OPTICAL SWITCHING BY SURYA ANJANI.Y. COMMUNICATION SYSTEMS MANIPAL UNIVERSITY-DUBAI B.E.ECE( )

WHAT IS AN OPTICAL SWITCH? DEFINITION: A switch that enables signals in optical fibers or integrated optical circuits (IOCs) to be selectively switched from one circuit to another. OPERATION:  MECHANICAL MEANS such as physically shifting an optical fiber to drive one or more alternative fibers.  ELECTRO-OPTIC EFFECTS, MAGNETO-OPTICS, or other methods. TYPES OF OPTICAL SWITCHES(SPEED):  Slow optical switches, such as those using moving fibers, may be used for ALTERNATE ROUTING of an optical transmission path, e.g., routing around a fault.  Fast optical switches, such as those using electro-optic or magneto-optic effects, may be used to perform logic operations.

“SYSTEMS WHICH PERFORM THE FUNCTION OF OPTICAL SWITCHING BY PHYSICALLY SWITCHING LIGHT ARE REFERRED TO AS PHOTONIC.”

OPTICAL NETWORKS  A data network built on fiber-optics technology, which sends data digitally, as light, through connected fiber strands.  OPTICAL NETWORKS TYPES: 1)SDH/SONET SYSTEM 2)OEO(OPAQUE OPTICAL NETWORK) 3)OPTICAL NETWORKS WITH VARYING DEGREE OF TRANSPARENCY. 4)ALL-OPTICAL NETWORKS.

OPTICAL NETWORKS WITH VARYING DEGREE OF TRANSPARENCY  WDM(WAVELENGTH DIVISION MULTIPLEXING) AND OPTICAL SWITCHING ARE USED.  SWITCH AND NETWORK CONTROL IS CARRIED OUT BY ELECTRONICS.  CLASSIFIED IN TO 3 TYPES: i)If all nodes utilize opto-electronics conversion, the network becomes OPAQUE(OEO). ii)If no nodes utilize opto-electronics conversion, the network becomes TRANSPARENT. iii)Between both extremes is PARTIALLY TRANSPARENT.

ALL-OPTICAL NETWORKS NETWORKS WHERE ALL THE OPERATIONS AND FUNCTIONS,INCLUDING SWITCH CONTROL & NETWORK CONTROL,WOULD BE PERFORMED OPTICALLY. ALL OPTICAL SWITCH

 TRANSPARENCY INVOLVES THE NETWORK BEING ABLE TO TRANSFER ANY TYPE OF INFORMATION WITHOUT REGARD TO PROTOCOL AND CODING FORMATS,DATA RATES AND MODULATION TECHNIQUES.  ADVANTAGES:  Enables the optical network to support variety of higher layers concurrently.  Enables network to be designed cost-effectively.  Evolve easily in future together with protocols and technologies. MEMS BASED-ALL OPTICAL SWITCH

OPTICAL SWITCHING  OPTICAL CIRCUIT SWITCHING  OPTICAL PACKET SWITCHING  OPTICAL BURST SWITCHING

OPTICAL CIRCUIT SWITCHING In OCS, the network is configured to establish a circuit, from an entry to an exit node, by adjusting the optical cross connect circuits in a manner that the data signal can travel in an All-optical manner. When OCS is based on light path,it is called as OWS(optical wavelength switching). OPTICAL CIRCUIT SWITCH

 DISADVANTAGES  DATA TRAFFIC.  The circuits require time to set up and to destroy.  When the circuit is established, there sources will not be efficiently used due to the unpredictable nature of network traffic.

OPTICAL PACKET SWITCHING  MUST BE ALL-OPTICAL.  It requires a Packet header, header processing.  Control is fully performed in optical domain on a packet-by packet basis.  Increased bandwidth compared to optical circuit switching.  Supports bursty data traffic more efficiently than OCS by means of statistical multiplexing.

 Unlike OBS, OPS does not require burst assembly algorithms, separate control wavelength channel, nor any offset time.  OPS networks face challenges due to lack of optical RAM & difficulty to execute complex computations & logical operations using only optics & photonics without OEO conversion.  General optical packet format consists of :  Header  Payload  Additional guard bands before & after payload OPTICAL PACKET FORMAT

OPTICAL BURST SWICTHING Introduced as a compromise of OCS and OPS. OBS is packet based and hence more bandwidth efficient than OCS. Technological requirements to implement OBS are relaxed as compared to OPS. In OBS network, packets are assembled into larger data bursts(DB).For every burst,a burst header project(BHP),DB assembly and BHP generation is created in OBS edge nodes. Each DB/BHP pair is routed to their destination through the nodes. The burst is transmitted over a data channel and BHP is sent over a dedicated control channel to the same node. While data bursts switch optically,BHPS are converted to the electrical domain for processing and converted back to optical domain to transfer to the next node.

OPTICAL BURST SWITCH

SWITCHING TYPE TECHNOLOGIES/OPTICAL SWITCHES  MECHANICAL SWITCH  Each individual fiber is manually moved.  optical fiber is physically moved to drive alternate fibers.  Physically shifting an optical fiber to drive one or more alternative fibers.  ELECTRO-OPTIC SWITCH  Change in electric field that varies slowly in comparison to the speed or intensity of light.

 MAGNETO-OPTIC SWITCH By use of electro-magnetic forces, the switch can be made to transfer the data from one fiber to the other.  THERMO-OPTIC SWITCH Utilizes thermo optic effect in optical waveguides.(main materials are silica and polymers)  ACOUSTIC-OPTIC SWITCHING  It employs the acousto-optic effect.  In acousto-optic Q-switches, an ultrasonic wave is launched into a block of transparent optical material, usually fused silica. By switching on the acoustic field,a fraction of the energy of the main beam is diffracted out of the resonator, that prevents laser action(due to loss).  When acoustic field is switched off, full transmission through the Q-switch cell is restored and a laser pulse is created.

 IMPORTANCE OF OPTICAL SWITCHING 1.LESS CROWDED NETWORK 2.REDUCED PROTOCOL ISSUES 3.INCREASED BANDWIDTH 4.INCREASED DISTANCE 5.WIDE RANGE OF USE  APPLICATIONS  COMPUTER AND NETWORKING PURPOSES.  PHONE SYSTEMS  LIGHTENING AND STORMS  OADM(OPTICAL ADD/DROP MULTIPLEXERS)  OXC(OPTICAL CROSS-CONNECTS)  PROTECTION SWITCHING

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