RTU 2016 Question Paper Semester VIII Electronics and Communication Engineering Optical Communication

lr
"*:'*!{ ii}t,ti.

A,
\J
o\
.-t
B.Tech. VIil Semester (Old Back) Examination,ApriUMay 2016
-\f,
Electronics and Communication
rd
€ 8EC3 (O) Optieal Communication

Time : 3 Hours Maxirnum Marks : 80
Min. Passing Marks : 24

Inslractions to Cundidates:
Attempt any ftve questions. Selecting one question from each unit. All questions
carry equal marlcs. (Schematic diagrams must be shown wherever necessqry.
Any data you feel missing suitubly be assumed and stated clearly.)
Units of quantities used/calculated must'be stated clearly.

Unit - I
1.. a) Explain and classiff the fiber and compare single mode with multimode step
. index and graded index fiber (8)
b) A multimode step index f,rber is operatir-rg at a wave length of 0.85 pn witha
core diameter is 80 un and a relative index differen*e of llVo if the refractive
index of core is 1.48 determine
r) The normalized frequercy forthe fiber (4)
ii) The number of guided moele (4)
OR
1. a) What is dispersion. Explain dispersion shifted and flattened fibers with neat
diagram (8)
b) List the different types of materials use for manufacturing of fiber. Explain
modified chemical vapour. Deposition (MCVD) process for optical fiber
manufacnring. (8)

8E4090 /zoro (1) [Contd...

Unit - II
In
for optical fiber communication' (8)
) a) Describe the common LED structure
particular compass surface
ae'ices
"d;;;;;ittinf
principle of an injection semiconductor
r :
b) Whatis LASER? Explain the working (8)
LASERwithneatdiagram
OR
one is
gap materials?- Explain and which
6qv -r
2. a)
' what are direct anrl indirect band
'r,* (8)
used for LED and why? .1
b)ArubyLASERcontainsacrystallength4cm.witharefractiveindexofl.TS"
device is 0'55 pm ' Determine
the
peak d;i;;".f.nht-ilo*-ttt"
The
number of d;iffit "1*"aJ. and their frequency separation
Unit - ilI
of PIN p]rgtgietector using schematic circuit
3. a) Expiain the physic-al principle
s' the operation of RAFD
;i#am. Ario 6^prui"
wavelength of 0'9 r m
b) A P-N photodiode has a quantum efficiency 50o/o ata
calculate
Q)
D Its resPonsivitY x0'9 Pn t n-A,
ii)Thereceivedopticalpoweriftherneanphotocurrentis10.6A(3)
(3)
photons at this wavelength
iii) The corresponding number of received
OR
3. a)Explainthevariousdifferenttypesofnoisesincpticaldetectors(8)
b)Whataretheimportantcharacteristicsofan"ryi:,{1?::iver.Explaindifferent
communication (8)
types of optical receiver t"t i" upiical
LInit - IV
urrrvrv^rv -J r -
4. a)Whatismeantbysplicing?Explaindifferenttypesofsplicesandcompare
^vro'r (8)
with the connectors
and a of2'}isjointed
b) A 80/125 prn gradedLndex (GI) frber wi-trr 1|le of0'25 are
and a of 1'9' The fiber axes
with 60/12 s i* Olfiberwith anNA of 0'21 joint
gap' calculate the insertion loss at a
perfectly aligned and there i, no ui,
and backward directions'
(8)
for the signi transmission in,n. fo*utd
OR
4.
description-oiThe t*r;?i" b. ;il;,"diiTinr.
O"tig,
a)Explainthelinkdesignforopticalcommunicationsystem.Givebrief
(8)

rvrur!rrrv'>---D (wDM)
\ use in optical fiber
/rDr.,,D Multiplexing
b) Describe.the wavelen$hDevisions (8)
communlcation.

orr,lnon (2)

Unit - V
5. a) Explain the measurement of retractive index profile parameter of fiber with
neatdiagram (S)
b) A 2km length _of multimode fiber is attached to apparatus for spectral loss
measurement. The measured output voltage from tlie photoreceiver using the
full2km fiber length is 21.V at a wavelength of0.85 pm.Whenthe fiber is then
cut back to leave a 2m length the output voltage increases to 10.7v. Determine
tnn
the attenuation per kilometer for the fiber at a wavelength of 0.85 (S)

OR
5. a) What is Optical Time Domain Reflectometry(OTDR)? Explain the principle
and measurement technique with neat diagram
f8l
b) Discuss with the aid of suitable diagram the measurement of scattering losses
in optical fibers. (S)

8E4090 (3)