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47 48 49 50 OVERVIEW 9.1 BASICS OF OPTICAL Overview 9.1.1 Optical Business Drivers 9.1.2 Fiber-Optic Systems 9.1.3 Fiber-Optic Transmission System 9.1.4 Light 11 9.1.5 Optical Transmission .14 9.1.6 Reflection and Refraction 16 Summary 18 9.2 OPTICAL FIBERS .19 Overview 19 9.2.1 Fiber Types 20 9.2.2 Multimode 21 9.2.3 Single Mode 22 9.2.4 Fiber Geometry .23 9.2.5 Loss Factors .24 9.2.6 Attenuation .27 9.2.7 Dispersion 29 9.2.8 Fiber Capacity 31 9.2.9 Optical Filter Technology 33 9.2.10 EDFA 34 Summary 36 9.3 OPTICAL TRANSMISSION AND MULTIPLEXING 37 Overview 37 9.3.1 SONET Technology 38 9.3.2 SONET/SDH 40 9.3.3 DWDM Systems 42 9.3.4 E/O/E Conversion .43 9.3.5 Data Transmission 44 9.3.6 DWDM Advantages 45 Summary 47 9.4 OPTICAL TECHNOLOGY SOLUTIONS 48 Overview 48 9.4.1 Metro DWDM 49 9.4.2 First- Generation Optical Protection 50 9.4.3 Second- Generation Optical Protection .51 9.4.4 Next- Generation Optical Protection 52 9.4.5 All Optical Infrastructure 53 9.4.6 IP Transport Alternatives 54 9.4.7 Optical IP Backbones 55 Summary 56 SUMMARY .57 51 52 53 9-2 Cisco Certified Network Associate Basics (CCNAB) v2.0 Copyright 2002, Cisco Systems, Inc 54 55 56 57 58 59 60 61 62 63 Overview Optical networks are an extremely efficient means of conveying data such as text, video, and voice This module teaches you how optical networks provide speed, data transportation, capacity, and scalability You will learn about optical network function, the enhanced scalability provided by dense wavelength-division multiplexing (DWDM), and the solutions that optical networks provide Upon completing this module, you will be able to: ■ Describe how an optical system transports information 64 ■ Describe fiber optic types and the light loss factors in fiber 65 ■ Explain how DWDM enhances optical networks 66 ■ Differentiate between available optical solutions 67 68 69 70 Outline This module contains these lessons: ■ Overview 71 ■ Basics of Optical 72 ■ Optical Fibers 73 ■ Optical Transmission and Multiplexing 74 ■ Optical Technology Solutions 75 ■ Summary 76 77 Copyright 2002, Cisco Systems, Inc Module 9: Optical Networking Fundamentals 9-3 78 9.1 Basics of Optical 79 Overview 80 81 82 83 This lesson describes the key drivers of the optical networks and the features of fiber-optic systems This lesson also discusses the optical transmission components and their features Objectives 84 85 86 87 Upon completing this lesson, you will be able to: ■ Identify the key drivers of optical networks 88 ■ Describe the features of fiber-optic systems 89 90 ■ Describe the communication components in a optical communication system 91 ■ Identify the wavelength of the light used in optical transmission 92 93 ■ Identify the features of the light emitting devices used in optical transmission 94 ■ Describe one of the important design characteristics of fiber Outline 95 96 97 98 This lesson includes these sections: ■ Overview 99 ■ Optical Business Drivers 100 ■ Fiber-Optic Systems 101 ■ Fiber-Optic Transmission system 102 ■ Light 103 ■ Optical Transmission 104 ■ Reflection and Refraction 105 ■ Summary 106 9-4 Cisco Certified Network Associate Basics (CCNAB) v2.0 Copyright 2002, Cisco Systems, Inc 106 107 9.1.1 Optical Business Drivers Figure 1: Optical Business Drivers Key Drivers Descriptions Capacity/Scalability Efficiently meet capacity and scalability requirements in both metropolitan and long-haul network infrastructures Scale with the rapid growth of the Internet while providing unrivaled reliability Reliability Accelerated Profits Reduce costs and accelerate profitable new service revenue simultaneously Broad Coverage Reach long distances End-to-End Flexibility Provide the ability to build a flexible, end-to-end optical solution that meets the requirements of carrier-class reliability Be adaptable through an open system architecture Adaptability Space Efficiency 108 109 110 111 112 113 114 115 116 117 118 119 120 Networks must also be able to transmit data and video quickly, efficiently, and costeffectively In comparison to any other resource, fiber optics is the most efficient medium for transmitting information It offers the highest bandwidth capacity for network traffic, and its growth is predicted to be enormous The burgeoning Internet economy and surging amounts of data traffic call for scalable, multiservice platforms with the ability to support next-generation, IP-based services and security Today service providers are looking for networks with the following characteristics: ■ Capacity/scalability 121 ■ Reliability 122 ■ Accelerated profits 123 ■ Broad coverage 124 ■ End-to-end flexibility 125 ■ Adaptability 126 ■ Space efficiency 127 ■ Security 128 Reduce point-of-presence (POP) physical space requirements Figure [1] lists the detailed description for each characteristic Copyright 2002, Cisco Systems, Inc Module 9: Optical Networking Fundamentals 9-5 Practice 129 130 131 132 133 134 135 136 137 138 Which of the following are the key drivers of the optical networks? A Efficiently meet capacity and scalability requirements in both metropolitan and long-hual network infrastructure B Reduce costs and accelerate profitable new service revenues simultaneously C Reach long distances D Be adaptable through a closed system architecture ** 139 9-6 Cisco Certified Network Associate Basics (CCNAB) v2.0 Copyright 2002, Cisco Systems, Inc 926 927 928 929 930 931 932 933 934 935 936 937 938 939 940 941 942 943 944 945 946 947 948 949 9.3.4 E/O/E Conversion Figure 1: E/O/E Conversion Within the DWDM system a device called a transponder converts the SONET/SDHcompliant optical signal from the client back to an electrical signal The electrical signal is then used to drive a WDM laser The WDM laser is a very precise laser operating within the 1500-nm wavelength range Each transponder within the system converts its client's signal to a slightly different wavelength The wavelengths from all the transponders in the system are then optically multiplexed onto a single fiber In the receive direction of the DWDM system, the reverse process occurs Individual wavelengths are filtered from the multiplexed fiber and fed to individual transponders, which convert the signal to electrical and drive a standard SONET/SDH interface to the client Practice What is the device within the DWDM system used to convert the SONET/SDHcompliant optical signal? A B C D Transceiver Transformer Converter Transponder ** 950 Copyright 2002, Cisco Systems, Inc Module 9: Optical Networking Fundamentals 9-43 950 9.3.5 Data Transmission 951 Figure 1: Data Transmission 10 Gbps 10 Gbps 10 Gbps 10 Gbps 952 953 954 Figure 2: Analog Modem Standards 955 956 957 958 959 960 961 962 963 964 965 966 967 In a system with each channel carrying 10 Gbps (10 billion bits per second), the optical fiber can deliver up to trillion bits per second Because each channel is demultiplexed at the end of the transmission back into the original source, different data formats can be transmitted together at different data rates From both technical and economic perspectives, the ability to provide potentially unlimited transmission capacity is the most obvious advantage of DWDM technology The current investment in fiber plant not only can be preserved, but also can be optimized by a factor of at least 32 As demands change, more capacity can be added without expensive upgrades, either by simple equipment upgrades or by increasing the number of lambdas on the fiber Practice 968 969 970 971 972 973 974 975 976 977 978 From technical and economic perspectives, what is the most obvious advantages of DWDM technology? A B C D 9-44 The ability to transmitted a lot of data at a time The ability to provide potentially unlimited transmission capacity ** Easy installation Low cost Cisco Certified Network Associate Basics (CCNAB) v2.0 Copyright 2002, Cisco Systems, Inc 978 979 9.3.6 DWDM Advantages Figure1: Analog Modem Standards Multiplexer 980 981 982 983 984 985 986 987 988 989 990 991 992 993 994 995 996 997 998 999 1000 Figure1: Analog Modem Standards Bandwidth aside, the most compelling technical advantages of DWDM are flexibility, transparency, scalability, and dynamic provisioning Flexibility DWDM is extremely flexible Specifically, Internet Protocol (IP), SONET, and Asynchronous Transfer Mode (ATM) data can all be traveling at the same time within the optical fiber Transparency Because DWDM is a physical layer architecture, it can transparently support both TDM and data formats such as ATM, Gigabit Ethernet, ESCON, and Fibre Channel with open interfaces over a common physical layer Scalability DWDM provides economical, scalable bandwidth growth DWDM can take advantage of the abundance of dark fiber in many metropolitan-area and enterprise Copyright 2002, Cisco Systems, Inc Module 9: Optical Networking Fundamentals 9-45 1001 1002 1003 1004 1005 1006 1007 1008 1009 1010 1011 1012 1013 1014 networks to quickly meet demand for capacity on point-to-point links and on spans of existing SONET/SDH rings Dynamic Provisioning Fast and simple, dynamic provisioning of network connections gives providers the ability to provide high-bandwidth services in days rather than months Selling Points Traditional ways of increasing bandwidth include using faster electronics, which are expensive, or using more fiber The problems with the latter include a slower time to market, expensive engineering, limited right of way, and duct exhaust WDM increases bandwidth without these issues while maintaining fiber compatibility DWDM provides fiber capacity release, a fast time to market, a lower cost of ownership, and the utilization of existing TDM equipment Practice 1015 1016 1017 1018 1019 1020 1021 1022 1023 1024 1025 1026 1027 1028 1029 1030 1031 1032 Identify the most compelling technical advantages of DWDM (Check all that apply) A B C D E High flexibility ** Scalability ** High capacity Transparency ** Low maintenance 1033 1034 1035 9-46 Cisco Certified Network Associate Basics (CCNAB) v2.0 Copyright 2002, Cisco Systems, Inc 1035 1036 1037 1038 1039 1040 Summary This section summarizes the key points you learned in this lesson ■ SONET/SDH are standards for optical transport The SONET standard is used in North America, while the SDH standard is used everywhere outside of North America and Japan 1041 ■ DWDM puts data from different sources together on an optical fiber 1042 1043 ■ A transponder is a device that converts the SONET/SDH-compliant optical signal to electrical signal and vice versa 1044 ■ DWDM can transmit different data formats together at different data rates 1045 1046 ■ The most compelling technical advantages of DWDM are flexibility, transparency, scalability, and dynamic provisioning 1047 Copyright 2002, Cisco Systems, Inc Module 9: Optical Networking Fundamentals 9-47 1048 9.4 Optical Technology Solutions 1049 Overview 1050 1051 This lesson introduces various optical technology solutions Objectives 1052 1053 1054 1055 Upon completing this lesson, you will be able to: ■ Describe the features of metropolitan DWDM 1056 ■ Describe the features of first-generation optical protection 1057 ■ Describe the features of second-generation optical protection 1058 ■ Describe the features of next-generation optical protection 1059 ■ Describe the features of an all-optical infrastructure 1060 1061 ■ Identify the key point in reducing the numbers of layer in the IP over fiber stack 1062 ■ Identify optical IP backbones technology Outline 1063 1064 1065 1066 This lesson includes these sections: ■ Overview 1067 ■ Metro DWDM 1068 ■ First-Generation Optical Protection 1069 ■ Second-Generation Optical Protection 1070 ■ Next-Generation Optical Protection 1071 ■ All Optical Infrastructure 1072 ■ IP Transport Alternatives 1073 ■ Optical IP Backbones 1074 ■ Summary 1075 1076 9-48 Cisco Certified Network Associate Basics (CCNAB) v2.0 Copyright 2002, Cisco Systems, Inc 1076 1077 1078 1079 1080 1081 1082 1083 1084 1085 1086 1087 1088 1089 1090 1091 1092 9.4.1 Metro DWDM Figure1: Metro DWDM ■ Maximizes service density per wavelength ■ Support subwavelength TDM and wavelength services ■ Is fundamentally different than long-haul DWDM ■ Is driven by demand for fast service provisioning Metropolitan (metro) DWDM maximizes the service density, or revenue potential per wavelength by supporting both subwavelength TDM services and wavelength services, such as Gigabit Ethernet, fiber connectivity (FICON), Enterprise System Connection (ESCON), and more on a single DWDM backbone The metro DWDM is fundamentally different from long-haul DWDM and is driven by demand for fast service provisioning, not fiber exhaust Practice Which of the following does not describe metro DWDM? A B C D Metro DWDM is very similar to long-haul DWDM ** Metro DWDM supports subwavelength TDM and wavelength services Metro DWDM is driven by demand for fast service provisioning Metro DWDM maximizes service density per wavelength 1093 1094 1095 Copyright 2002, Cisco Systems, Inc Module 9: Optical Networking Fundamentals 9-49 1095 9.4.2 First- Generation Optical Protection 1096 Figure1: First-Generation Optical Protection First-Generation System-Level Redundancy 1097 1098 1099 1100 1101 1102 In first-generation equipment, redundancy is at the system level Parallel links connect redundant systems at either end Switchover in case of failure is the responsibility of the client equipment, such as a switch or router, while the DWDM systems themselves provide only capacity Practice 1103 1104 1105 1106 1107 1108 1109 In first-generation optical eqipment, what is the function of DWDM system? A B C D Routing Switching Capacity ** None of the above 1110 1111 9-50 Cisco Certified Network Associate Basics (CCNAB) v2.0 Copyright 2002, Cisco Systems, Inc 1111 1112 9.4.3 Second- Generation Optical Protection Figure 1: Second-Generation Optical Protection Second Generation Card-Level Redundancy 1113 1114 1115 1116 1117 1118 1119 1120 1121 1122 1123 1124 1125 1126 1127 In second-generation equipment, redundancy is at the card level Parallel links connect single systems at either end that contain redundant transponders, multiplexers, and CPUs Here protection has migrated to the DWDM equipment, with switching decisions under local control Practice In the second-generation optical equipment, what equipment provides protection? A B C D Client DWDM ** WDM TDM 1128 1129 1130 Copyright 2002, Cisco Systems, Inc Module 9: Optical Networking Fundamentals 9-51 1130 9.4.4 Next- Generation Optical Protection 1131 Figure 1: Next-Generation Optical Protection 1132 1133 1134 1135 1136 1137 1138 The capacity of systems will grow as technologies advance to allow closer spacing and, therefore, higher numbers, of wavelengths DWDM is also moving beyond transport to all-optical networking with wavelength provisioning and mesh-based protection Switching at the photonic layer and routing protocols that allow light path travel across the network will enable this evolution Practice 1139 1140 1141 1142 1143 1144 1145 1146 Which of the following could be offered by the next-generation optical protection system? A B C D All-optical networking Wavelength provisioning and mesh-based protection Higher numbers of wavelengths All of the above ** 1147 1148 9-52 Cisco Certified Network Associate Basics (CCNAB) v2.0 Copyright 2002, Cisco Systems, Inc 1148 1149 1150 1151 1152 1153 1154 1155 1156 1157 1158 1159 1160 1161 1162 1163 9.4.5 All Optical Infrastructure Figure 1: All Optical Infrastructure Advances are converging so that an all-optical infrastructure can be envisioned Figure [2] shows an infrastructure, using mesh, ring, and point-to-point topologies at the optical layer to support the needs of enterprise, metropolitan access, and metropolitan core networks Practice Which of the following topologies can be used by the all-optical infrastructure at the optical layer? A B C D Mesh Ring Point-to-Point All of the above ** 1164 1165 Copyright 2002, Cisco Systems, Inc Module 9: Optical Networking Fundamentals 9-53 9.4.6 IP Transport Alternatives 1165 1166 Figure 1: IP Transport Alternatives 1167 1168 1169 1170 1171 1172 1173 1174 Various stacks are being utilized to transport high-speed IP over fiber, as shown in Figure [1] The key point in reducing the number of layers in the stack is to minimize capital expenditure and reduce overhead to maximize useful transport bandwidth This also minimizes provisioning complexity, operations, fault detection and resolution, network planning, engineering, and network restoration [STM-4; STM-16 in both figures] Practice 1175 1176 1177 1178 1179 1180 1181 What is the key point in reducing the numbers of layers in the stack? A B C D Minimizes capital expenditure ** Maximizes provisioning complexity Maximizes the fault detection and resolution operations Minimizes useful transport bandwidth 1182 9-54 Cisco Certified Network Associate Basics (CCNAB) v2.0 Copyright 2002, Cisco Systems, Inc 1182 1183 1184 1185 1186 1187 1188 1189 1190 1191 1192 1193 1194 1195 1196 9.4.7 Optical IP Backbones Figure 1: Optical IP Backbone – SONET/SDH Connect to tributary interfaces on SONET/SDH multiplexers (OC-3c/STM-1 to OC-48c/STM-16) Figure 2: Optical IP Backbone – DWDM System Connect to transponder-based DWDM system (typically OC-12c/STM-4 to OC-48c/STM-16) Today's optical IP backbones include those that connect to tributary interfaces on SONET/SDH multiplexers and those that connect to a transponder-based DWDM system Practice Today’s optical IP backbones include those that connect to multiplexers and those that connect to a transponder-based system ** SONET/SDH; DWDM 1197 Copyright 2002, Cisco Systems, Inc Module 9: Optical Networking Fundamentals 9-55 Summary 1197 1198 1199 1200 1201 This section summarizes the key points you learned in this lesson ■ Metro DWDM maximizes the service density per wavelength by supporting both subwavelength TDM and wavelength services 1202 1203 ■ Metro DWDM is driven by demand for fast service provisioning, not fiber exhaust 1204 1205 ■ In the first-generation optical protection, basic system just provides capacity 1206 1207 ■ In the second-generation optical protection, protection migrates to DWDM equipment 1208 1209 ■ In the next-generation optical protection, DWDM is moving to all-optical networking with wavelength provisioning and mesh-based protection 1210 1211 1212 ■ Optical IP backbones being deployed today includes those that connect to tributary interfaces on SONET/SDH multiplexers and those that connect to transponder-based DWDM systems 1213 9-56 Cisco Certified Network Associate Basics (CCNAB) v2.0 Copyright 2002, Cisco Systems, Inc 1214 1215 1216 1217 1218 1219 Summary This module includes these key points: ■ Optical-fiber networks are made of thin glass strands that carry rapid light pulses faster and more reliably than copper wires at speeds of up to 10 Gbps 1220 1221 ■ Optical-fiber networks connect both distant cities and many points within a metropolitan area 1222 1223 ■ In optical-fiber networks, information is carried by modulating light power, not by the wavelength or frequency of light 1224 ■ Reflection, refraction, and fiber type all affect network efficiency 1225 1226 ■ DWDM transmits multiple signals simultaneously at different wavelengths that allow a single fiber to operate as if it were multiple fibers 1227 1228 ■ DWDM is a scalable solution that increases the information-carrying capacity of existing fiber 1229 1230 1231 ■ Optical filter technologies, amplifiers, and the EDFA help boost signal performance In addition, advances are converging in such a way that an alloptical infrastructure can now be envisioned Copyright 2002, Cisco Systems, Inc Module 9: Optical Networking Fundamentals 9-57 ... Inc Module 9: Optical Networking Fundamentals 9-3 78 9.1 Basics of Optical 79 Overview 80 81 82 83 This lesson describes the key drivers of the optical networks and the features of fiber-optic... Figure 3: Fiber-Optic Wavelength Single Mode 230 231 Copyright 2002, Cisco Systems, Inc Module 9: Optical Networking Fundamentals 9-1 1 232 233 Figure 4: Fiber-Optics Power Fiber-Optics Power... Systems, Inc Module 9: Optical Networking Fundamentals 9-1 3 9.1.5 Optical Transmission 272 273 Figure 1: WDM Wavelength-Division Multiplexing 274 275 276 Figure 2: Light Emitting Devices Single-Mode