Back to Subject

Unit 3 - Practice Quiz

PHY110 50 Questions
0 Correct 0 Wrong 50 Left
0/50

1 What is the fundamental principle behind light propagation in an optical fiber?

A. Refraction
B. Diffraction
C. Total Internal Reflection
D. Polarization

2 In the structure of an optical fiber, what acts as the dielectric waveguide?

A. The jacket
B. The cladding only
C. The core and cladding assembly
D. The buffer coating

3 If is the refractive index of the core and is the refractive index of the cladding, which condition is necessary for light guidance?

A.
B.
C.
D.

4 The critical angle at the core-cladding interface is given by which formula?

A.
B.
C.
D.

5 What is the 'Acceptance Angle' in fiber optics?

A. The critical angle at the core-cladding boundary
B. The maximum angle with the fiber axis at which light can enter the fiber to be guided
C. The angle of refraction inside the core
D. The Brewster angle of the material

6 The Numerical Aperture (NA) of an optical fiber is a measure of its:

A. Attenuation capability
B. Dispersion limit
C. Light gathering ability
D. Bending radius

7 Mathematically, the Numerical Aperture (NA) for a step-index fiber in air is given by:

A.
B.
C.
D.

8 What is the relative refractive index difference, , approximately equal to?

A.
B.
C.
D.

9 How is Numerical Aperture (NA) related to the relative refractive index difference ?

A.
B.
C.
D.

10 Calculate the Numerical Aperture if the refractive indices of the core and cladding are 1.50 and 1.48 respectively.

A. 0.02
B. 0.144
C. 0.244
D. 0.50

11 The V-number (normalized frequency) of an optical fiber determines:

A. The amount of attenuation
B. The number of modes propagating in the fiber
C. The critical angle
D. The speed of light in the core

12 What is the formula for the V-number of a fiber with core radius and wavelength ?

A.
B.
C.
D.

13 For a step-index fiber to support only a single mode, the V-number must be:

A. Greater than 2.405
B. Less than or equal to 2.405
C. Equal to 0
D. Greater than 10

14 Which of the following best describes the refractive index profile of a Step Index fiber?

A. It varies parabolically from the center to the cladding.
B. It is constant throughout the core and changes abruptly at the cladding boundary.
C. It decreases linearly from the axis to the cladding.
D. It is constant throughout the entire fiber including cladding.

15 In a Graded Index (GRIN) fiber, how does the refractive index of the core vary?

A. It is constant.
B. It increases from the center to the cladding.
C. It decreases continuously (usually parabolically) from the axis to the cladding.
D. It changes randomly.

16 The path of a light ray in a Graded Index (GRIN) fiber is:

A. Zig-zag straight lines
B. Helical or Sinusoidal
C. Strictly linear along the axis
D. Random scattering

17 The approximate number of modes () in a Step Index multimode fiber is related to the V-number by:

A.
B.
C.
D.

18 The approximate number of modes () in a parabolic Graded Index fiber is related to the V-number by:

A.
B.
C.
D.

19 Attenuation in optical fibers is usually measured in:

A. Volts per meter (V/m)
B. Decibels per kilometer (dB/km)
C. Watts (W)
D. Hertz (Hz)

20 If the input power is and output power is , the attenuation loss () in dB is given by:

A.
B.
C.
D.

21 Rayleigh scattering in optical fibers is caused by:

A. Absorption by OH ions
B. Microscopic density fluctuations in the fiber material
C. Bending of the fiber
D. Metallic impurities

22 Rayleigh scattering loss is proportional to:

A.
B.
C.
D.

23 What is the primary cause of extrinsic absorption in optical fibers?

A. Electronic transitions in the UV region
B. Atomic vibration in the IR region
C. Hydroxyl (OH) ions (water) impurities
D. Density fluctuations

24 Dispersion in optical fibers results in:

A. Decrease in signal amplitude
B. Pulse broadening
C. Increase in frequency
D. Change in polarization

25 Intermodal dispersion is most significant in:

A. Single mode step index fibers
B. Multimode step index fibers
C. Graded index fibers
D. Plastic fibers only

26 Which type of fiber has the least intermodal dispersion?

A. Multimode Step Index
B. Multimode Graded Index
C. Single Mode Step Index
D. Plastic Optical Fiber

27 Material dispersion is caused by:

A. The variation of refractive index with wavelength
B. The waveguide structure
C. Bending of the fiber
D. Multiple modes taking different paths

28 Microbending losses are caused by:

A. Wrapping fiber around a spool
B. Microscopic imperfections or deformations in the fiber geometry
C. Absorption by impurities
D. Rayleigh scattering

29 Macrobending loss occurs when:

A. The fiber is bent with a radius of curvature large compared to the fiber diameter
B. The fiber has microscopic bumps
C. The fiber is straight
D. Light scatters backward

30 Why is silica () the preferred material for optical fibers?

A. It is highly conductive
B. It has very high loss
C. It has low transmission loss and high chemical stability
D. It is opaque to visible light

31 What is the function of the buffer coating or jacket in an optical fiber?

A. To guide the light
B. To provide mechanical strength and protection
C. To increase the refractive index
D. To generate light

32 Meridional rays in an optical fiber:

A. Always pass through the fiber axis
B. Never pass through the fiber axis
C. Travel in a helical path
D. Are not confined to the core

33 Skew rays in an optical fiber:

A. Intersect the fiber axis
B. Do not intersect the fiber axis and follow a helical path
C. Are evanescent waves
D. Travel only in the cladding

34 The transmission bandwidth of an optical fiber is primarily limited by:

A. Attenuation
B. Dispersion
C. The V-number
D. The fiber diameter

35 The 'optical windows' (low loss regions) for silica fibers are typically located around:

A. 400 nm, 500 nm, 600 nm
B. 850 nm, 1300 nm, 1550 nm
C. 1 mm, 2 mm, 3 mm
D. 10 GHz, 20 GHz

36 In a Multimode Step Index fiber, if the core diameter is increased while keeping other parameters constant, the number of modes will:

A. Decrease
B. Increase
C. Remain the same
D. Become zero

37 A fiber has a core index of 1.5 and a cladding index of 1.45. What is the acceptance angle in air ()?

A.
B.
C.
D.

38 The phenomena where a small portion of light energy travels in the cladding near the interface is called:

A. Rayleigh scattering
B. Evanescent wave propagation
C. Dispersion
D. Reflection

39 Which fiber type is best suited for long-distance, high-bandwidth communication?

A. Multimode Step Index
B. Multimode Graded Index
C. Single Mode Step Index
D. Plastic Optical Fiber

40 Waveguide dispersion is caused by:

A. Light traveling in both the core and cladding with different effective velocities
B. Impurities in the core
C. Scattering of light
D. Bending of the fiber

41 The cut-off wavelength is the wavelength above which:

A. The fiber becomes opaque
B. The fiber supports only a single mode
C. The fiber melts
D. TIR stops working

42 Calculate the critical angle for a fiber with core index 1.5 and cladding index 1.48.

A.
B.
C.
D.

43 Fractional index change is related to Numerical Aperture (NA) by . If is decreased, the bandwidth of a multimode fiber generally:

A. Decreases
B. Increases
C. Remains constant
D. Becomes zero

44 Intrinsic absorption loss in the ultraviolet region is due to:

A. Atomic vibrations
B. Electronic absorption bands
C. Rayleigh scattering
D. Bending

45 Intrinsic absorption loss in the infrared region is due to:

A. Electronic transitions
B. Atomic vibration bands (molecular resonance)
C. Scattering
D. Dispersion

46 Which of the following is NOT an advantage of fiber optics over copper wire?

A. High Bandwidth
B. Immunity to Electromagnetic Interference (EMI)
C. High signal security
D. Ease of splicing and joining

47 The typical core diameter of a single-mode fiber is approximately:

A. 8 - 10
B. 50 - 62.5
C. 100 - 200
D. 1 mm

48 The typical core diameter of a multimode fiber is approximately:

A. 2
B. 8
C. 50 - 100
D. 1 cm

49 In the context of fiber optics, what does the acronym 'TIR' stand for?

A. Total Infrared Reflection
B. Total Internal Refraction
C. Total Internal Reflection
D. Total Internal Resonance

50 If an optical fiber has a loss of 0.2 dB/km, what is the total loss over a 50 km link?

A. 1 dB
B. 10 dB
C. 25 dB
D. 100 dB
Previous MCQ
Unit 2
Next MCQ
Unit 4