Fiber Optic Communication By

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Fiber Optic CommunicationBy

• Engr. Muhammad Ashraf Bhutta

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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

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SONET Protocol Hierarchy
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STS-1 Building BLock
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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

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SONET Cell Mapping
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SONET Topologies

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

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SONET Topologies

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

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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

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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

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SONET Ring
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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)

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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

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SONET over WDM
Complete it?
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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

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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.

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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.

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Benefits of SONET

• Reduced Cabling Elimination of DSX Panels
• SONET allows for hub configuration, reducing the
  need for back-to-back terminals
• Enhanced OAMP
• 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.