Georgia Tech - PSYC - 6750

Georgia Tech - PSYC - 6750

Georgia Tech - PSYC - 6750

Georgia Tech - PSYC - 6750

Georgia Tech - PSYC - 6750

Georgia Tech - PSYC - 6750

Georgia Tech - PSYC - 6750

Georgia Tech - PSYC - 6750

Georgia Tech - PSYC - 6750

Georgia Tech - ECE - 6543

Georgia Institute of TechnologyFiber Optic NetworksLecture 1 Stephen Ralph Stephen E. Ralph Spring 2011Georgia Institute of TechnologyECE6543 S. E. RalphMeeting Time and Place:MWF 9:00-10:00pm, C341 Van LeerInstructor:Stephen E. Ralph Office: TSRB

Georgia Tech - ECE - 6543

2Introduction to Optical Networkscost of bandwidth. This reduced cost of bandwidth in turn spurs the development of a new set of applications that make use of more bandwidth and affects behavioral patterns. A simple example is that as phone calls get ch

Georgia Tech - ECE - 6543

1.4The Optical Layer15Optical networks based on the architecture described above are already being deployed. OLTs have been widely deployed for point-to-point applications. OADMs are now used in long-haul and metro networks. OXCs are beginning to be de

Georgia Tech - ECE - 6543

22Introduction to Optical Networks1.5Transparency and All-Optical NetworksA major feature of the lightpath service provided by second-generation networks is that this type of service can be transparent to the actual data being sent over the lightpath

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24Introduction to Optical NetworksOEOAll-optical subnet l2 l1 LightpathOEOWavelength conversion OEORegeneration OEO Adaptation OEO l1l2All-optical subnetAll-optical subnet OEOFigure 1.10 An optical network consisting of all-optical subnetworks i

Georgia Tech - ECE - 6543

26Introduction to Optical NetworksThe mission of optical packet switching is to enable packet-switching capabilities at rates that cannot be contemplated using electronic packet switching. However, designers are handicapped by several limitations with r

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30Introduction to Optical Networksand ( )dB = 30 dB. In this context, a signal being attenuated by a factor of 1000 would equivalently undergo a 30 dB loss. A signal being amplied by a factor of 1000 would equivalently have a 30 dB gain. We usually meas

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48Propagation of Signals in Optical FiberFinally, the phemomena discussed in this chapter also apply to various components. Some of these components are designed not to minimize effect on the propagating signal but rather to produce some desired interac

Georgia Tech - ECE - 6543

2.2Intermodal Dispersion51(ZiFr4 ) in order to realize the low loss that is potentially possible by operating at these wavelengths [KK97, p. 69].2.1.1Bending LossOptical bers need to be bent for various reasons both when deployed in the eld and part

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58Propagation of Signals in Optical Fiberplanned for the future. An important type of laser used for these applications is the vertical cavity surface-emitting laser (VCSEL; see Subsection 3.5.1). These lasers transmit at 850 nm and up to 10 Gb/s. VCSEL

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70Propagation of Signals in Optical Fiber2.4Chromatic DispersionDispersion is the name given to any effect wherein different components of the transmitted signal travel at different velocities in the ber, arriving at different times at the receiver. W

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78Propagation of Signals in Optical Fiberstandard single-mode ber but has a higher refractive index. This leads to a large negative chromatic dispersion. This core is surrounded by a ring of lower refractive index, which is in turn surrounded by a ring

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2.6Solitons99ber. Its effects in positive chromatic dispersion ber can be minimized by using lower power levels. (In the next section, we will see that due to the same interaction between SPM and chromatic dispersion that causes modulation instability,

Georgia Tech - ECE - 6543

2.7Other Fiber Technologies103transmission in a 25-channel WDM system at a bit rate of 40 Gb/s per channel, over a distance of 1500 km, has been demonstrated in the laboratory [SKN01].2.7Other Fiber TechnologiesWe will discuss two ber types that are

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114ComponentsInput 1Output 1Fibers or waveguides l (coupling length)Input 2Output 2Figure 3.1 A directional coupler. The coupler is typically built by fusing two bers together. It can also be built using waveguides in integrated optics.3.1Coupler

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118Componentswhere I is the identity matrix. Note that this relation follows merely from conservation of energy and can be readily generalized to a device with an arbitrary number of inputs and outputs. For a 2 2 directional coupler, by the symmetry of

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3.3Multiplexers and Filters121SWP SOP Fiber inFaraday rotator/2 plateSWPFiber out (a)SWP Fiber inFaraday rotator/2 plateSWPFiber out (b)Figure 3.5 A polarization-independent isolator. The isolator is constructed along the same lines as a pola

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3.4Optical Ampliers157any periodic lter can be used as an interleaver by matching its period to the desired channel spacing. For example, a ber-based Mach-Zehnder interferometer is a common choice. These devices are now commercially available, and inte

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172Components3.5TransmittersWe will study many different types of light sources in this section. The most important one is the laser, of which there are many different types. Lasers are used as transmitters as well as to pump both erbium-doped and Ram

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198ComponentsFigure 3.61 Block diagram of a receiver in a digital communication system.3.6DetectorsA receiver converts an optical signal into a usable electrical signal. Figure 3.61 shows the different components within a receiver. The photodetector

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3.7Switches205front-end amplier can handle. This may not be an important consideration for many optical communication links since the power level seen by the receivers is usually more or less xed. However, dynamic range of the receivers is a very impor

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3.8Wavelength Converters221the interconnections are not difcult. However, practical considerations of power dissipation and board space dictate the necessity for having multiple printed circuit boards and perhaps multiple racks of equipment. The interc

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248Modulation and DemodulationIn practice, the NRZ format is used in most high-speed communication systems, ranging from speeds of 155 Mb/s to 10 Gb/s. Scrambling is widespread and used in most communication equipment ranging from PC modems to high-spee

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4.3Spectral Efciency251allow a small clipping probability (a few percent), which substantially reduces the power requirement while introducing only a small amount of signal distortion.4.2.2Applications of SCMSCM is widely used by cable operators tod

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256Modulation and DemodulationPhotodetectorFront-end amplifierReceive filter Clock/timing recoverySamplerDecision circuitFigure 4.5 Block diagram showing the various functions involved in a receiver.turn impose additional limits on channel capacit

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4.5Error Detection and Correction273Input signal w0t w1t w2t w3t w4SummerOutput signalFigure 4.12 A transversal lter, a commonly used structure for equalization. The output (equalized) signal is obtained by adding together suitably delayed versi

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290Transmission System EngineeringTransmitter TransmitterReceiver Receiver Power amplifier Mux Line amplifier Preamplifier DemuxTransmitter.ReceiverFigure 5.1 Components of a WDM link.margin provided in the system. Usually the required bit error r

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292Transmission System Engineeringset its threshold at the average received power and would have a somewhat higher bit error rate. However, the power penalties turn out to be the same in both cases. This penalty is given by PPsig-dep = 5 log P1 P1 . (5.

Georgia Tech - ECE - 6543

294Transmission System EngineeringNote that on the one hand this penalty represents the decrease in signal-to-noise ratio performance of a system with a nonideal extinction ratio relative to a system with innite extinction ratio, assuming the same avera

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5.5Optical Ampliers295Table 5.2 Typical sensitivities of different types of receivers in the 1.55 m wavelength band. These receivers also operate in the 1.3 m band, but the sensitivity may not be as good at 1.3 m.Bit Rate 155 622 2.5 2.5 10 10 40 Mb/s

Georgia Tech - ECE - 6543

304Transmission System Engineeringl90% Data channels 10% 10%90% Data channelsl Loop filterFigure 5.8 Optical automatic gain control circuit for an optical amplier.loop is encountered with ampliers in the loop, and the total gain in the loop is comp

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314Transmission System Engineeringare concerned only with one channel, we could align the center wavelengths exactly by temperature-tuning the individual mux/demuxes. However, other channels could become even more misaligned in the process (tuning one c

Georgia Tech - ECE - 6543

328Transmission System EngineeringTo understand how PMD can be compensated optically, recall that PMD arises due to the ber birefringence and is illustrated in Figure 2.7. The transmitted pulse consists of a fast and a slow polarization component. The p

Georgia Tech - ECE - 6543

5.9Wavelength Stabilization3415.9Wavelength StabilizationLuckily for us, it turns out that the wavelength drift due to temperature variations of some of the key components used in WDM systems is quite small. Typical multiplexers and demultiplexers ma

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342Transmission System Engineeringcurrent to be increased as the laser ages, inducing a small wavelength shift. With typical channel spacings of 100 GHz or thereabouts, this is not a problem, but with tighter channel spacings, it may be desirable to ope

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5.11 Design of Dispersion-Managed Soliton Systems343Here, the distance and time are measured in terms of the chromatic dispersion length of the ber and the pulse width, respectively. The pulse U (, + )ei(t+2 /2(5.29)is also a soliton for any frequen

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5.12 Overall Design Considerations347Note from Figure 5.34 that the NRZ system is not sensitive to the excess local chromatic dispersion. This is because the NRZ system essentially operates in the linear regime. Note also that the DM soliton system can

Georgia Tech - ECE - 6543

6.1SONET/SDH371Table 6.1 Transmission rates for asynchronous and plesiochronous signals, adapted from [SS96].Level 0 1 2 3 4 North America 0.064 Mb/s 1.544 Mb/s 6.312 Mb/s 44.736 Mb/s 139.264 Mb/s Europe 0.064 Mb/s 2.048 Mb/s 8.448 Mb/s 34.368 Mb/s 13

Georgia Tech - ECE - 6543

6.2Optical Transport Network389All-optical Optical layer Optical Broadband SONET layer Wideband NarrowbandWavelength, waveband, fiber grooming STS-48 grooming DS3 grooming DS1 grooming DS0 groomingFigure 6.9 Different types of crossconnect systems.t

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396Client Layers of the Optical Layermix of ODU1s and ODU2s can be multiplexed into an ODU3. OTN also supports virtual concatenation. Here, we will limit the discussion to the OTN frame of an ODU2 carrying four ODU1s. OTU2 frames are organized into mult

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6.4Ethernet399Point-to-pointBusStarMeshFigure 6.14 Ethernet topologies.GFP Client-Specic AspectsA client-specic function is the mapping of client signals to a GFP frame using a frame mapped GFP (GFP-F) or a transparent mapped GFP (GFP-T). As we m

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6.5IP411MPLS, PBB-TE connections can be routed to efciently utilize network bandwidth or to achieve certain performance criteria such as maximum latencies, minimum throughput, or maximum loss rates. Note that resources can be provisioned to guarantee s

Georgia Tech - ECE - 6543

6.6Multiprotocol Label Switching415to improve this state of affairs so as to offer some quality-of-service (QoS) assurance to the users of the network. Within IP, a mechanism called Diff-Serv (differentiated services) has been proposed. In Diff-Serv, p

Georgia Tech - ECE - 6543

6.7Resilient Packet Ring421connection. T-MPLS reuses the architecture of MPLS and simplies it for transport. It adds features to support bidirectional connections, since MPLS is a unidirectional technology. Since T-MPLS connections are expected to have

Georgia Tech - ECE - 6543

6.8Storage-Area Networks425its local fair rate, node k sends this rate to its upstream nodes. An upstream node will then limit its own ingress trafc rate with node k s local fair rate. In this way, node k can reduce the ingress trafc rate of upstream n

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436WDM Network ElementsNon ITU l IP router Non ITU l SONET SONETTransponder O/E/O O/E/OITU l1 Mux/demux ITU l2 ITU l3 l1 l2 l3 lOSC Laser Receiver Optical line terminal lOSCFigure 7.2 Block diagram of an optical line terminal. The OLT has wavelength

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438WDM Network Elementsl1, l2, . . ., lW lOSC Raman pump laser ReceiverDispersion compensator OADM lOSCGain stageGain stageLaserFigure 7.3 Block diagram of a typical optical line amplier. Only one direction is shown. The amplier uses multiple erbiu

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452WDM Network ElementsWe can modify the two example architectures in Figure 7.9 by replacing the power splitters with 1 N WSSs. For these designs as well as the designs in Figure 7.8, using WSSs rather than optical splitters or couplers has the advanta

Georgia Tech - ECE - 6543

476Control and Management8.2Optical Layer Services and InterfacingThe optical layer provides lightpaths to other layers such as the SONET/SDH, IP/MPLS, and Ethernet layers, as well as the electronic layer of the Optical Transport Network (OTN), which

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478Control and ManagementElectronic layer OTU OCh Optical layer OMS OTS OTS OMSODU OTU OCh OMS OTS OTSOLTOADMAmplifier Transponders/regeneratorsFigure 8.2 Layers within OTN. The optical layers are the optical channel layer (OCh), optical multiplex

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8.4Multivendor Interoperability479Thus, a 10 Gb/s connection between two nodes that is carried through without any electronic multiplexing/demultiplexing would be considered a lightpath. Each link between OLTs or OADMs represents an optical multiplex s

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8.5Performance and Fault Management481equipment from a single vendor. For example, a subnet could simply be a WDM link with some intermediate add/drops. Therefore, a service provider could deploy vendor As equipment on one link and vendor Bs equipment