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Multiple Choice Questions:

Each question is for 1 mark

1. The scheme WDM is similar to

a) FDM for RF transmission                                            b) TDM
c) OFDM                                                                       d) OTDM

2.  Bluetooth is a type of radio wave information transmission system that is good for about

a) 30 feet               b) 30 years                 c) 30 miles              d) 300 miles

3. Which of the following fibres is suitable for wavelength division multiplexing of signal?

a) dispersion optimized       b) dispersion shifted   c) dispersion flattened   d) any fibre

4. Frequency reuse factor of a cellular system is given by...............

a) 1/2N                      b) 1/N2                  c) 1/N                     d) 2N

5. In GPRS, an user is able to achieve a data rate of....................

a) 171.1 kbps      b) 171.2 kbps    c) 171.3 kbps              d) 171.4 kbps

6. The material for making an efficient LED should be

a) Metal                                                  b) A direct band gap semiconductor
c) Indirect band gap semiconductor      d) An insulator

7.  In the c-band transponders the uplink and the downlink frequencies are respectively

a) 6 GHz and 4 GHz   b) 4 GHz and 6 GHz  c) 11 GHz and 14 GHz  d) 14 GHz and 11 GHz

8. Light is guided within the core of a step-index-fibre by

a) refraction at the core-air interface.
b) total internal reflection at the core-cladding interface.
c) the total of internal reflection of the outer side of the cladding.
d) change in the speed of light within the core.

9. Amplified output is given by the detector

a) p-n photodiode                           b) p-i-n photodiode
c) avalanche photodiode                  d) photovoltaic diode

10. A ray of light is passing from a silica glass of refractive index 1·48 to another silica of refractive index 1·46. What range of angles (measured with respect to the interface) for which this ray will undergo total internal reflection ?

a) 0° – 80°                                    b) 81° – 90°
c) 90° – 180°                                 d) 180° – 360°.

Short Answer Type Questions

Each question is for 5 marks

1. Derive Newtons law of gravitation and show that the orbit is elliptical in nature.
2. Discuss the LED-based different modulation drive circuits and explain their functionalities.
3. Define fibre acceptance angle and numerical aperture of a fibre. How are they
related ? If numerical aperture of an optical fibre is 0·3, what will be its acceptance
4. Draw and explain the schematic diagram of an Optical Communication System? Discuss the direct and indirect band gap semiconductor? (2+3)

Long Answer Type Questions

Each question is for 15 marks

1. Discuss the attenuation characteristics of SMF. Why 1550 nm wavelength is suitable for optical communication systems? What is optical power budgeting? Why is system margin provided? Derive the expression for orbital velocity of a satellite. (2+5+8)

2. Draw the GSM Architecture and explain it. Discuss in details, whats is the GPRS Location Management procedure? How data transfer and routing occurs through GPRS Network? Explain technically. (3+7+5)

3. a) The dispersion for a standard SMF is 17 ps/nm-km. To manage the dispersion of 80 km long fibre, what would be the dispersion of DCF of length 1.5 metre? What is the meaning of dispersion shifted
   b) What is optical power budgeting ? Why is system margin provided?
  c) Discuss the attenuation characteristics of SMF. Why the wavelength of 1550 nm is most suitable for optical communication system? (4+4+7)

4. a) What are  the desirable requirements of the optical source that are suitable for optical communication.
   b) Draw the structure of semiconductor LASER diode. A GAAS ILD has an optical cavity of length 250 micrometre and width 100 micrometre. At normal operating temperature the gain factor is 21 × 10–3 Acm–3 and the loss coefficient per cm is 10. Determine the threshold of current density and also find the threshold current for the device. Given the reflectivity of the mirrors r1 = r2 = 0.32.
   c) Explain the operation of LED with suitable diagram. What could be direct bandgap semiconductors which are chosen as LED material ? (3+7+5)

advance communication system, advance communication system viva questions
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