remain as residue after purification.

The amount of absorption by these impurities depends on their concentration and light wavelength. IN 3 Intrinsic absorption by basic constituent atom of fiber. Absorption by Atomic Defects x Atomic defects are imperfections in the atomic structure of the fiber materials such as TS missing molecules, high density clusters of atom groups. These absorption losses are negligible compared with intrinsic and extrinsic losses. The radiation dames the internal structure of fiber. The damages are proportional to the intensity of ionizing particles.

This results in increasing attenuation due to atomic defects and absorbing optical energy. The total dose a material receives is expressed in rad Si , this is the unit for measuring D radiation absorbed in bulk silicon. A major source of attenuation is from transition of metal impurity ions such as iron, chromium, cobalt and copper. The effect of metallic impurities can be reduced by glass refining techniques.

IN impurities dissolved in glass. Vibrations occur at wavelengths between 2. The absorption peaks occurs at , and nm. These are first, second and third overtones respectively. Between these absorption TS peaks there are regions of low attenuation. Thus intrinsic absorption sets the fundamental lower limit on absorption for any particular material.

Absorption occurs when a photon interacts with an electron in the valene band and excites it to a higher energy level. The inherent IR absorption is due to interaction between the vibrating band and the electromagnetic field of optical signal this results in transfer of energy from field to the band, thereby giving rise to absorption, this absorption is strong because of many bonds present in the fiber.

CI x The loss in infrared IR region above 1. As glass is composed by randomly connected network of molecules and several oxides e. These two effects results to variation in refractive index and Rayleigh type scattering of light. There are two causes during the manufacturing of fiber.

The random changes. IN because of this are impossible to eliminate completely. When light ray strikes such zones it gets scattered in all directions. The amount of scatter depends on the size of the discontinuity compared with the wavelength of the light so the shortest TS wavelength highest frequency suffers most scattering.

The overall losses in this fibers are more as compared to single mode fibers. Mie Scattering: Careful control of manufacturing process can reduce mie scattering to insignificant levels. This is shown in Fig. TS CI x As the core bends the normal will follow it and the ray will now find itself on the wrong side of critical angle and will escape.

The sharp bends are therefore avoided.

EN k is wave propagation constant. This small microbending is TS not visible. The losses due to this are temperature related, tensile related or crush related. These effects can be minimized during installation and testing. IN Macrobending x The change in spectral attenuation caused by macrobending is different to microbending. Usually there are no peaks and troughs because in a macrobending no light is coupled TS back into the core from the cladding as can happen in the case of microbends.

The losses are eliminated when the bends are straightened. The losses can be minimized by not exceeding the long term bend radii. IN where, P r is power density of that model at radial distance r. Pulse spreading in fiber is EN referred as dispersion. Dispersion is caused by difference in the propagation times of light rays that takes different paths during the propagation.

The light pulses travelling down the fiber encounter dispersion effect because of this the pulse spreads out in time domain. Dispersion limits the information bandwidth. The distortion effects can be analyzed by D studying the group velocities in guided modes. Information Capacity Determination TU x Dispersion and attenuation of pulse travelling along the fiber is shown in Fig.

At certain distance the pulses are not even distinguishable and error will occur at receiver. Therefore the information capacity is specified by bandwidth- distance product MHz. For step index bandwidth distance product is 20 MHz. Group Delay x Consider a fiber cable carrying optical signal equally with various modes and each mode.

IN contains all the spectral components in the wavelength band. All the spectral components travel independently and they observe different time delay and group delay in the direction of propagation.

The velocity at which the energy in a pulse travels along the fiber is known as group velocity. Group velocity is given by, TS … 2. Material Dispersion. IN x Material dispersion is also called as chromatic dispersion. Material dispersion exists due to change in index of refraction for different wavelengths. The time delay is different for different wavelength components.

This results in time dispersion of pulse at TS the receiving end of fiber. The amount of material dispersion depends upon the chemical composition of glass. TU Example 2. An LED operating at nm has a spectral width of 45 nm. What is the pulse spreading when a laser diode having a 2 nm spectral width is used?

Fiber Optic Communications PALAIS

Find the the material-dispersion-induced pulse spreading at nm for an LED with a 75 nm spectral width [Jan. Since multimode optical fibers carry hundreds of modes, they will not have observable waveguide dispersion. EN x As frequency is a function of wavelength, the group velocity of the energy varies with frequency.

The produces additional losses waveguide dispersion. The propagation constant b varies with wavelength, the causes of which are independent of material dispersion. D Chromatic Dispersion TU x The combination of material dispersion and waveguide dispersion is called chromatic dispersion. These losses primarily concern the spectral width of transmitter and choice of correct wavelength. TS x A graph of effective refractive index against wavelength illustrates the effects of material, chromatic and waveguide dispersion.

Attenuation is therefore also at minimum and makes nm a highly attractive operating wavelength. Modal Dispersion x As only a certain number of modes can propagate down the fiber, each of these modes carries the modulation signal and each one is incident on the boundary at a different.

IN angle, they will each have their own individual propagation times. The net effect is spreading of pulse, this form o dispersion is called modal dispersion. It is moderately present in graded index fibers and almost eliminated in single mode step index fibers.

Higher Order Dispersion x Higher order dispersive effective effects are governed by dispersion slope S. Also, where,. The pulse broadening is studied with the help of wave equation. TS Chirped Gaussian Pulses x A pulse is said to b e chirped if its carrier frequency changes with time.

IN where, S is dispersion slope. This results in pulse broadening is know as polarization mode dispersion PMD. The effects of PMD must be compensated.

The higher order modes travelling in outer regions of the core, will travel faster than the lower order modes travelling in high refractive index region. If the index profile is carefully controlled, then the transit times of the individual modes will be identical, so eliminating modal dispersion.

S pulse width due to intermodal delay distortion. S pulse width resulting from pulse broadening within each mode. D From this the expression for intermodal pulse broadening is given as: Solving the expression gives: IN coupling.

The energy from one mode is coupled to other mods because of: TS - Refractive index variations. D The improvement in pulse spreading by mode coupling is given as: TU where, C is constant independent of all dimensional quantities and refractive indices.

For a CI graded index fiber, the effect of distance on pulse broading for various coupling losses are shown in Fig. IN TS x Significant mode coupling occurs of connectors, splices and with other passive components of an optical link. TU - Low attenuation. TS x Basic design — optimization includes the following: CI - Bending loss.

Refractive Index Profile x Dispersion of single mode silica fiber is lowest at nm while its attenuation is minimum at nm. For archiving maximum transmission distance the dispersion null should be at the wavelength of minimum attenuation. Therefore a variety of core-cladding refractive idex configuration fivers. Such as nm — optimized fibers, dispersion shifted fibers, dispersion — flattened fibers and large effective core area fibers.

The two configurations of nm — optimized single mode fibers are: IN b Dressed cladding fibers. Typical diameter is 9. Typical diameter is 8. Fig 2.

Two configurations of dispersion shifted fibers are: Dispersion Flattened x Dispersion flattened fibers are more complex to design. It offers much broader span of wavelengths to suit desirable characteristics. Two configurations are: Different formulae are used to. IN calculate dispersions for variety of fiber at different wavelength. Cut-off Frequency of an Optical Fiber x The cut-off frequency of an optical fiber is determined not only by the fiber itself modal dispersion in case of multimode fibers and waveguide dispersion in case of single mode fibers but also by the amount of material dispersion caused by the spectral width of transmitter.

IN Bending Loss Limitations x The macrobending and microbending losses are significant in single mode fibers at nm region, the lower cut-off wavelengths affects more. D EN TU x The bending losses are function of mode-filed diameter, smaller the mode-field diameter, the smaller the bending loss.

If the bend radius is TS less, the losses are more and when the radius is more, the bending losses are less. Briefly explain material dispersion with suitable sketch. Give expression of pulse broadening in graded index fiber.

State the significance of mode coupling in optic fiber communication. Explain in detail the design optimization of single mode fibers. Elaborate dispersion mechanism in optical fibers. The optical signal is then launched into the fiber. Optical source is the major component in an optical transmitter. Characteristics of Light Source of Communication TS x To be useful in an optical link, a light source needs the following characteristics: EN iii For fiber links, the wavelength of the output should coincide with one of transmission windows for the fiber type used.

D v To reduce material dispersion in an optical fiber link, the output spectrum should be narrow. TU vi The power requirement for its operation must be low.

TS ix Better linearity of prevent harmonics and intermodulation distortion.UNIT 2: LEDs are best suitable optical source. Fiber couplers The first layer that is deposited forms the cladding and by changing the constituents of the incoming gas the refractive index can be modified to produce the core. What is mean by mode of a fiber? In this case the detector works very slow, and output is approximately logarithmic to the input light level.

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