Deck 2: Optical Fibers: Refraction, Transmission Losses, and Dispersion

Question 1

Refraction is the

A)bending of light waves
B)reflection of light waves
C)diffusion of light waves
D)refraction of light waves

Answer 1

bending of light waves

Question 2

The phenomenon which occurs when an incident wave strikes an interface at an angle greater than the critical angle with respect to the normal to the surface is called as

A)refraction
B)partial internal reflection
C)total internal reflection
D)limiting case of refraction

Answer 2

total internal reflection

Question 3

 Photonic crystal fibers also called as

A)conventional fibers
B)dotted fibers
C)stripped fibers
D)holey fibers

Answer 3

holey fibers

Question 4

Conventional optical fibers has more transmission losses than photonic crystal fibers. State whether the statement is true or false.

Question 5

Losses in photonic crystal fibers are reduced to a level of

A)0.1db/km
B)0.2db/km
C)0.3db/km
D)0.4db/km

Question 6

The high index contrast enables the PCF core to be reduced from around 8 ?min conventional fiber to

A)less than 1?m
B)more than 5?m
C)more than 3?m
D)more than 2?m

Question 7

The periodic arrangement of cladding air holes in photonic band gap fibers provides for the formation of a photonic band gap in the

A)h-plane of fiber
B)e-plane of fiber
C)e-h-plane of fiber
D)transverse plane of fiber

Question 8

In index-guided photonic crystal fiber structure, the dark areas are air holes. What does white areas suggests?

A)air
B)silica
C)water
D)plasma

Question 9

The unit of measurement of attenuation in optical fibers is

A)km
B)db
C)db/km
D)coulomb's

Question 10

The optical fiber incurs a loss in signal power as light travels down the fiber which is called as

A)scattering
B)attenuation
C)absorption
D)refraction

Question 11

If the input power 100?W is launched into 6 km of fiber, the mean optical power at the fiber output is 2?W. What is the overall signal attenuation through the fiber assuming there are no connectors or splices?

A)15.23db
B)16.98db
C)17.12db
D)16.62db

Question 12

A device which reduces the intensity of light in optical fiber communications is

A)compressor
B)optical attenuator
C)barometer
D)reducer

Question 13

. A decibel may be defined as the ratio of input and output optical power for a particular optical wavelength.

Question 14

. When the input and output power in an optical fiber is 120?W & 3?W respectively and the length of the fiber is 8 km. What is the signal attenuation per km for the fiber?

A)3db/km
B)2db/km
C)1db/km
D)4db/km

Question 15

A multimode step index fiber has a normalized frequency of 72. Estimate the number of guided modes.

A)2846
B)2592
C)2432
D)2136

Question 16

A graded-index fiber has a core with parabolic refractive index profile of diameter of 30?m, NA=0.2, ?=1?m. Estimate the normalised frequency.

A)19.32
B)18.84
C)16.28
D)17.12

Question 17

A step-index fiber has core refractive index 1.46 and radius 4.5?m. Find the cutoff wavelength to exhibit single mode operation. Use relative index difference as 0.25%.

A)1.326?m
B)0.124?m
C)1.214?m
D)0.123?m

Question 18

One of the given statements is true for intermodal dispersion. Choose the right one.

A)low in single mode and considerable in multimode fiber
B)low in both single mode and multimode fiber
C)high in both single mode and multimode fiber
D)high in single mode and low in multimode fiber

Question 19

For lower bandwidth applications,

A)single mode fiber is advantageous
B)photonic crystal fibers are advantageous
C)coaxial cables are advantageous
D)multimode fiber is advantageous

Question 20

Most of the optical power is carried out in core region than in cladding. State true or false:

Question 21

Meridional rays in graded index fibers follow

A)straight path along the axis
B)curved path along the axis
C)path where rays changes angles at core-cladding interface
D)helical path

Question 22

What is the unit of normalized frequency?

A)hertz
B)meter/sec
C)coulombs
D)it is a dimensionless quantity

Question 23

. Skew rays follow a

A)hyperbolic path along the axis
B)parabolic path along the axis
C)helical path
D)path where rays changes angles at core-cladding interface

Question 24

A graded-index fiber has a core with parabolic refractive index profile of diameter of 30?m, NA=0.2, ?=1?m. Estimate the normalised frequency.

A)19.32
B)18.84
C)16.28
D)17.12

Question 25

A step-index fiber has core refractive index 1.46 and radius 4.5?m. Find the cutoff wavelength to exhibit single mode operation. Use relative index difference as 0.25%.

A)1.326?m
B)0.124?m
C)1.214?m
D)0.123?m