Digital Communication System MCQs

Question 1

Pulse spread due to modal dispersion in graded-index fibers is given by n A

Accepted Answer

co where A ?c nci A2 ? c

Answer

co where A CO ncl co n A2

Answer

co where A ? ca a = core radius n A2

Question 2

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

Accepted Answer

much less

Answer

much more

Answer

same as material dependent of A. only

Answer

none of these

Question 3

An optical fiber has a specification of 50 ps/km/nm material dispersion whenused with an optical beam from a laser diode at 0.88 pm with AX = 10A. What will be the overall pulse spread in nonoseconds due to material dispersion for a fiber of 2 km length

Accepted Answer

0.1

Answer

1

Answer

10

Answer

100

Question 4

Higher the angle of acceptance (0a) in a given fiber optic set-up,

Accepted Answer

higher is the magnitude of Numerical aperture as NA = sin OA

Answer

lower is the magnitude of Numerical aperture as NA = cos OA

Answer

lower is the fiber length that can be used for a given light power

Answer

none of these

Question 5

The channel capacity is exaclty equal to which of the following?

Accepted Answer

Amount of information per second

Answer

Noise rate in the channel

Answer

Bandwidth of demand

Answer

None of the above

Question 6

In a communication system, noise is most likely to effect the signal in the

Accepted Answer

channel

Answer

transmitter

Answer

information source

Answer

any of the above

Question 7

Dit is a unit of

Accepted Answer

information

Answer

channel capacity

Answer

entropy

Answer

rate of information

Question 8

The maximum possible value of entropy is

Accepted Answer

1

Answer

6

Answer

10

Answer

infinity

Question 9

Which of the following filters is used only at higher frequency?

Accepted Answer

Ladder

Answer

Half lattice

Answer

Crystal gate

Answer

Full lattice