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.
| 101. |
Nonlinear effects which are defined by the intensity – dependent refractive index of the fiber are called as |
| A. | scattering effects |
| B. | kerr effects |
| C. | raman effects |
| D. | tomlinson effects |
| Answer» C. raman effects | |
| 102. |
In waveguide dispersion, refractive index is independent of |
| A. | bit rate |
| B. | index difference |
| C. | velocity of medium |
| D. | wavelength |
| Answer» E. | |
| 103. |
The optical source used in a fiber is an injection laser with a relative spectral width σλ/λ of 0.0011 at a wavelength of 0.70μm. Estimate the RMS spectral width. |
| A. | 1.2 nm |
| B. | 1.3 nm |
| C. | 0.77 nm |
| D. | 0.98 nm |
| Answer» D. 0.98 nm | |
| 104. |
What is pulse dispersion per unit length if for a graded index fiber, 0.1μs pulse broadening is seen over a distance of 13 km? |
| A. | 6.12ns/km |
| B. | 7.69ns/km |
| C. | 10.29ns/km |
| D. | 8.23ns/km |
| Answer» C. 10.29ns/km | |
| 105. |
A multimode graded index fiber exhibits a total pulse broadening of 0.15μsover a distance of 16 km. Estimate the maximum possible bandwidth, assuming no intersymbol interference. |
| A. | 4.6 mhz |
| B. | 3.9 mhz |
| C. | 3.3 mhz |
| D. | 4.2 mhz |
| Answer» D. 4.2 mhz | |
| 106. |
The maximum bit rate that may be obtained on an optical fiber link is 1/3Γ. State whether the given statement is true or false. |
| A. | true |
| B. | false |
| Answer» C. | |
| 107. |
When two components are equally excited at the fiber input, then for polarization maintaining fibers δΓgshould be around |
| A. | 1.5ns/km |
| B. | 1 ns/km |
| C. | 1.2ns/km |
| D. | 2ns/km |
| Answer» C. 1.2ns/km | |
| 108. |
A polarization maintaining fiber operates at a wavelength 1.2μm and have a modal birefringence of 1.8*10-3. Calculate the period of perturbation. |
| A. | 0.7 seconds |
| B. | 0.6 seconds |
| C. | 0.23 seconds |
| D. | 0.5 seconds |
| Answer» C. 0.23 seconds | |
| 109. |
The beat length in a single mode optical fiber is 8 cm, when light from a laser with a peak wavelength 0.6μm is launched into it. Estimate the modal birefringence. |
| A. | 1×10-5 |
| B. | 3.5×10-5 |
| C. | 2×10-5 |
| D. | 4×10-5 |
| Answer» B. 3.5×10-5 | |
| 110. |
A single-mode optical fiber has an attenuation of 0.3dB/km when operating at wavelength of 1.1μm. The fiber core diameter is 4μmand bandwidth is 500 MHz. Find threshold optical power for stimulated Brillouin scattering. |
| A. | 11.20 mw |
| B. | 12.77 mw |
| C. | 13.08 mw |
| D. | 12.12 mw |
| Answer» C. 13.08 mw | |
| 111. |
0.4 dB/km, 1.4μm, 6μm, 550MHz. Find threshold optical power for stimulated Raman scattering. |
| A. | 1.98 w |
| B. | 1.20 w |
| C. | 1.18 w |
| D. | 0.96 w |
| Answer» D. 0.96 w | |
| 112. |
For suitable power confinement of fundamental mode, the normalized frequency v should be maintained in the range 1.5 to 2.4μm and the fractional index difference must be linearly increased as a square function while the core diameter is linearly reduced to keep v constant. This confinement is achieved by- |
| A. | increasing level of silica doping in fiber core |
| B. | increasing level of germanium doping in fiber core |
| C. | decreasing level of silica germanium in fiber core |
| D. | decreasing level of silica doping in fiber core |
| Answer» C. decreasing level of silica germanium in fiber core | |
| 113. |
The fibers which relax the spectral requirements for optical sources and allow flexible wavelength division multiplying are known as- |
| A. | dispersion-flattened single mode fiber |
| B. | dispersion-enhanced single mode fiber |
| C. | dispersion-compressed single mode fiber |
| D. | dispersion-standardized single mode fiber |
| Answer» B. dispersion-enhanced single mode fiber | |
| 114. |
An alternative modification of the dispersion characteristics of single mode fibers involves achievement of low dispersion gap over the low-loss wavelength region between – |
| A. | 0.2 and 0.9μm |
| B. | 0.1 and 0.2μm |
| C. | 1.3 and 1.6μm |
| D. | 2 and 3μm |
| Answer» D. 2 and 3μm | |
| 115. |
The dispersion due to material, waveguide and profile are -2.8nm-1km-1, 20.1nm-1km-1 and 23.2nm-1km-1respectively. Find the total first order dispersion? |
| A. | 36.2psnm-1 km-1 |
| B. | 38.12psnm-1 km-1 |
| C. | 40.5psnm-1 km-1 |
| D. | 20.9psnm-1 km-1 |
| Answer» D. 20.9psnm-1 km-1 | |
| 116. |
A single mode fiber has a zero dispersion wavelength of 1.21μm and a dispersion slope of 0.08 psnm-2km-1. What is the total first order dispersion at wavelength 1.26μm. |
| A. | -2.8psnm-1 km-1 |
| B. | -3.76psnm-1 km-1 |
| C. | -1.2psnm-1 km-1 |
| D. | 2.4psnm-1 km-1 |
| Answer» C. -1.2psnm-1 km-1 | |
| 117. |
Γg= dβ / C*dk. What is β in the given equation? |
| A. | attenuation constant |
| B. | propagation constant |
| C. | boltzmann’s constant |
| D. | free-space |
| Answer» C. boltzmann’s constant | |
| 118. |
. A multimode fiber has RMS pulse broadening per km of 12ns/km and 28ns/km due to material dispersion and intermodal dispersion resp. Find the total RMS pulse broadening. |
| A. | 30.46ns/km |
| B. | 31.23ns/km |
| C. | 28.12ns/km |
| D. | 26.10ns/km |
| Answer» B. 31.23ns/km | |
| 119. |
Sharp bends or micro bends causes significant losses in fiber. State true or false |
| A. | true |
| B. | false |
| Answer» B. false | |
| 120. |
How the potential macro bending losses can be reduced in case of multimode fiber? |
| A. | by designing fibers with large relative refractive index differences |
| B. | by maintaining direction of propagation |
| C. | by reducing the bend |
| D. | by operating at larger wavelengths |
| Answer» B. by maintaining direction of propagation | |
| 121. |
A single mode fiber has refractive indices n1=1.50, n2= 2.23, core diameter of 8μm, wavelength=1.5μm cutoff wavelength= 1.214μm. Find the radius of curvature? |
| A. | 12 mm |
| B. | 20 mm |
| C. | 34 mm |
| D. | 36 mm |
| Answer» D. 36 mm | |
| 122. |
A multimode fiber has refractive indices n1= 1.15, n2=1.11 and an operating wavelength of 0.7μm. Find the radius of curvature? |
| A. | 8.60μm |
| B. | 9.30μm |
| C. | 9.1μm |
| D. | 10.2μm |
| Answer» C. 9.1μm | |
| 123. |
In the given equation, state what αr suggests; |
| A. | radius of curvature |
| B. | refractive index difference |
| C. | radiation attenuation coefficients |
| D. | constant of proportionality |
| Answer» D. constant of proportionality | |
| 124. |
Which of the following statements best explain the concept of material absorption? |
| A. | a loss mechanism related to the material composition and fabrication of fiber. |
| B. | a transmission loss for optical fibers. |
| C. | results in attenuation of transmitted light. |
| D. | causes of transfer of optical power |
| Answer» B. a transmission loss for optical fibers. | |
| 125. |
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 |
| Answer» D. path where rays changes angles at core-cladding interface | |
| 126. |
. 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 |
| Answer» D. path where rays changes angles at core-cladding interface | |
| 127. |
A step-index fiber has core refractive index 1.46 and radius 4.5μm. Find the cutoff wavelength to exhibit single mode operation. Use relative index difference as 0.25%. |
| A. | 1.326μm |
| B. | 0.124μm |
| C. | 1.214μm |
| D. | 0.123μm |
| Answer» D. 0.123μm | |
| 128. |
A graded-index fiber has a core with parabolic refractive index profile of diameter of 30μm, NA=0.2, λ=1μm. Estimate the normalised frequency. |
| A. | 19.32 |
| B. | 18.84 |
| C. | 16.28 |
| D. | 17.12 |
| Answer» C. 16.28 | |
| 129. |
. When the input and output power in an optical fiber is 120μW & 3μW 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 |
| Answer» C. 1db/km | |
| 130. |
. A decibel may be defined as the ratio of input and output optical power for a particular optical wavelength. State whether the following statement is true or false. |
| A. | true |
| B. | false |
| Answer» B. false | |
| 131. |
A device which reduces the intensity of light in optical fiber communications is |
| A. | compressor |
| B. | optical attenuator |
| C. | barometer |
| D. | reducer |
| Answer» C. barometer | |
| 132. |
If the input power 100μW is launched into 6 km of fiber, the mean optical power at the fiber output is 2μW. 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 |
| Answer» C. 17.12db | |
| 133. |
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 |
| Answer» C. absorption | |
| 134. |
The high index contrast enables the PCF core to be reduced from around 8 μmin conventional fiber to |
| A. | less than 1μm |
| B. | more than 5μm |
| C. | more than 3μm |
| D. | more than 2μm |
| Answer» B. more than 5μm | |
| 135. |
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» D. limiting case of refraction | |
| 136. |
Refraction is the |
| A. | bending of light waves |
| B. | reflection of light waves |
| C. | diffusion of light waves |
| D. | refraction of light waves |
| Answer» B. reflection of light waves | |
| 137. |
A monochromatic wave propagates along a waveguide in z direction. These points of constant phase travel in constant phase travel at a phase velocity Vp is given by |
| A. | vp=ω/β |
| B. | vp=ω/c |
| C. | vp=c/n |
| D. | vp=mass/acceleration |
| Answer» B. vp=ω/c | |
| 138. |
When λ is optical wavelength in vacuum, k is given by k=2Π/λ. What does k stand for in the above equation? |
| A. | phase propagation constant |
| B. | dielectric constant |
| C. | boltzmann’s constant |
| D. | free-space constant |
| Answer» B. dielectric constant | |
| 139. |
The difference between the modes’ refractive indices is called as |
| A. | polarization |
| B. | cutoff |
| C. | fiber birefringence |
| D. | fiber splicing |
| Answer» D. fiber splicing | |
| 140. |
A single mode fiber has mode field diameter 10.2μmand 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. | |
| 141. |
An optical fiber has a core radius 2μmand a numerical aperture of 0.1. Will this fiber operate at single mode at 600 nm? |
| A. | yes |
| B. | no |
| Answer» B. no | |
| 142. |
Who proposed the idea of transmission of light via dielectric waveguide structure? |
| A. | christian huygens |
| B. | karpon and bockham |
| C. | hondros and debye |
| D. | albert einstein |
| Answer» D. albert einstein | |
| 143. |
Who proposed the use of clad waveguide structure? |
| A. | edward appleton |
| B. | schriever |
| C. | kao and hockham |
| D. | james maxwell |
| Answer» D. james maxwell | |
| 144. |
Which law gives the relationship between refractive index of the dielectric? |
| A. | law of reflection |
| B. | law of refraction (snell’s law). |
| C. | millman’s law |
| D. | huygen’s law |
| Answer» C. millman’s law | |
| 145. |
The light sources used in fibre optics communication are : |
| A. | led’s and lasers |
| B. | phototransistors |
| C. | xenon lights |
| D. | incandescent |
| Answer» B. phototransistors | |
| 146. |
What is the numerical aperture of the fiber if the angle of acceptance is 16 degree |
| A. | 0.50 |
| B. | 0.36 |
| C. | 0.20 |
| D. | 0.27 |
| Answer» E. | |
| 147. |
Light incident on fibers of angles________the acceptance angle do not propagate into the fiber |
| A. | less than |
| B. | greater than |
| C. | equal to |
| D. | less than and equal to |
| Answer» C. equal to | |
| 148. |
The ________ ray passes through the axis of the fiber core. |
| A. | reflected |
| B. | refracted |
| C. | meridional |
| D. | shew |
| Answer» D. shew | |
| 149. |
The ratio of speed of light in air to the speed of light in another medium is called as_________ |
| A. | speed factor |
| B. | dielectric constant |
| C. | reflection index |
| D. | refraction index |
| Answer» E. | |
| 150. |
When a ray of light enters one medium from another medium, which quality will not change |
| A. | direction |
| B. | frequency |
| C. | speed |
| D. | wavelength |
| Answer» C. speed | |