Postacademic Interuniversity Course in Information Technology – Module C1p1 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 C1p2 Snell’s Law sin  1 sin  2 = n2n1n2n1 22 11 n2n2 n1n1   cc n2n2 n1n1 >c>c n2n2 n1n1 n2 < n1

Postacademic Interuniversity Course in Information Technology – Module C1p3 Optical Fibers (step index) n1n2 n2 < n1 Protective coating

Postacademic Interuniversity Course in Information Technology – Module C1p4 Multimode Fiber Diameter : > 50  Low cost but limited bandwidth * distance due to multimode dispersion Step index fiber Graded index fiber

Postacademic Interuniversity Course in Information Technology – Module C1p5 Multimode Dispersion Step index fiber : < 50 MHz.Km Graded Index Fiber : < 1000 MHz.Km (1990) < 5000 MHz.Km (2000) t t

Postacademic Interuniversity Course in Information Technology – Module C1p6 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 C1p7 Wave Domain Multiplexing Each color can carry an independent data flow. In 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 C1p8 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 C1p9 Optical Switching From IEEE Com.Mag.V39,N1, Jan 2001.

Postacademic Interuniversity Course in Information Technology – Module C1p10 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 C1p11 Coaxial Cables Protective coating Insulator Conductor 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 C1p12 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 C1p13 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)