MCQs in Fiber Optics Communications Part V

Compiled MCQs in Fiber Optics Communications Part 5 of the series as one topic in Electronic System and Technologies (Communications Engineering) in the ECE Board Exam.

This is the Multiples Choice Questions Part 5 of the Series in Fiber Optics Communications as one of the Communications Engineering topic. In Preparation for the ECE Board Exam make sure to expose yourself and familiarize in each and every questions compiled here taken from various sources including but not limited to past Board Examination Questions in Electronic System and Technologies, Communications Books, Journals and other Communications References.

Online Questions and Answers Topic Outline

• MCQs in Principles of Light Transmission
• MCQs in Types of Light Sources, Laser, LED
• MCQs in Light Detectors
• MCQs in Modulation and Waveform
• MCQs in System Design
• MCQs in General application
• MCQs in System Bandwidth
• MCQs in Splicing Techniques

MCQs in Fiber Optics Communications Series

Following is the list of multiple choice questions in this brand new series:

Optical Fiber Communications MCQs
PART 1: MCQs from Number 1 – 50                        Answer key: PART I
PART 2: MCQs from Number 51 – 100                   Answer key: PART II
PART 3: MCQs from Number 101 – 150                 Answer key: PART III
PART 4: MCQs from Number 151 – 200                 Answer key: PART IV
PART 5: MCQs from Number 201 – 250                 Answer key: PART V
PART 6: MCQs from Number 251 – 300                 Answer key: PART VI

Continue Practice Exam Test Questions Part V of the Series

201. In refraction that occurs in air/glass interfaces, among the visible light, which is the bent the least?

• A. violet
• B. blue
• C. red
• D. orange

202. Ratio of the velocity of propagation of a light ray in free space to the velocity of propagation of a light ray in free space in a given material.

• A. refractive index
• B. standing wave ratio
• C. velocity factor
• D. propagation velocity

203. It is the angle at which the propagating ray strikes the interface with respect to the normal.

• A. refracted angle
• B. incident angle
• C. reflected angle
• D. critical angle

204. It is the angle formed between the propagating ray and the normal after the ray has entered the second medium.

• A. angle of incidence
• B. angle of reflection
• C. propagation angle
• D. angle of refraction

205. Between silicon and gallium arsenide, which has the greatest index of refraction?

• A. Gallium arsenide
• B. Neither of silicon nor gallium arsenide
• C. Silicon
• D. They are equal

206. A fiber-optic cable has a loss of 15 dB/km. The attenuation in a cable 1000 ft. long is

• A. 4.57 dB
• B. 9.3 dB
• C. 24 dB
• D. 49.2 dB

207. Medium 1 is a glass (n1 = 1.5) and medium 2 is an ethyl alcohol (n2 = 1.36). For an angle of incidence of 30 degrees, determine the angle of refraction.

• A. 44.5 degrees
• B. 14.56 degrees
• C. 33.47 degrees
• D. 75 degrees

208. The minimum angle of incidence at which the light ray may strike the interface of two media and result in an angle of refraction of 90 degrees or greater.

• A. optimum angle
• B. angle of refraction
• C. refracted angle
• D. critical angle

209. The higher the index number

• A. the higher the speed of light
• B. the lower the speed of light
• C. has no effect on the speed of light
• D. the shorter the wavelength propagation

210. The maximum angle in which external light rays may strike the air/glass interface and still propagate down the fiber.

• A. Acceptance cone half-angle
• B. Acceptance cone
• C. Critical angle
• D. Angle of incidence

211. It is the figure of merit used to measure the magnitude of the acceptance angle.

• A. acceptance angle
• B. numerical aperture
• C. index profile
• D. refractive index

212. The effect of a large magnitude of the numerical aperture

• A. The amount of external light the fiber will accept is greater.
• B. The amount of external light the fiber will accept is less.
• C. The amount of modal dispersion will be less.
• D. The amount of chromatic dispersion will be greater.

213. Only one path for light rays to take down the fiber

• A. Multimode
• B. Step-index
• C. Single mode

214. More than one path for light rays to take down the fiber

• A. Multimode
• B. Step-index
• C. Single mode

215. The three major groups of the optical system are

• A. the components, the data rate and the response time
• C. the transmitter, the cable and the receiver
• D. the source, the link and the detector

216. Infrared light has a wavelength that is

• A. less than 400 nm
• B. more than 700 nm
• C. less than 700 nm
• D. a little over 400 nm

217. How many modes possible with a multimode step-index with a core diameter of 50 um, a core refractive index of 1.6, a cladding refractive index of 1.584, and a wavelength of 1300 nm.

• A. 456
• B. 213
• C. 145
• D. 372

218. It is a graphical representation of the magnitude of the refractive index across the fiber.

• A. mode
• B. index profile
• C. numerical aperture
• D. refractive index

219. A type of index profile of an optical fiber that has a central core and outside cladding with a uniform refractive index

• A. multimode
• C. step-index
• D. single mode

220. A type of index of an optical fiber that has no cladding and whose central core has a non-uniform refractive index.

• B. multimode
• C. single mode
• D. step-index

221. Results in reduction in the power of light wave as it travels down the cable.

• A. power loss
• B. absorption loss
• C. resistive loss
• D. heat loss

222. Which of the following is not a factor in cable light loss?

• A. reflection
• B. absorption
• C. scattering
• D. dispersion

223. It is analogous to power dissipation to copper cables, impurities in the fiber absorb the light and covert it to heat.

• A. power loss
• B. absorption loss
• C. resistive loss
• D. heat loss

224. It is caused by valence electrons in the silica material from which the fiber are manufactured.

• A. ion resonance absorption
• B. infrared absorption
• C. ultraviolet absorption
• D. visible light absorption

225. It is a result of photons of light that are absorbed by the atoms of the glass core molecule.

• A. ion resonance absorption
• B. infrared absorption
• C. ultraviolet absorption
• D. visible light absorption

226. It is caused by hydroxide ions in the material

• A. visible light absorption
• B. infrared absorption
• C. ultraviolet absorption
• D. ion resonance absorption

227. Which type of fiber-optic cable has the least modal dispersion?

• A. single-mode step-index
• B. multimode step-index

228. For a single mode optical cable with 0.25 dB/km loss, determine the optical power 100 km from a 0.1-mW light source.

• A. -45 dBm
• B. -15 dBm
• C. -35 dBm
• D. –25 dBm

229. Light rays that are emitted simultaneously from an LED and propagated down an optical fiber do not arrive at the far end of the fiber at the same time results to

• A. intramodal dispersion
• B. pulse length dispersion
• C. modal dispersion
• D. wavelength dispersion

230. Chromatic dispersion can be eliminated by __________.

• A. using a monochromatic light source
• B. using a very small numerical aperture fiber
• C. using a graded-index fiber
• D. using a very sensitive photo detector

231. Type of bend that occurs as a result of differences in thermal contraction rates between the core and the cladding material.

• A. Macrobending
• B. Microbending

232. These bends are caused by excessive pressure and tension and generally occur while fiber are bent during handling or installation.

• A. microbending
• B. macrobending
• D. kinks

233. As light is coupled in a multiport deflective device, the power is reduced by

• A. 1.5 dB
• B. 0.1 dB
• C. 0.5 dB
• D. 0.001 dB

234. It is caused by the difference in the propagation time of light rays that take different paths down the fiber.

• A. modal dispersion
• B. microbending
• C. Rayleigh scattering
• D. chromatic dispersion

235. How can modal dispersion reduced entirely?

• A. Use a graded index fiber
• B. Use a single-mode fiber
• C. Use a monochromatic light source
• D. Use a very sensitive light detector

236. It indicates what signal frequencies can be propagated through a given distance of fiber cable.

• A. Bandwidth Distance Product
• B. Pulse width dispersion
• C. Rise time
• D. Cutoff frequency

237. For a 300-m optical fiber cable with a bandwidth distance product of 600 MHz-km, determine the bandwidth.

• A. 5 GHz
• B. 1 GHz
• C. 2 GHz
• D. 3 GHz

238. For an optical fiber 10 km long with a pulse spreading constant of 5 ns/km, determine the maximum digital transmission rates using Return to Zero (RZ) and Nonreturn to Zero (NRZ).

• A. 5 Mbps and 10 Mbps
• B. 10 Mbps and 5 Mbps
• C. 10 Mbps and 20 Mbps
• D. 20 Mbps and 10 Mbps

239. What is the spectral width of a standard LED?

• A. 20 to 40 nm
• B. 30 to 50 nm
• C. 10 to 30 nm
• D. 40 to 60 nm

240. What is the spectral width of an ILD?

• A. 0.1 nm to 1 nm
• B. 2 nm to 5 nm
• C. 1 nm to 3 nm
• D. 3 nm to 4 nm

241. When connector losses, splice losses and coupler losses are added, what is the limiting factor?

• A. source power
• B. fiber attenuation
• C. connector and splice loss
• D. detector sensitivity

242. A pn-junction diode emits light by spontaneous emission

• A. LED
• B. APD
• C. PIN
• D. Zener diode

243. Which type of fiber optic cable is best for very high speed data?

• A. single-mode step-index
• B. multimode step-index

244. A measure of conversion efficiency of a photodetector.

• A. Efficiency
• B. Responsivity
• C. Dark current
• D. Spectral response

245. The leakage current that flows through a photodiode with no light input

• A. dark voltage
• B. dark impedance
• C. dark power
• D. dark current

246. The time it takes a light induced carrier travel across the depletion region of the semiconductor.

• A. dispersion
• B. response time
• D. transit time

247. The range of wavelength values that a given photodiode will respond.

• A. spectral response
• B. permeance
• C. dark current
• D. reluctance

248. The term responsivity as it applies to a light detector is best described as

• A. the time required for the signal to go from 10 to 90 percent of maximum amplitude
• B. the ratio of the diode output current to the input optical power
• C. the ratio of the input power to output power
• D. the ratio of output current to input current

249. The minimum optical power a light detector can receive and still produce a usable electrical output signal.

• A. light responsivity
• B. light sensitivity
• C. light collectivity
• D. illumination

250. Type of lasers that uses a mixture of helium and neon enclosed in glass tube.

• A. gas lasers
• B. solid lasers
• C. semiconductor lasers
• D. liquid lasers

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