Optical fibers communicatiobyom

Prof.Byomakesh MahapatraAssistant ProfessorUniversity of BombayProf. Byomakesh Mahapatra
Prof. Byomakesh Mahapatra

Holger Mller Hansen in his workshop.Courtesy Holger Mller HansenHeinrich Lamm as a Germanmedical student in 1929, about the timehe made the first bundle of fibers totransmit an image. Courtesy MichaelLammPeople behind OFC DevelopmentProf. Byomakesh Mahapatra

Brian OBrien, who suggestedthat cladding would guide light along fiber.Charles K. Kao making optical measurements at StandardTelecommunications LaboratoriesProf. Byomakesh Mahapatra

General and Optical Communication systemsProf. Byomakesh Mahapatra

Need for Fiber Optical CommunicationIncrease of the bandwidth and decreases of the cost per transmitted bit for optical communication systems during the 1990s.Prof. Byomakesh Mahapatra

Different frequency range:-Prof. Byomakesh Mahapatra

Different frequency range:-
EHz:-Exahertz
PHz :- Petahertz

The Electromagnetic SpectrumShortest wavelengths(Most energetic photons)Prof. Byomakesh Mahapatra

Properties of light:-There are three theories are used to explain light:
Ray theory
Wave theory
Quantum theoryProf. Byomakesh Mahapatra

Properties of light/ important terms:- RefractionReflectionRefractive indexTotal internal reflection Geometrical opticsAbsorptionDispersion scatteringOptical wave guide Wave front Isotropic mediumPlane wavepolarization
Ray theoryRelated to optical fiber propagation lossWave propagationProf. Byomakesh Mahapatra

Ray theory:-It state that light is a stream minute particles and travel in a straight line .
A beam of light is a group of rays called as ray congruence.
A ray is the is the thinnest pencil of light with a well defined boundaries with out diffraction. apertureLight patchProf. Byomakesh Mahapatra

Wave theory of light :- Light is considered as an electromagnetic radiation. It consists of two components i.e., the electric component and the magnetic component which oscillate perpendicular to each other as well as to the direction of path of radiation.
It propagates in a particular direction according to this E&H components known as polarization.Prof. Byomakesh Mahapatra

Quantum theory:-Max Planck proposed Quantum theory by considering light to possess particle nature.1) Energy is emitted due to vibrations of charged particles in the black body.
2) The radiation of energy is emitted or absorbed discontinuously in the form of small discrete energy packets called quanta.
3) Each quantum is associated with definite amount of energy which is given by the equation E=h.Whereh = planck's constant = 6.625 x 10-34 J. sec = 6.625 x10-27 erg. sec
= frequency of radiationProf. Byomakesh Mahapatra

Quantum theory:-4) The total energy of radiation is quantized i.e., the total energy is an integral multiple of h. It can only have the values of 1 h or 2 h or 3 h. It cannot be the fractional multiple of h.5) Energy is emitted and absorbed in the form of quanta but propagated in the form of waves.Photo electric effectProf. Byomakesh Mahapatra

There was a problem with wave theoryIn the early 20th century, several effects were observed which could not be understood using the wave theory of light. Two of the more influential observations were: 1) The Photo-Electric Effect
2) The Compton Effect Prof. Byomakesh Mahapatra

Photoelectric Effect (I)No electrons were emitted until the frequency of the light exceeded a critical frequency, at which point electrons were emitted from the surface! (Recall: small l large n)electrons emitted ?Increase energy by increasing amplitudeClassical Methodelectrons emitted ?Prof. Byomakesh Mahapatra

Reflection:-Incident ray Reflected raysMirrorProf. Byomakesh Mahapatra

sameProf. Byomakesh Mahapatra

Refraction:-Refraction is when waves ____ __ or slow down due to travelling in a different _________. A medium is something that waves will travel through. When a pen is placed in water it looks bent from the normal position.In this case the light rays are slowed down by the water and are _____, causing the pen to look odd. The two mediums in this example are ______ and _______.Words speed up, medium, bent, water, air,

Refraction:-Prof. Byomakesh Mahapatra

Ex:-Light banding due to refractionProf. Byomakesh Mahapatra

Snells Laws Snell's law gives the relationship between angles of incidence and refraction for a wave impinging on an interface between two media with different indices of refraction. The law follows from the boundary condition that a wave be continuous across a boundary, which requires that the phase of the wave be constant on any given plane. Prof. Byomakesh Mahapatra

Refractive index :-The ratio of speed of light in vacuum to that in matter is the index of refraction (n) n = c/vwhere c = speed of light in vacuum and v = speed of light in the mediumRefractive index of air: 1.0003 water: 1.33 glass: 1.4 1.7 silicon : 3.96 GaP : 3.5 Gas :3.9 diamond :2.41 LiNbO3 :2.21

Total Internal Reflection:-When there is a change the incident angle of the light on the block, the reflected light varies. At a certain angle, called the critical angle all the light is reflected, and none is refracted. When this happens we have total internal reflection.TIR in optical fiberProf. Byomakesh Mahapatra

Geometrical optics Geometrical optics, or ray optics, describes light propagation in terms of "rays". It include all the ray properties of the light like reflection ,refraction and corresponding optics lenses polarizer, mirror etcThe "ray" in geometric optics is an abstraction, or "instrument", which can be used to approximately model how light will propagate.Prof. Byomakesh Mahapatra

Geometrical optics Prof. Byomakesh Mahapatra

Absorption:-When light enter some of its energy is dissipated as heat energy and loose some of its intensity.
When the absorption of energy occur selectively for a certain wave length the wave length only reflected which are not absorbed.

Dispersion:- When the light ray passes through a prism it is separate in to a ray of constituent color this phenomenon is known as dispersion.
It can also be define as the broadening of the light plus in an optical wave propagation in an optical fiber there are different kind of dispersion is phenomenon is found
Intermodal or chromatic dispersion
Polarization mode dispersion
Material dispersionWave guide dispersionMaterial dispersion:-It occur due to the varying material properties which provide different velocity to the light in an optical fiber. Prof. Byomakesh Mahapatra

Fiber Dispersion
Polarization Mode DispersionPolarization mode dispersion (PMD) occurs when different planes of light inside a fiber travel at slightly different speeds, making it impossible to transmit data reliably at high speeds(multimode fiber)Waveguide dispersion- Waveguide dispersion occurs because the mode propagation constant is a function of the size of the fiber's core relative to the wavelength of operation. Waveguide dispersion also occurs because light propagates differently in the core than in the cladding. Total DispersionTotal dispersion is due to all types of dispersion Prof. Byomakesh Mahapatra

Modal dispersionProf. Byomakesh Mahapatra

Scattering:-Scattering can be broadly defined as the redirection of radiation out of the original direction of propagation, usually due to interactions with molecules and particles Reflection, refraction, diffraction etc. are actually all just forms of scattering Matter is composed of discrete electrical charges (atoms and molecules dipoles) Light is an oscillating EM field excites charges, which radiate EM waves These radiated EM waves are scattered waves, excited by a source external to the scattered The superposition of incident and scattered EM waves is what is observedrainbowProf. Byomakesh Mahapatra

Scattering geometryForward scatteringBackward scattering(backscattering)Prof. Byomakesh Mahapatra

What is Rayleigh scattering?(or why is the sky blue)The shorter the wavelength, the more ligh

Optical fibers communicatiobyom

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