Optical Communication — Summer 2022

Define following terms: 1) Critical angle 2) Total internal reflection 3) Index difference

Compare Graded index fiber with Step index fiber.

Discuss advantages and disadvantages of optical link over conventional copper system.

Define following terms: 1) Numerical Aperture 2) Skew ray 3) Meridional ray

Compare Single-mode fiber with Multi-mode fiber.

What are the various methods of glass fiber fabrication? Explain one method briefly.

Amultimode step index fiber with a core diameter of 80 µm and a relative index difference of 1.5% is operating at a wavelength of 0.85 µm. If the core refractive index is 1.48, estimate: (a) the normalized frequency for the fiber;

the number of guided modes.

State and explain Snell’s law.

What is inter symbol interference? How it can be eliminated?

Draw schematic of surface emitting LED and explain structure.

Compare direct-band gape and indirect-gape materials.

Explain scattering loss in optical fiber.

Compare LED with laser and give merits and demerits of both. Mention materials used.

Explain intermodal dispersion in brief.

Define following terms: 1) Radiance 3) Carrier confinement 2) Quantum efficiency 4) Optical confinement

Explain working of RAPD with appropriate sketch.

Explain population inversion.

Explain following terms: 1) Power launching 2) Coupling efficiency

List various fiber splicing technique. Explain any one technique in brief.

What are bending losses in fiber optic communication? Describe Micro bending losses.

How does Raman amplifier works?1

List and explain various Lensing schemes to provide coupling between the source and the diode.

List the key transition processes involved in laser action. Explain any one in brief.

Explain the basic principles of WDM and DWDM with respect to optical fiber system.

State methods for dispersion measurement in laboratory. Explain the experimental setup for one of them.