DES. See Data Encryption current distribution, 235 Standard radiation from, 228-230, Database integrity in SDH Deygout knife edge diffraction 283-284 networks, 340 method, 239-240, 242 Dirac impulses, 10-11 D layer in ionosphere, 266 DFEs. See Decision Feedback Direct-detection optical systems, Data channels (D-channels), Equalizers 167, 198 373-374 D flip-flops, 19 Direct Sequence Spread Data Communication Equipment Diagnostic Rhyme Test (DRT), 7 Spectrum (DSSS), 105 (DCE), 366, 369 Dielectric media, 112-113, 126, Directivity of antennas, 279-280, Data Encryption Standard (DES), Differential delay Discard-Eligible (DE) packets, Data Link Connection Identifiers multimode fibers, 122-123 (DLCIs), 368-369 virtual concatenation, 348 Discrete Cosine Transform Data Terminal Equipment (DTE), Differential Group Delay (DGD) (DCT), 61, 64-66, 71 PMD, 191-193 Dispersion, 33 Data transmission. See single-mode fibers, 129-130 chromatic. See Chromatic Transmission Differential Phase Shift Keying dispersion DCE. See Data Communication (DPSK), 40 multimode fibers, 122, 127 Equipment Differential Pulse Code Modu- optical fibers, 118-120 DCF. See Dispersion- lation (DPCM), 6, 61-62 single-mode fibers, 127-131 Compensating Fiber Differentiated Services (DiffServ) Dispersion-Compensating Fiber D-channels, 373-374 technique, 78, 392-393 (DCF), 184-185 DCMs. See Dispersion- Diffraction Dispersion-Compensating Compensating Modules Fresnel, 223-225 Modules (DCMs), 184-185 DCSs. See Digital Cross-Connect knife edge, 238-240, 242 Dispersion management, 182-185 Systems over sea paths, 240 Dispersion maps, 182, 209 DCT. See Discrete Cosine surface, 240 Dispersion-Shifted Fiber (DSF), 4, Transform DiffServ Code Points (DSCPs), DE. See Discard-Eligible packets 392-393 Dissipation losses, 232-233, 280 Decision decoding, 90 Digital cellular networks, 7 Distance in block coding, 89 Decision Feedback Equalizers Digital Cross-Connects (DXCs), Distortion (DFEs), 196 aliasing, 11-13 Decoders Digital Cross-Connect Systems delay, 41 channel noise pow