Deck 5: Fiber Optics and Dispersion

Question 1

3dB optical bandwidth is always ___________ the 3dB electrical bandwidth.

A)smaller than
B)larger than
C)negligible than
D)equal to

Answer 1

larger than

Question 2

A multimode graded index fiber exhibits a total pulse broadening of 0.15?sover a distance of 16 km. Estimate the maximum possible bandwidth, assuming no intersymbol interference.

A)4.6 mhz
B)3.9 mhz
C)3.3 mhz
D)4.2 mhz

Answer 2

3.3 mhz

Question 3

What is pulse dispersion per unit length if for a graded index fiber, 0.1?s pulse broadening is seen over a distance of 13 km?

A)6.12ns/km
B)7.69ns/km
C)10.29ns/km
D)8.23ns/km

Answer 3

7.69ns/km

Question 4

Chromatic dispersion is also called as intermodal dispersion. State whether the given statement true or false.

Question 5

Chromatic dispersion is also called as intermodal dispersion. State true or false

Question 6

The optical source used in a fiber is an injection laser with a relative spectral width ??/? of 0.0011 at a wavelength of 0.70?m. Estimate the RMS spectral width.

A)1.2 nm
B)1.3 nm
C)0.77 nm
D)0.98 nm

Question 7

In waveguide dispersion, refractive index is independent of

A)bit rate
B)index difference
C)velocity of medium
D)wavelength

Question 8

 Intermodal dispersion occurring in a large amount in multimode step index fiber results in

A) propagation of the fiber
B)propagating through the fiber
C)pulse broadening at output
D)attenuation of waves

Question 9

After Total Internal Reflection the Meridional ray

A)makes an angle equal to acceptance angle with the axial ray
B)makes an angle equal to critical angle with the axial ray.
C)travels parallel equal to critical angle with the axial ray
D)makes an angle equal to critical angle with the axial ray

Question 10

Consider a single mode fiber having core refractive index n1= 1.5.

A)1.00?sec
B)0.06?sec
C)0.90?sec
D)0.30?sec

Question 11

A 4 km optical link consists of multimode step index fiber with core refractive index of 1.3 and a relative refractive index difference of 1%. Find the delay difference between the slowest and fastest modes at the fiber output.

A)0.173 ?sec
B)0.152 ?sec
C)0.96 ?sec
D)0.121 ?sec

Question 12

A multimode step-index fiber has a core refractive index of 1.5 and relative refractive index difference of 1%. The length of the optical link is 6 km. Estimate the RMS pulse broadening due to intermodal dispersion on the link.

A)92.6 ns
B)86.7 ns
C)69.3 ns
D)68.32 ns

Question 13

The differential attenuation of modes reduces intermodal pulse broadening on a multimode optical link.

Question 14

The index profile of a core of multimode graded index fiber is given by-

A)n (r) = n1 [1 - 2?(r2/a)2]1/2; rB)n (r) = n1 [3 - 2?(r2/a)2]1/2; rC)n (r) = n1 [5 - 2?(r2/a)2]1/2; r>a
D)n (r) = n1 [1 - 2?(r2/a)2]1/2; r

Question 15

Intermodal dispersion in multimode fibers is minimized with the use of step-index fibers.

Question 16

Estimate RMS pulse broadening per km due to intermodal dispersion for multimode step index fiber where length of fiber is 4 km and pulse broadening per km is 80.6 ns.

A)18.23ns/km
B)20.15ns/km
C)26.93ns/km
D)10.23ns/km

Question 17

Practical pulse broadening value for graded index fiber lies in the range of

A)0.9 to 1.2 ns/km
B)0.2 to 1 ns/km
C)0.23 to 5 ns/km
D)0.45 to 8 ns/km

Question 18

The nonlinear effects in optical fibers are large.

Question 19

How many categories of nonlinear effects are seen in optical fibers?

A)one
B)two
C)three
D)four

Question 20

Which of the following is not related to Kerr effects?

A)self-phase modulation
B)cross-phase modulation
C)four-wave mixing
D)stimulated raman scattering

Question 21

Linear scattering effects are _______ in nature.

A)elastic
B)non-elastic
C)mechanical
D)electrical

Question 22

Which thing is more dominant in making a fiber function as bidirectional optical amplifier?

A)core material
B)pump source
C)cladding material
D)diameter of fiber

Question 23

_________ semiconductor laser sources generally have broader bandwidths.

A)injection
B)pulsed
C)solid-state
D)silicon hybrid

Question 24

Nonlinear effects which are defined by the intensity - dependent refractive index of the fiber are called as

A)scattering effects
B)kerr effects
C)raman effects
D)tomlinson effects

Question 25

Self-phase modulation causes modifications to the pulse spectrum.