# Optical fiber Dispersion MCQ || Dispersion in optical fiber Questions and Answers

2. ________ is the spreading of light pulse as its travels down the length of an optical fiber.

1. Transmission
2. Dispersion
3. Diffusion

Explanation:

Dispersion is the spreading of the light pulse as its travels down the length of an optical fiber. Optical fiber dispersion describes the process of how an input signal broadens/spreads out as it propagates/travels down the fiber. Normally, dispersion in fiber optic cable includes modal dispersion, chromatic dispersion, and polarization mode dispersion.

4. In waveguide dispersion, refractive index is independent of ______________

1. Bit rate
2. Index difference
3. Velocity of medium
4. Wavelength

Explanation:

• The waveguide dispersion occurs because the propagation constant is a function of the fiber parameters (core radius and difference between refractive indices in fiber core and cladding) and at the same time is a function of wavelength.
• The longer the wavelength, the more power in the cladding.
• The effect of waveguide dispersion on pulse spreading can be approximated by assuming that the refractive index of a material is independent of wavelength.
• In material dispersion, the refractive index is a function of optical wavelength. It varies as a function of wavelength.
• In wavelength dispersion, group delay is expressed in terms of normalized propagation constant instead of wavelength.

5. ______  dispersion occurs because the propagation constant is a function of the fiber parameters.

1. Intramodal Dispersion
2. Chromatic Dispersion
3. Waveguide Dispersion
4. Intermodal Dispersion

Explanation:

• The waveguide dispersion occurs because the propagation constant is a function of the fiber parameters.
• Waveguide dispersion occurs because a single-mode fiber confines only about 80 percent of the optical power to the core.
• The dispersion thus arises, since the 20 percent of the light propagating in the cladding travels faster than the light confined to the core.
• The amount of waveguide dispersion depends on the fiber design since the modal propagation constant β is a function of a/ (the optical fiber dimension relative to the wavelength λ; here a is the core radius.)

6. For no overlapping of light pulses down on an optical fiber link, the digital bit rate BT must be ___________

7. Which of the following are types of optical fiber dispersion?

1. Intramodal Dispersion
2. Waveguide Dispersion
3. Material Dispersion
4. All of the above

Explanation:

The term dispersion describes the pulse broadening effect in fibres.

The types of dispersion are

1. Intramodal Dispersion
2. Material Dispersion
3. Waveguide Dispersion
4. Intermodal Dispersion
5. Polarization mode Dispersion

9. The total dispersion produced by the fiber depends directly on its ______.

1. Bandwidth
2. Length
3. Power
4. Refractive Index