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Photonics Systems Introduction Sergiusz Patela, Dr Sc Room I/48, Th. 13:00-16:20, Fri. 9:20-10:50 [email protected] eportal.pwr.wroc.pl Copying and processing permitted for noncommercial purposes, on condition that proper reference to the source is given. © Sergiusz Patela, 2001-6 www.patela.net Fiber-optic-transmission milestones 1854 - Demonstration of optical waveguide principle in water jets (J. Tyndal) 1960 - Laser (ruby, T. Maiman) 1972 - 4 dB/km multimode fiber 1982 - Single mode fiber reported 1991 - SONET telecommunications standards created 1995 - DWDM deployment began 1998 - > 1 Tb/s in one fiber 2000 - L-band system introduced (1570-1610nm) 40 Gb/s transmission in one channel. © Sergiusz Patela, 2001-6 Photonics Systems - Introduction 2/23 Fiber optic link Light source (transmitter) „noise” Light detector (receiver) Electrical output signal Electrical input signal © Sergiusz Patela, 2001-6 Lightguide with splices connectors and couplers Photonics Systems - Introduction 3/23 Light wave Light wave: electromagnetic wave (signal carrier) characterized by intensity, phase (coherence level), wavelength (frequency), polarization and propagation direction. Physical phenomena and effects that explain how waveguide works: • Light wave frequency Light = electromagnetic wave of frequency 3x1014Hz, (almost million GHz). • Total internal reflection effect and extremely low glass attenuation Fibers can guide light at long distances without regeneration • Wave nature of light and fiber modes Many waveguide parameters and construction details can be explained only if one takes into account that light is a wave guided by a structure of very low cross-section. © Sergiusz Patela, 2001-6 Photonics Systems - Introduction 4/23 Construction of optical fiber Core © Sergiusz Patela, 2001-6 Cladding Photonics Systems - Introduction Cover 5/23 Total internal reflection n2 n1 Total internal reflection at the border core-cladding Fiber diameter: 10 to 50 µm at 1 m distance creates 10 000 reflections. For the reflection coefficient of 99% after 1 m the signal will be attenuated by 0.9910 000 = 10-44 © Sergiusz Patela, 2001-6 Photonics Systems - Introduction 6/23 Waveguides’ classification 1. Mode structure (SM, MM) 2. Material (silica, plastic, …) 3. Geometry: planar and fiber waveguides 4. Refractive index distribution (step, gradient index) © Sergiusz Patela, 2001-6 Photonics Systems - Introduction 7/23 Optical fibers Multimode step index fiber Cladding Core Multimode graded index fiber Cladding Core Single mode (step index) Cladding Core © Sergiusz Patela, 2001-6 Photonics Systems - Introduction 8/23 Lightwave spectrum Wavelength (µm) Wavelength (nm) 1625 - 1650 106 L : 1570-1620 C : 1525-1560 S : 1450-1510 4×104 Far 6×103 Middle 1: 1550 2: 1300 3: 850 1.5×103 770 622 Fiber optics telecomm bands 587 Fiber optics windows 577 492 455 390 Note: 1625 - 1650 band is used to continuously monitor the integrity of the fiber without interfering with the signals at 1550 or 1310 © Sergiusz Patela, 2001-6 Near IR Red Orange Yellow Green 200 Microwaves Infrared Visible Ultraviolet Blue X-rays Violet UV 300 250 Radio waves Gamma rays Near Far 10 Photonics Systems - Introduction Cosmic rays 1014 1013 1012 1011 1010 109 108 107 106 105 104 103 102 10 1 10-1 10-2 10-3 10-4 10-5 10-6 10-7 10-8 10-9 10-10 10-11 10-12 10-13 10-14 9/23 Attenuation of optical fibers III transmission window [dB/km] 50 I window 10 Attenuation II window 30 5 3 1 0.5 0.3 0.1 0.6 0.8 1.0 1.2 1.4 1.6 1.8 [µm] wavelength Spectral attenuation of silica glass fiber © Sergiusz Patela, 2001-6 Photonics Systems - Introduction 10/23 10 advantages of optical fibers 1. High information capacity of a single fiber 2. Low loss = repeaterless transmission at long distances 3. Total immunity for EMI (electro magnetic interference) 4. Low weight 5. Small dimensions (diameter) 6. High work safety (low risk of fire, explosion, ignition) 7. Transmission safety (data taping almost impossible). 8. Relatively low cost (getting lower). 9. High reliability 10 Simplicity of installation. © Sergiusz Patela, 2001-6 Photonics Systems - Introduction 11/23 Optical fiber networks technology enablers and stimuli 1. Gigabit Ethernet, 2. vertical-cavity surface-emitting lasers (VCSELs), 3. 100Base-SX, 4. small-form-factor (SFF) connectors, 5. quick-cure adhesives, 6. mechanical connectors, 7. centralized cabling, 8. reduced cost of ferrules, 9. reduced cable costs, 10. preterminated cables Eric R. Pearson, Lightwave Magazine, Ten Reasons Fiber is Becoming More Cost-Effective in the Horizontal © Sergiusz Patela, 2001-6 Photonics Systems - Introduction 12/23 Installations cost, comparison Comparison of 50 m fiber waveguide and copper links (Cat. 5 UTP). C a te g o ry 5 U T P F ib e r Socket $ 5 .3 5 $ 5 .7 0 P a tc h p a n e l $ 5 .0 6 $ 5 .1 9 C o n n e c to rs N ot needed $ 1 8 .2 4 C ab el (5 0 m ) $ 4 1 .5 8 $ 4 3 .5 6 In s ta lla tio n c o s t $ 7 1 .2 5 $ 6 6 .7 5 $ 1 2 3 .2 4 $ 1 3 9 .4 4 T o ta l © Sergiusz Patela, 2001-6 Photonics Systems - Introduction 13/23 Light sources - definitions Light Emitting Diode (LED) A semiconductor junction device that emits incoherent optical radiation when biased in the forward direction Laser Acronym for Light Amplification by Stimulated Emission of Radiation. A device that produces a coherent beam of optical radiation by stimulating electronic, ionic, or molecular transitions to higher energy levels so that when they return to lower energy levels they emit energy Laser Diode (LD, Synonyms - injection laser diode, semiconductor laser ) A laser that uses a forward biased semiconductor junction as the active medium © Sergiusz Patela, 2001-6 Photonics Systems - Introduction 14/23 Light sources - types Light Emitting Diode (LED) Surface Light Emitting Diode (SLED) Edge Light Emitting Diode (ELED) Resonance Cavity Enhanced (RCE) LED Laser FP (Fabry-Perot) DFB (Distributed Feed-Back) DBR (Distributed Bragg Reflectors) VCSEL (Vertical Cavity Surface Emitting Lasers) © Sergiusz Patela, 2001-6 Photonics Systems - Introduction 15/23 Light sources - LED parameters Both LED’s and LD’s emitting wavelengths are set by material selection: AlGaAs: 780-860 nm, InGaAsP: 1300, 1550 nm. LED parameters type material wave- fiber coupled power length - fiber type spectral width bandwidth 3 dB (FWHM) nm µW nm MHz 860 95 - 62.5/125 60 - 50/125 2.5 - 9/125 50 50 ELED InGaAsP 1300 20 - 9/125 60 350 ELED InGaAsP 1550 8 - 9/125 SLED AlGaAs © Sergiusz Patela, 2001-6 Photonics Systems - Introduction 16/23 Light sources - LD parameters Fiber optics LD are available in pigtailed versions and with standard fiber optic receptacles LD type wavelength laser power fiber coupled power nm mW mW FP 1310 5 1 9/125 FP 1310 5 2 62.5/125 FP 1550 5 1 9/125 DFB 1550 5 1 9/125 © Sergiusz Patela, 2001-6 Photonics Systems - Introduction fiber type 17/23 Detectors - definition Definition A device that is responsive to the presence or absence of a stimulus Stimulus Detector Output In an optical communications receiver is a device that converts the received optical signal to another form. Note: Currently, this is conversion is from optical to electrical power, however optical-to-optical techniques are under development © Sergiusz Patela, 2001-6 Photonics Systems - Introduction 18/23 Detector - construction For fiber optic applications detectors are available in standardized packages, • pigtailed or • combined with standard receptacles ST SC FC © Sergiusz Patela, 2001-6 Photonics Systems - Introduction 19/23 Detectors - parameters Detector type wavelength (high respons. range) responsivity dark current material nm A/W nA InGaAs 1300 (1000-1700) 0.75 0.1 Si 850 (400-1100) 0.45 1 Ge 1300 (800-1500) 0.65 350 detectors are available as pin or APD structures © Sergiusz Patela, 2001-6 Photonics Systems - Introduction 20/23 Splices and connectors Standard and SFF connectors (~ 1dB) Fiber splicing (~0.1dB) electric arc Fusion splicing fiber fiber index matching gel Mechanical splice fiber fiber alignment sleeve © Sergiusz Patela, 2001-6 Photonics Systems - Introduction 21/23 Literature G. P. Agrawal, Fiber-optic communications systems, John Willey & Sons 1992 © Sergiusz Patela, 2001-6 Photonics Systems - Introduction 22/23 Summary Creating fiber optic networks is an adventure not comparable to any other technical task today . Designer have to select everything hardware type, „standards“, topology and protocols. On the other hand, properly designed and build networks can be in use even after 20 years - they can be used and evaluated by our children. © Sergiusz Patela, 2001-6 Photonics Systems - Introduction 23/23