Journal of Emerging Technologies in Web Intelligence Contents

JOURNAL OF EMERGING TECHNOLOGIES IN WEB INTELLIGENCE, VOL. 2, NO. 2, MAY 2010 143proposed and studied in the literature. Figure 1 illustratesa structure of multistage interconnection network, whichare representatives of a general class of networks. Thisfigure shows the connection between p inputs and boutputs, and connection between these is via number ofstages. Multistage interconnection network is actually acompromise between crossbar and shared bus networksof various types of multiprocessor interconnectionsnetworks [1]. Multistage interconnection networksattempt to reduce cost and decrease the path lengthspeed mismatch occur due to the high speed of opticalsignals. The second approach is all-optical switching.This has removed the problem that occurred with thehybrid approach but, such systems will not becomepractical in the future and hence only hybrid opticalMINs are considered. In hybrid optical MINs, theelectronically controlled optical switches, such as lithiumniobate directional couplers, can have switching speedsfrom hundreds of picoseconds to tens of nanoseconds.A. Switching in optical networksIn optical networks, circuit switching is used. Packetswitching is not possible with Optical MultistageInterconnection Networks. If packet switching is used,the address information in each packet must be decodedin order to determine the switch state. In a hybrid MIN, itmeans it require conversions from optical signals toelectronic ones, which could be very costly [4]. For thisreason, circuit switching is usually preferred in opticalMINs.Figure 1: A MultistageNetworkMINsTABLE IPROPERTIES OF DIFFERENT INTERCONNECTIONTECHNIQUESOPTICALELECTRONICProperty Bus Crossbar MultistageSpeed Low High HighCost Low High ModerateReliability Low High HighConfigurability High Low ModerateComplexity Low High ModerateHYBRIDGUIDEDWAVEALL OPTICSSPACEOPTICSIII. OPTICAL MULTISTAGE INTERCONNECTIONNETWORKSAn optical MIN can be implemented with either freespaceoptics or guided wave technology. It uses the TimeDivision Multiplexing. To exploit the huge opticalbandwidth of fiber, the Wavelength DivisionMultiplexing (WDM) technique can also be used. WithWDM, the optical spectrum is divided into manydifferent logical channels, and each channel correspondsto a unique wavelength. Optical switching, involves theswitching of optical signals, rather than electronic signalsas in conventional electronic systems. Two types ofguided wave optical switching systems can be used [5].The first is a hybrid approach in which optical signals areswitched, but the switches are electronically controlled.With this approach, the use of electronic control signalsmeans that the routing will be carried out electronically.As such, the speed of the electronic switch control signalscan be much less than the bit rate of the optical signalsbeing switched. So, with this approach there is a bigFigure 2: Types of Multistage NetworksB. Comparison of Electronic and Optical NetworksThere are lots of benefits of optical networks overthe electronic ones. The main benefit of the opticalnetworks over the electronic network is the high speed ofthe Optical signals. In the optical networks light istransmitted which has a very good speed but in theelectronic Multistage interconnection networks electricityis used which has very slow speed. The second advantageis the Bandwidth. Now a day’s applications incommunication require high bandwidth, the opticalnetworks gives combination of very high bandwidth andlow latency. Therefore, they have been used in theparallel processing applications. Optical MINs are alsoused in wide area networks, which require less errorprobability and very high bandwidth. Fiber optic© 2010 ACADEMY PUBLISHER