Optical Fibre Questions and Answers

Engineering Physics Questions and Answers – Optical Fibre

This set of Engineering Physics Multiple Choice Questions & Answers (MCQs) focuses on “Optical Fibre”.

1. In which of the following there is no distortion?
a) Graded index fibre
b) Multimode step-index fibre
c) Single step-index fibre
d) Glass fibre

Explanation: Because of the differences in their spectra, light travels at various speeds in different routes. It travels quicker at the edge than near the centre, but due to the helical course, practically all of the rays arrive at the exit end at the same time. As a result of the lack of dispersion in the pulses, the output is not distorted.

2. Which of the following loss occurs inside the fibre?
a) Radiative loss
b) Scattering
c) Absorption
d) Attenuation

Explanation: Scattering is a loss that is wavelength dependant. The disordered structure of glass utilised in the production of fibres will cause some oscillations in the refractive index inside the fibre. Rayleigh scattering is the result of this.

3. What causes microscopic bend?
a) Uniform pressure
b) Non-uniform volume
c) Uniform volume
d) Non-uniform pressure

Explanation: Non-uniformities inside the fibre induce micro-bend losses. The non-uniform pressures induced during fibre cabling cause micro-bends in the fibre.

4. When more than one mode is propagating, how is it dispersed?
a) Dispersion
b) Inter-modal dispersion
c) Material dispersion
d) Waveguide dispersion

Explanation: Inter modal dispersion occurs when more than one mode propagates through a fibre. Because there are so many modes propagating, they will have varied wavelengths and propagate at varying speeds.

5. A fibre optic telephone transmission can handle more than thousands of voice channels.
a) True
b) False

Explanation: Because optical fibre has a higher bandwidth, it can handle a greater number of communication channels.

6. Which of the following is known as fibre optic back bone?
a) Telecommunication
b) Cable television
c) Delay lines
d) Bus topology

Explanation: The optical wiring architecture known as bus topology, which is an application known as fibre optic back bone, connects each computer on the network to the rest of the computers.

7. Calculate the numerical aperture of an optical fibre whose core and cladding are made of materials of refractive index 1.6 and 1.5 respectively.
a) 0.55677
b) 55.77
c) 0.2458
d) 0.647852

Explanation: Numerical aperture = n12n22−−−−−−−−√
Numerical aperture = 0.55677.

8. A step-index fibre has a numerical aperture of 0.26, a core refractive index of 1.5 and a core diameter of 100micrometer. Calculate the acceptance angle.
a) 1.47°
b) 15.07°
c) 2.18°
d) 24.15°

Explanation: sin i = (Numerical aperture)/n
sin i = 15.07°.

9. What is the principle of fibre optical communication?
a) Frequency modulation
b) Population inversion
c) Total internal reflection
d) Doppler Effect

Explanation: Light entering an optical fibre does not encounter any new surfaces; instead, it repeatedly hits the same surface. Total internal reflection is the rationale for confining the light beam inside the fibres.

10. What is the other name for a maximum external incident angle?
a) Optical angle
b) Total internal reflection angle
c) Refraction angle
d) Wave guide acceptance angle

Explanation: Only those rays that pass through the acceptance angle are completely reflected. As a result, light that strikes the core at the maximum external incidence angle can be linked into the fibre and propagated. A wave guide acceptance angle is the name for this angle.

11. A single mode fibre has low intermodal dispersion than multimode.
a) True
b) False

Explanation: The refractive indices will be in step in both single and multimode fibres. Because a single mode has less dispersion than a multimode, the intermodal dispersion of a single mode step index fibre is lower than that of a multimode step index fibre.

12. How does the refractive index vary in Graded Index fibre?
a) Tangentially
b) Radially
c) Longitudinally
d) Transversely

Explanation: The core’s refractive index is highest along the fibre axis and subsequently declines. The refractive index of the fibre varies radially from the axis. As a result, it’s known as graded index fibre.

13. Which of the following has more distortion?
a) Single step-index fibre
b) Graded index fibre
c) Multimode step-index fibre
d) Glass fibre

Explanation: There will be a variation in reflected angles when rays traverse longer distances. As a result, high-angle rays arrive after low-angle rays. As a result, the signal pulses are widened, resulting in a distorted output.

A flexible, transparent optical fibre (or fibre in British English) is manufactured by pulling glass (silica) or plastic to a diameter slightly larger than that of a human hair. Optical fibres are most commonly used to convey light[a] between two ends of the fibre and are widely employed in fiber-optic communications, allowing transmission over longer distances and at higher bandwidths (data transfer speeds) than electrical connections. Signals pass through fibres with less loss than through metal wires, and fibres are immune to electromagnetic interference, an issue that metal wires suffer from.

Leave a Reply

Your email address will not be published. Required fields are marked *