MCQOPTIONS
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MCQOPTIONS
This section includes 271 Mcqs, each offering curated multiple-choice questions to sharpen your Electronics and Telecommunication Engineering [ENT knowledge and support exam preparation. Choose a topic below to get started.
| 1. |
Determine CW operating lifetime for LED with βrt = -0.58 and degradation rate βr= 7.86*10-11 h-1. |
| A. | 32.12 |
| B. | 42 |
| C. | 22.72 |
| D. | 23.223 |
| Answer» D. 23.223 | |
| 2. |
Determine degradation rate βrif 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 |
| Answer» B. 7.91*10-11 | |
| 3. |
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 |
| Answer» C. 47.6 | |
| 4. |
The optical power at 20 MHz is 246.2 μW. 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 |
| Answer» B. 6.42*10-9 | |
| 5. |
When a constant d.c. drive current is applied to device, the optical o/p power is 320 μm. 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 |
| Answer» E. | |
| 6. |
The optical bandwidth is _____________ the electrical bandwidth. |
| A. | smaller |
| B. | greater |
| C. | same as |
| D. | zero with respect to |
| Answer» C. same as | |
| 7. |
The optical 3 dB point occurs when currents ratio is equal to |
| A. | ⅝ |
| B. | ⅔ |
| C. | ½ |
| D. | ¾ |
| Answer» D. ¾ | |
| 8. |
The overall power conversion efficiency of electrical lens coupled LED is 0.8% and power applied 0.0375 V. Determine optical power launched into fiber |
| A. | 0.03 |
| B. | 0.05 |
| C. | 0.3 |
| D. | 0.01 |
| Answer» B. 0.05 | |
| 9. |
Determine the overall power conversion efficiency of lens coupled SLED having forward current of 20 mA and forward voltage of 2 V with 170 μWof optical power launched into multimode step index fiber. |
| A. | 1.256*10-5 |
| B. | 4.417*102 |
| C. | 4.25*10-3 |
| D. | 2.14*10-3 |
| Answer» D. 2.14*10-3 | |
| 10. |
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 | |
| 11. |
Estimate optical power coupled into fiber of DH SLED having emission area of 1.96*10-5, radiance of 40 W/rcm2, numerical aperture of 0.2 and Fresnel reflection coefficient of 0.03 at index matched fiber surface. |
| A. | 5.459*10-5 |
| B. | 1.784*10-3 |
| C. | 3.478*102 |
| D. | 9.551*10-5 |
| Answer» E. | |
| 12. |
A DH surface emitter LED has an emission area diameter of 60μm. Determine emission area of source |
| A. | 1.534*10-6 |
| B. | 5.423*10-3 |
| C. | 3.564*10-2 |
| D. | 2.826*10-9 |
| Answer» E. | |
| 13. |
13. In a GaAs LED, compute the loss relative to internally generated optical power in the fiber when there is small air gap between LED and fiber core. (Fiber coupled = 5.5 * 10-4Pint) |
| A. | 34 db |
| B. | 32.59 db |
| C. | 42 db |
| D. | 33.1 db |
| Answer» C. 42 db | |
| 14. |
For a GaAs LED, the coupling efficiency is 0.05. Compute the optical loss in decibels. |
| A. | 12.3 db |
| B. | 14 db |
| C. | 13.01 db |
| D. | 14.6 db |
| Answer» D. 14.6 db | |
| 15. |
A planar LED is fabricated from GaAs is having a optical power emitted is 0.018% of optical power generated internally which is 0.018% of optical power generated internally which is 0.6 P. Determine external power efficiency. |
| A. | 0.18% |
| B. | 0.32% |
| C. | 0.65% |
| D. | 0.9% |
| Answer» E. | |
| 16. |
A planar LED fabricated from GaAs has a refractive index of 2.5. Compute the optical power emitted when transmission factor is 0.68. |
| A. | 3.4 % |
| B. | 1.23 % |
| C. | 2.72 % |
| D. | 3.62 % |
| Answer» D. 3.62 % | |
| 17. |
The Lambertian intensity distribution __________ the external power efficiency by some percent. |
| A. | reduces |
| B. | does not affects |
| C. | increases |
| D. | have a negligible effect |
| Answer» B. does not affects | |
| 18. |
Compute power internally generated within a double-heterojunction LED if it has internal quantum efficiency of 64.5 % and drive current of 40 mA with a peak emission wavelength of 0.82 μm. |
| A. | 0.09 |
| B. | 0.039 |
| C. | 0.04 |
| D. | 0.06 |
| Answer» C. 0.04 | |
| 19. |
The excess density of electrons Δnand holes Δpin an LED is |
| A. | equal |
| B. | Δpmore than Δn |
| C. | Δn more than Δp |
| D. | does not affects the led |
| Answer» B. Δpmore than Δn | |
| 20. |
An MQW cascaded laser is more advantageous because of: |
| A. | mode hopping |
| B. | auger recombination |
| C. | control over layers of material |
| D. | properties of material |
| Answer» D. properties of material | |
| 21. |
In a QC laser, a same electron can emit number of photons. State the given statement is true or false? |
| A. | true |
| B. | false |
| Answer» B. false | |
| 22. |
A technique based on inter-sub band transition is known as |
| A. | auger recombination |
| B. | frequency chirping |
| C. | inter-valence band absorption |
| D. | quantum cascading |
| Answer» E. | |
| 23. |
The diode-cladding-pumped Erbium praseodymium-doped fluoride device operates at wavelength. |
| A. | around 3 μm |
| B. | 4 μm |
| C. | 2.6 μm |
| D. | 1.04 μm |
| Answer» B. 4 μm | |
| 24. |
The thulium doped fiber laser when pumped with alexandrite laser output at 0.786 μm, the laser emits at |
| A. | 0.6 μm |
| B. | 0.8 μm |
| C. | 2.3 μm |
| D. | 1.2μm |
| Answer» D. 1.2μm | |
| 25. |
Lasing obtained in __________ when 191 mW of pump light at a wavelength of 0.477 μm is launched into laser. |
| A. | ternary pbsnsete alloy laser |
| B. | quaternary pbsnsete alloy laser |
| C. | doped fluoro-zirconate fiber |
| D. | ternary pbeute alloy laser |
| Answer» D. ternary pbeute alloy laser | |
| 26. |
What is the widest tuning range obtained in optical fiber laser structure? |
| A. | 60 nm |
| B. | 80 nm |
| C. | more than 100 nm |
| D. | 100 nm |
| Answer» D. 100 nm | |
| 27. |
The lasing line-width of Fox-smith resonator is ____________________ |
| A. | less than 1 mhz |
| B. | 1 mhz |
| C. | 2 mhz |
| D. | greater than 3 mhz |
| Answer» B. 1 mhz | |
| 28. |
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 |
| Answer» B. 1.2 to 1.5 nm | |
| 29. |
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 |
| Answer» B. refractive index and index difference | |
| 30. |
_______________ 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 |
| Answer» E. | |
| 31. |
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 |
| Answer» D. alumina | |
| 32. |
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 |
| Answer» B. mode hopping | |
| 33. |
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 |
| Answer» E. | |
| 34. |
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» E. | |
| 35. |
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» E. | |
| 36. |
Determine the threshold current density for an AlGaAs injection laser with T0=180k at 30°C. |
| A. | 6.24 |
| B. | 9.06 |
| C. | 3.08 |
| D. | 5.09 |
| Answer» E. | |
| 37. |
The narrow line-width obtained under the CW operation for quarter wavelength shifted DFB laser is ________________ |
| A. | 2 mhz |
| B. | 10 mhz |
| C. | 3 mhz |
| D. | 1 mhz |
| Answer» D. 1 mhz | |
| 38. |
The InGaAsP/InP double channel planar DFB-BH laser with a quarter wavelength shifted first order grating provides a single frequency operation and incorporates a phase shift of ______________ |
| A. | π/2 radians |
| B. | 2π radians |
| C. | π radians |
| D. | 3π/2 radians |
| Answer» B. 2π radians | |
| 39. |
Fabry-Perot devices with BH geometries high modulation speeds than DFB-BH lasers. State whether the given statement is true or false |
| A. | true |
| B. | false |
| Answer» C. | |
| 40. |
DBF-BH lasers exhibit low threshold currents in the range of ________________ |
| A. | 40 to 50 ma |
| B. | 21 to 30 ma |
| C. | 2 to 5 ma |
| D. | 10 to 20 ma |
| Answer» E. | |
| 41. |
The semiconductor lasers employing the distributed feedback mechanism are classified in _________________ categories |
| A. | one |
| B. | two |
| C. | three |
| D. | four |
| Answer» C. three | |
| 42. |
In the given equation, corrugation period is given by lλb/2Ne. If λb is the Bragg wavelength, then what does ‘l’ stand for? |
| A. | length of cavity |
| B. | limitation index |
| C. | integer order of grating |
| D. | refractive index |
| Answer» D. refractive index | |
| 43. |
Multi-quantum devices have superior characteristics over |
| A. | bh lasers. |
| B. | dh lasers. |
| C. | gain guided lasers. |
| D. | single-quantum-well devices. |
| Answer» C. gain guided lasers. | |
| 44. |
Better confinement of optical mode is obtained in |
| A. | multi quantum well lasers. |
| B. | single quantum well lasers. |
| C. | gain guided lasers. |
| D. | bh lasers. |
| Answer» B. single quantum well lasers. | |
| 45. |
Strip geometry of a device or laser is important. State whether the given statement is true or false. |
| A. | true |
| B. | false |
| Answer» B. false | |
| 46. |
Quantum well lasers are providing high inherent advantage over |
| A. | chemical lasers. |
| B. | gas lasers. |
| C. | conventional dh devices. |
| D. | bh device. |
| Answer» D. bh device. | |
| 47. |
Quantum well lasers are also known as |
| A. | bh lasers. |
| B. | dh lasers. |
| C. | chemical lasers. |
| D. | gain-guided lasers. |
| Answer» C. chemical lasers. | |
| 48. |
A correct DH structure will restrict the vertical width of waveguide region |
| A. | 0.5μm. |
| B. | 0.69 μm |
| C. | 0.65 μm |
| D. | less than 0.4 μm |
| Answer» E. | |
| 49. |
Single longitudinal mode operation is obtained by |
| A. | eliminating all transverse mode |
| B. | eliminating all longitudinal modes |
| C. | increasing the length of cavity |
| D. | reducing the length of cavity |
| Answer» E. | |
| 50. |
Laser modes are generally separated by few |
| A. | tenths of micrometer |
| B. | tenths of nanometer |
| C. | tenths of pico-meter |
| D. | tenths of millimeter |
| Answer» C. tenths of pico-meter | |