FIBER OPTIC COMMUNICATION

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1. Optical Fiber Communications Chapter 1 Overview of Optical Fiber Communications Dr R. S. Kaler Senior Professor, ECED Email:[email protected]

2. Motivations for light wave communications: The path to optical Networks Prior to 1980: Electrical transmission mechanism 1837: Invention of telegraph by Samuel Morse 1876: Alexander G raham Bell 1950: Patents for two-layer waveguide 1960: LASER used as light source 1970: Refining of manufacturing process 1980: Optical fiber technology 1990: Increase demand on communication network assets for bandwidth-hungry services

3. The internet traffic is growing at a faster rate to fulfill the demand of diverse services : high-definition video streaming multimedia smart phone users online shopping cloud computing online gaming Optical fiber : Heart of networking architectures supporting extremely high data rate and capacity To cope up with an exponential growth in internet traffic there exists a vital requirement for high-capacity optical networks. Growing demand for Internet Traffic

4. Growing demand for Internet Traffic Global IP traffic expected to exceed 2 zettabytes /month by 2020 Growing demand for Internet Traffic

5. Electromagnetic Spectrum Optical frequencies : several orders of magnitude higher than Electrical communication system Optical Fiber (2.55 μ m to 800 nm)

6. Advantages of Optical Fibers Long distance transmission lower transmission losses compared to Cu Large information capacity wider bandwidth than Cu wires Small size and low weight advantage over heavy, bulky wire cables Immunity to electrical interference dielectric material not conduct electricity Enhanced safety no problems of sparks, ground loops Increase signal security

7. Applications Defense Electronics Medical SHM Lab On Chip Key Hole Surgery Food Quality Monitoring

8. Optic spectral Bands Electromagnetic Energy: Planck’s Law E=h ν where , h= 6.63 x 10 -34 J-s = 4.14 x 10 -15 eV -s

9. Optic spectral Bands Windows and spectral bands: 850 nm 1310 nm 1550 nm

10. Optic spectral Bands

11. Decibel Units Consideration when designing and implementing an optical fiber link: Establish, Measure and Interrelate the optical signal levels at each of the elements of a transmission link Periodically placed amplifiers compensate for energy losses along a link Power ratio in dB = P1 and P2: electrical or optical power levels of a signal at points 1 and 2, log: base-10 logarithm Power levels differing by many orders of magnitude can be compared easily when in dB form

12. Example of pulse attenuation in a link: Decibel Units Power ratio in dB = 3-dB attenuation or loss If an amplifier is inserted into the link at this point to boost the signal back to its original level, then amplifier has a 3-dB gain

13. Decibel Units Example of signal attenuation and amplification in a link: The signal level in dB at point 4: = (loss in line 1) + (amplifier gain)+(loss in line 2) = (-9 dB) + (14 dB) +(-3dB) = + 2 dB The signal has a 2-dB gain in power in going from Point 1 to Point 4

14. Decibel Units Decibel (dB) : refer to ratios or relative units no indication of the absolute power level to measure the changes in the strength of a signal (one merely adds or subtracts the decibel numbers between two different points) Power ratio in dB = dBm : refer to the power level as a logarithmic ratio of P referred to 1 mW absolute value of power level commonly used in optical fiber communication Power level (in dBm ) A rule of thumb for optical fiber communications: 0dBm=1mW

15. Decibel Units Power dBm equivalent 200 mW 23 100 mW 20 10 mW 10 1 mW 100 μ W -10 10 μ W -20 1 μ W -30 100 nW -40 10 nW -50 1 nW -60 100 pW -70 10 pW -80 1 pW -90 Examples of Optical power levels and their dBm equivalents

16. Decibel Units Example: Consider three different light sources having the following optical output powers: 50 μ W, 1 mW and 50 mW. What are the power levels in dBm units? Power level (in dBm ) The optical output powers level in dBm are calculated by above: For optical source 50 μ W , Power level (in dBm )= -13 dBm For optical source 1 mW , Power level (in dBm )= 0 dBm For optical source 50 mW , Power level (in dBm )= +17 dBm

17. Key Elements of Optical Fiber Systems

18. Network Information Rates Continuous rising demand for high bandwidth services from users worldwide Implementation of digital multiplexing techniques by telecommunication companies worldwide

19. Network Information Rates Telecom signal multiplexing/Time Division Multiplexing (TDM) To send these services, network providers combine the signals from many different users and send the aggregate signal over a single transmission line N independent information streams, each running at a data rate of R b/s are interleaved electrically into a single information stream operating at higher rate of N x R b/s S.No Service type Data rate 1. Video on demand/ Interactive TV 1.5 to 6 Mb/s 2. Video games 1 to 2 Mb/s 3. Remote Education 1.5 to 3 Mbps 4. Electronic Shopping 1.5 to 6 Mb/s 5. Data transfer or telecommuting 1 to 3 Mb/s 6. Video conferencing 0.384 to 2 Mb/s 7. Voice(single telephone channels) 33.6 to 56 Mb/s

20. Network Information Rates Early applications of fiber optic transmission links were mainly for large capacity telephone lines These links consisted of time division multiplexed 64-kb/s voice channels Developed in the 1960s and based on PDH (Plesiochronous digital hierarchy) Digital transmission hierarchy used in the North American telephone networks DS: Digital System

21. Digital transmission hierarchy used in the European telephone networks Network Information Rates PDH level hierarchy used in Europe Rates derived from 2.048 Mbps basic rate including bit stuffing in 30 channel (each 64 kbps ) 2.048 x 4 gives 8.448 Mbps (120 channels) 8.448 x 4 gives 34.368 Mbps (480 channels) 34.368 x 4 gives 139.264 Mbps (1920 channels) 139.264 x 4 gives 564.992 Mbps (7680 channels)

22. Limitations of PDH : In PDH, different frame is used for transmission in data layer. Hence multiplexing and de-multiplexing is very complex . Accessing lower tributary requires the whole system to be de-multiplexed. The maximum capacity for PDH is 566 Mbps, which is limited in bandwidth. Allows only Point-to-Point configuration and does not support Hub. Every manufacturer has its own standards; PDH also has different multiplexing hierarchies making it difficult to integrate interconnecting networks together. Network Information Rates

23. Digital multiplexing levels in North America, Europe and Japan Digital Multiplexing level Number of 64-kb/s channels Bit rate North America Europe Japan DS0 1 0.064 0.064 0.064 DS1 24 1.544 1.544 30 2.048 48 3.152 3.152 DS2 96 6.312 6.312 120 8.448 DS3 480 34.368 32.064 672 44.736 1344 91.053 1440 97.728 DS4 1920 139.264 4032 274.176 5760 397.200

24. SONET/ SDH Multiplexing Hierarchy Fiber optics use synchronous optical network (SONET) standards. Service providers established a standard signal format SONET in North America and synchronous digital hierarchy (SDH) in other parts of the world. The initial SONET standard is OC-1 , this level is Synchronous transport level 1 (STS-1) Synchronous frame structure at a speed of 51.840 Mbps OC-1: envelope containing a DS 3 signal(28 DS1 signals or 672 channels) SONET level Electrical level SDH level Line rate(Mb/s) Popular rate name OC-1 STS-1 ------ 51.84 ---------- OC-3 STS-3 STM-1 155.52 155 Mb/s OC-12 STS-12 STM-4 622.08 622 Mb/s OC-48 STS-48 STM-16 2488.32 2.5 Gb /s OC-192 STS-192 STM-64 9953.28 10 Gb /s OC-768 STS-768 STM-256 39813.12 40 Gb /s Common SDH and SONET line rates and their numerical name

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