Comparison between Frequency Modulation(FM) & Amplitude Modulation(AM)

 

Frequency Modulation	Amplitude Modulation
1) The amplitude of FM signal is constant and in depth of Modulation.	1) Amplitude of AM signal varies depending on Modulation index.
2) It requires much wider channel (7-15 times) as compared to AM	2) Band width, is very small, which is one of the biggest disadvantages.
3) Transmitters are complex and hence expensive	3) Relatively simple and cheap
4) Area of reception is small since it is limited to line of sight	4) Area of reception is large
5) Noise can be easily minimized. Amplitude variations can be eliminated by using limiter.	5) More susceptible to noise, interference & low signal to noise ratio. Difficult to eliminate effects of noise.
6) Average power in frequency modulated wave is same as contained in un-modulated wave.	6) Average power in modulated wave is greater than carrier power. This added power is provided by modulating source.
7) No restriction is placed on modulated index.	7) Maximum modulation index is 1 otherwise over modulation would result in distortion.
8) Possible to operate several independent transmitters on same frequency.	8) Not possible to operate out interference.

Advantages of Optic Fibers

1. Optical fibers have greater information carrying capacities than metallic conductors.

2. Fibers and fiber cables are very strong and flexible. So fibres are so slender that they do not break when wrapped around.

3. One of the most important advantages of fibers is that they can carry large amount of information in either digital or analog form.

4. An optical fiber is well protected from external interference and coupling with other communication channels. It is because an optic fiber made of  either glass or plastic is an insulator.

5. Electromagnetic interference caused by lightning and sparking etc doesn't effect fibers.

6. As compared to Copper, corrosion due to water or chemicals is less for glass. Glass fiber themselves can withstand high temperature before deteriorating. 

7. Fiber offers a degree of security and privacy. Because fibers do not radiate energy with in them, it is difficult for an intruder to detect signal being transmitted.