M.Sc. (Semester IV) (CBCS) Examination Nov/Dec-2018
Electronics Science
FIBER OPTIC COMMUNICATION
Time 2½ Hours Max. Marks: 70
Instructions: Q.1 and Q.2 are compulsory.
Attempt any three questions from Q. 3 to Q.7.
All questions carry equal marks.
Use of nonprogrammable calculator is allowed.
Q.1 Select the correct alternatives:- 06
In spontaneous emission process the atom returns to ground or lower
energy state in
Predefined way Randomly
Uniformly All the above
n1 sin φ1 n2 sin
Snells law Newton's law
Aperture law None of these
In optical fiber the calorimetric methods are used to measure
Impuring in manufacturing process
Attenuation loss
Scattering loss
None of these
The vapor axial deposition process is
Batch process
Continuous process
Outside layer deposition process
Inside layer deposition process
Fresnel reflection at a fiber-fiber connection can be reduced to a very
low level through use of in the gap between the jointed fibers.
An index matching fluid Insulator
Amplifier Impedance
A photodiode has a quantum efficiency of 70% when photon of energy
1.8x10-19J is incident upon it, then the responsivity of photodiode is
0.694 0.723
0.369 0.623
Q.1 State true and false 08
The tracing helical path through fiber gives changes in direction of 2r at
each reflection, where r is radius of fiber known as skew ray.
When the angle of refraction is 900 and refracted ray emerges parallel
to interface between dielectric, the angle of incidence must be less than
900. This limiting case is known as Acceptance angle.
When optical signal travels along the fiber, it broadens due to
dispersion loss.
Attenuation per KM is expressed in decibel per KM.
The LED can operate at lower current density than Laser.
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SLR-VH-250
Response of avalanche photodiode is limited by the transit time of
carriers.
The fundamental step for manufacturing of optical fiber is variation in
refractive index of fiber.
The BER of optical receiver normally varies between 10-4 to 10-8.
Q.2 Write a shorts notes.
Explain the injecting laser characteristics? 05
Compare linear and non linear scattering mechanisms in optical fiber? 05
Write a shot note on photo transistor? 04
Q.3 A multimode graded index fiber exhibits total pulse broadening of 0.1μs
over a distance of 15 KM. Estimate
The maximum possible bandwidth on the link assuming no
intersymbol interference.
The pulse dispersion per unit length.
The bandwidth length product for fiber using dispersion
08
Write a note on dispersion modified single mode fiber? 06
Q.4 Briefly explain the liquid phase deposition technique for preparing optical
fiber.
08
Write a note on requirements of cable design structures? 06
Q.5 Explain different types of fiber alignment losses? 08
Explain the following terms with reference to the detector.
Quantum Efficiency
Responsivity
06
Q.6 Derive the rate equation for laser diode? 06
A planer LED is fabricated from gallium arsenide which has a refective
index of 3.6.
Calculate the optical power emitted into the air as a percentage of
internal optical power for the device when the transmission factor at
the crystal-air interface is 0.68.
When the optical power generated internally is 50% of the electric
power supplied, determine the external power efficiency.
08
Q.7 Explain any one method for fiber dispersion measurement? 08
Explain any one method used to measure fiber refractive index. 06