Download AKTU B-Tech 7th Sem 2016-2017 NEC 701 Optical Communication Question Paper

Download AKTU (Dr. A.P.J. Abdul Kalam Technical University (AKTU), formerly Uttar Pradesh Technical University (UPTU) B-Tech 7th Semester (Seventh Semester) 2016-2017 NEC 701 Optical Communication Question Paper

Printed Pages: 4 NEC -701
(Following Paper ID and Roll No. to be ?lled in your
Answer Books)
Roll No.
B.TECH
Regular Theory Examination (Odd Sem-VII), 2016-17
OPTICAL COMMUNICATION
T ime : 3 Hours Max. Marks : 100
SECTION - A
1. Attempt all parts. All parts carry equal marks. Write
answer of each part in short. (10X2=20)
a) Write down the wavelength regions corresponding
to ?rst, second and third windows.
b) A silica optical ?ber with a core refractive index
of 1.50 and a cladding refractive index of 1.47.
Determine the numerical aperture for the ?ber.
c) List the properties of optical ?ber that results in
signal degradation.
(1) How does the source spectral width affect the
information carrying capacity of a ?ber.
e) Compare the spectrum of a Laser Source and an
LED source.
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NEC - 701
f) De?ne polarization.
g) Draw the diagram to show the effect ofwaveguide
dispersion in single mode ?ber.
h) How does quantum noise arise?
i) Mention the noise present in optical receiver.
j) What is meant by quantum limit? Express it
mathematically.
SECTION ? B
2. Attempt any ?ve questions from this section
(5X 10:50)
a) 1) An optical ?ber in air has an NA of 0.4. In that
?ber, skew rays which change direction by
1000 at each re?ection. Find out the acceptance
angle of skew rays.
ii) Two polarization maintain ?bers operating at
a wavelength of 1.3 ,um have beat lengths of
0.7mm and 80m. Determine the model
birefringence in each case.
b) Compare the step index ?ber and graded index ?ber
on their performance parameters.
ic) Enumerate the principle of operation ofAPD.
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d)
f)
g)
11)
NEC -701
Analyze the light propagation in dielectric slab
waveguide.
Describe the scheme for realizing the dispersion
shifted ?ber.
How to measure the BER and Q factor in digital
transmission.
Discuss the waveguide dispersion with relevant
mathematical treatment.
Derive an expression for the photo current in the
case of a homodyne and heterodyne optical receiver
systems.
Section - C
Note: Attempt any two Questions from this section.
3. a)
b)
4 a)
(2x15=30)
Explain in detail with relevant circuit diagrams the
different types of optical pre-ampli?ers. (7)
Discuss the digital link design using the rise time
budget. (8)
With a neat diagram, enumerate the different
mechanisms that contribute to attenuation in optical
?bers. (12)
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NEC - 701
b) A multimode graded index ?ber exhibits total pulse
broadening of 0.1 gs over a distance of 15km and
dispersion is 6.67ns.km". Estimate
i) The maximum possible bandwidth on the link
ii) The bandwidth length product for the ?ber.(3)
5. Elucidate the principle ofoperation of a Laser diode and
derive an expression for the lasing threshold current
density. F ind the external quantum ef?ciency for a
GaHA 1 XAslaser diode (with x=0.03) Which has an optical
power versus drive current relationship of 0.5 mW/mA.
(15)
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