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M, Tech. in Optoelectronics and Laser Technolory(First Semester) EXAMINATION, 2008

oE-14

Paper FourthOPTICAL COMMUNICATION

Time : Three HoursMax. Marks : 100

) Note : Solve any five questions in all, selecting one question from each unit.

UNIT - I

Draw a basic-block diagram of Fiber optic communicationlink and explain in brief the function of each biock. Alsoexplain the need of fiber optical communication. 10

Justify that Attenuation in single mode tlber is smaller thanin multimode fiber. Explain the mechanism that causesattenuation in optical fiber. 10

OR

Discuss the nonlinear phenomena that are most relevant forfiber-optic communications. Define stimulated fight andBrillouin scattering. 10

Describe group velocity Dispersion and inter-modaldispersion phenomenon in single mode fiber. Discuss howdoes Group velocity Dispersion limits the performance of

*, , \lr

(b)

light wave system used in optical fiber system. 10

Ya)

Q2(a)

Ij)

( Q4.

i

I

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)

o)

aN^)

IINIT - V

Describe synchronous optical Network (SONET) givingstructure, Basic Building Block and STS-N frames. 10Describe the principal of operation of WDM opticalswitches. 10

OR

Describe Synchronous Digital Hierarchy (SDH) givingstandard bit rates and fiame structure. 10Describe the function WDM (wavelength divisionmultiplexing) multiplexer and its channei profile type. 10

{,

Define the following functional parameters of optical passivqdevices- 10 \.,

UNIT - II

Define the corediameter of optical fiber. Describe the typesof optical fiber giving fiber construction and refractive indexprofile. Explain how different modes propagates through an'optical fiber. What are microbends and macrobends ? 10

Describe the following process of fabrication of optical fiber.(i) OVPO (outside vapour Phau Oxidation)(iD MCVD (Modified chemical vapour deposition) 10Discuss merits and demerits also.

ORDraw and explain ideal and real characteristics of a WDMoptical filter. Define the following parameters- 10(i) Centre frequency (ii) Pass Bandwidth(iit Stop Bandwidth (iv) Isolation(v) Ripple.

(t Insertion Loss (IL)(ii) Retum Loss (RL)(iii) Reflectance(i") Operatingwavelength(v) Transfer matrix for a Fiber optic Branching Device.

UNIT - III

Describe the principai of operation of Erbium doped fiberAmplifier. Discuss its gain spectrum. 10

Discuss the advantages and disadvantages of analogdisital modulation scheme used in ootical fiber svstems.

ORDescribe the principal of operation of Raman Amplifier.Define Raman Gain and Band width. 10Discuss the purpose of use of optical ampliliers(Application) in the design of fiber optic cornmunication. 10

UNIT_W

Discuss the design of optical Transmitter with respect tofollowine -(D Source fiber coupling(ii) Ddving circuitry(iii) Opticalmodulators

OR

Discuss the following noise generated in Receiver

).

Q,3 (a)

(b)

Q5(a)

4b)

20

10

(b)

(D Short Noise(iD Thermal NoiseDescribe the following basicdefectors -(i) Responsivity (ii)(iiD Band width.

concepts common to all photo10

quantum efficiency

and10,p

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*ud( K!,k^-M,Tech. in Optoeleclronics and Laser Technology

(First Semester) f,xamination,2008

oE-l3

Paper ThirdOPTOELECTRONICS

Time : Three Hours

Note : Answer any five Questions. Selecting one from each unit. All questions carryequal marks.

UNIT - I

i1. What is relation between absorption and emission spectra ? Describe a rnethodfor measurement ofabsorption and Luminescence specha.

OR

Describe the process ofelectron-hole pair formation and rec,ombination insemiconductors with suitable diasrams.

UNIT - II

. Discuss the nematic, Smectic aad cholosteric phases ofliquid crystals.Describe the operation oftwisted nematic display.

OR

Describe any two ofthe following growth methods ofoptoelectronic materialand enumerate their advartages ard disadvantages

(i) MBE(ii) MocvD(iii) Plasma CVD

UNIT _ III

Q.| Describe the principle c'f working chamcteristics and fabrication ol

a/ photodiode.Classifyphotodiode.

Write a short note on any two -(i) Neno electronics(ii) Luminescent materials(i i i) Solar cells.

OR

UNIT _ IV

Q.4. Describe the electrcnic statcs in conjugated molecular solids. How singlet andtriplet states are farmed. Discuss fluorescence & phosphorescence in molecularsolids with the help ofsuitable diagram.

OR

Max. Marks : 100/,/Descdbe any one ofthe followiug in detail -

(i) TIIF method(ii) Bossier Model

UNIT_V

;ffi. Describe fabrication and working principle of organic light emitting diode. Ona what factors does the efficiencv ofOLED deoands.

OR

Describe in detail construction and principle ofworking oforganicphotovoltaic. Discuss fill factor Voc, Isc and efficiency ofOPV.

juq ku \o,.Code:S-739

M.Tech. in Optoelectronics & Laser Tecblologr(First Semester) Examination, 2008

QE- 12Paper - Second

(LASER TECHNOLOGY)

Time : Three Hours Max Mark. 100

Note - Attempt all five questions. Each question carry equal marks.

Unit - I

1. a. Why minimum three energy levels a:e required to cause population inver-sion between two levels ?

b. Explain purpose and working of optical resonators. Discuss the condi-tions for oscillator stabilitv in laser resonator.

Z Dir"u* th" o"""u"u4, u.d ,uffi3lt corditioos fo, laser actior.

. Describe in short the line broadening mechanism of emitted laser beam.Out ofthese broadening which one is the most dominating ?

Unit - [2. a. Describe tlle role ofmaroscopic polarization on dispersion and gain in a

laser oscillator.

b. Explain design and analysis of any one popular optically pumped solidstate laser using proper illustrations.

OR

-,Explain

the following topics in short :a. Q-switching and mode lockingb. Turable laser

Unit - I3. Describe the principle and strucfl[e ofheterojunction lasers. Discuss im-

portant factors responsible for lesses in heterojunction lasers. Name someimportant hetedunction laser materials and their relative merits.

OR

\

,r"y' Explain how population inversion and lasing action occuls in direct bandgap' semiconductors. Compare the structure and properties of semiconductor

laser and light emitting diodes (LEDs;.

,,1( Discuss the working principle ofrare earth doped lasers.

,. Unit-N4./ Explantrnportant characteristics ofultrashorl pulse lasers. How ulfia short, / : . purse lasers are generated /

b7 Discuss some impofiant applications of ultrashort pulse lasers. Explain/ broadband coherent excitation in short.

ORa. What are standing wave and travelling wave resonators ? Discuss ary one

active mode locking scheme.

b. How non-linear effects are used for enhanced mode locking ? Discussmeasmement techniques associated with ultrashorl laser pulses.

Unit - Vi Explain the appiication oflaser in foilowirrg :t a. Measurement of rotation

b. Medicine and surgeryOR

a. Describe the applications oflasers in oplical - fibre communications.

b. Explain the term holopaphy and holographic intenferomety. Discuss ap-plication ofholography in data storage.

0-0-0

s-738M.Tech. jn Optoelectronics and Laser Technology

@irst Semester) EXAMINATION, 2008.t l

) un,l kUtn^ /vv' / -oE-rr: - \ / - PaperFirst

MODERN OPTICS

Time : Three Hou.t tax. Marks : 100

Note : All questions carry equal marks./

.t. (7) Describe the different optical coeffrcients that determine the propertiesolthe medium at the macroscopic level.

'rd *" reflectivity of silicon at 633 nm is 35% and the absorption

'/ coefficient is j.8 x t0-t m-1. Calculate the tansmission and opticaldensity of a sample with a thickness of 1 0 pm.

OR

Discuss in details about the Atomic oscillators & vibrationaloscillators.

/ Explain the excitation and relaxation in Photoluminescence and also\"/ explainPbotoluminescencespectroscopy.

ORDefme Electroluminescence and explair the principle and working oflight emitting diodes. Give any two applications of LED's.

/ -+

/ Derive the expression for the elecfic field strength 6 , tle polarization<_/

i and the electric displacement i and defrne them.OR

Explain Quantum tra$ition rates in detail.

I Discuss the physical origin of optical nonlinearities and explain thenonlinear frequency mixing. Also explain the non resona.nt ardresonart nonlineadties.

Discuss Rayleigh, Brillouin and Raman scatteriry including non-linear/ effects.

s,/ Wrile short notes on.-/ (a) Fourier transform

(b) Spatial and temporal coherenceOR

Wlat is Holography? Discuss Holographic tecbniques & applications.