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Fiber Optic Communication By

Fiber Optic Communication By. Engr. Muhammad Ashraf Bhutta. History of SONET. Digital carrier systems The hierarchy of digital signals that the telephone network uses. Trunks and access links organized in DS (digital signal) hierarchy Problem: rates are not multiples of each other.

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Fiber Optic Communication By

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  1. Fiber Optic CommunicationBy Engr. Muhammad Ashraf Bhutta

  2. History of SONET • Digital carrier systems • The hierarchy of digital signals that the telephone network uses. • Trunks and access links organized in DS (digital signal) hierarchy • Problem: rates are not multiples of each other. • Telco's needed to replace aging copper wire networks • Telco's wanted a global standard to connect a fiber optic network • SONET first proposed by Bellcore, in 1984 • Synchronous Digital Hierarchy (SDH) was used in Europe • Agreement was made in 1998 to merge the two similar standards

  3. SONET Protocol Hierarchy

  4. STS-1 Building BLock

  5. STS-1 Building BLock • Basic building block of SONET • Rate 51.84Mbps usually depicted 9 rows X 90 columns = 810 8bit bytes • With a rate of 8000 frames/sec. Each frame has a duration of 125 microseconds. • At 6480 bits per frame x, 8000 frames a second equals 51,840,000bps or 51.84Mbps

  6. SONET Cell Mapping

  7. SONET Topologies • Point-to-Point • 2 devices connected by optical fiber • Entry level PTE for an organization • Inputs/Outputs identical

  8. SONET Topologies • Point-to-Multipoint • Uses Add-Drop Multiplexing (ADM) to drop circuits off along the way • Suitable for large national corporate networks

  9. SONET Topologies • Hub & Spoke • Accommodates unexpected growth or change more easily than point-to-point • Hub concentrates traffic at a central site to allow for easy reprovisioning of the circuits

  10. SONET Topologies • Ring • ADM is building block for SONET ring architecture. • Multiple ADMs within a ring topology can either be bidirecitonal or unidirectional • Main advantage is survivability - if a fiber cable is cut, the multiplexers have the intelligence send via an alternative path through the ring without interruption

  11. ADM ADM DCC ADM DCC ADM ADM ADM SONET Ring

  12. Synchronous Digital Hierarchy (SDH) • European Standard analogous to the North American SONET • Basic building block is the STM-1 Frame that consists of: • 270 columns x 9 rows = 2430 octets • 9 columns x 9 rows = 81 octet section overheads • Will be discussed in next lecture(14-05-2005)

  13. SONET over WDM • SONET • Single wavelength optical network. • Uses fiber as transmission media, • Does all switching, routing, processing electronically. Wavelength Division Multiplexing (WDM) • Wavelength routing • Carry multiple wavelengths in a single fiber

  14. WADM λ1 WADM WADM λ3 WADM SONET over WDM Complete it?

  15. Plesiochronous Transmission • Means “almost synchronous” • Bits are stuffed into the frame as padding when various occur on the timing of the line • Factors that affect transmission rates over fiber optic lines: • Temperature differences along the cable can affect light signaling and clock timing • Photonic and Laser technology is a limiting factor in the evolution of higher data rates over SONET

  16. Benefits of SONET • Pointers, MUX/DEMUX • SONET allows very flexible allocation and alignment of payload within transmission envelop. • Reduced Back-to-Back Multiplexing • Because of synchronization, an entire optical signal does not have to be demultiplexed – only the VT or STS signals need to be accessed. • Optical Interconnectivity • Allows interconnection between network providers regardless of equipment manufacturer.

  17. Benefits of SONET • Multipoint Configurations • Network providers no longer need to own and maintain customer-located equipment • ATM • Because of the bandwidth capacity offered by SONET, it is a logical carrier for ATM • Grooming • SONET networks can eliminate inefficient techniques like back-hauling, which is expensive to do on asynchronous systems • SONET can also conveniently segregate switched and non-switched traffic.

  18. Benefits of SONET • Reduced Cabling & Elimination of DSX Panels • SONET allows for hub configuration, reducing the need for back-to-back terminals • Enhanced OAM&P • Remote positioning provides centralized maintenance, reduced travel for maintenance personnel, hence reduced savings. • Enhanced Performance Monitoring • SONET allows for quicker troubleshooting and detection of failures before they because of the substantial overhead information.

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