FOC Assignment

Question Bank

Principle of an optical fiber (total internal reflection)

 1. Explain briefly 'basic principle of an optical fiber'.

Ans. Optical fibres works on the principle of total internal reflection. When light ray strikes at the internal surface of optical fibre cable called such that incidence angle is greater than critical angle, then incident light ray reflects in the same medium and this phenomenon repeats.

or

Explain the principle of total internal reflection.

Ans. Total internal reflection: When a light ray travels from denser medium to rarer medium, the angle of incidence is greater than critical angle then it reflects into the same medium. This phenomenon is called total internal reflection.

Acceptance angle and Numerical aperture

2. Explain the terms numerical aperture and acceptance angle.

Ans.The numerical aperture is determined by the core and cladding. The acceptance angle is determined by core, cladding, and the outside. The greater the difference in the index of refraction between the core and cladding, the smaller the critical angle and the larger the acceptance angle.

or

Derive expressions for the numerical aperture and fraction change in refractive index change of an optical fiber.

Ans.

Optical fiber communication system

3. Explain the advantages of an optical fiber communication system.

Ans.Optical fiber is rising in both telecommunication and data communication due to its unsurpassed advantages: faster speed with less attenuation, less impervious to electromagnetic interference (EMI), smaller size and greater information carrying capacity

4. Draw the block diagram of fiber optic communication system and explain the function of each block Applications of optical fibers

5. Write a note on the applications of an optical fiber.

Ans. Applications. Optical fiber is used by telecommunications companies to transmit telephone signals, Internet communication and cable television signals. It is also used in other industries, including medical, defense, government, industrial and commercial.

Fibers classification

 6. Explain how the optical fibers are classified.

7. Describe different types of fibers by giving the refractive index profiles and propagation details.

8. Distinguish between

Step index fiber graded index fiber Single mode and multimode optical fiber.

Construction of an optical fiber

9. With the help of suitable diagram explain the principle, construction and working of an optical fiber as a waveguide. Problems

Ans.

10. An optical fiber has a core material of refractive index of 1.55 and cladding material of refractive index of 1.50. The light is launched it in air. Calculate the its numerical aperture.

11. Calculate the angle of acceptance of a given optical fiber, if the refractive indices os the core and cladding are 1.563 and 1.498 respectively.

Ans.

12. The numerical aperture of an optical fiber is 0.39. If the difference in the refractive indices of the material of its core and cladding is 0.05. Calculate refractive index of the core material.

13. Calculate fractional change in refractive for a given optical fiber if the refractive indices of the core and the cladding are 1.563 and 1.498 respectively.

Ans