Multiple Choice Questions and Answers on Optical Fiber Communication


1)   In an optical fiber communication system, which among the following is not a typical transmitter function?

DRex Electronics

a. Coding for error protection
b. Decoding of input data
c. Electrical to optical conversion
d. Recoding to match output standard

ANSWER: (d) Recoding to match output standard

2)   Which among the following is provided by an optical receiver for the regeneration of data signal with minimum error?

a. Photo-diode
b. Signal Processing Circuits
c. Linear Circuitry
d. None of the above

ANSWER: (c) Linear Circuitry

3)   For a sine wave, the frequency is represented by the cycles per ______

a. Second
b. Minute
c. Hour
d. None of the above

ANSWER: (a) Second

4)   Which property/ies of PCM stream determine/s the fidelity to original analog signal?

a. Sampling rate
b. Bit depth
c. Both a and b
d. None of the above

ANSWER: (c) Both a and b

5)   In single-mode fibers, how does the fraction of energy traveling through bound mode appear in the cladding?

a. As a crescent wave
b. As a gibbous wave
c. As an evanescent wave
d. All of the above

ANSWER: (c) As an evanescent wave

6)   What is the typical value of refractive index for an ethyl alcohol?

a. 1
b. 1.36
c. 2.6
d. 3.4

ANSWER:(b) 1.36

7)   If a light travels in a certain medium and it gets reflected off an optically denser medium with high refractive index, then it is regarded as _______

a. External Reflection
b. Internal Reflection
c. Both a and b
d. None of the above

ANSWER: (a) External Reflection

8)   In an optical fiber, the concept of Numerical aperture is applicable in describing the ability of __________

a. Light Collection
b. Light Scattering
c. Light Dispersion
d. Light Polarization

ANSWER:(a) Light Collection

9)   Which among the following do/does not support/s the soot formation process?

d. All of the above


10)   Which type of photonic crystal fiber exhibit/s its/their similarity to the periodic crystalline lattice in a semiconductor?

a. Index guiding fiber
b. Photonic bandgap fiber
c. Both a and b
d. None of the above

ANSWER: (b) Photonic bandgap fiber

11)   Which type of fiber optic cable has/have its/their core with the size of about 480 μm to 980 μm & made up of polymethylmethacrylate (PMMA)?

a. Glass fiber optic cable
b. Plastic fiber optic cable
c. Plastic clad silica fiber optic cable
d. All of the above

ANSWER: (b) Plastic fiber optic cable

12)   In multifiber cable system, which form of outer jacket/s consist/s of polyolefin compounds and are regarded as halogen free?

d. All of the above


13)   During the design of FOC system, which among the following reasons is/are responsible for an extrinsic absorption?

a. Atomic defects in the composition of glass
b. Impurity atoms in glass material
c. Basic constituent atoms of fiber material
d. All of the above

ANSWER: (b) Impurity atoms in glass material

14)   Which among the following represent/s the measure/s to minimize the inhomogenities for Mie scattering reduction?

a. Extrusion Control
b. Increase in relative R.I. difference
c. Removal of imperfections due to glass manufacturing process
d. All of the above

ANSWER: (d) All of the above

15)   In Kerr effect, induced index change has its proportionality with respect to _________

a. square of electric field
b. cube of electric field
c. cube root of electric field
d. one-fourth power of electric field

ANSWER: (a) square of electric field

16)   Which among the following is regarded as an inelastic scattering of a photon?

a. Kerr Effect
b. Raman Effect
c. Hall Effect
d. Miller Effect

ANSWER: (b) Raman Effect

17)   Which kind/s of misalignment assist/s in the reduction of overlap region in fiber?

a. Angular
b. Longitudinal
c. Lateral
d. All of the above

ANSWER: (c) Lateral

18)   Which is the correct order of sequential steps for an electric arc fusion technique?

A. Pressing of fiber ends for fusion
B. Application of heat for smoothening of end-surfaces
C. Alignment of broken fiber edges

a. A, B, C
b. B, A, C
c. C, B, A
d. C, A, B

ANSWER: (c) C, B, A

19)   Which splicing technique involves the alignment and locking of broken fiber edges by means of positioning devices & optical cement?

a. Fusion
b. Mechanical
c. Both a and b
d. None of the above

ANSWER:(b) Mechanical

20)   By using Springroove splicing technique, what is the value of mean insertion loss for multi mode graded index fiber?

a. 0.01
b. 0.03
c. 0.05
d. 0.09

ANSWER: (c) 0.05

21)   In the fiber optic link, power transfer from one fiber to another and from fiber to detector must take place with _________coupling efficiency.

a. maximum
b. stable
c. minimum
d. unpredictable

ANSWER: (a) maximum

22)   In spontaneous emission, the light source in an excited state undergoes the transition to a state with _______

a. Higher energy
b. Moderate energy
c. Lower energy
d. All of the above

ANSWER: (c) Lower energy

23)   Which among the following is a key process adopted for the laser beam formation as it undergoes the light amplification?

a. Spontaneous Emission
b. Stimulated Emission
c. Both a and b
d. None of the above

ANSWER: (b) Stimulated Emission

24)   While coupling of LEDs with fiber, on which factor/s does the size of source and lighting angle generated within the semiconductor depend/s?

a. Geometry of die
b. Refractive index of semiconductor
c. Encapsulation Medium
d. All of the above

ANSWER: (d) All of the above

25)   Which among the following results in the removal of LED lens interface for achieving high coupling efficiency?

a. Spherical lens
b. Cylindrical lens
c. Integral lens LED
d. All of the above

ANSWER: (c) Integral lens LED

26)   For a photo-diode with responsivity of 0.50 A/W & optical power of about 12μW, what would be the value of generated photocurrent?

a. 3 μA
b. 6 μA
c. 9 μA
d. 12 μA

ANSWER: (b) 6 μA

27)   Which component of an optical receiver is a linear frequency shaping filter used for the compensation of signal distortion and Inter Symbol Interference (ISI)?

a. Photodetector
b. Amplifier
c. Equalizer
d. None of the above

ANSWER: (c) Equalizer

28)   In digital receivers, which codes are used to designate the sampled analog signals after their quantization into discrete levels?

a. Binary
b. Decimal
d. Excess-3

ANSWER: (a) Binary

29)   Which feature of an eye-diagram assists in the measurement of additive noise in the signal?

a. Eye opening (height, peak to peak)
b. Eye overshoot/ undershoot
c. Eye width
d. None of the above

ANSWER: (a) Eye opening (height, peak to peak)

30)   Which method determines the dispersion limitation of an optical link?

a. Link power budget
b. Rise time budget
c. Both a and b
d. None of the above

ANSWER: (b) Rise time budget

31)   Which phenomenon causes the dynamic line width broadening under the direct modulation of injection current?

a. Modal Noise
b. Mode-partition Noise
c. Frequency Chirping
d. Reflection Noise

ANSWER: (c) Frequency Chirping

32)   Speckle pattern is generated due to interference of nodes from a coherent source especially when the coherence time of source is _________ the intermodal dispersion time in the fiber.

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

ANSWER: (b) Greater than

33)   Which among the following is/are determined by the fiber characterization?

a. Fiber integrity & performance for desired transmission rate
b. Installation practices
c. Service Implementation
d. All of the above

ANSWER: (d) All of the above

34)   From the tests carried out in fiber characterization, which among the following measures the total light reflected back to the transmitter caused by the fiber as well as the components like connector pairs and mechanical splices?

a. ORL
c. LTS
d. PMD


35)   In fiber fault location, the equation of length (l) for time difference (t) is expressed as L = ct / 2n1 . Which factor in this equation implies that the light travels a length from source to break point and then through another length on the return trip?

a. L
b. c
c. t
d. 2

ANSWER: (d) 2

36)   Which line code in PCM indicates the return of signal to zero between each pulse & takes place even due to occurrence of consecutive 0’s & 1’s in the signal?

a. Return-to-zero (RZ)
b. Non-Return to zero space
c. Return to zero inverted
d. Non-return to zero inverted

ANSWER: (a) Return-to-zero (RZ)

37)   In the structure of fiber, the light is guided through the core due to total internal ______

a. reflection
b. refraction
c. diffraction
d. dispersion

ANSWER: (a) reflection

38)   In the structure of a fiber, which component provides additional strength and prevents the fiber from any damage?

a. Core
b. Cladding
c. Buffer Coating
d. None of the above

ANSWER: (c) Buffer Coating

39)   Which is the transmission medium for VLF electromagnetic waves especially applicable for aeronautical and submarine cables?

a. Paired wires
b. Coaxial cable
c. Waveguide
d. Wireless

ANSWER: (a) Paired wires

40)   Which rays exhibit the variation in the light acceptability ability of the fiber?

a. Meridional
b. Skew
c. Leaky
d. All of the above

ANSWER: (b) Skew

41)   If a fiber operates at 1400nm with the diameter of about 10 μm, n1 = 1.30, Δ = 0.80% , V = 3.5, then how many modes will it have?

a. 6.125
b. 9.655
c. 12.95
d. 16.55

ANSWER: (a) 6.125

42)   Which kind of dispersion phenomenon gives rise to pulse spreading in single mode fibers?

a. Intramodal
b. Intermodal
c. Material
d. Group Velocity

ANSWER: (a) Intramodal

43)   With respect to single mode and graded index fibers, which parameter specifies the propagation of polarization modes with different phase velocities & the difference between their effective refractive indices?

a. Mode field diameter
b. Birefringence
c. Fiber beat length
d. Spot Size

ANSWER: (b) Birefringence

44)   On which of the following factor/s do/does the ‘Hydrogen Effect’ depend/s?

a. Type of fiber & Cable Design
b. Operating Wavelength
c. Installation Method
d. All of the above

ANSWER: (d) All of the above

45)   Consider the statements given below. Which among them is not a drawback of double crucible method?

a. Utility in mass production of fibers
b. High attenuation
c. High OH content in drawn fiber
d. Addition of impurity while the fiber is drawn

ANSWER: (a) Utility in mass production of fibers

46)   Consider the assertions given below. Which is the correct sequential order of process adopted in glass fiber preparation?

A. Drawing of fiber
B. Production of pure glass
C. Pulling of fiber
D. Conversion of pure glass into preform

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

ANSWER: (a) B, D, A, C

47)   At which level of temperature does the oxidation process occur in MCVD?

a. Low
b. Moderate
c. High
d. Unpredictable

ANSWER: (c) High

48)   Assuming no ISI, the maximum possible bandwidth of a multimode graded index fiber with 5 MHz, shows the total pulse broadening of 0.1s for the distance of about 12km. What would be the value of bandwidth length product?

a. 40 MHz
b. 60 MHz
c. 90 MHz
d. 120 MHz

ANSWER: (b) 60 MHz

49)   In Rayleigh scattering of light in glass, at which type of temperature does the glass attain the state of thermal equilibrium and exhibits its relativity to annealing temperature?

a. Junction
b. Fictive
c. Breakdown
d. Decomposition

ANSWER: (b) Fictive

50)   Which type of scattering occurs due to interaction of light in a medium with time dependent optical density variations thereby resulting into the change of energy (frequency) & path?

a. Stimulated Brilliouin Scattering (SBS)
b. Stimulated Raman Scattering (SRS)
c. Mie Scattering
d. Rayleigh Scattering

ANSWER: (a) Stimulated Brilliouin Scattering (SBS)

51)   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

52)   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

53)   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

54)   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

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

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

ANSWER: (d) 1000

56)   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

57)   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

58)   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

59)   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

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

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

ANSWER: (b) Equally

61)   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

62)   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

63)   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

64)   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

65)   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

66)   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

67)   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

68)   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

69)   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

70)   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

71)   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

72)   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

73)   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

74)   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

75)   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

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

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

ANSWER: (a) moisture

77)   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

78)   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

79)   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

80)   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

81)   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

82)   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

83)   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

84)   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

85)   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

86)   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

87)   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

88)   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

89)   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

90)   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

91)   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

92)   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

93)   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

94)   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

95)   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

96)   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

97)   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%

98)   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

99)   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

100)   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