AKTU Solve Paper
Optical Fiber Communication
Year - 2019 - 20
Q24. What causes microscopic bend?
Ans. Non-uniform pressure.
Q25. When more than one mode is
propagating, how is it dispersed?
Ans. Inter-modal dispersion.
Q26. Calculate the numerical aperture of an
optical fiber whose core and cladding are made of materials of refractive index
1.6 and 1.5 respectively?
Ans. 0.55677.
Q27. A step index fiber has a numerical
aperture of 0.26, a core refractive index of 1.5 and a core diameter of 100
micrometre. Calculate the acceptance angle.
Ans.
15.070
Q28. Which of the following is a unique property
of laser?
Ans. Coherence.
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Q29. Which of the following is an example
of optical pumping?
Ans. Ruby laser.
Q30. Calculate the wavelength of radiation
emitted by an LED made up of a semiconductor material with band gap energy
2.8ev.
Ans. 4430.8A
Q31. The information carrying capacity of a
laser is enormous due to its large __________
Ans. Bandwidth.
Q32. What is the region enclosed by the
optical cavity called?
Ans. Optical resonator.
Q33. Photons emitted by spontaneous
emission are___________
Ans. Non-coherent and non-monochromatic.
Q34. During population inversion, which of
the following process is dominant?
Ans. Stimulated absorption.
Q35. Which of the following is a four level
laser?
Ans. He-Ne.
Q36. The microscopic bending losses show an
exponential increase due to________ in radius of curvature
Ans. Decrease.
Q37. In stimulated emission which among the
following parameter of generated photon is/are similar to the photons of
incident wave
Ans.
A) phase
B) frequency
C) polarization and direction of
travel.
D) all of the above.
Q38. In a laser structure the existence of
standing wave is possible at frequencies for which the distance between the
mirrors is an integral number of
Ans. λ/2
Q39. In lambertian output of LED the source
is ________ bright from all directions
Ans. Equally.
Q40. Which of the preamplifier place a
crucial role in reducing the effect of thermal noise
Ans. High impedance preamplifier.
Q41. In high impedance preamplifier how are
the source kept to minimum level
Ans. A) by reducing dark current with protodiode.
B)
by reducing thermal noise of biasing register.
C) by using high impedance amplifier.
D) all of the above.
Q42. Which among the following is / are
responsible for generating attenuation of an optical power in fibre.
Ans. A) absorption.
B) scattering.
C) waveguide effect.
D) all of the above.
Q43. In the structure of fibre optic cable
the refractive index of core is always _______ the refractive index of the
cladding
Ans. greater than
Q44. Which among the following represents
the lateral shift of a light beam on reflection at a dielectric interface?
Ans. Goos haenchen’s shift.
Q45. Why are the plastic clad silica fibre
optic cables not used widely?
Ans. A) difficulty in connector application due to
excessive plasticity in cladding.
B) difficulty in bonding .
C) insolubility in organic solvents.
D) all of the above.
Q46. Which reason is responsible for
occurrence of the nonlinear cross phase modulation
Ans. Intensity dependence of refractive index.
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