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201. |
The ratio r = (n1 – n)/ (n1 – n) indicates |
A. | fresnel reflection |
B. | reflection coefficient |
C. | refraction coefficient |
D. | angular power distribution coefficient |
Answer» B. reflection coefficient |
202. |
A GaAs optical source having a refractive index of 3.2 is coupled to a silica fiber having a refractive index of 1.42. Determine Fresnel reflection at interface in terms of percentage. |
A. | 13.4% |
B. | 17.4% |
C. | 17.6% |
D. | 14.8% |
Answer» D. 14.8% |
203. |
A particular GaAs fiber has a Fresnel reflection magnitude of 17.6% i.e. 0.176. Find the power loss between the source and the fiber? |
A. | 0.86 db |
B. | 0.78 db |
C. | 0.84 db |
D. | 0.83 db |
Answer» C. 0.84 db |
204. |
Two joined step index fibers are perfectly aligned. What is the coupling loss of numerical aperture are NAR= 0.26 for emitting fiber? |
A. | -0.828 db |
B. | -0.010 db |
C. | -0.32 db |
D. | 0.32 db |
Answer» B. -0.010 db |
205. |
Two joined graded index fibers that are perfectly aligned have refractive indices αR=1.93for receiving fiber αE= 2.15 for emitting fiber. Calculate the coupling loss |
A. | 0.23 db |
B. | 0.16 db |
C. | 0.82 db |
D. | 0.76 db |
Answer» A. 0.23 db |
206. |
How many types of misalignments occur when joining compatible fiber? |
A. | one |
B. | two |
C. | five |
D. | three |
Answer» D. three |
207. |
Losses caused by factors such as core-cladding diameter, numerical aperture, relative refractive index differences, different refractive index profiles, fiber faults are known as |
A. | intrinsic joint losses |
B. | extrinsic losses |
C. | insertion losses |
D. | coupling losses |
Answer» A. intrinsic joint losses |
208. |
A step index fiber has a coupling efficiency of 0.906 with uniform illumination of all propagation modes. Find the insertion loss due to lateral misalignment? |
A. | 0.95 db |
B. | 0.40 db |
C. | 0.42 db |
D. | 0.62 db |
Answer» C. 0.42 db |
209. |
A graded index fiber has a parabolic refractive index profile (α=2) and core diameter of 42μm. Estimate an insertion loss due to a 2 μm lateral misalignment when there is index matching and assuming there is uniform illumination of all guided modes only. |
A. | 0.180 |
B. | 0.106 |
C. | 0.280 |
D. | 0.080 |
Answer» D. 0.080 |
210. |
Determine coupling efficiency if the misalignment loss in a graded index fiber is 0.102 |
A. | 0.136 |
B. | 0.898 |
C. | 0.982 |
D. | 0.684 |
Answer» B. 0.898 |
211. |
In a single mode fiber, the losses due to lateral offset and angular misalignment are given by 0.20 dB and 0.46 dB respectively. Find the total insertion loss |
A. | 0.66 db |
B. | 0.26 db |
C. | 0.38 db |
D. | 0.40 db |
Answer» A. 0.66 db |
212. |
The intrinsic loss through a multimode fiber joint is independent of direction of propagation. State whether the given statement is true or false |
A. | true |
B. | false |
Answer» B. false |
213. |
The expanded beam connectors use ____________ for beam expansion and reduction. |
A. | square micro-lens |
B. | oval micro-lens |
C. | spherical micro-lens |
D. | rectangular micro-lens |
Answer» C. spherical micro-lens |
214. |
Lens-coupled expanded beam connectors exhibit average losses of _________ in case of single mode and graded index fibers. |
A. | 0.3 db |
B. | 0.7 db |
C. | 0.2 db |
D. | 1.5 db |
Answer» B. 0.7 db |
215. |
Sapphire ball lens expanded beam design is successful than spherical lens coupled design. State whether the given statement is true or false. |
A. | true |
B. | false |
Answer» A. true |
216. |
The fiber is positioned at the ________ of the lens in order to obtain a collimated beam and to minimize lens-to-lens longitudinal misalignment effects. |
A. | aperture |
B. | focal length |
C. | curve |
D. | exterior circumference |
Answer» B. focal length |
217. |
___________ exhibits a parabolic refractive index profile with a maximum at the axis similar to graded index fiber. |
A. | lens coupled design |
B. | sapphire ball lens |
C. | spherical micro-lens |
D. | grin-rod lens |
Answer» D. grin-rod lens |
218. |
The GRIN-rod lens can produce a collimated output beam with a divergent angle αof between _____________ from a light source situated on, or near to, the opposite lens face. |
A. | 1 to 5 degrees |
B. | 9 to 16 degrees |
C. | 4 to 8 degrees |
D. | 25 to 50 degrees |
Answer» A. 1 to 5 degrees |
219. |
In the given equation, if r is the radial distance, n is the refractive index; what does z stands for? |
A. | focal length |
B. | distance along the optical axis |
C. | axial angle |
D. | diameter |
Answer» B. distance along the optical axis |
220. |
The majority of the GRIN-rod lenses have diameters in the range of ____________ |
A. | 2 to 2.5 mm |
B. | 3 to 4 mm |
C. | 0.1 to 0.4 mm |
D. | 0.5 to 2 mm |
Answer» D. 0.5 to 2 mm |
221. |
Which of the following factors does not cause divergence of the collimated beam from a GRIN-rod lens? |
A. | lens cut length |
B. | size of fiber core |
C. | refractive index profile |
D. | chromatic aberration |
Answer» C. refractive index profile |
222. |
GRIN-rod lens connectors have loss characteristics which are independent of the modal power distribution in the fiber. State whether the given statement is true or false. |
A. | true |
B. | false |
Answer» A. true |
223. |
A permanent joint formed between two different optical fibers in the field is known as a |
A. | fiber splice |
B. | fiber connector |
C. | fiber attenuator |
D. | fiber dispersion |
Answer» A. fiber splice |
224. |
How many types of fiber splices are available? |
A. | one |
B. | two |
C. | three |
D. | four |
Answer» B. two |
225. |
The insertion losses of the fiber splices are much less than the Fresnel reflection loss at a butted fiber joint. State whether the given statement is true or false. |
A. | true |
B. | false |
Answer» A. true |
226. |
What is the main requirement with the fibers that are intended for splicing? |
A. | smooth and oval end faces |
B. | smooth and square end faces |
C. | rough edge faces |
D. | large core diameter |
Answer» B. smooth and square end faces |
227. |
In score and break process, which of the following is not used as a cutting tool? |
A. | diamond |
B. | sapphire |
C. | tungsten carbide |
D. | copper |
Answer» D. copper |
228. |
The heating of the two prepared fiber ends to their fusing point with the application of required axial pressure between the two optical fibers is called as |
A. | mechanical splicing |
B. | fusion splicing |
C. | melting |
D. | diffusion |
Answer» B. fusion splicing |
229. |
Which of the following is not used as a flame heating source in fusion splicing? |
A. | microprocessor torches |
B. | ox hydric burners |
C. | electric arc |
D. | gas burner |
Answer» D. gas burner |
230. |
Average insertion losses as low as _________ have been obtained with multimode graded index and single-mode fibers using ceramic capillaries. |
A. | 0.1 db |
B. | 0.5 db |
C. | 0.02 db |
D. | 0.3 db |
Answer» A. 0.1 db |
231. |
_____________ are formed by sandwiching the butted fiber ends between a V-groove glass substrate and a flat glass retainer plate. |
A. | springroove splices |
B. | v-groove splices |
C. | elastic splices |
D. | fusion splices |
Answer» B. v-groove splices |
232. |
Mean splice insertion losses of 0.05 dB are obtained using multimode graded index fibers with the Springroove splice. State whether the given statement is true or false. |
A. | true |
B. | false |
Answer» A. true |
233. |
Alignment accuracy of the order ___________ is obtained using the three glass rod alignment sleeve. |
A. | 0.23 μm |
B. | 0.15 μm |
C. | 0.05 μm |
D. | 0.01 μm |
Answer» C. 0.05 μm |
234. |
In case of multiple fusion, splice losses using an electric arc fusion device with multimode graded index fiber range from |
A. | 0.01 to 0.04 db |
B. | 0.19 to 0.25 db |
C. | 0.12 to 0.15 db |
D. | 0.04 to 0.12 db |
Answer» D. 0.04 to 0.12 db |
235. |
The heating of the two prepared fiber ends to their fusing point with the application of required axial pressure between the two optical fibers is called as |
A. | mechanical splicing |
B. | fusion splicing |
C. | melting |
D. | diffusion |
Answer» B. fusion splicing |
236. |
The rounding of the fiber ends with a low energy discharge before pressing the fibers together and fusing with a stronger arc is called as |
A. | pre-fusion |
B. | diffusion |
C. | crystallization |
D. | alignment |
Answer» A. pre-fusion |
237. |
_____________ is caused by surface tension effects between the two fiber ends during fusing. |
A. | pre-fusion |
B. | diffusion |
C. | self-alignment |
D. | splicing |
Answer» C. self-alignment |
238. |
Mean splice insertion losses of 0.05 dB are obtained using multimode graded index fibers with the Springroove splice. State whether the given statement is true or false. |
A. | true |
B. | false |
Answer» A. true |
239. |
When considering source-to-fiber coupling efficiencies, the ________ is an important parameter than total output power. |
A. | numerical aperture |
B. | radiance of an optical source |
C. | coupling efficiency |
D. | angular power distribution |
Answer» B. radiance of an optical source |
240. |
It is a device that distributes light from a main fiber into one or more branch fibers. |
A. | optical fiber coupler |
B. | optical fiber splice |
C. | optical fiber connector |
D. | optical isolator |
Answer» A. optical fiber coupler |
241. |
Optical fiber couplers are also called as ________________ |
A. | isolators |
B. | circulators |
C. | directional couplers |
D. | attenuators |
Answer» C. directional couplers |
242. |
How many types of multiport optical fiber couplers are available at present? |
A. | two |
B. | one |
C. | four |
D. | three |
Answer» D. three |
243. |
The optical power coupled from one fiber to another is limited by |
A. | numerical apertures of fibers |
B. | varying refractive index of fibers |
C. | angular power distribution at source |
D. | number of modes propagating in each fiber |
Answer» D. number of modes propagating in each fiber |
244. |
________ couplers combine the different wavelength optical signal onto the fiber or separate the different wavelength optical signal output from the fiber. |
A. | 3-port |
B. | 2*2-star |
C. | wdm |
D. | directional |
Answer» C. wdm |
245. |
How many fabrication techniques are used for 3 port fiber couplers? |
A. | one |
B. | two |
C. | three |
D. | four |
Answer» B. two |
246. |
The most common method for manufacturing couplers is ____________ |
A. | wavelength division multiplexing |
B. | lateral offset method |
C. | semitransparent mirror method |
D. | fused bi-conical taper (fbt) technique |
Answer» D. fused bi-conical taper (fbt) technique |
247. |
Couplers insertion loss is same as that of excess loss. State whether the given statement is true or false. |
A. | true |
B. | false |
Answer» B. false |
248. |
A four-port multimode fiber FBT coupler has 50 μWoptical power launched into port 1. The measured output power at ports 2,3 and 4 are 0.003, 23.0 and 24.5 μW respectively. Determine the excess loss. |
A. | 0.22 db |
B. | 0.33 db |
C. | 0.45 db |
D. | 0.12 db |
Answer» A. 0.22 db |
249. |
A four-port FBT coupler has 60μW optical power launched into port one. The output powers at ports 2, 3, 4 are 0.0025, 18, and 22 μW respectively. Find the split ratio? |
A. | 42% |
B. | 46% |
C. | 52% |
D. | 45% |
Answer» D. 45% |
250. |
How many manufacturing methods are used for producing multimode fiber star couplers? |
A. | two |
B. | one |
C. | three |
D. | five |
Answer» A. two |
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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