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Telecommunications Essentials

Telecommunications Essentials. CHAPTER 11 OPTICAL NETWORKING. Optical Cost Trends. Cost of fiber is declining Bit rate per wavelength is increasing WDM Repeater spacing is increasing Cost/bit = 0.006% of the cost in 1996. Nortel’s WDM System. Fiber Networks. Large Networks

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Telecommunications Essentials

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  1. Telecommunications Essentials CHAPTER 11 OPTICAL NETWORKING

  2. Optical Cost Trends • Cost of fiber is declining • Bit rate per wavelength is increasing • WDM • Repeater spacing is increasing • Cost/bit = 0.006% of the cost in 1996 Nortel’s WDM System

  3. Fiber Networks • Large Networks • Dual Counter-rotating SONET Rings • 50 mSec switchover when cut

  4. Fiber Optic Cable www.arcelect.com/

  5. Optical Equipment • End-to-end optical (signal path) • EDFA – Erbium doped fiber amplifiers • DWDM • OADM – Optical add/drop multiplexers • Optical switches FTTH Terminal Box Fiber Optic Pigtails CATV Amplifier

  6. Traditional Repeaters • OEO • Optical to electrical to optical • ~ ½ the cost of an optical network • Required to regenerate & retime the signals • Repeaters are needed ~ 200 miles

  7. EDFA • All optical repeater • 50 – 100 km spacing • Uses erbium doped fiber • Operates at 1550 nm • Energy is pumped in at 980 nm • Supports DWDM • Encyclopedia of Laser Physics & Technology

  8. WDM • Each wavelength 2.5 – 10 Gbps • OC-48 to OC-192 • Experimental systems at 40 Gbps • OC-768 • Each wavelength supports a separate service • CWDM< 16 wavelengths

  9. DWDM • WDM by MRV • Cisco • OC-48 systems may carry 60 – 160 wavelengths • OC-192 systems may contain 8 – 32 wavelengths • Theoretically 15,000 wavelengths

  10. DWDM Issues • Wavelength stability • Tunable lasers • Initially used in point-to-point links • Need to provision as rings • Need add/drop for MANs • 95% of fiber can not handle DWDM • Wavelength crosstalk • Routing • Interoperability standards

  11. OADM • Optical add/drop multiplexer • Use filters to drop off a wavelength • Each wavelength is assigned • Specific protocol (ATM, IP, etc.) • Specific customer (essentially point-to point) Optical Filter

  12. Optical Switch • Also called optics cross-connect or wavelength router • Connects the light from one fiber to another

  13. Optical Switching Fabrics • MEMS – micro-electromechanical • Uses microscopic mirrors • Lucent Lambda router - 256 x 256 ports • Xros – 1024 x 1024 ports • DLPflash demo

  14. Optical Switching Fabrics • Bubble Switch • Liquid filled cavities • Heated to a gas to switch

  15. Optical Switching Fabrics • Thermo-optical switch • Refractive index is a function of temperature • The glass is heated or cooled

  16. Optical Switching Fabrics • LCD • The LCD polarizes and rotates light • Tunable laser

  17. Fiber Attenuation • Intrinsic Absorption • Due to the nature of glass • Extrinsic Absorption • Impurities • Rayleigh Scattering

  18. Other Fiber Components • Lasers • Gratings • Filters • Dispersion Compensators • Variable attenuators • Passive splitters • Raman Amplifiers

  19. IP Over Optical Standards • MPlS • IETF’s Multiprotocol Lambda Switching initiative • OIF • Optical Internetworking Forum

  20. Managing Optical Networks • There are no network management standards • There are no error correcting protocols • Digital Wrappers • WaveWrapper by Lucent • Part of submarine cabling systems

  21. Future Developments • Wavelength changer • ROADM • Nonzero Dispersion-Shifted Fiber

  22. Optical Dispersion • Passive Optical Network

  23. For More Information • Optoelectronics World • Photonics.com

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