Sunday, November 7, 2010

Optical Communication question paper with solution for Engineering Students

  1. Define Mode-field diameter.
The fundamental parameter of a single mode fiber is the mode-field diameter. This can be determined from the mode field distribution of the fundamental LP01 mode

  1. What is the necessity of cladding for an optical fiber?
a) To provide proper light guidance inside the core
b) To avoid leakage of light from the fiber
c) To avoid mechanical strength for the fiber
d) To protect the core from scratches and other mechanical losses

  1. Define acceptance angle.
The maximum angle Φmax’ with which a ray of light can enter through the entrance end of the fiber and still be totally internally reflected is called acceptance angle of the fiber

  1. Why do we prefer step index single mode fiber for long distance communication?
Step index single mode fiber has low attenuation due to smaller core diameter & higher bandwidth & very low dispersion.

  1. What are meridional rays & skew rays?
Meridional rays are the rays following Zig Zag  path when they travel through fiber and for every reflection it will cross the fiber axis.
Skew rays are the rays following the helical path around the fiber axis when they travel through the fiber and they would not cross the fiber axis at any time.

  1. What is pulse broadening?
Dispertion induced signal distortion is that a light pulse will broaden as it travels along the fibre.This pulse broadening causes a pulse to overlap with neighbouring pulses.After a time t,the adjacent pulses can no longer be individually distinguished at the receiver and error will occur.

  1. What is polarization Mode Dispersion (PMD)?
The difference in propagation times between the two orthogonal polarization modes will result in pulse spreading.This is called as polarization Mode Dispersion.

Part – B                                              (3x 12 =36)
(Answer any three questions)

  1. What is waveguide dispersion? Derive its expression.

Wave-guide dispersion, which occurs because a single mode fiber confines only 80% of the optical power to the core. Dispersion thus arises since the 20% of the light propagating in the cladding travels faster than the light confined to the core. The amount of wave-guide dispersion depends on the fiber design, since the modal dispersion constant β is a fn of (a / λ)

  1. Explain in detail about various attenuation losses.

v  Absorption Loss:

In optical fibers, the electromagnetic waves are absorbed by the material resulting in increase in attenuation.

Absorption is caused by three different mechanisms in detail with relevant diagram.

·         Absorption by atomic defects in glass composition
·         Extrinsic absorption by impurity atoms in the glass material
·         Intrinsic absorption by the basic constituent atoms of the fiber materials.

v  Scattering Loss:
Scattering losses in glass arise from microscopic variations in the materials density, from compositional fluctuations, and from structural in homogeneities or defects occurring during fiber manufacture.

v  Bending Loss:

Radiative losses occur whenever an optical fiber undergoes a bend of finite radius of curvature. Fibers can be subjected to two types of bends

1.      Macroscopic bends
2.      Microscopic bends

v  Explanation with relevant diagrams

  1.  Briefly explain about Graded index fiber structure & single-mode fiber.

Graded index fiber:
In the graded index fiber design the core refraction index decreases continuously with increasing radial distance ‘r’ from the center of the fiber.
·         Equation
·         Diagram
Single-mode fiber
    Dimensions of core diameter
    Mode-field diameter
Distribution of light in a single-mode fiber above its cutoff wavelength
    Propagation modes i.  Fiber birefringence ii. Fiber beat length


  1. Fiber Optic Solutions Miami We are Authorized Partners Dealers in the brands you know and trust... such as Panasonic, NEC, Plantronics and Panalog. Our highly skilled technicians are trained in structured wiring such as Cat5e, Cat6, Coaxial Cabling and Fiber Optic. We offer service in 24 hours a day, 7 days a week. Attach Communications Corporation has delighted American consumers with products for the home and business. Attach Communications Corporation's consumer technology products range from communications solutions, networkable office solutions, security systems.

  2. Fonebell is pitching to provide a comprehensive cloud based IVR solution to different industries for facilitating their growth and development. Looking best and affordable Automatic Call Distribution (ACD) System, call management, call center software solutions, cloud telephony services and more. You can contacting us by following details has given below.

    Fonebell Automatic Call Distribution (ACD) | New Delhi, India - 110058 | 1800 3000 1127

  3. Thanks for sharing this wonderful idea with us. we are really like it. buy toll free number India

  4. Thanks for Sharing!!
    LeadNXT, provides Fax to Email Services Provider company for all your faxing requirements in a cost-efficient way. It allows you to send your fax online through email from your smart devices like mobile phone, tablet or laptop.

  5. LeadNXT is the most experienced Cloud Telephony Services, who offers complete business communication services to keep your customers satisfied and happy.