Contents Communications Theory Parallel vs serial transmission Transmission

Contents • Communications Theory – Parallel vs. serial transmission – Transmission Capacity (Shannon) – Error detection and correction • Communications Media – Optical fibers – Coaxial cables – Twisted pairs – Wireless Postacademic Interuniversity Course in Information Technology – Module C 1 p 1

Snell’s Law sin 1 sin 2 2 n 1 n 2 n 1 1 c = n 2 n 1 > c n 2 < n 1 Postacademic Interuniversity Course in Information Technology – Module C 1 p 2

Optical Fibers (step index) n 2 < n 1 n 2 n 1 Protective coating Postacademic Interuniversity Course in Information Technology – Module C 1 p 3

Multimode Fiber Diameter : > 50 Step index fiber Graded index fiber Low cost but limited bandwidth * distance due to multimode dispersion Postacademic Interuniversity Course in Information Technology – Module C 1 p 4

Multimode Dispersion t t Step index fiber : < 50 MHz. Km Graded Index Fiber : < 1000 MHz. Km (1990) < 5000 MHz. Km (2000) Postacademic Interuniversity Course in Information Technology – Module C 1 p 5

Monomode Fiber Diameter : < 5 Only one propagation mode possible Higher cost due to end equipment but enormous bandwidth*distance product 10 Gb/s over 500 Km optical sections (1995) Postacademic Interuniversity Course in Information Technology – Module C 1 p 6

Wave Domain Multiplexing Each color can carry an independent data flow. In 2000 40 colors carrying each 10 Gb/s or 80 colors carrying each 2. 5 Gb/s were commercially available Postacademic Interuniversity Course in Information Technology – Module C 1 p 7

Optical amplifiers Pump laser Erbium doped fiber Erbium atoms are pumped into a higher energy state by the light of the pump laser, they fall back in synchronism with the incoming light, amplifying it. Postacademic Interuniversity Course in Information Technology – Module C 1 p 8

Optical Switching From IEEE Com. Mag. V 39, N 1, Jan 2001. Postacademic Interuniversity Course in Information Technology – Module C 1 p 9

Contents • Communications Theory – Parallel vs. serial transmission – Transmission Capacity (Shannon) – Error detection and correction • Communications Media – Optical fibers – Coaxial cables – Twisted pairs – Wireless Postacademic Interuniversity Course in Information Technology – Module C 1 p 10

Coaxial Cables Insulator Conductor Protective coating Monomode propagation for all data applications Transmission rates up to some Gb/s Distance limited by electrical attenuation Postacademic Interuniversity Course in Information Technology – Module C 1 p 11

Contents • Communications Theory – Parallel vs. serial transmission – Transmission Capacity (Shannon) – Error detection and correction • Communications Media – Optical fibers – Coaxial cables – Twisted pairs – Wireless Postacademic Interuniversity Course in Information Technology – Module C 1 p 12

Twisted Pairs Performance highly dependant on cable quality Transmission speed up to several 100 Mb/s for distances of up to 100 m. with better cables (class 5 or 6) Postacademic Interuniversity Course in Information Technology – Module C 1 p 13