Download PTU Fiber Optics Overview_0 Question Bank

Download PTU (Punjab Technical University) Fiber Optics Overview_0 Question Bank

Overview - Fiber Optics

1. What is optical Fiber
2. How optical fiber is better than coaxial copper cable (i.e. advantages of using optical
fibers) - more data carrying capacity (band width, band width is proportional to frequency
of carrier wave), more security, least electromagnetic interference (EMI).
3. Principle of working - Total Internal Reflection
4. Explain Total Internal Reflection
5. Composition/structure of optical fiber (discuss three layers core, clad and protective
sheath along with materials i.e. glass or plastic)
6. How light propagates through fiber - Explain qualitatively and show with the help of
diagram.
7. Define acceptance angle, acceptance cone and numerical aperture. Find their
mathematical expression/relation. Give physical significance of each.
8. What is ? - fractional change in refractive index and express numerical aperture in
terms of ?.
9. What is mode?
10. Classification of optical fibers :
(i) Based on Index Profile of core -Step Index (SI) and Graded Index (GRIN). Plot the
respective index profiles.
(ii) Based on number of modes - Single Mode Fiber (SMF) and Multimode Fiber
(MMF)
11. What is V-no of fiber -
?
? N.A. a 2
V = , where a is core radius, ? is wavelength of
carrier wave; N.A. is numerical aperture of fiber. Cut off value of V is 2.405, if V<2.405,
fiber is SMF and if V>2.405, fiber is MMF. Note that V-no of fiber is also known as
Normalized frequency.
12. Various losses through fiber - absorption, scattering, material, bending, coupling loss
etc.
13. Attenuation coefficient
out
in
P
P
log
L
10

10
= ? , where L is length of fiber in km, P
in
is input
power launched into fiber and P
out
is output power from the fiber. Units of ? are dB/km.
14. Joints in optical fibers - (i) Splice - permanent joint to increase the length of fiber - two
types: mechanical splice n fusion splice (ii) Connector - semi-permanent/temporary joint
to connect fiber with transmitter and/or receiver - can be of two types - mechanical
(ferrule type) and extended beam connectors (iii) Coupler: device to split and/or combine
optical signal from one port to many ports or many to one.
15. Applications of optical fibers - communication system, sensors.
16. Disadvantages of using optical fibers

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