MCQOPTIONS
Saved Bookmarks
MCQOPTIONS
This section includes 259 Mcqs, each offering curated multiple-choice questions to sharpen your Electrical Engineering knowledge and support exam preparation. Choose a topic below to get started.
| 151. |
External modulation for                  modulation format allows the most sensitive coherent detection mechanism. |
| A. | fsk |
| B. | dsk |
| C. | psk |
| D. | ask |
| Answer» D. ask | |
| 152. |
                       offers the potential for improving the coherent optical receiver sensitivity by increasing the choice of signalling frequencies. |
| A. | mfsk |
| B. | mdsk |
| C. | mpsk |
| D. | mask |
| Answer» B. mdsk | |
| 153. |
The frequency deviation at frequencies above 1 MHz is typically |
| A. | 10 to 20 ma-1 |
| B. | 100 to 500 ma-1 |
| C. | 1000 to 2000 ma-1 |
| D. | 30 to 40 ma-1 |
| Answer» C. 1000 to 2000 ma-1 | |
| 154. |
                 does not require an external modulator. |
| A. | fsk |
| B. | dsk |
| C. | psk |
| D. | ask |
| Answer» B. dsk | |
| 155. |
Almost                    of the transmitter power is wasted in the use of external modulators. |
| A. | half |
| B. | quarter |
| C. | one-third |
| D. | twice |
| Answer» B. quarter | |
| 156. |
                           is essentially a crude form of Amplitude shift keying. |
| A. | analog modulation |
| B. | digital intensity modulation |
| C. | photodetector |
| D. | receiver structure |
| Answer» C. photodetector | |
| 157. |
Considering the values given below, calculate the mode separation in terms of free space wavelength for a laser. (Frequency separation = 2GHz, Wavelength = 0.5 μm) |
| A. | 1.4×10-11 |
| B. | 1.6×10-12 |
| C. | 1×10-12 |
| D. | 6×10-11 |
| Answer» C. 1×10-12 | |
| 158. |
Longitudinal modes contribute only a single spot of light to the laser output. |
| A. | true |
| B. | false |
| Answer» B. false | |
| 159. |
An injection laser has active cavity losses of 25 cm-1 and the reflectivity of each laser facet is 30%. Determine the laser gain coefficient for the cavity it has a length of 500μm. |
| A. | 46 cm-1 |
| B. | 51 cm-1 |
| C. | 50 cm-1 |
| D. | 49.07 cm-1 |
| Answer» E. | |
| 160. |
A semiconductor laser crystal of length 5 cm, refractive index 1.8 is used as an optical source. Determine the frequency separation of the modes. |
| A. | 2.8 ghz |
| B. | 1.2 ghz |
| C. | 1.6 ghz |
| D. | 2 ghz |
| Answer» D. 2 ghz | |
| 161. |
Doppler broadening is a homogeneous broadening mechanism. |
| A. | true |
| B. | false |
| Answer» C. | |
| 162. |
43 μm. Determine the number of longitudinal modes. |
| A. | 1×102 |
| B. | 3×106 |
| C. | 2.9×105 |
| D. | 2.2×105 |
| Answer» E. | |
| 163. |
The lower energy level contains more atoms than upper level under the conditions of |
| A. | isothermal packaging |
| B. | population inversion |
| C. | thermal equilibrium |
| D. | pumping |
| Answer» D. pumping | |
| 164. |
                                     in the laser occurs when photon colliding with an excited atom causes the stimulated emission of a second photon. |
| A. | light amplification |
| B. | attenuation |
| C. | dispersion |
| D. | population inversion |
| Answer» B. attenuation | |
| 165. |
An incandescent lamp is operating at a temperature of 1000K at an operating frequency of 5.2×1014 Hz. Calculate the ratio of stimulated emission rate to spontaneous emission rate. |
| A. | 3×10-13 |
| B. | 1.47×10-11 |
| C. | 2×10-12 |
| D. | 1.5×10-13 |
| Answer» C. 2×10-12 | |
| 166. |
Which process gives the laser its special properties as an optical source? |
| A. | dispersion |
| B. | stimulated absorption |
| C. | spontaneous emission |
| D. | stimulated emission |
| Answer» E. | |
| 167. |
How many types of sources of optical light are available? |
| A. | one |
| B. | two |
| C. | three |
| D. | four |
| Answer» D. four | |
| 168. |
A device which converts electrical energy in the form of a current into optical energy is called as |
| A. | optical source |
| B. | optical coupler |
| C. | optical isolator |
| D. | circulator |
| Answer» B. optical coupler | |
| 169. |
The active layer of E-LED is heavily doped with |
| A. | zn |
| B. | eu |
| C. | cu |
| D. | sn |
| Answer» B. eu | |
| 170. |
The InGaAsP is emitting LEDs are realized in terms of restricted are |
| A. | length strip geometry |
| B. | radiance |
| C. | current spreading |
| D. | coupled optical power |
| Answer» B. radiance | |
| 171. |
Mesa structured SLEDs are used |
| A. | to reduce radiance |
| B. | to increase radiance |
| C. | to reduce current spreading |
| D. | to increase current spreading |
| Answer» D. to increase current spreading | |
| 172. |
In a multimode fiber, much of light coupled in the fiber from an LED is |
| A. | increased |
| B. | reduced |
| C. | lost |
| D. | unaffected |
| Answer» D. unaffected | |
| 173. |
0375 V. Determine optical power launched into fiber. |
| A. | 0.03 |
| B. | 0.05 |
| C. | 0.3 |
| D. | 0.01 |
| Answer» B. 0.05 | |
| 174. |
Internal absorption in DH surface emitter Burros type LEDs is |
| A. | cannot be determined |
| B. | negligible |
| C. | high |
| D. | very low |
| Answer» E. | |
| 175. |
The techniques by Burros and Dawson in reference to homo structure device is to use an etched well in GaAs structure. |
| A. | true |
| B. | false |
| Answer» B. false | |
| 176. |
In surface emitter LEDs, more advantage can be obtained by using |
| A. | bh structures |
| B. | qc structures |
| C. | dh structures |
| D. | gain-guided structure |
| Answer» D. gain-guided structure | |
| 177. |
As compared to planar LED structure, Dome LEDs have                              External power efficiency                        effective emission area and                            radiance. |
| A. | greater, lesser, reduced |
| B. | higher, greater, reduced |
| C. | higher, lesser, increased |
| D. | greater, greater, increased |
| Answer» C. higher, lesser, increased | |
| 178. |
The amount of radiance in planer type of LED structures is |
| A. | low |
| B. | high |
| C. | zero |
| D. | negligible |
| Answer» B. high | |
| 179. |
The                              system is best developed and is used for fabricating both lasers and LEDs for the shorter wavelength region. |
| A. | inp |
| B. | gasb |
| C. | gaas/gasb |
| D. | gaas/alga as dh |
| Answer» E. | |
| 180. |
How many types of hetero-junctions are available? |
| A. | two |
| B. | one |
| C. | three |
| D. | four |
| Answer» B. one | |
| 181. |
A homo-junction is an interface between two adjoining single-crystal semiconductors with different band-gap energies. |
| A. | true |
| B. | false |
| Answer» C. | |
| 182. |
A GaAs injection laser with an optical cavity has refractive index of 3.6. Calculate the reflectivity for normal incidence of the plane wave on the GaAs-air interface. |
| A. | 0.61 |
| B. | 0.12 |
| C. | 0.32 |
| D. | 0.48 |
| Answer» D. 0.48 | |
| 183. |
A GaAs injection laser has a threshold current density of 2.5*103Acm-2 and length and width of the cavity is 240μm and 110μm respectively. Find the threshold current for the device. |
| A. | 663 ma |
| B. | 660 ma |
| C. | 664 ma |
| D. | 712 ma |
| Answer» C. 664 ma | |
| 184. |
Population inversion is obtained at a p-n junction by |
| A. | heavy doping of p-type material |
| B. | heavy doping of n-type material |
| C. | light doping of p-type material |
| D. | heavy doping of both p-type and n-type material |
| Answer» E. | |
| 185. |
Which impurity is added to gallium phosphide to make it an efficient light emitter? |
| A. | silicon |
| B. | hydrogen |
| C. | nitrogen |
| D. | phosphorus |
| Answer» D. phosphorus | |
| 186. |
21*10-10cm3s-1. |
| A. | 2ns |
| B. | 1.39ns |
| C. | 1.56ns |
| D. | 2.12ms |
| Answer» C. 1.56ns | |
| 187. |
The recombination in indirect band-gap semiconductors is slow. |
| A. | true |
| B. | false |
| Answer» B. false | |
| 188. |
                                   is used when the optical emission results from the application of electric field. |
| A. | radiation |
| B. | efficiency |
| C. | electro-luminescence |
| D. | magnetron oscillator |
| Answer» D. magnetron oscillator | |
| 189. |
The majority of the carriers in a p-type semiconductor are |
| A. | holes |
| B. | electrons |
| C. | photons |
| D. | neutrons |
| Answer» B. electrons | |
| 190. |
The energy-level occupation for a semiconductor in thermal equilibrium is described by the |
| A. | boltzmann distribution function |
| B. | probability distribution function |
| C. | fermi-dirac distribution function |
| D. | cumulative distribution function |
| Answer» D. cumulative distribution function | |
| 191. |
A perfect semiconductor crystal containing no impurities or lattice defects is called as |
| A. | intrinsic semiconductor |
| B. | extrinsic semiconductor |
| C. | excitation |
| D. | valence electron |
| Answer» B. extrinsic semiconductor | |
| 192. |
Plastic fibers are less widely used than glass fibers. |
| A. | true |
| B. | false |
| Answer» B. false | |
| 193. |
Numerical aperture is constant in case of step index fiber. |
| A. | true |
| B. | false |
| Answer» B. false | |
| 194. |
How many propagation modes are present in single mode fibers? |
| A. | one |
| B. | two |
| C. | three |
| D. | five |
| Answer» C. three | |
| 195. |
The difference between the modes’ refractive indices is called as |
| A. | polarization |
| B. | cutoff |
| C. | fiber birefringence |
| D. | fiber splicing |
| Answer» D. fiber splicing | |
| 196. |
A single mode fiber has mode field diameter 10.2μm and V=2.20. What is the core diameter of this fiber? |
| A. | 11.1μm |
| B. | 13.2μm |
| C. | 7.6μm |
| D. | 10.1μm |
| Answer» E. | |
| 197. |
Which equation is used to calculate MFD? |
| A. | maxwell’s equations |
| B. | peterman equations |
| C. | allen cahn equations |
| D. | boltzmann’s equations |
| Answer» C. allen cahn equations | |
| 198. |
What is needed to predict the performance characteristics of single mode fibers? |
| A. | the intermodal delay effect |
| B. | geometric distribution of light in a propagating mode |
| C. | fractional power flow in the cladding of fiber |
| D. | normalized frequency |
| Answer» C. fractional power flow in the cladding of fiber | |
| 199. |
An optical fiber has a core radius 2μm and a numerical aperture of 0.1. Will this fiber operate at single mode at 600 nm? |
| A. | yes |
| B. | no |
| Answer» B. no | |
| 200. |
An optical fiber has core-index of 1.480 and a cladding index of 1.478. What should be the core size for single mode operation at 1310nm? |
| A. | 7.31μm |
| B. | 8.71μm |
| C. | 5.26μm |
| D. | 6.50μm |
| Answer» E. | |