KIIT University 2008 B.Tech Electronics and Tele-Communication Engineering OPTICAL AND SATELLITE COMMUNICATION - Question Paper
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OPTICAL AND SATELLITE COMMUNICATION
-------------5TH SEMESTER------------------
O&SC EC 506 (E&TC)
FIFTH SEMESTER EXAMINATION-2008 OPTICAL & SATELLITE COMMUNICATION [ EC 506 ]
Time: 3 Hours
Full Marks: 70
Answer any SIX questions including Question No.l which is compulsory.
The figures in the margin indicate full marks.
Candidates are required to give their answers in their own words as far as practicable and of all parts of a question should be answered at one place only.
1. a) Draw index profile of a graded index fiber.
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b) Write the significance of V No.
c) If pulse widttTfs-gtven as'Z'85 nland total dispersion is given as 2.5 ns. What is the maximum allowed bit rate?
d) What do you understand by NEP. Write unit of NEP.
e) Draw input-output characteristics of LED.
f) What do you understand by E1RP?
g) What is Look angle?
h) What are the three axises considered for 3-axis stabilization system? Specify the directions.
i) It down link carrier to noise ratio is 20 dB and uplink carrier to noise ratio is 25dB. Calculate overall carrier to noise ratio, j) What is atmospheric scintillation?
(i)
KIIT-U/2008/A ulumn End Semester Examination-2008
2. a) Describe briefly about inter modal dispersion. Derive inter-modal dispersion for step index fiber.
b) Calculate the dispersion per km of length and the total dispersion in a 10km length of step index fiber if the Numerical apereture is given as 0.3534 with refractive index of the core being 1.55.
c) Which type of dispersion can not be avoided any way? Discuss briefly.
. a) Discuss about No of modes possible in a step index fiber and graded index fiber. Also state the condition to generate a unique mode.
b) Discuss about the types of modes possible in step index fiber and graded index fiber with diagram.
c) A single mode step index fiber operates at 850 nm with refractive index of core and cladding 1.48 and 1.465 respectively. Find the maximum core radius and maximum value required for normalised difference. Also calculate the maximum acceptance angle.
4. a) Describe briefly about the types of noises generated at the photo-detector end. Calculate the signal to noise ratio considering all. Also calculate SNR for the shot noise limited case,
b) A fiber link is to have the following characteristics At Transmitter: Laser diode minimum P =0 dBm (1 mw) Receiver: Minimum Pr = -57 dBm at a maximum bit
error rate 1 in 1,000,000,000.
Port Losses: L . L r = 6dB each
pi. V'
Connector Losses (2): Lc = 1 .OdB (each) splices (5): Ls = 0.5dB (each)
Fiber Loss : L( = 2 dB/km
Loss Margin : M = 5 dB
Fiber total dispersion : A t = 0.505 ns/km
maximum bit rate: B=35 M bits/sec
a) Find Loss Limited Fiber Length
b) Find the maximum B.W for the Loss Limited Length
c) Find the dispersion Limited Fiber Length
d) Also find the repeater spacing
>. a) Derive the height of the Geo-Stationary orbit taking suitable assumptions.
b) What do you understand by orbital elements? Write down the element set commonly used for satellite communication. Also describe briefly each element.
c) If the orbital period for Geostationary Satellite orbit is taken as 23 hour 56 min and 4.09s. Calculate the orbital height from surface of earth assuming earth radius of 6378.173 km.
[\1 = 3.986004418 x 105 km3/S2 ]
6. a) How many methods are employed to stabilize a satellite in the orbit? Discuss briefly with diagram.
b) What is the requirement for a double conversion transponder? Describe the operation with block diagram.
c) Calculate the Gain of the receiving antenna in terms of 03dB beam width with a efficiency of 55%.
FIFTH
7. a) A satellite orbiting earth at a height of 38,500 kms and connected from ground station with uplink frequency of 14.15 GHz. The diameter of the transmitting antenna is
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5 meters and efficiency is 68%. The gain of the receiving antenna is 31 dB with an off axis Loss of 2dB. In addition to path loss, the link experiences an atmospheric loss of 1dB. The Noise band width of the digital signal is 27MHz with a system noise temperature of 500K. Calculate the uplink power budget to determine transmitting power of antenna if minimum required carrier to Noise ratio is given as 30dB.
Discuss on atmospheric effect for the transmitting signal.
Write short notes on any four.
a) Analog and Digital modulation with LED
b) Microbending and Macrobending Losses
c) Master Antenna TV System
d) Inospheric effect
e) Photodetector
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KUT-tJ/2008/Autumn End Semester Examination-2008
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