M.Sc. (Semester IV) (CBCS) Examination Oct/Nov-2017
Electronics Science
FIBER OPTIC COMMUNICATION
Day Date: Wednesday, 22-11-2017 Max. Marks: 70
Time: 02.30 PM to 05.00 PM
Instructions: Q. 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 Choose the alternatives given below. 06
The laser source provides the light signal that is
Coherent with light source Possible to modulate at frequency
Low divergence beam All the above
The first step for preparation of fiber is
Ultra pure material powder
Conventional glass refining technique
Impure fiber preparation
All the above
The optical carrier frequency is in the range of
1013 to 1016 Hz 1014 to 1016 Hz
1013 to 1017 Hz 1011 to 1016 Hz
Semiconductor photodiode without internal gain generate per
absorbed photons.
Two electron hole pair Three electron hole pair
One electron hole pair None of these
Microscopic meandering of the fiber core axis, known as
Micro Bending Linear Bending
Nonlinear Bending Circular Bending.
In optical fibers the Cut-Back technique is used to measure
Spectral loss Dispersion loss
Absorption loss None of these
State True or false. 08
Material absorption is a loss mechanism related to the material composition
and the fabrication process for the fiber.
Meridional ray which passes through the cross section of fiber.
Photon energy is inversely proportional to wavelength.
Insertion loss is to measure the diameter of optical fiber.
A permanent joint formed between two individual optical fibers in the field or
factory is known as a Fiber Splice.
The typical best bandwidth length product for single mode step index fiber
is 100MHZ KM.
The most common on-line measurement technique uses fiber image
projection (Shadow method) for the measurement of outer diameter of fiber.
Laser is non-coherent source of light.
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Q.2 Write short notes.
Explain optical fiber communication system in brief. 05
Explain the principle of PIN photodiode. 05
Explain the various advantages of optical fiber. 04
Q.3 Using the simple ray theory of light, describe the mechanism for the
transmission of light within an optical fiber.
08
An optical fiber has a numerical aperture of 0.20 and a cladding refractive
index of 1.59. Determine the acceptance angle for the fiber in water which
has a refractive index of 1.33.
06
Q.4 Briefly write about how fluoride glass fibers are prepared? 08
Explain material absorption losses in brief. 06
Q.5 Explain the concept of double heterojunction LED with a neat sketch. 08
A P-N Photodiode has a quantum efficiency of 60% at a wavelength of 0.9
Calculate
06
Its responsibility at 0.9
Received optical power if mean photocurrent is 10-6 A.
Q.6 The radiative and nonradiative recombination lifetime of the minority carriers
in the active region of a double heterojunction LED are 60ns and 100ns,
respectively. Determine the total carrier recombination lifetime and power
internally generated within the device when peak emission wavelength is
0.87 at a drive current of 40mA.
08
Explain the different advantages and disadvantages of LED compared to
Laser.
06
Q.7 Briefly explain how numerical aperture is measured in optical fiber? 08
Explain what do you mean by FDDI? 06