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Electronics Engineering Objective Questions { Digital Communication System }

113. Small values of Numerical Aperture (NA) decrease the pulse dispersion but increase losses due to
A. Absorption
B. Bending
C. Scttering
D. Microbending
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114. Optical fibers rely for their operation on the phelomenon of
A. Reflection
B. Refraction
C. Dispersion
D. Total internal reflection
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115. What is normally the difference in the refractive indices of fiber core and fiber cladding in commercially available fibers?
A. neo 10 nei
B. neo oz--- 0.1 noi
C. the difference is from 0.1% to 1%
D. neo 2 noi
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116. The optical fiber characterised by SELF FOCUSSING effect
A. is the monomode optical fiber
B. is the graded index fiber
C. is the step-index fiber
D. is not useful for very high data bit rates
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117. For a given freespace wavelength (X0), the number of propagation modes that are possible
A. is independent of normalised fiber frequency
B.increases with normalised fiber frequency
C. decreases with normalised fiber frequency
D. none of these
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118. Pulse spread due to modal dispersion in graded-index fibers is given by n A
A.co where A CO ncl co n A2
B. co where A ? ca a = core radius n A2
C. co where A ?c nci A2 ? c
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119. For the some optical fiber, the material dispersion at 900 nm from a coherent source, as compared to the material dispersion at 900 nm obtained from a noncoherent source, will be
A. much less
B. much more
C. same as material dependent of A. only
D. none of these
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