Deck 15: Key Concepts in Laser and Optical Fiber Communication Technology

Question 1

The phenomenon occurring when the electron and photon population within the structure comes into equilibrium is known as

A)auger recombination
B)inter-valence band absorption
C)carrier leakage
D)relaxation oscillations

Answer 1

relaxation oscillations

Question 2

When a current pulse reaches a laser having parasitic capacitance after the initial delay time, that pulse will

A)have no effect
B)will get vanished
C)becomes narrower
D)gets broader

Answer 2

gets broader

Question 3

Reducing delay time and ____________ are of high importance for lasers.

A)auger recombination
B)inter-valence band absorption
C)carrier leakage effects
D)relaxation oscillations

Answer 3

relaxation oscillations

Question 4

Dynamic line-width broadening under the direct modulation of injection current is known as

A)auger recombination
B)inter-valence band absorption
C)carrier leakage effects
D)frequency chirping

Question 5

A particular characteristic or parameter that occurs during analog transmission of injection lasers is

A)noise
B)mode hopping
C)carrier leakage effects
D)frequency chirping

Question 6

Intensity of output from semiconductor injection lasers leading to optical intensity noise is due to

A)fluctuations in amplitude
B)mode hopping
C)carrier leakage effects
D)frequency chirping

Question 7

In multimode lasers the optical feedback from unnecessary external reflections affecting stability of frequency and intensity is

A)remains unaffected
B)increased gradually
C)reduced
D)gets totally vanished

Question 8

Reduction in the number of modes in multimode fiber increases the mode partition noise.

Question 9

The behavior of laser occurring when current is increased above threshold particularly is

A)mode hopping
B)auger recombination
C)frequency chirping
D)noise

Question 10

____________________ lasers are presently the major laser source for optical fiber communications

A)semiconductor
B)non-semiconductor
C)injection
D)solid-state

Question 11

Which of the following is not a property of Nd: YAG laser that enables its use as an optical fiber communication source?

A)single mode operation
B)narrow line-width
C)long lifetime
D)semiconductors and integrated circuits

Question 12

In a three level system, the threshold power decreases inversely with the length of the fiber gain medium.

Question 13

Which of the following co-dopant is not employed by neodymium and erbium doped silica fiber lasers?

A)phosphorus pent oxide
B)germania
C)nitrogen
D)alumina

Question 14

_______________ fibers include addition of lead fluoride to the core glass in order to raise the relative refractive index.

A)solid-state
B)gaas
C)semiconductor
D)zblanp

Question 15

In Fabry-perot laser, the lower threshold is obtained by

A)increasing the refractive index
B)decreasing the refractive index
C)reducing the slope efficiency
D)increasing the slope efficiency

Question 16

Y3Al5 O12 Is a molecular formula for _____________

A)ytterbium aluminate
B)yttrium oxide
C)ytterbium oxy-aluminate
D)yttrium-aluminum garnet

Question 17

Which of these factors are critical in affecting the system performance in the case of coherent optical fiber transmission?

A)laser line-width and stability
B)refractive index and index difference
C)core cladding diameter
D)frequency

Question 18

_______________ occurs as a result of the change in lasing frequency with gain

A)frequency multiplication
B)dispersion
C)attenuation
D)line-width broadening

Question 19

Laser cavity length can be extended by

A)increasing the refractive index
B)reducing frequency
C)introduction of external feedback
D)using grin-rod lenses

Question 20

What is the purpose of wavelength dispersive element is LEC lasers?

A)wavelength selectivity
B)reduction of line-width
C)frequency multiplication
D)avalanche multiplication

Question 21

An effective method to reduce the line-width is to make the cavity longer.

Question 22

Which devices are used to modulate the external cavity in order to achieve the higher switching speeds?

A)electromagnetic
B)acousto-optic
C)dispersive
D)lead

Question 23

How many techniques are used to tune monolithic integrated devices (lasers)?

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

Question 24

_________________ laser can be produced when a coupler section is introduced between the amplifier and phase sections of a structure

A)sg-dbr
B)gcsr
C)y 4-shifted
D)dsm

Question 25

The rare-earth-doped fiber lasers have spectral line-width in the range of _________________

A)0.1 to 1 nm
B)1.2 to 1.5 nm
C)6 to 10 nm
D)2 to 2.3 nm