Fiber optic communication

Optical communication system, Optical transmitter &Receiver Light propagation in optical fibers, , Transmission properties of
optical fibers, Optical fiber cable types, fiber connectors, Area of applicatons, dvantages &disadvantages

1. FIBER OPTIC COMMUNICATION BY S.SIVARAMAKRISHNAN

2. Optical Fiber Communication System Information source E le c tri c al source O pti c al source Optical fiber cable Optical d e t ec t or Electrical receive r D e s tin a tion Fiber Optic cable The primary objective of optical fiber communication system also is to transfer the signal containing information (voice, data, video) from the source to the destination by sending light through an optical fiber . The light forms an electromagnetic carrier wave that is modulated to carry information The process of communicating using fiber-optics involves the following basic steps: Creating the optical signal using a transmitter, Relaying the signal along the fiber, ensuring that the signal does not become too distorted or weak, and Receiving the optical signal and converting it into an electrical signal.

3. 23 Optical Fiber Communication System

4. Optical Transmitter & Receiver Attenuator External modulator Temp monitoring Cooler Light source Driver circuitry Electronic preprocessing Optical monitoring Wires Input Electronic Interface Fiber Output Optical Interface Optical Detector Low Noise Amplifier Main Amplifier Demodulator Light signal Electrical Output

5. Primary Elements of Optical Communication System

6. Regenerative Repeaters and Optical Amplifiers Because of loss or dispersion, there is always a limit to the length of a single span of fiber-optic cable. When distances are great, some form of gain must be provided, using one of two different ways: Change the signal to electrical form, amplify it, regenerate it if it is digital, and then convert it back to an optical signal Simply amplify the optical signal Signal Source Optical Transmitter Optical Receiver Signal Destination Regenerative Repeater Signal Source Optical Transmitter Optical Receiver Signal Destination Optical Receiver Optical Transmitter Pulse Shaper Signal Source Optical Transmitter Optical Receiver Signal Destination Optical Amplifier

7. Need of Fiber Optic Communications E xtremely high data rates, Suitable for long-distance transmission No need to amplify and retransmit along the way. Speed limit of electronic processing , L imited bandwidth of copper/coaxial cables. Optical fiber has very high-bandwidth (~30 THz) Optical fiber has very low loss (~0.25dB/km @1550nm )

8. Electromagnetic Spectrum

9. Electromagnetic Spectrum

10. Fiber Transmission

11. Transmission windows Band Description Wavelength Range O band original 1260 to 1360 nm E band extended 1360 to 1460 nm S band short wavelengths 1460 to 1530 nm C band conventional (erbium window) 1530 to 1565 nm L band long wavelengths 1565 to 1625 nm U band Ultra-long wavelengths 1625 to 1675 nm

12. The simplest way to view light in fiber optics is by ray theory . In this theory, the light is treated as a simple ray , shown by a line . An arrow on the line shows the direction of propagation. The speed of light in vacuum is: c = 300,000 km/s However , the speed of light in medium is more slowly , v = c / n . The ratio of the velocity of light, c, in vacuum, to the velocity of light in the medium, v, is the refractive index , n . n = c / v Light Propagation in Optical Fibers

13. Light traveling from one material to another causes the change of speed, which results in the change of light traveling direction. This deflection of light is called refraction . Light Propagation in Optical Fibers

14. The relation between incident ray and reflection ray:  r =  i ( Law of reflection ) The relation between incident ray and refraction ray: n 1 sin  i = n 2 sin  t ( Snell’s law ) where n 1 and n 2 are refractive indices of the incident and transmission regions, respectively. Light propagation in optical fibers

15. Light propagation in optical fibers

16. Total internal reflection From Snell’s law , n 1 sin  i = n 2 sin  t if n 1 > n 2 , then sin  i = (n 2 /n 1 ) sin  t < sin  t , which leads to  i <  t , i.e. the angle of refraction is always greater than the angle of incidence . Thus , when the angle of refraction  t = 90  as sin  i = (n 2 /n 1 ) sin  t = (n 2 /n 1 ) sin90  = n 2 /n 1 < 1 the angle of incidence,  i , must be less than 90  . Light propagation in optical fibers

17. Critical angle The angle of incidence that yields an angle of refraction  t = 90  is called the critical angle ,  C . sin  C = n 2 /n 1 When the angle of incidence is greater than the critical angle , the light will be reflected back into the originating dielectric medium. This is known as total internal reflection . Light propagation in optical fibers

18. Light guiding In order to propagate a long distance in the optical fiber, the light beam must satisfy the conditions for total internal reflection Conditions for total internal reflection in optical fiber Refractive index of fiber core, n 1 , is greater than refractive index of fiber cladding n 2 , i.e. n 1 > n 2 The incident angle is larger than the critical angle.  i >  C Light propagation in optical fibers

19. Acceptance angle Acceptance angle ,  a , is the maximum angle over which light rays entering the fiber will be guided along its core. Light propagation in optical fibers

20. The acceptance angle is usually measured as the numerical aperture (NA) . Numerical aperture At the air-core interface, n sin  a = n 1 sin  2 = n 1 sin(90  -  C ) = n 1 cos  C = n 1 (1 – sin 2  C ) 1/2 = n 1 [1 – (n 2 /n 1 ) 2 ] 1/2 = (n 1 2 - n 2 2 ) 1/2 = NA The value of NA represents the light collecting ability . Light propagation in optical fibers

21. The light beam with larger  i experience total internal reflection earlier , light beam with smaller  i travels longer distance until it experience total internal reflection. Light propagation in optical fibers

22. Single-mode fiber Carries light pulses along single path Multi-mode fiber Many pulses of light generated by LED travel at different angles Modes of P ropagation

23. An optical fiber consists of a core surrounded by a cladding . There are two types of fibers: step-index fibers and graded-index fibers . Modes of P ropagation

24. STEP INDEX A step-index fiber has a central core with a uniform refractive index. An outside cladding that also has a uniform refractive index surrounds the core; however, the refractive index of the cladding is less than that of the central core. GRADED INDEX In graded-index fiber , the index of refraction in the core decreases continuously. This causes light rays to bend smoothly as they approach the cladding, rather than reflecting abruptly from the core-cladding boundary. Modes of P ropagation

25. Modes of P ropagation

26. Modes of P ropagation

27. Light propagation in graded-index fiber It guides light by refraction . Its refractive index decreases gradually away from its center, dropping to the same as the cladding at the edge of the core. The change in refractive index causes refraction , bending light rays back toward the axis as they pass through layers with lower refractive index. Modes of P ropagation

28. 28 fiber optic multimode step-index fiber optic multimode graded-index fiber optic single mode Modes of P ropagation

29. Fibre Attenuation Attenuation limits how far a signal can travel through a fiber before it becomes too weak to be detected. Fibre attenuation is a function of wavelength and it gives a measure of the loss suffered by the light in the fibre per km of length travelled. The attenuation constant,  , is given by where L is the length of the fibre, P in is the input light power and P out is the output light power. Transmission properties of optical fibers

30. Fiber Attenuation is the loss of the optical power. Fiber Attenuation in optical fiber take place due to elements like coupler, splices, connector and fiber itself. A fiber lower attenuation will allow more power to reach a receiver than with a higher attenuation. Fiber Attenuation may be categorised as – (a) Intrinsic (b) Extrinsic A t t enu a ti on I n t r i ns ic Absorption S c a t t e r ing Extrinsic Macrobending Microbending Transmission properties of optical fibers

31. Main types of fiber attenuation : Absorption , scattering and light coupling loss Absorption Absorption is related to the material composition and the fabrication process for the fiber, which results in the dissipation of some of the transmitted optical power as heat in the waveguide. Optical power → heat  Optical power loss Transmission properties of optical fibers

32. Scattering Scattering refers to the process by which the light wave encounters a particle smaller than its wavelength , with the results that energy is sent to a new direction . Transmission properties of optical fibers

33. Bend loss Bend loss is the loss resulting from bend. Bend can cause the change of incident angle at which the light hits the core-cladding boundary. Transmission properties of optical fibers

34. Transmission properties of optical fibers Coupling Losses

35. Dispersion Dispersion is the spreading of a light pulse . Dispersion limits digital transmission speed by causing pulses to overlap, so they cannot be distinguished. The bit rate must be low enough to ensure that pulses do not overlap. Transmission properties of optical fibers

36. Three main types of dispersion Material dispersion Material dispersion occurs because the refractive index of the material changes with the optical wavelength . As n = n(  ), and n = c / v , then v = c / n(  ) Different wavelength elements travel at different velocities through a fiber , even in the same mode . Transmission properties of optical fibers

37. Waveguide dispersion It is equivalent to the angle between the ray and the fiber axis varying with wavelength . From For a given mode (e.g. m = 1) Different  lead to different values of  1 and hence results in different transmission time (in the same mode). Transmission properties of optical fibers

38. Mode dispersion Mode dispersion arises because rays follow different paths through the fiber and consequently arrive at the other end of the fiber at different times . Different modes travel with different speeds. Transmission properties of optical fibers

39. Loss Budget The most basic limitation on the length of the fiber-optic link is loss in the fiber, connectors, and splices If the length is too great, the optical power level at the receiver will be insufficient to produce an acceptable signal-to-noise ratio Given the optical power output of the transmitter and the signal level required by the receiver, a loss budget may be drawn up If the losses along the line are enough to reduce the power at the receiver below minimum requirements, then one of the following needs to occur: Increase the transmitter power Increase receiver sensitivity Decrease the length of the cable Transmission properties of optical fibers

40. Optical Modulator

41. Simple Fiber Transceiver

42. Application Example

43. Optical Fiber Cable relatively new transmission medium used by telephone companies in place of long-distance trunk lines also used by private companies in implementing local data networks require a light source with injection laser diode (ILD) or light-emitting diodes (LED) fiber to the desktop in the future 43

44. An optical fiber consists of a very thin glasses core (5 mm to 50 mm in diameter) surrounded by a glass coating called cladding. The glass core and cladding are enclosed in a protective jacket made of plastic. The refractive index of the glass used for making core (m) is a little more than the respective index of the glass used for making the cladding (m2) i.e.m1> m2. In optical fiber, the value of refractive index of core is 1.52 and the value of refractive index of cladding is 1.48 respectively. Most optical fibers are made of glass, although some are made of plastic Optical Fiber Cable

45. Core – central tube of very thin size made up of optically transparent dielectric medium and carries the light form transmitter to receiver. Cladding – O uter optical material surrounding the core having reflecting index lower than core. It traps the light in the core by the principle of total internal reflection. Buffer Coating – plastic coating made of silicon rubber which protects the glass fiber from physical damage and moisture. Modern cables come in a wide variety of sheathings and armor, designed for direct burial in trenches, high voltage isolation submarine installation, and insertion in paved streets. Optical Fiber Cable

46. Optical Fiber Cable 46

47. Structure of single-mode fiber 1. Core: 8 µm diameter 2. Cladding: 125 µm dia. 3. Buffer: 250 µm dia. 4. Jacket: 400 µm dia. Optical Fiber Cable

48. Types of Optical fiber cable 16

49. 18 Types of Optical fiber cable

50. Single-Mode Fibers Single-mode fibers – used to transmit one signal per fiber (used in telephone and cable TV). They have small cores(9 microns in diameter) and transmit infra-red light from laser. Single-mode fiber’s smaller core (<10 micrometers) necessitates more expensive components and interconnection methods, but allows much longer, higher-performance links.

51. Multi-Mode Fibers Multi-mode fibers – used to transmit many signals per fiber (used in computer networks). They have larger cores(62.5 microns in diameter) and transmit infra-red light from LED. Multimode fiber has a larger core (≥ 50 micrometres ), allowing less precise, cheaper transmitters and receivers to connect to it as well as cheaper connectors. However, multi-mode fiber introduces multimode distortion which often limits the bandwidth and length of the link. Furthermore, because of its higher dopant content, multimode fiber is usually more expensive and exhibits higher attenuation .

52. Multi-Mode Fibers

53. Wavelength-Division Multiplexing Several light sources, each operating at a different wavelength, can be coupled into the same fiber This scheme, called wavelength-division multiplexing, requires lasers with narrow bandwidth which is limited only by dispersion WDM is really a form of frequency-division multiplexing One difference between WDM and FDM is that for FDM, the separation between carriers is limited by the sidebands created by modulation, whereas with lasers, the width of the carrier signal itself determines the signal bandwidth Diachronic Filter Receiver A Destination A Receiver B Destination B Directional Coupler Source A Transmitter A Source B Transmitter B

54. Fiber Color Codes

55. Color Code for Fibers

56. Fiber Optic Cable Types

57. FOC-Jacket Color Codes

58. FOC-Connector Color Codes

59. 19 Fiber Connectors

60. 20 Fiber Connectors

61. Advantages & Disadvantages The fiber optic system has enabled the communication industry to rapidly develop new advancements in technology. Advantages : Less expensive for higher transmission system. Higher carrying capacity. Lower power requirements. Non-flammable. Flexible and light weight Limitations : More expensive for lower transmission system. Hard to install and maintain.

62. Application Areas Communications (wiring systems for buildings and industry) Energy (mining, wind, solar, nuclear, petroleum, utilities) Mechanical and Plant Engineering (drag chains and switches) Automation and Robotics (high-performance lasers) Transportation Engineering (air and space travel, transport) Defense (system components and tactical field cables) Laser Technology ( for laser welding/laser processing) Audio / Video / Multimedia Medicine & Life Sciences (laser probes, endoscopic equipment) Sensor Technology/Analytics(sensor technology, environmental engg .) Lighting Technology Naval & Maritime Engineering (steering control cables)

63. Fiber Optic Communication Sub-system

64. IBM microprocessors Medical , Military & Electronics Applications

65. The Endoscope There are two optical fibres One for light, to illuminate the inside of the patient One for a camera to send the images back to the doctor. Key hole surgery

66. Military Applications Military applications include communications ,command and control links on ships and aircraft, data links for satellite earth stations, and transmission lines for tactical command-post communications. The important fiber characteristics are low weight ,small size EMI rejection, and no signal radiation. On aircraft and ships the reduced shock, fire, and spark hazards are significant assets.

67. Industrial Internet An enormous amount of data is collected, transported, and analyzed - all which requires a vast number of high-bandwidth interconnections between a myriad of nodes such as machines, sensors, facilities, computers, data centers, and people. Industrial Ethernet is becoming the communication standard to network all of these devices.

68. ETHERNET – INDUSTRIAL CONNECTIVITY

69. Comparison of Fiber Optic Characteristics Characteristic Industrial Legacy Industrial Internet Protocol Proprietary Ethernet(Industrial) Data rates 12Mb/s 125Mb/s, 1Gb/s Link Distance Meters Hundreds of meters, Kilometers Link Reliability Moderate High Flexibility Low High Cost Low Low Source LED Laser(VCSEL and DFB) Digital Diagnostics None Yes Form-factors Discrete Tx and Rx modules Board mounted Transceivers Pluggable Transceivers Compact board mount Transceivers Active Optical Cables Power Consumption Medium Low

70. Structure of Submarine Cable The use of fiber optics for underwater telephone cables is a logical application. Short fiber-optic cables with lengths under about 100 km are generally built without repeaters Coaxial cables have traditionally been used, but these have less bandwidth, and the number of repeaters required is greater

71. Global Undersea Fiber Systems

72. Seismic Signal Sensing

73. The Synchronous Optical Network (SONET) The S ynchronous O ptical NET work ( SONET) standard was especially developed for fiber-optic transmission SONET is an American standard; the European equivalent is called the synchronous digital hierarchy (SDH) and is very similar to SONET It allows greater flexibility in adding new services to existing SONET in installation. The basic SONET transmission rate is OC-1 at 51.8 Mbps the electrical equivalent is STS-1 Transmission (Electrical) Designation (Optical) Data Rate (Mbps) STS-1 OC-1 51.84 STS-3c OC-3 155.52 STS-12 OC-12 622.08 STS-24 OC-24 1244.16 STS-48 OC-48 2488.32

74. Local Telephone Applications Nearly all new trunk lines for long-distance telephony are now fiber Most fiber trunks use single-mode fiber operating at 1.3 micrometers Many local loops remain on copper because of the cost to upgrade infrastructure and the need to install electrical-to-optical interfaces within the systems Two terms used within telephony when referring to fiber: a. Fiber in the loop (FITL ) b. Fiber to the curb (FTTC)

75. Fiber in Local Area Networks Most LANs use twisted-pair or coaxial cable Fiber optics have started to become more popular in LANs because of the greater bandwidth and lower losses Of the three common topologies used with LANs (star, ring, bus), the ring topology lends itself best for use with fiber optics Most fiber LANs use one of three technologies: Fiber distributed data interface (FDDI) High-speed Ethernet Gigabit Ethernet

76. Fiber in Local Area Networks

77. Fiber Distributed Data Interface (FDDI) FDDI stands for Fiber Distributed Data Interface. It is a high speed, high-bandwidth network based on optical transmissions. It is most often used as a network backbone, for connecting high-end computers, and for LANs connecting high-performance engineering, graphics, and other workstations that demand a rapid transfer of large amounts of data. It can transport data at a rate of 100 Megabits per second and can support up to 500 stations on a single network.

78. FDDI TOPOLOGY FDDI is an efficient network topology, regarding fault-tolerance and integrated network management functions. FDDI guarantees high aggregated throughput rates, even in large and high traffic networks. FDDI can be added easily to existing network topologies (such as Ethernet and Token Ring) as a strong backbone to eliminate severe network bottlenecks in existing LANs.

79. Ethernet on Fiber Fiber can be used instead of copper for both 10-and 100-Mb/s data transmission rates. Multimode glass fiber is used and LED sources operating at 1300 nm. The network is a logical bus, but a physical star. The main advantage of using fiber with Ethernet is the longer distances that are possible

80. Gigabit Ethernet The gigabit Ethernet system is originally designed to be implemented using fiber optics, though it can be used with twisted-pair copper for short distances. For short distances, multimode fiber is used with low-cost laser diodes operating at 850 nm and increased up to 5 km using laser diodes operating at 1300 nm and single-mode fiber

81. Ca ble T ele v ision System (CATV) Cable television systems collect and distribute a large number of color channels. The distances covered range from a few tens of meters to several kilometers. CATV systems obtain their signals from various sources. These sources are satellite earth stations, microwave links, antennas picking up broadcasts from nearby transmitters, and local studios where programming originates. All these sources can be connected to the central distribution location (the CATV head-end) by fibers.

82. Cable-Television Applications CATV systems are switching to fiber because of the increased bandwidth and the decrease in signal loss, requiring fewer repeaters Fiber systems lend themselves to compressed digital transmission CATV systems are also now providing Internet services to customers and fiber lends itself to the high bandwidth required

83. Number of Voice Channels Transmission Designation Signaling Designation Data Rate 1 64kbps 24 T1 DS-1 1.544 Mbps 48 (2T1 systems) T1C DS-1C 3.152 Mbps 96 (4T1 systems) T2 DS-2 6.312 Mbps 672 (7T2 systems) T3 DS-3 44.736 Mbps 1344(2T3systems) T3C DS-3C 91.053 Mbps 4032(6T3systems) T4 DS-4 274.175 Mbps 6048(9T3systems) 405 Mbps 8064(12T3systems) 565 Mbps Digital Transmission Rates of Telephone System

84. Highly Interactive Optical Visual Information System (Hi-OVIS) The system consists of a center, sub-center, and home terminals linked by optic transmission lines. The lines connect computers and video equipment. Each home terminal has a TV set, camera, microphone, and keyboard. Two way interactive communication is obtained. Services: Video request service, Home study course, Information about local events, medical facilities, train timetables etc.

85. Metallic communication links Metallic communications links installed along electrified railway tracks suffer from electromagnetic interference from the electricity powering the vehicles. Because of fiber rejection of EMI, signals traveling through fibers laid along the track do not degrade. Optic communications are compatible with electrified railways. Similarly, fibers can be placed near high voltage power lines without adverse effects, whereas wire systems would be noisy. Fibers can even pass unaffected through area where electrical power is generated or through power substations. Optic cables can be suspended directly from power line towers, or poles, if clearance space permits and if the load can be tolerated

86. Digital Optical Link(Metallic and Fiber) BUFFER THRESHOLD DETECTOR AMPLIFIER PHOTO DETECTOR FIBER OPTIC CONNECTOR FIBER OPTIC CONNECTOR OPTICAL SOURCE OPTICAL SOURCE MODULATOR BUFFER METALLIC METALLIC METALLIC OPTICAL OPTICAL OPTICAL FIBER RECEIVER TRANSMITTER DATA IN DATA OUT

87. Fiber System for Digital Data Transmission Fiber system are particularly suited for transmission of digital data such as that generated by computers. Interconnections can be made between the central processing unit (CPU) and peripherals, between CPUs and memory, and between CPUs. Example: the connection of several hundred cathode ray-tube (CRT) terminals, located throughout a high-rise, to a processor located on one of the floors.

88. Optically Powered Measurement System Remote Equipment Processing Transmitter PV Array + Power Convertor Base Station Receiver Laser Sensor Fiber Link Sensor Output Power Input

89. Optical FM Link

90. To conclude?!.... This is all about the basic elements of the fiber optic communication system.  Though there are some negatives of optical fiber communication system in terms of fragility, splicing, coupling, set up expense etc. but it is an un avoidable fact that optical fiber has revolutionized the field of communication. As soon as computers will be capable of processing optical signals, the total area of communication will become optical immediately.

91. OHM SAI PROJECTRONICS Engineering Projects 02 01 04 03 06 05 08 07 Solar/Inverter systems LCD / LED TV Servicing Training Courses Home Theatre Assembly Lab Equipments Servicing Web Design IoT Design & Deployment 194/5, Bharathiyar Road Karaikal-609605 [email protected] 9443319462 S.SIVARAMAKRISHNAN Project Development Engineer

92. Thank You ! Queries?....