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Optical Concepts Global Professional Services ECI Training services Milestones in Optics Laser development Fiber optics development First fiber production with attenuation of dB/km Production of fiber with attenuation of dB/km Mass production of fiber with attenuation of . dB/km for nm First field trial using fiber optics in Chicago Production of Single Mode fiber with attenuation of .dB/km for nm Mass production of Single Mode Fiber Development of optical amplifiers . Optical Concepts and data over substantial distances between customer and network sites . Reliability Microwave Fiber Optics A communications network is one that conveys / transports information audio. Optical Concepts .Why Fiber Optics Capacity. video. Twisted Pair Coax Networks Distance. Mbps Mbps . Mbps Kbps Network Providers combine the signals from different users and send them over a single transmission Optical Concepts . .Basic Network Information Rates Examples of information rates for some typical voice. Mbps . video and data services Video on demand/interactive TV Video games Remote education Electronic shopping Data transfer Videoconferencing Voice . Mbps Mbps . Optical Concepts .The Optical Fiber Very thin strands of pure silica glass through which laser light travels in optical networks . Optical Concepts .The Optical Fiber . . Optical Concepts . The wavelength nature Of light . Optical Concepts .The Light Theory The Quantum nature Vs. The Quantum Nature of Light When a photon insides on an atom. Optical Concepts . exciting it to a higher energy level Photon E E E Energy levels E. E. it transfers its energy to an electron within this atom.E . with exactly the same energy This energy equals h. to be absorbed Conversely. photon frequency . an electron in an excited state can drop to a lower energy state by emitting a photon.Photon Absorption and Emission Energy Spontaneous emission E Excited State Level EE h E Absorption E Ground Level The energy of the photon must be exactly equal to that required to excite the electron to a higher energy level. Optical Concepts . h Plank constant. In spontaneous emission the high energy state lifetime is between nanoseconds to milliseconds In stimulated emission the emitted photon is identical in wavelength. phase and direction to the incident photon Optical Concepts .Photons Behavior Spontaneous emission Stimulated emission Photon Photon E E E E E E . Optical Amplification Energy Population Inversion E gt E Stimulated emission amplification E Amplification E E The amount of electrons in stimulated level must be higher than those in ground level . Optical Concepts . Optical Concepts .The Wavelength Nature Wavelength is the distance between identical points in the adjacent cycles of a waveform signal propagated in space or along a wire Wavelength is specified in nanometers units of meter . Electromagnetic Spectrum . Optical Concepts . the shorter its wavelength c / f c .Wavelength Vs Frequency The higher the frequency of the signal. m/s The standard unit of frequency is Hertz If a wave completes one cycle per second.. then f Hz THz cycles per second . Optical Concepts . sometimes called loss A natural consequence of signal transmission over long distances The extent of attenuation is usually expressed in dB dB a common unit of measurement for the relative difference between two power levels dB logPout / Pin log Pout .Optical Parameters Attenuation refers to any reduction in the strength of a signal Attenuation occurs with any type of signal. log Pin dBm a measure of absolute power dBm log Pmw . Optical Concepts . Characteristics of Different Wavelengths in Pure Silica Fiber Beginning of the s Beginning of the s Today . Optical Concepts . Optical Concepts .Optical Parameters Dispersion refers to the expansion or widening of the signal by the time it reaches the receiving end Dispersion is due to the fact that different wavelengths propagate in different velocities Dispersion does not alter the wavelength frequency but it directly affects the bit rate Measured as the amount of delay in picoseconds seconds per km of fiber per nm change in the wavelength . Optical Concepts Distance along fiber .Dispersion Pulse Shape and Amplitudes Input pulses Output pattern Intersymbol interference . Dispersion Types Modal dispersion Material dispersion Waveguide dispersion Polarization dispersion Chromatic Dispersion Before After t t . Optical Concepts . Modal Dispersion Depends on the diameter of the core and the critical angle Significant in Multimode fibers and not in Singlemode fibers l l Input Surface Refraction Jacket t l l t t Core Pulse entering the fiber Cladding t Pulse exiting the fiber . Optical Concepts . Optical Concepts .Chromatic Dispersion Material dispersion Effect of the fiber material on the propagation velocity of the wave Waveguide dispersion relates to the ratio between core radius and wavelength Input Surface Refraction Jacket Core Cladding . Chromatic Dispersion Material dispersion and Waveguide dispersion may act in opposite ways Fiber is engineered in order to give a resultant chromatic dispersion near to zero . Optical Concepts . Gps . Optical Concepts .Dispersion Penalty Dispersion Penalty The dispersion of the signal causes attenuation dB per km for . Optical Concepts . older fibers etc. external stress. . material properties. the noncircular core of the fiber may contribute to cause PD Caused by several sources core shape.Polarization Dispersion This kind of dispersion is significant in higher bitrates. from Gbps Due to manufacturing imperfections. G.Wavelength Vs Dispersion G. lt . G. lt . ZeroDispersion Optical Concepts . / G. Fiber ZeroDispersion NonZeroDispersion ITUT Standard G. . l nm Dispersion ps/nm km Attenuation dB/ km lt . G. G. Optical Concepts .Limits How Far dB/km Dispersion .km The How far and How fast are not only fiberdependent .Limits How Fast ps/nm.Optical Parameters Attenuation . Light Amplification by Stimulated Emission of Radiation Typical Transmittance Profile of a Laser Diode Transmittance f f f f The frequencys lasers output is uniform . Optical Concepts .LASER .