Ece Vii Optical Fiber Communication 10ec72 Question Paper

8/12/2019 Ece Vii Optical Fiber Communication 10ec72 Question Paper

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Optical Fiber Communication 10EC72

Department of ECE/SJBIT Page 1

QUESTION BANK

Unit 1

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.


6. Discuss the necessary mathematical condition that the angle of incidence must satisfyfor

the optical rays to propagate in a dielectric slab waveguide.


7. A multimode step index fiber with a core diameter of 80 m and a refractive index difference

of 1.5 % is operating at a wavelength of 0.85 m. 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 m, find the numerical aperture. [Jan./Feb.-2009, 4 Marks]

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


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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 m. Determine the normalized frequency for the fiber when the light at a

wavelength of 0.9 m is transmitted. Further, estimate the number of guided modes

propagatingin the fiber. [July/Aug.-2009, 4 Marks]

12.Explain briefly the halide glass, active glass and chalgenide glass fibers.


13.With neat sketch, describe the vapour, phase axial depositions method of drawing optical

fibers. [July/Aug.-2009, 8 Marks]


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Unit 2

1. Derive an expression for pulse spreading and dispersion, which is a function of wavelength

using time delay. [July/Aug.-2010, 8 Marks]

2.

Describe the significance of measure of the information capacity. [July/Aug.-2010, 6Marks]

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

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

8. Describe the material dispersion and waveguide dispersion.


9. Optical power launched into fiber at transmitter end is 150 W. 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 W. Same length system working in third window has 50

% of launched power.Calculate fiber attenuation for each case and mention avelength ofperation. [Jan./Feb.-2009, 4 Marks]

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


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11.What do you mean by material dispersion and waveguide dispersion? Describe briefly.

[July./Aug.-2009, 6 Marks]


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UNIT 3

1. Explain the operation of DFB and DBR LASERS. [Jan./Feb.-2012, 8 Marks]

2. Explain the operation of an APD. [Jan./Feb.-2012, 6 Marks]

3. Sketch and explain the FabryPerot 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. [Jan./Feb.-2009, 5 Marks]

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 m at a drive current of 40 mA. [July/Aug.-2009, 6 Marks]

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

Photodiode. [July/Aug.-2009, 8 Marks]


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Dept of ECE/SJBIT Page 6

UNIT 4

1. For a step-graded index fibers which are misaligned with an axial offset of d, prove ?


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. [July/Aug.-2010, 5 Marks]

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.


6. Explain with neat diagram working of butt-joint and expanded beam optical connectors.


7. Describe the different aspects of fiber-to-fiber-joints. [July.Aug.-2011, 6 Marks]


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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]


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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.


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]


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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]


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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. [July/Aug.-2011, 8 Marks]

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]

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Ece Vii Optical Fiber Communication 10ec72 Question Paper