SINGLE-MODE AND MULTI MODE TRANSMISSION

Fibre Optic Cable has two types of transmission modes these are Multi-mode and Single-mode, the difference between these two modes are the amount of fibres. Multi-mode has, as the name suggests multiple fibres, this means multi modes of propagation for the rays of light. These range from low order mode to high order mode, the low order mode take the most direct path, straight down the middle. The high order mode takes the longest path, as they bounce from one side to the other all the way down the fibre. This scatters the signal because the rays form one pulse of light, arrive at the far end at different times this is know as Intermodal Dispersion. The “best way to get rid of this Intermodal Dispersion was to only allow one mode of propagation. So a smaller core size means higher bandwidth and greater distance. (Network Cabling Help (online), 2001, http://www.datacottage.com/nch/fibre.htm [Accessed 14th March 2002])” This is known as Single-mode fibre. The single mode cable can transmit data at 2 giga bytes per second, this speed will continue to increase as the technology for encoding and decoding devices improve. Also du to the lack of standardized connectors and the lack of personal trained in splicing techniques, the cost of this technology is very high, but the cost will soon decrease as the development of standardized connectors increases, it will then cost roughly the same as twisted pair cable.