Multiple Choice Questions and Answers on Optical Fiber Communication(Part-2)

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1)   The macroscopic bending losses show an exponential increase due to ________ in radius of curvature.

a. Increase
b. Decrease
c. Stability
d. None of the above

ANSWER: (b) Decrease

2)   Which type of mechanical splicing exhibits the permanent bonding of prepared fiber ends with the rigid alignment of the tube?

a. Snug Tube Splicing
b. Loose Tube Splicing
c. Elastomeric Splicing
d. Precision Pin Splicing

ANSWER: (a) Snug Tube Splicing

3)   Which component of fiber-optic connector has a provision of entry for the fiber along with the fixation to connector housing?

a. Ferrule
b. Cable
c. Connector Housing
d. Coupling Device

ANSWER: (b) Cable

4)   Which among the following is regarded as a keyed bayonet connector along with its feasibility of easiest insertion and removal from the fiber optic cable?

a. FC Connectors
b. LC Connectors
c. MT-RJ Connectors
d. ST Connectors

ANSWER: (d) ST Connectors

5)   How many mating cycles are being rated by typically matched SC Connectors?

a. 500
b. 600
c. 800
d. 1000

ANSWER: (d) 1000

6)   In Stimulated Emission, which among the following parameters of generated photon is/are similar to the photon of incident wave?

a. Phase
b. Frequency
c. Polarization & direction of travel
d. All of the above

ANSWER: (d) All of the above

7)   Consider a crystal of ruby laser whose length is 6 cm and the refractive index is 1.8, emits the wavelength of about 0.55 μm. What will be the value of number of longitudinal modes?

a. 3.9 x 105
b. 4.9 x 105
c. 5.6 x 105
d. 7.7 x 105

ANSWER: (a) 3.9 x 105

8)   In a laser structure, the existence of standing waves is possible at frequencies for which the distance between the mirrors is an integral number of ________

a. λ / 2
b. λ / 4
c. λ / 6
d. λ / 8

ANSWER: (a) λ / 2

9)   The small section of fiber which is coupled to the optical source is known as _________

a. Flylead
b. Pigtail
c. Both a and b
d. None of the above

ANSWER: (c) Both a and b

10)   In Lambertian output pattern of LED, the source is ______ bright from all directions.

a. Less
b. Equally
c. More
d. Unpredictably

ANSWER: (b) Equally

11)   In pyroelectric photodetectors, the consequent increase in dielectric constant due to temperature variation by the photon absorption, is generally measured as change in _______

a. resistance
b. inductance
c. admittance
d. capacitance

ANSWER: (d) capacitance

12)   Which type of preamplifier plays a crucial role in reducing the effect of thermal noise?

a. Low Impedance Pre-amplifier
b. High Impedance Preamplifier
c. Transimpedance Preamplifier
d. None of the above

ANSWER: (b) High Impedance Preamplifier

13)   In high impedance preamplifier, how are the noise sources kept to minimum level?

a. By reducing dark current with proper selection of photodiode
b. By reducing thermal noise of biasing resistor
c. By using high impedance amplifier
d. All of the above

ANSWER: (d) All of the above

14)   Which among the following are the disadvantages of an optical feedback transimpedance receiver?

A. Increase in receiver input capacitance
B. Increase in dark current
C. Decrease in receiver input capacitance
D. Decrease in dark current

a. A & B
b. C & D
c. A & D
d. B & C

ANSWER: (a) A & B

15)   Which category/ies of wavelength division multiplexer comprise/s two 3dB couplers where the splitting of an incident beam takes place into two fiber paths, followed by the recombination with second 3-dB coupler?

a. Interference filter based devices
b. Angular dispersion based devices
c. Mach-Zehnder Interferometers
d. All of the above

ANSWER: (c) Mach-Zehnder Interferometers

16)   Which among the following controls the length of Fabry-Perot interferometer so that it can act as a tunable optical filter?

a. Transducer
b. Tachometer
c. Multimeter
d. Phase-meter

ANSWER: (a) Transducer

17)   In circulator, an optical path of signal follows _______

a. An open loop
b. A closed loop
c. Both a and b
d. None of the above

ANSWER: (b) A closed loop

18)   Which among the following is/are responsible for generating attenuation of an optical power in fiber?

a. Absorption
b. Scattering
c. Waveguide effect
d. All of the above

ANSWER: (d) All of the above

19)   Consider the assertions/ characteristics given below. Which type of attenuation measurement technique exhibits these characteristics?

1. Necessity of accessing both ends of fiber.
2. Measurements corresponding to specific wavelengths.
3. Requirement of spectral response over a range of wavelengths.

a. Cutback Technique
b. Insertion Loss Technique
c. Use of OTDR Technique
d. None of the above

ANSWER: (a) Cutback Technique

20)   For neglecting the pulse dispersion in the digital systems, the rms width of fiber impulse response must be _________one-quarter of the pulse spacing.

a. Less than
b. Equal to
c. Greater than
d. None of the above

ANSWER: (a) Less than

21)   If a noisy channel has a bandwidth of 4 MHz with signal to noise ratio of about 1, what would be the maximum capacity of the channel?

a. 2 Mb/sec
b. 4 Mb/sec
c. 6 Mb/sec
d. 8 Mb/sec

ANSWER: (b) 4 Mb/sec

22)   In the structure of fiber optic cable, the refractive index of core is always _______the refractive index of cladding.

a. Less than
b. Equal to
c. Greater than
d. None of the above

ANSWER: (c) Greater than

23)   The order of mode is equal to the number of field____ across the guide.

a. Zeros
b. Poles
c. Ones
d. All of the above

ANSWER: (a) Zeros

24)   Which among the following represents the lateral shift of a light beam on reflection at a dielectric interface?

 a. Doppler’s Shift
b. Goos-Haenchen’s Shift
c. Frequency Shift
d. Phase Shift

ANSWER: (b) Goos-Haenchen’s Shift

25)   Why are plastic clad silica fiber optic cables not used widely?

a. Difficulty in connector application due to excessive plasticity in cladding
b. Difficulty in bonding
c. Insolubility in organic solvents
d. All of the above

ANSWER: (d) All of the above

26)   In cables, water is prevented from filling the spaces with __________resistant compounds.

a. moisture
b. pressure
c. temperature
d. stress

ANSWER: (a) moisture

27)   Which reason/s is/are responsible for the occurrence of non-linear Cross Phase Modulation (XPM)?

a. Difference in transmission phase of peak pulse & leading or trailing edges of pulse
b. Third-order optical non-linearity
c. Intensity dependence of refractive index
d. All of the above

ANSWER: (c) Intensity dependence of refractive index

28)   What is/ are the consequence/s of Self Phase Modulation in non-linear optics?

a. Modification in pulse spectrum
b. Limited transmission rate
c. Dispersion effect
d. All of the above

ANSWER: (d) All of the above

29)   Which type of fiber-optic coupler causes the distribution of an optical power from more than two input ports among the several output ports?

 a. Star Coupler
b. Tree Coupler
c. X Coupler
d. All of the above

ANSWER: (a) Star Coupler

30)   Which optical devices are adopted or applicable for routing signals from one waveguide to another?

a. Optical Combiner
b. Optical Splitter
c. Optical Coupler
d. None of the above

ANSWER: (c) Optical Coupler

31)   Which among the following characteristics of Laser light specifies the precise movement of all individual light waves together through time and space?

 a. Monochromatic
b. Directional
c. Coherent
d. Brightness

ANSWER: (c) Coherent

32)   Which modes are acknowledged due to their association with electromagnetic field and beam profile in the direction perpendicular to the plane of pn junction?

a. Longitudinal Modes
b. Transverse Modes
c. Lateral Modes
d. All of the above

ANSWER: (b) Transverse Modes

33)   Which type of injection laser involves the use of geometry for fabrication of the multimode injection laser with a single or small number of lateral modes?

a. Gain guided laser
b. Index guided laser
c. Quantum well laser
d. Quantum dot laser

ANSWER: (a) Gain guided laser

34)   In the dynamic response of Injection Laser Diode (ILD), the delay which is followed by ____ frequency damped oscillations give rise to the generation of relaxation oscillations.

a. Low
b. Medium
c. High
d. All of the above

ANSWER: (c) High

35)   The spectral response of an ideal photodetector depicts its efficiency as a function of _________

a. amplitude
b. frequency
c. period
d. wavelength

ANSWER: (d) wavelength

36)   According to frequency response of photo-detector, the modulation frequency at which the output current decreases to ________of peak value.

a. one-third
b. one-fourth
c. half
d. one-tenth

ANSWER: (c) half

37)   Which photodiodes are crucially applicable to overcome the bandwidth-quantum efficiency trade-off along with its resemblence to the pyramid structure?

a. Mushroom Waveguide Photodiode
b. Traveling Wave Photodiode
c. Resonant Cavity Photodiode
d. All of the above

ANSWER: (a) Mushroom Waveguide Photodiode

38)   When an optical signal is incident on a photo-detector, which noise originate/s due to statistical nature of production and collection of photoelectrons?

a. Dark Current Noise
b. Quantum Noise
c. Surface Leakage Current noise
d. All of the above

ANSWER: (b) Quantum Noise

39)   In an eye-diagram, digital signals with very bad interference resembles the shape of _____

a. circle
b. rectangle
c. triangle
d. straight line

ANSWER:(d)  straight line

40)   On which factor/s do/does the response time of photodiode depend/s?

a. Diffusion time of photo carriers outside the depletion region
b. Diffusion time of photo carriers within the depletion region
c. RC time constant
d. All of the above

ANSWER: (d) All of the above

41)   Which nature of charge carriers give rise to the current fluctuations thereby resulting into the generation of shot noise?

a. Continuous
b. Discrete
c. Sampled
d. All of the above

ANSWER: (b) Discrete

42)   Which among the following parameters is/are decided by the front-end of a receiver?

a. Sensitivity
b. Bandwidth
c. Both a and b
d. None of the above

ANSWER: (c) Both a and b

43)   In an optical network, increase in the number of lasers ________the bit rate.

a. Increases
b. Stabilizes
c. Decreases
d. None of the above

ANSWER: (a) Increases

44)   Which band/s specify/ies the operation range of Erbium doped fiber amplifier (EDFA)?

a. By O band
b. By C band
c. By S band
d. All of the above

ANSWER: (b) By C band

45)   Basically, solitons are pulses which propagates through the fiber without showing any variation in ______

a. Amplitude
b. Velocity
c. Shape
d. All of the above

ANSWER: (d) All of the above

46)   Why is an electrical isolation required between several portions of an electronic circuit?

a. Provision of high voltage protection
b. Reduction in noise level
c. Both a & b
d. None of the above

ANSWER: (c) Both a & b

47)   For measuring the shape of input pulse in time-domain intermodal dispersion method, the test fiber is replaced by another fiber whose length is less than ___ of the test fiber.

a. 1%
b. 5%
c. 10%
d. 20%

ANSWER: (a) 1%

48)   In chromatic dispersion, which parameter for the modulation of the received signal is measured with the help of a vector voltmeter?

a. Amplitude
b. Frequency
c. Phase
d. Period

ANSWER: (c) Phase

49)   Which among the following stages is/are adopted in Splice Loss Experiment?

a. Translational
b. Rotational
c. Both a and b
d. None of the above

ANSWER: (c) Both a and b

50)   Which among the following misalignments give/gives rise to the occurrence of splice loss?

a. Longitudinal separation between the end-faces of fiber
b. Angular tilt between fiber ends
c. Transverse offset between fiber ends
d. All of the above

ANSWER: (d) All of the above