Network Connections in Software Drawer qr-codes in Software Network Connections

Network Connections using software topaint qr-code for web,windows application isbn 13 Last, in the TDM/T-WDMA c Software QR Code JIS X 0510 ase, LCs must be sorted out by combined actions at the -channel level (receiver tuning) and at the transmission channel level (time division demultiplexing). These connectivity alternatives reappear, coupled with the added possibilities of switching optical paths, as we examine the properties of LLNs..

Routing and Channel Assignment The two constraints on op Software qrcode tical connections applicable to wavelength-routed networks (wavelength continuity and distinct channel assignment) also apply to LLNs. But when each waveband contains multiple channels (a condition unique to LLNs), additional constraints apply within each waveband. These are r Inseparability: Channels combined on a single ber and situated within the same waveband cannot be separated within the network.

r Distinct source combining (DSC): Only signals from distinct sources are allowed to be combined on the same ber. Inseparability is a consequence of the fact that the LDCs operate on the aggregate power carried within each waveband without distinguishing among signals on different channels within the band; that is, inseparability is a condition imposed by the architecture of the optical switch combined with the choice of channel spacing. Figure 3.

21(a) illustrates inseparability. It shows two point-to-point optical connections (1, 1 ) and (2, 2 ) assumed to be within the same waveband. Connection (1, 1 ) is routed via the minimum-hop path 1, 1 comprising nodes A B C F G, and connection (2, 2 ) is routed along its own minimum-hop path via nodes A B D E.

The label Si on a link in Figure 3.21 denotes a signal generated at a source station i. Observe that power from both sources is combined on ber a.

Thus, the DCA condition requires them to be on distinct channels. For example, they might be carried on different wavelengths within the same waveband (WDMA) or on the same wavelength but in different time slots (TDMA). Because the two signals are in the same waveband, they cannot be separated at node B.

Thus, to route them both to their destinations, node B must multicast both signals to nodes C and D, expanding the intended point-to-point paths to multicast optical paths 1, {1 , 2 } and 2, {1 , 2 } an unavoidable result of inseparability. Note the appearance of unintended destinations (underlined). We call these unintended destinations fortuitous destinations and refer to the unintended paths as fortuitous paths.

In Figure 3.21, intended paths are shown as solid lines and fortuitous paths are indicated with dashed lines. These extra paths may potentially cause interference at the receivers.

However, as long as the DCA condition is observed, interference among superimposed channels can be avoided by tuning in the desired channel and tuning out the undesired one. For example, in the case of WDMA this would mean tuning the optical receiver to select the correct wavelength and reject any others, implying that the selectivity is implemented in the -channel layer. However, if TDMA is used to distinguish the superimposed channels, the receiving station would select the intended.

Multiwavelength Optical Networks 1 A a B D 1* C F E S2 (a) S1 G S2 S1 2*. 1 S1 A S2 a B D E C F S1 G 3* 3 (b) S2 2*. Figure 3.21 Inseparability. channel in its RP by capt Software QR Code 2d barcode uring information in the proper time slots. In this case, selectivity is implemented in the transmission channel layer.21 Inseparability causes connections that share a common ber on a common waveband to branch out of their original paths, fanning out onto an optical path in the form of a directed tree, with new, fortuitous destinations added to the tree as new paths are activated within the same waveband.

The set of destinations (both intended and fortuitous) for each source consists of all destinations downstream on the tree from that source. Fortuitous destinations tend to waste ber resources and power and are therefore to be avoided if possible. In this case, the fortuitous destinations could have been avoided by rerouting (2, 2 ) on a longer path, via node H , as shown in Figure 3.

21(b). Inseparability does not apply to connections in different wavebands, which are routed independently of one another. Thus, fortuitous paths associated with inseparability do not exist in wavelengthrouted networks.

In WRNs all optical paths are point-to-point so connections from different source stations on the same wavelength are never combined on the same ber. Now let us examine the distinct source combining constraint.22 The DSC condition forbids a signal from splitting, taking multiple paths in the network, and then recombining with itself.

Figure 3.22 shows two ways a source may combine with itself. In Figure 3.

22(a), the signal power is split into two parallel paths and then later recombined. Fortuitous paths occurred in the broadcast star example of Figure 3.2 without referring to them as such. For example, using WDM/WDMA, all signals reach all three destination stations, but each signal is only intended for one of them.

Without calling it by that name, the DSC requirement was invoked in Section 2.3.1.

1 in discussing power relations in directional couplers..
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