M.Sc.- (Electronics Science) (Semester-IV) (CBCS)
Examination, 2017
FIBER OPTIC COMMUNICATION
Day Date: Monday, 24-04-2017 Max. Marks: 70
Time: 02.30 PM to 05.00 PM
Instructions and are compulsory.
Answer any three questions from Q.3 to Q.7
All questions carry equal marks.
Use of nonprogrammable calculator is allowed.
Q.1 Select the most correct alternative 06
Stimulated emission occur when the following condition is
satisfied………


The drawback with LED is…………..
Low optical power coupled into a fiber
Usually lower modulated bandwidth
Harmonic distortion
All the above
The response of avalanche photo diode is limited by……..
The transit time of the carrier across the absorption
region.
Diffusion time of carrier
None of above
All the above
The ray of light that passes through the axis of a fiber optic is
called as……..
Accepted ray Meriditional ray P
Critical ray None of these.
The OTDM stands for……..
Orthogonal time duplex multiplexing
Optical time duplex multiplexing
Orthogonal time division multiplexing
Optical time division multiplexing.
Page 2 of 3
In optical cable design the strain on the fiber in cable does
not exceed…….
0.2% 2.2% 0.8%
State TRUE or FALSE 08
The Mid-infrared range used for optical transmissions is 0.8
to 1.55
A ray of light travels more slowly in an optical dense medium
than in one that is less dense.
SBS (Stimulated Brilloum scattering) is mainly a backward
process.
For an acceptance angle of numerical aperture should
be 0.8666.
The internal quantum efficiency of LED decreases with
decrease in temperature.
Surface emitting LED offers constant spectral line width.
Demodulation means receiving information
Semiconductor photodiode without internal gain generate two
electron-hole pairs per absorbed photon.
Q2 Write a short notes.
Explain Advantages and disadvantages of optical fibers? 05
Explain the different types of scattering mechanisms in optical
fiber?
05
Explain the benefits and drawbacks of avalanche photodiode? 04
Q3 When the mean optical power launched into an 8KM length of
fiber is 120 the mean optical power at the fiber output is
3 W. Calculate
08
The overall signal attenuation or loss in decibels through the
fiber assuming there are no connectors or splice.
ii) The signal attenuation per KM
iii) The overall attenuation for a 10KM optical link using the
same fiber with splices at 1km Interval, each giving an
attenuation of 1dB.
iv) The numerical input/output power ratio.
Briefly write about fiber joint losses? 06
Q4 Write note on Avalanche photodiode. 08
Write a note on fiber bending losses? 06
Q5 Briefly explain the vapour phase deposition technique for optical
fiber preparation.
08
B Explain how fluoride glass fiber is manufactured. 06
Q6 Defined the terms LED Power, LED efficiency and derive the
expression between them
08
What are the important factors that limit speed response of the
photodiode?
06
Q7 Explain any one technique used to measured the cutoff 08
wavelength of optical fiber.
Write a note on effect of noise on receiver performance?