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. 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

SONET Protocol Hierarchy

STS-1 Building BLock

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

SONET Cell Mapping

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

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

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

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

SONET Ring DCC ADM

9 columns x 9 rows = 81 octet section overheads 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)

SONET over WDM SONET Wavelength Division Multiplexing (WDM) 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

SONET over WDM WADM λ3 λ1 Complete it?

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

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.

Benefits of SONET Multipoint Configurations ATM Grooming 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.

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.