Deck 18: Optical Communication and Led Performance Analysis

Question 1

Linearizing circuit techniques are used for LEDs.

Answer 1

True

Question 2

The internal quantum efficiency of LEDs decreasing _______________ with ________________ temperature.

A)exponentially, decreasing
B)exponentially, increasing
C)linearly, increasing
D)linearly, decreasing

Answer 2

exponentially, increasing

Question 3

To utilize _____________________ of SLDs at elevated temperatures, the use of thermoelectric coolers is important.

A)low-internal efficiency
B)high-internal efficiency
C)high-power potential
D)low-power potential

Answer 3

high-power potential

Question 4

For particular materials with smaller bandgap energies operating in _____________ wavelength, the linewidth tends to ______________

A)2.1 to 2.75 ?m, increase
B)1.1 to 1.7 ?m, increase
C)2.1 to 3.6 ?m, decrease
D)3.5 to 6 ?m, decrease

Question 5

The active layer composition must be adjusted if a particular center wavelength is desired.

Question 6

In optical fiber communication, the electrical signal dropping to half its constant value due to modulated portion of optical signal corresponds to _______

A)6 db
B)3 db
C)4 db
D)5 db

Question 7

The optical 3 dB point occurs when currents ratio is equal to

A)?
B)?
C)½
D)¾

Question 8

The optical bandwidth is _____________ the electrical bandwidth.

A)smaller
B)greater
C)same as
D)zero with respect to

Question 9

When a constant d.c. drive current is applied to device, the optical o/p power is 320 ?m. Determine optical o/p power when device is modulated at frequency 30 MHz with minority carrier recombination lifetime of LED i.e. 5ns.

A)4.49*10^-12
B)6.84*10^-9
C)1.29*10^-6
D)2.29*10^-4

Question 10

The optical power at 20 MHz is 246.2 ?W. Determine dc drive current applied to device with carrier recombination lifetime for LED of 6ns.

A)3.48*10^-4
B)6.42*10^-9
C)1.48*10^-3
D)9.48*10^-12

Question 11

Determine the 3 dB electrical bandwidth at 3 dB optical bandwidth Bopt of 56.2 MHz.

A)50.14
B)28.1
C)47.6
D)61.96

Question 12

The 3 dB electrical bandwidth B is 42 MHz. Determine 3dB optical bandwidth Bopt:

A)45.18
B)59.39
C)78.17
D)94.14

Question 13

Determine degradation rate ?rif constant junction temperature is 17 degree celsius.

A)7.79*10^-11
B)7.91*10^-11
C)6.86*10^-11
D)5.86*10^-11

Question 14

Determine CW operating lifetime for LED with ?rt = -0.58 and degradation rate ?r= 7.86*10^-11 h-1.

A)32.12
B)42
C)22.72
D)23.223