Describe the different modes of fibre optic cable with neat diagram. Compare fibre optic cable with UTP cable.
asked Jun 29 in Computer Hardware & Maintenance by
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STEP-INDEX MULTIMODE FIBER has a large core, up to 100 microns in diameter. As a result, some of the light rays that make up the digital pulse may travel a direct route, whereas others zigzag as they bounce off the cladding. These alternative pathways cause the different groupings of light rays, referred to as modes, to arrive separately at a receiving point. The pulse, an aggregate of different modes, begins to spread out, losing its well-defined shape. The need to leave spacing between pulses to prevent overlapping limits bandwidth that is, the amount of information that can be sent. Consequently, this type of fiber is best suited for transmission over short distances, in an endoscope, for instance.

GRADED-INDEX MULTIMODE FIBER contains a core in which the refractive index diminishes gradually from the center axis out toward the cladding. The higher refractive index at the center makes the light rays moving down the axis advance more slowly than those near the cladding. Also, rather than zigzagging off the cladding, light in the core curves helically because of the graded index, reducing its travel distance. The shortened path and the higher speed allow light at the periphery to arrive at a receiver at about the same time as the slow but straight rays in the core axis. The result: a digital pulse suffers less dispersion.

SINGLE-MODE FIBER has a narrow core (eight microns or less), and the index of refraction between the core and the cladding changes less than it does for multimode fibers. Light thus travels parallel to the axis, creating little pulse dispersion. Telephone and cable television networks install millions of kilometers of this fiber every year. 

Parameters
UTP
Fiber optic cable
Transmission rate 
It has low transmission rates
It has high transmission rates
Ease of installation
It is easy to install as compared to fiber cables.
It does take a bit longer to terminate fiber than copper.
Security
It can be easily eavesdrop.
It is very secured.
Cost
UTP is cheaper as compared to fiber optic cables.
Fiber is more expensive than copper due to the light emitting equipment and cost.
answered Jun 29 by