Friday, August 17, 2012

EC2402 OPTICAL COMMUNICATION AND NETWORKING PREVIOUS YEAR ANNA UNIVERSITY QUESTION PAPER /MODEL QUESTION PAPER NOV/DEC 2011


B.E./B.Tech. DEGREE EXAMINATION, NOVEMBER/DECEMBER 2011.
Seventh Semester
Electronics and Communication Engineering
EC 2402 — OPTICAL COMMUNICATION AND NETWORKING
(Regulation 2008)
Time : Three hours Maximum : 100 marks
Missing data could be suitably assumed.
Answer ALL questions.
PART A — (10 × 2 = 20 marks)
1. What is the energy of a single photon of the light whose λ = 1550 nm, in eV?
2. Assume that there is a glass rod of refractive index 1.5, surrounded by air. Find the critical incident angle.
3. Define the attenuation coefficient of a fiber.
4. Calculate the cut-off wavelength of an optical signal through a fiber with its core refractive index of 1.50 and that of cladding = 1.46. The core radius of 25 μm. The normalised frequency is 2.405.
5. Why silicon is not used to fabricate LED or Laser diode?
6. Calculate the external differential quantum efficiency of a laser diode operating at 1.33 μm. The slope of the straight line portion of the curve for the emitted optical power P versus drive current I is given by 15 mW/mA.
7. Define ‘quantum efficiency’ of a photo detector and write the expression.
8. Mention the error sources in fiber optic receiver.
9. What are the three common topologies used for fiber optical network? Give the schematic of any one network?
10. Calculate the number of independent signals that can be sent on a single fiber in the 1525-1565 nm band. Take the spectral spacing as per ITU-T recommendation G.692.
PART B — (5 × 16 = 80 marks)
11. (a) (i) What is numerical aperture of an optical fiber? Deduce an expression for the same. (12)
(ii) Calculate NA of silica fiber with its core refractive index (n1) of 1.48 and cladding refractive index of 1.46. What should be the new value of ‘n1’ in order to change the NA to 0.23. (4)
Or
(b) (i) Explain the phenomenon of total internal reflection using Snell's law with figures and calculations. (12)
(ii) Distinguish step-index from graded index fibers. (4)
12. (a) (i) What do you mean by pulse broadening? Explain its effect on information carrying capacity of a fiber. (12)
(ii) An LED operating at 850 nm has a spectral width of 45 nm. What is the pulse spreading in ns/km due to material dispersion? What is the pulse spreading when a laser diode having a 2 nm spectral width is used? The material dispersion is 90 ps/nm km. (4)
Or
(b) (i) What is meant by ‘fiber splicing’? Explain fusion splicing of optical fibers. (8)
(ii) Explain expanded beam fiber connector with a neat schematic.(8)
13. (a) (i) Compare LED with a laser diode. (4)
(ii) With the help of a neat diagram explain the construction and working of a surface emitting LED. (12)
Or
(b) (i) Explain the structure and working of a silicon APD. (12)
(ii) Define S/N ratio of a photodetector. What conditions should be met to achieve a high SNR? (4)

14. (a) (i) Explain the fiber optic receiver operation using a simple model and its equivalent circuit. (8)
(ii) Explain the operation of a pre-amplifier built using a FET. (8)
Or
(b) Explain the measurement technique used in the case of
(i) Numerical aperture
(ii) Refractive index profile


(iii) Fiber cut-off wave length
(iv) Fiber diameter. (16)
15. (a) Explain the architecture of SONET and discuss nonlinear effects on Network performance. (16)
Or
(b) Write short notes on
(i) Wavelength routed networks. (8)
(ii) Optical CDMA. (8)

PROTECTION AND SWITCHGEAR EE2402 ANNA UNIVERSITY NOV/DEC 2011 PREVIOUS YEAR QUESTION PAPER DOWNLOAD


B.E./B.Tech. DEGREE EXAMINATION, NOVEMBER/DECEMBER 2011.
Seventh Semester
Electrical and Electronics Engineering
EE 2402 — PROTECTION AND SWITCHGEAR
(Regulation 2008)
Time : Three hours Maximum : 100 marks
Answer ALL questions.
PART A — (10 × 2 = 20 marks)
1. What is surge absorber? How do they differ from surge diverter?
2. Define the term ‘‘Insulation Coordination”.
3. Compare Static and Electromagnetic relay.
4. A relay is connected to 400/5 ratio current transformer with current setting of 150%.
Calculate the Plug Setting Multiplier when circuit carries a fault current of 4000 A.
5. Explain the secondary of current transformer should not be open.
6. What is meant by time-graded system protection?
7. Distinguish between recovery voltage and restriking voltage.
8. List the factors affecting the transient recovery voltage.
9. Give the advantage of SF6 circuit breaker over Air blast circuit breaker.
10. What are the basic requirements of circuit breaker?
PART B — (5 ×16 = 80 marks)
11. (a) Discuss and compare the various methods of neutral earthing. (16)
Or
(b) (i) Describe the essential qualities of a protective relaying. (8)
(ii) Briefly explain the various methods of overvoltage protection of overhead transmission line. (8)
12. (a) Describe the construction and operation of an inductive type directional overcurrent
relay with a neat diagram. Also explain its operational characteristics. (16)
Or
(b) Explain the principle of distance relays stating clearly the difference between impedance relay, reactance and mho relay. Indicate the difference on R-X diagrams and show where each type is suitable. (16)
13. (a) (i) Explain the factors which cause difficulty in applying Merz-Price circulating current principle to a power transformers. (8)
(ii) A three phase transformer of 220/11000 Line Volts is Connected in star / delta. The protective transformers on 220 V side have a current ratio of 600/5. What should be the current transformer ratio on 11000 V side? (8)
Or
(b) Describe the differential pilot wire method of protection of feeder. (16)
14. (a) (i) Explain how arc is initiated and sustained when the circuit breaker contacts break. (6)


(ii) Explain in detail the various methods of arc extinction in a circuit breaker. (10)
Or
(b) (i) What is current Chopping? Explain how can the effect of current chopping be
minimized? (8)
(ii) Derive an expression for the Rate of Rise of Restriking Voltage (RRRV) in a
C.B. (8)
15. (a) Explain with a neat sketch, the construction and working of minimum oil circuit
breaker. Also give its merits and demerits. (16)
Or
(b) (i) Describe the various types of rating of a circuit breaker. (8)
(ii) Describe the various methods of testing of circuit breaker. (8)