Optical Fibre Communication (EC-801) - Important Questions

Derive the expression for numerical aperture and acceptance angle of a step-index optical fiber in terms of core and cladding refractive indices.

A step-index fiber has core refractive index n1=1.48 and cladding index n2=1.46. Calculate the numerical aperture, critical angle at core-cladding interface, and acceptance / maximum entrance angle in air.

What is OTDR? Explain its working principle and its applications in measurement of fiber losses and faults.

Discuss absorption losses in optical fibers including intrinsic and extrinsic mechanisms and how absorption can be reduced.

Explain the principle and working of a PIN diode with suitable diagram.

What is quantum efficiency? Derive its expression in terms of recombination lifetime.

Explain link power budget analysis for optical link design, deriving the power budget equation including source power, fiber attenuation, connector and splice losses, receiver sensitivity, and system margin.

Calculate the maximum bit rate that may be achieved on a 50 km fiber link without repeaters using NRZ format. Given transmitter rise time 4 ns, intermodal rise time 5 ns, intramodal rise time 1 ns and receiver rise time 3 ns.

Explain the architecture and working of SONET and SDH.

Explain the working principle of EDFA.

Explain ray theory transmission in step-index optical fiber.

Discuss signal degradation in optical fiber due to attenuation and dispersion, explaining their causes, types and effect on system performance.

A ruby laser containing a crystal length 4 cm with refractive index 1.78 and peak emission wavelength 0.55 micron. Determine the number of longitudinal modes and their frequency separation.

Explain the different types of optical fiber connectors used, their characteristics and insertion loss.

Write short notes on any two of the following: (i) Raman amplifier (ii) Passive Optical Networks (iii) WDM systems (iv) Optical coupler parameters.