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1. Introduction to Optical Communication Systems Optical Communication Systems and Networks Lecture 1: Introduction to Optical Communication Systems 2/ 52 Historical perspective • 1626: Snell dictates the laws of reflection and refraction of light • 1668: Newton studies light as a wave phenomenon – Light waves can be considered as acoustic waves • 1790: C. Chappe “invents” the optical telegraph – It consisted in a system of towers with signaling arms, where each tower acted as a repeater allowing the transmission coded messages over hundred km. – The first Optical telegraph line was put in service between Paris and Lille covering a distance of 200 km. • 1810: Fresnel sets the mathematical basis of wave propagation • 1870: Tyndall demonstrates how a light beam is guided through a falling stream of water • 1830: The optical telegraph is replaced by the electric telegraph, (b/s) until 1866, when the telephony was born • 1873: Maxwell demonstrates that light can be considered as electromagnetic waves http://en.wikipedia.org/wiki/Claude_Chappe Optical Communication Systems and Networks Lecture 1: Introduction to Optical Communication Systems 3/ 52 Historical perspective • 1800: In Spain, Betancourt builds the first span between Madrid and Aranjuez • 1844: It is published the law for the deployment of the optical telegraphy in Spain – Arms supporting 36 positions, 10º separation Alphabet containing 26 letters and 10 numbers – Spans: Madrid - Irún, 52 towers. Madrid - Cataluña through Valencia, 30 towers. Madrid - Cádiz, 59 towers. • 1855: It is published the law for the deployment of the electrical telegraphy network in Spain • 1880: Graham Bell invents the “photofone” for voice communications TRANSMITTER RECEIVER The transmitter consists of a The receiver is also a mirror made to be vibrated by parabolic reflector in which a the person’s voice, and then selenium cell is placed in its modulating the incident light focus to collect the variations beam towards the receiver. of the light intensity. Pictures: http://en.wikipedia.org/wiki/Photo phone Optical Communication Systems and Networks Lecture 1: Introduction to Optical Communication Systems 4/ 52 Historical perspective • 1910: D. Hondros and P. Debye use glass rods as waveguides (circular cylindrical dielectric structures were patented by French in 1934 for voice transmission) • 1927: Baird and Hansell patent a system for images transmission through silica fibers • 1936: EEUU begins to use optical fibers in communications • 1960: First LASER (light amplification by stimulated emission of radiation) is presented • 1970: Corning Glass Works achieves optical fibers with 20dB/km attenuation at 633 nm • 1978: First singlemode optical fibers are built, achieving an attenuation of 0.2 dB/km at 1550 nm in 1979 Optical Communication Systems and Networks Lecture 1: Introduction to Optical Communication Systems 5/ 52 Historical perspective The Nobel Prize in Physics 2009 was awarded jointly to three American pioneers whose researches have supposed pillars of the modern Information Society: Charles Kuen Kao, Willard Sterling Boyle y George Elwood Smith. “… for their contribution to the materials research and development that resulted in practial low loss optical fibers, one of the cornerstones of optical communication technology…” Optical Communication Systems and Networks Lecture 1: Introduction to Optical Communication Systems 6/ 52 Wavelength (m) Frequency (Hz) Bands Applications − 1024 10-15 − 10-15 rays Food irradiation Cancer therapy E.M. Spectral region used for − 1021 10-12 − 10-12 Optical Communications X rays Medical diagnosis 18 -9 − 10-9 10 (nm) − 10 (nmUltraviolet) Sterelization Visible 15 -6 − 10-6 10 (m)− 10 (m) VISIBLE Infrared Nigth vision ULTRAVIOLET INFRARED 12 (nm) -3 − 10 (THz) Millimetrics 2 -3 10 3 104 10 (mm) − 10 (mm) EHF (30 – 300 GHz) Radar, space exploration 10 =1m Windows for optical SHF (3 – 30 GHz) Radar, Satellite communication communications 9 f (GHz) − 10 (GHz) UHF (300 – 3000 MHz) Tadar, TV, navegation 4 1 (m) − 1 (m) 106 105 10 VHF (30 – 300 MHz) TV, FM, police, mobile radio HF (3 – 30 MHz) Facsimil, short wave radio 6 E (eV) − 10 (MHz) MF (300 – 3000 kHz) AM, maritime radio, 103 (km) − 103 (km) 10 1 0.1 LF (30 – 300 Khz) Navegation, radio signals GaAs Si GaP Gap VLF (3 – 30 kHz) Navegation, sonar InP − 103 (kHz) energy 106 (Mm) − 106 (Mm) ULF (300 – 3000 Hz) Audio interval for telephony SLF (30 – 300 Hz) Submarine communication ELF ( 3 – 30 Hz) Metals detection − 1 (Hz) Optical Communication Systems and Networks Lecture 1: Introduction to Optical Communication Systems 7/ 52 Frequency – Wavelength Duality . Frequency scale or magnitude has been traditionally used in Telecommunication Engineering for desinging spectrum bands comprised between DC and microwaves region . In Optical Communications, frequencies around 1014 Hz are used, resulting a little impractical four such magnitudes . It is very common to use the wavelength scale, being the nanometer scale (1nm = 10-9 m) and micron scale (1µm = 10-6 m) the most used . The specturm band usually employed in Optical Communications is comprised between 800 and 1600 nm f Sinusoidal and monochromatic E.M. 1 wave propagated along z axis f1 2 f2 Approx. 1 2 Optical Communication Systems and Networks Lecture 1: Introduction to Optical Communication Systems 8/ 52 Optical Communication Systems Optical Communications Physic Optics + Quantum Electronics + Communication Theory (1970, Procedings IEEE) Physics of Materials + Quantum Physics + Information Theory + Nonlinear Optics + Interaction of Radiation with Matter CHANNEL Optical signal Receiver Transmitter Guided Communication optical fiber Non-guided communication free space Optical Communication Systems and Networks Lecture 1: Introduction to Optical Communication Systems 9/ 52 Introduction Carrier signal Unmodulated Laser (optical emision in continuous wave, CW) spectrum Delta (ideally) Unmodulated LED spectrum t f f0 Modulating signal (Baseband Modulation electrical signal) Baseband process (directly spectrum or externally) t f Modulated signal (optical domain/format) t f f0 TIME DOMAIN SPECTRAL DOMAIN Modulation is the process of varying one or more properties The modulating signal contains information of a high-frequency periodic waveform (carrier signal) to be transmitted Optical Communication Systems and Networks Lecture 1: Introduction to Optical Communication Systems 10/ 52 Modulation formats Optical carrier: E(t) = A0 cos(0t − 0) ê “1” “0” “1” “0” “1” “0” Electric signal (Bit sequence) • Amplitude modulation A0: ASK, Amplitude-shift keying ASK • Phase modulation 0: PSK, Phase-shift keying • Frequency modulation 0: FSK, Frequency-shift PSK keying • Polarization modulation ê: PoSK, information FSK coded by polarization state (not allowed in optical systems based on fiber) . Most commercial systems are based on ASK (These systems are also known as on–off keying, OOK) IM/DD (intensity modulation and Direct Detection) . First Differential PSK (DPSK) are being deployed recently Optical Communication Systems and Networks Lecture 1: Introduction to Optical Communication Systems 11/ 52 Free-Space Optics (FSO) Technology . Nowadays, FSO systems are used for covering connection needs in last-mile access networks, point-to-point interconnections, as a redundant support in temporal or permanent links, etc. Provides robust links with the following advantages: − RF / EM free interferences − High rate systems − Operation license not required − Quick deployment − Network survivability Optical Communication Systems and Networks Lecture 1: Introduction to Optical Communication Systems 12/ 52 RedIris: An example of Optical Networks in Spain . Rediris is the Spanish National Research and Education ENTITIES IN THE COMMUNITY OF VALENCIA Network wich serves over 370 institutions, including all Spanish universities and the main public research entities. GVA Generalitat Valenciana, DICV.CSIC Delegación del CSIC en la Comunidad de . It is built over a dark fiber-based infraestructure with over Valencia, FIB Fundacion Valenciana de 12500 km of optical fiber for nation wide-coverage. Investigaciones, Institutos.CSIC, IBV.CSIC Instituto de Biomedicina de Valencia,, IN.UMH.CSIC Instituto de Neurociencias, INGENIO.CSIC Instituto de Gestión de la Innovación y del Conocimiento, IMPIVA Instituto de la Mediana y Pequeña Industria Valenciana, IVE Institut Valencia d'Estadistica, IVIE Instituto Valenciano de Investigaciones Economicas, UA Universitat d'Alacant, UCH-CEU Universidad Cardenal Herrera, UJI Universitat Jaume I, UMH Universidad Miguel Hernández de Elche, UPV Universitat Politécnica de Valéncia, UV Universitat de Valéncia. Source: www.rediris.es Optical Communication Systems and Networks Lecture 1: Introduction to Optical Communication Systems 13/ 52 FTTH: An example of the evolution of Optical Networks in Spain Optical Communication Systems and Networks Lecture 1: Introduction to Optical Communication Systems 14/ 52 Operation Spectral Windows in Guided Optical Communications 1st window 2nd window 3rd window 850 nm 1310 nm 1550 nm Optical amplifiers Attenuation optical fiber photodetectors Fiber InGaAs Optical Responsivity attenuation sources EDFA (W/A in sources) Si (dB/km) (A/W in detectors) AR Tema 1: Introducción Tema GaAlAs Ge InGaAsP Based on figure published in “Sistemas y Redes Ópticas de InGaAsP Comunicaciones” J. A. Martín Pereda”Ed. Pearson 2004 700 900 1100 1300 1500 1700 Wavelength (nm) Optical Communication Systems and Networks Lecture 1: Introduction to
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