McqMate
These multiple-choice questions (MCQs) are designed to enhance your knowledge and understanding in the following areas: Electronics and Telecommunication Engineering [ENTC] .
| 251. |
Calculate the splitting loss if a 30×30 port multimode fiber star coupler has 1 mW of optical power launched into an input port. |
| A. | 13 db |
| B. | 15 db |
| C. | 14.77 db |
| D. | 16.02 db |
| Answer» C. 14.77 db | |
| 252. |
A _____________ coupler comprises a number of cascaded stages, each incorporating three or four-port FBT couplers to obtain a multiport output. |
| A. | star |
| B. | ladder |
| C. | wdm |
| D. | three-port |
| Answer» A. star | |
| 253. |
A number of three-port single-mode fiber couplers are used in the fabrication of a ladder coupler with 16 output ports. The three-port couplers each have an excess loss of 0.2 dB along with a splice loss of 0.1 dB at the interconnection of each stage. Determine the excess loss. |
| A. | 1.9 db |
| B. | 1.4 db |
| C. | 0.9 db |
| D. | 1.1 db |
| Answer» D. 1.1 db | |
| 254. |
An FBG is developed within a fiber core having a refractive index of 1.30. Find the grating period for it to reflect an optical signal with a wavelength of 1.33μm. |
| A. | 0.51 μm |
| B. | 0.58 μm |
| C. | 0.61 μm |
| D. | 0.49 μm |
| Answer» A. 0.51 μm | |
| 255. |
It is a passive device which allows the flow of optical signal power in only one direction and preventing reflections in the backward direction. |
| A. | fiber slice |
| B. | optical fiber connector |
| C. | optical isolator |
| D. | optical coupler |
| Answer» C. optical isolator | |
| 256. |
Which feature of an optical isolator makes it attractive to use with optical amplifier? |
| A. | low loss |
| B. | wavelength blocking |
| C. | low refractive index |
| D. | attenuation |
| Answer» B. wavelength blocking | |
| 257. |
Magneto-optic devices can be used to function as isolators. State whether the given statement is true or false. |
| A. | true |
| B. | false |
| Answer» A. true | |
| 258. |
How many implementation methods are available for optical isolators? |
| A. | one |
| B. | four |
| C. | two |
| D. | three |
| Answer» D. three | |
| 259. |
A device which is made of isolators and follows a closed loop path is called as a ____________ |
| A. | circulator |
| B. | gyrator |
| C. | attenuator |
| D. | connector |
| Answer» A. circulator | |
| 260. |
The commercially available circulators exhibit insertion losses around ________________ |
| A. | 2 db |
| B. | 0.7 db |
| C. | 0.2 db |
| D. | 1 db |
| Answer» D. 1 db | |
| 261. |
A combination of a FBG and optical isolators can be used to produce non-blocking optical wavelength division add/draw multiplexers. State whether the given statement is true or false. |
| A. | true |
| B. | false |
| Answer» B. false | |
| 262. |
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» A. optical source | |
| 263. |
How many types of sources of optical light are available? |
| A. | one |
| B. | two |
| C. | three |
| D. | four |
| Answer» C. three | |
| 264. |
The frequency of the absorbed or emitted radiation is related to difference in energy E between the higher energy state E2 and the lower energy state E1. State what h stands for in the given equation? |
| A. | gravitation constant |
| B. | planck’s constant |
| C. | permittivity |
| D. | attenuation constant |
| Answer» B. planck’s constant | |
| 265. |
The radiation emission process (emission of a proton at frequency) can occur in __________ ways. |
| A. | two |
| B. | three |
| C. | four |
| D. | one |
| Answer» A. two | |
| 266. |
Which process gives the laser its special properties as an optical source? |
| A. | dispersion |
| B. | stimulated absorption |
| C. | spontaneous emission |
| D. | stimulated emission |
| Answer» D. stimulated emission | |
| 267. |
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» B. 1.47×10-11 | |
| 268. |
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» C. thermal equilibrium | |
| 269. |
__________________ 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» A. light amplification | |
| 270. |
A ruby laser has a crystal of length 3 cm with a refractive index of 1.60, wavelength 0.43 μm. Determine the number of longitudinal modes. |
| A. | 1×102 |
| B. | 3×106 |
| C. | 2.9×105 |
| D. | 2.2×105 |
| Answer» D. 2.2×105 | |
| 271. |
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» C. 1.6 ghz | |
| 272. |
Doppler broadening is a homogeneous broadening mechanism. State whether the given statement is true or false. |
| A. | true |
| B. | false |
| Answer» B. false | |
| 273. |
An injection laser has active cavity losses of 25 cm-1and 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» D. 49.07 cm-1 | |
| 274. |
Longitudinal modes contribute only a single spot of light to the laser output. State whether the given statement is true or false. |
| A. | true |
| B. | false |
| Answer» A. true | |
| 275. |
Considering the values given below, calculate the mode separation in terms of free space wavelength for a laser. |
| A. | 1.4×10-11 |
| B. | 1.6×10-12 |
| C. | 1×10-12 |
| D. | 6×10-11 |
| Answer» B. 1.6×10-12 | |
| 276. |
____________________ lasers are presently the major laser source for optical fiber communications |
| A. | semiconductor |
| B. | non-semiconductor |
| C. | injection |
| D. | solid-state |
| Answer» C. injection | |
| 277. |
In Nd: YAG lasers, the maximum doping levels of neodymium is ____________ |
| A. | 0.5 % |
| B. | 1.5 % |
| C. | 1.8 % |
| D. | 2 % |
| Answer» B. 1.5 % | |
| 278. |
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 |
| Answer» D. semiconductors and integrated circuits | |
| 279. |
The Nd: YAG laser has a narrow line-width which is ________________ |
| A. | < 0.01 nm |
| B. | > 0.01 nm |
| C. | > 1 mm |
| D. | > 1.6 mm |
| Answer» A. < 0.01 nm | |
| 280. |
The strongest pumping bands is a four level system of Nd: YAG laser at wavelength of range_________________ |
| A. | 0.25 and 0.56 nm |
| B. | 0.75 and 0.81 nm |
| C. | 0.12 and 0.23 nm |
| D. | 1 and 2 nm |
| Answer» B. 0.75 and 0.81 nm | |
| 281. |
The Nd: YAG laser is costlier than earth-doped glass fiber laser. State whether the following statement is true or false |
| A. | true |
| B. | false |
| Answer» A. true | |
| 282. |
It is a resonant cavity formed by two parallel reflecting mirrors separated by a mirror separated by a medium such as air or gas |
| A. | optical cavity |
| B. | wheatstone’s bridge |
| C. | oscillator |
| D. | fabry-perot resonator |
| Answer» D. fabry-perot resonator | |
| 283. |
In a three level system, the threshold power decreases inversely with the length of the fiber gain medium. State whether the given statement is true or false. |
| A. | true |
| B. | false |
| Answer» B. false | |
| 284. |
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» C. nitrogen | |
| 285. |
Dopants levels in glass fiber lasers are generally ___________ |
| A. | low |
| B. | high |
| C. | same as that of grin rod lens laser |
| D. | same as that of semiconductor laser |
| Answer» A. low | |
| 286. |
. _______________ 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» D. zblanp | |
| 287. |
The lasing output of the basic Fabry-perot cavity fiber is restricted to between ____________ |
| A. | 1 and 2 nm |
| B. | 5 and 10 nm |
| C. | 3 and 6 nm |
| D. | 15 and 30 nm |
| Answer» B. 5 and 10 nm | |
| 288. |
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 |
| Answer» C. reducing the slope efficiency | |
| 289. |
When did the non-semiconductor laser developed? |
| A. | 1892 |
| B. | 1946 |
| C. | 1985 |
| D. | 1993 |
| Answer» C. 1985 | |
| 290. |
Y3Al5 O12 Is a molecular formula for _____________ |
| A. | ytterbium aluminate |
| B. | yttrium oxide |
| C. | ytterbium oxy-aluminate |
| D. | yttrium-aluminum garnet |
| Answer» D. yttrium-aluminum garnet | |
| 291. |
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» A. intrinsic semiconductor | |
| 292. |
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» C. fermi-dirac distribution function | |
| 293. |
What is done to create an extrinsic semiconductor? |
| A. | refractive index is decreased |
| B. | doping the material with impurities |
| C. | increase the band-gap of the material |
| D. | stimulated emission |
| Answer» B. doping the material with impurities | |
| 294. |
The majority of the carriers in a p-type semiconductor are__________. |
| A. | holes |
| B. | electrons |
| C. | photons |
| D. | neutrons |
| Answer» A. holes | |
| 295. |
_________________ is used when the optical emission results from the application of electric field. |
| A. | radiation |
| B. | efficiency |
| C. | electro-luminescence |
| D. | magnetron oscillator |
| Answer» C. electro-luminescence | |
| 296. |
In the given equation, what does p stands for? |
| A. | permittivity |
| B. | probability |
| C. | holes |
| D. | crystal momentum |
| Answer» D. crystal momentum | |
| 297. |
Calculate the radioactive minority carrier lifetime in gallium arsenide when the minority carriers are electrons injected into a p-type semiconductor region which has a hole concentration of 1018cm-3. The recombination coefficient for gallium arsenide is |
| A. | 2ns |
| B. | 1.39ns |
| C. | 1.56ns |
| D. | 2.12ms |
| Answer» B. 1.39ns | |
| 298. |
Which impurity is added to gallium phosphide to make it an efficient light emitter? |
| A. | silicon |
| B. | hydrogen |
| C. | nitrogen |
| D. | phosphorus |
| Answer» C. nitrogen | |
| 299. |
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» D. heavy doping of both p-type and n-type material | |
| 300. |
A GaAs injection laser has a threshold current density of 2.5*103Acm-2and length and width of the cavity is 240μmand 110μm respectively. Find the threshold current for the device. |
| A. | 663 ma |
| B. | 660 ma |
| C. | 664 ma |
| D. | 712 ma |
| Answer» B. 660 ma | |
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