SELECTION OF OPTICAL FIBER

Introduction:

Optical fibers are normally classified into two types, Single Mode Optical Fibers and Multi Mode Optical fibers, according to the number of modes the fiber carries. Further, Single mode optical fibers are classified into 3 categories by International Telecommunication Union (ITU). These fibers are differentiated by the Chromatic dispersion.

a.G.652-Dispersion Un-shifted Single Mode Fiber, also called as            Standard Single Mode Fiber.
b.G-653-Dispersion Shifted Single Mode Fiber.
c.G.655-Non Zero Dispersion Shifted Single Mode Fiber.

Since the invention of Single Mode fibers in early 1970s, Standard Single Mode Fibers were widely deployed in Telecom networks with Single Channel transmission at 1310nm. During 1990s Dispersion Shifted Single Mode Fiber was introduced to utilize low attenuation properties of fiber at 1550nm there by increasing the transmission distance without repeaters. With the availability of WDM technology, 1550nm transmission at higher bit rates was effected due to nearly Zero dispersion value at 1550nm. In order to achieve higher bit rate transmission and WDM transmission, Non-Zero Dispersion Shifted Single Mode Fiber was invented and is being deployed by Telecom carriers.

Multi Mode Fibers are available in Graded index and Step index type. Graded index type Multi Mode fibers are in use due to reduced modal dispersion and higher bandwidth. 50/125 m and 62.5/125 m are widely deployed Multi Mode fibers in Local Area Network (LAN). Recent developments and ratification of Gigabit Ethernet Standards for transmission at Gigabit speeds in LANs has brought the need for new type of Laser Optimized 50/125 m Multi Mode fiber with high bandwidth required by Gigabit Ethernet standard.

While choosing right type of Optical fiber for the networks, in general, the following factors shall be considered:
 > Present capacity requirements
 > Future demand and requirements
 > Active and Passive component costs