Ece Vii Optical Fiber Communication 10ec72 Question Paper

Optical Fiber Communication

10EC72

QUESTION BANK Unit1 1. Discuss the advantages of optical fiber communication system with respect to wavelength and attenuation.

[July/Aug.-2010/11/12, 6 Marks]

2. Light travelling in air strickes a glass plate at an angle I1=330 where I1 is measured b/w the incoming ray and glass surface. Upon striking the glass the part of the beam is reflected and part is refracted. If the refracted and refracted beams make an angle of 90o with each other, what is the refractive index of the glass? What is the critical angle for the glass? [July/Aug.-2011, 6 Marks] 3. Explain

with

necessary

diagrams

the

different

types

of

fiber

structures.

[Jan./Feb.-2012, 8 Marks] 4. what is numerical aperture ? derive an expression for numerical aperture and max acceptance angle in case of a step index optical fiber interms refractive index of core and cladding materials.

[Jan./Feb.-2012, 6 Marks]

5. Compare and contrast : i) Single mode Vs multimode fibers. Ii) Step index Vs index fibers. [July/Aug.-2012, 6 Marks] 6. Discuss the necessary mathematical condition that the angle of incidence θ must satisfy for the

optical

rays

to

propagate

in

a

dielectric

slab

waveguide.

[July/Aug.-2012, 8 Marks] 7. A multimode step index fiber with a core diameter of 80 µm and a refractive index difference of 1.5 % is operating at a wavelength of 0.85 µm. If the core refractive index is 1.48, estimate the normalized frequency for the fiber and the number of guided modes. [July./Aug.-2011, 6 Marks] 8. What are the advantages and disadvantages of multimode and single mode fibers? [Jan./Feb.-2010, 6 Marks] 9. A step index fiber has a normalized frequency V = 29.9 at 13.50 nm wavelength. If the core radius is 35 µm, find the numerical aperture.


10. Q.10 Show with neat diagrams the ray optics representation for the skew rays and meridional rays in a step index fiber and hence, derive an expression for numerical aperture of step Department of ECE/SJBIT

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10EC72

index fiber interms of refractive index and maximum ray entrance angle. [July/Aug.-2009, 10 Marks] 11. A step index in air has a numerical aperture of 0.16, a core refractive index of 1.45 and a core diameter of 60 µm. Determine the normalized frequency for the fiber when the light at a wavelength of 0.9 µm is transmitted. Further, estimate the number of guided modes propagatingin the fiber. 12. Explain

briefly

the

[July/Aug.-2009, 4 Marks] halide

glass,

active

glass

and

chalgenide

glass

fibers.

[July/Aug.-2009, 6 Marks] 13. With neat sketch, describe the vapour, phase axial depositions method of drawing optical fibers.

Department of ECE/SJBIT

[July/Aug.-2009, 8 Marks]

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10EC72

Unit 2 1. Derive an expression for pulse spreading and dispersion, which is a function of wavelength using time delay.


2. Describe the significance of measure of the information capacity.

[July/Aug.-2010, 6

Marks] 3. A continuous 12 km long optical fiber link has a loss of 1.5 dB/km. i) What is the minimum optical power level that must be launched into the fiber to maintain as optical power level of 0.3 µW at the receiving end? ii) What is the required input power if the fiber has a loss of 2.5dB/km?

[July/Aug.-2010, 6

Marks] 4. Discuss the following for optical fibers : i)Absorption ii) Waveguide dispersion iii) Material dispersion 5. iv) Bending loss.


6. Explain the three different mechanisms that cause absorption of optical energy in optical fibers.

[July/Aug.-2011, 6

Marks] 7. Explain the contributions of microscopic and macroscopic fiber bends towards the bending losses in optical fibers. 8. Describe

the

[July/Aug.-2011, 6 Marks] material

dispersion

and

waveguide

dispersion.

[July/Aug.-2011, 6 Marks] 9. Optical power launched into fiber at transmitter end is 150 µW. The power at the end of 10 km length of the link working in first window is – 38.2 dBm. Another system of same length working in second window is 47.5 µW. Same length system working in third window has 50 % of launched power.Calculate fiber attenuation for each case and mention avelength of peration.


10. A typical LED has spectral width of 40 nm, average value of dispersion 0.07 ns/(ns.km). link length 6 km, bandwidth 400 MHzkm and mode mixing parameter q = 0.7. Calculate tmat and tmod. Department of ECE/SJBIT

[Jan./Feb.-2009, 6 Marks] Page 3


10EC72

11. What do you mean by material dispersion and waveguide dispersion? Describe briefly. [July./Aug.-2009, 6 Marks]


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10EC72

UNIT 3 1.

Explain the operation of DFB and DBR LASERS.

2. Explain the operation of an APD.

[Jan./Feb.-2012, 8 Marks] [Jan./Feb.-2012, 6 Marks]

3. Sketch and explain the Fabry – Perot resonator cavity of laser. [July/Aug.-2010, 10 Marks; July/Aug.-2009, 6 Marks] 4. Explain the principle of laser action. Briefly explain the structure of VCSEL single mode laser with a near diagram.


5. The radiative and non-radiative recombination lifetimes of the minority carriers in the active region of a double hetero junction LED are 60 ns and 100 ns respectively. Determine the total recombination lifetime and the power internally generated within the device when peak emission wavelength is 0.87 µm at a drive current of 40 mA.


6. With the schematic representation and energy band diagram explain the working of a PIN Photodiode.



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10EC72

UNIT 4 1. For a step-graded index fibers which are misaligned with an axial offset of d, prove ? [July/Aug.-2010, 5 Marks] 2.

From the above expression Q.3, for d = 0.3 a. Calculate the coupling loss.[July/Aug.2007, 3 Marks]

3. Explain different types of fiber splicing techniques.


4. Show the PLED, step = Ps (NA)2 for rs < a. [Jan./Feb.-2011, 10 Marks] 5. Describe the different types of mechanical misalignment between the two joined fibers. [Jan./Feb.-2011, 6 Marks] 6. Explain with neat diagram working of butt-joint and expanded beam optical connectors. [Jan./Feb.-2009, 5 Marks] 7. Describe the different aspects of fiber-to-fiber-joints. [July.Aug.-2011, 6 Marks]

Dept of ECE/SJBIT

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10EC72

UNIT 5 1.

Discuss the different types of noise occur in laser diodes. [July/August-2010, 6 Marks]

2. With a schematic diagram explain the working of optical receiver. [July/August-2010, 8 Marks] 3. Discuss the possible sources of noise in optical receiver.

[July/August-2010, 6

Marks] 4. Discuss the different types of pre-amplifiers in optical receiver. [July/August-2011, 6 Marks] 5. Derive an expression for different noise sources in an optical receiver. [Jan./Feb.-2011, 10 Marks] 6. Derive an expression for the total mean-square noise carriers in a photodetector. [July/August-2012, 10 Marks]

Dept of ECE/SJBIT

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10EC72

UNIT 6 1. Discuss with a neat diagram, how digital signal

transmission takes place in a fiber

transmission link. [July/Aug.-2010, 12 Marks] 2. In order to design a simplex point-to-point link, what are all the choices available with regard to the components and their associate characteristics? Discuss. [July/Aug,2011, 10 Marks] 3. Draw the optical power loss model diagram for a point-to-point link and explain the concept of link power budget. [July/Aug.-2011, 6 Marks] 4. Explain briefly the NRZ codes and RZ codes used in line coding [July/Aug.-2008, 4 Marks] 5. Draw the block diagram of basic elements of an analog link and explain [July/Aug.-2012, 10 Marks] 6. What are the different noise sources in a photodiode? [Jan./Feb.-2012, 6 Marks] 7. Discuss how carrier-to-noise ratio changes with power level in an analog optical receiver. [Jan./Feb.-2009, 5 Marks] 8. Derive an expression for BER in a digital receiver. [Jan./Feb.-2009, 5 Marks] 9. What is RIN and how does it vary with bias current of laser diode? [Jan./Feb.-2009, 5 Marks] 10. What is graphical representation of a link loss budget? [Jan./Feb.-2012, 6 Marks]

Dept of ECE/SJBIT

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10EC72

UNIT 7 1. Explain the features of WDM and give an example of WDM component. [July/Aug.-2010, 10 Marks] 2. With a schematic diagram explain the working principle of star coupler and 2 x 2 fiber coupler. [July/Aug.-2010, 12 Marks] 3. A 2 x 2 biconical tapered fiber coupler has an input optical power level of P0 = 200 Microwatts. The output powers at the other three ports are P1 = 90 microwatts, P2 = 85 microwatts and P3 = 6.3 nanowatts, Find i) Coupling ratio ii) Excess loss iii) Insertion loss and iv) Cross talk. [July/Aug.-2010, 8 Marks]

4. What is WDM? How it is accomplished? [Jan./Feb.-2011, 6 Marks] 5. Describe 8 x 8 star coupler formed by inter connecting twelve 2 x 2 couplers. [Jan./Feb.2011, 8 Marks] 6. Explain the operational principle and implementation of WDM. [Jan./Feb.-2011, 7 Marks] 7. Describe 2 x 2 fiber coupler and its various losses. [Jan./Feb.-2012, 8 Marks]

Dept of ECE/SJBIT

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10EC72

UNIT 8 1. Draw the basic structure of an STS-1 SONET frame. Bring out relations among STS, OC and STM frames. [July/Aug.-2010, 10 Marks] 2.

An EDFA amplifer produce Ps out = 27 dBm for an in out level of 2 dBm at 1542 nm. i) Find the amplifier gain. ii) What is the minimum pump power required? [Jan./Feb.-2010, 10 Marks]

3. Describe i) SONET/SDH rings ii) SONET/SDH networks iii) Frame formant of SONET/SDH. [July/Aug.-2009, 12 Marks] 4. Write short notes on the fillowing : i) Optical LAN ii) Opticlal amplifers.


5. Describe the working of an Erbium doped fibre amplifer. [Jan./Feb.-2012, 6 Marks] 6. Write short notes on: 1) SONET/SDHstandards [Jan./Feb.-2009, 5 Marks] 7. What are four application of optical amplifier? [Jan./Feb.-2009, 5 Marks]

Dept of ECE/SJBIT

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Ece Vii Optical Fiber Communication 10ec72 Question Paper

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