PHY109 Unit 3: Fiber Optics - MCQ Practice | B. Tech. Aerospace Engineering

1 $What is the primary purpose of an optical fiber?$

Introduction to fiber optics Easy

A.

To transmit light signals

B.

To amplify sound waves

C.

To generate magnetic fields

D.

To store electric charge

2 $Which two main dielectric regions form an optical fiber?$

Optical fiber as a dielectric waveguide Easy

A.

Rotor and stator

B.

Anode and cathode

C.

Core and cladding

D.

Emitter and collector

3 $For an optical fiber to guide light, how should the core refractive index compare with the cladding refractive index ?$

Optical fiber as a dielectric waveguide Easy

A.

B.

C.

D.

4 $Total internal reflection occurs when light travels from which type of medium to which other type?$

Total internal reflection Easy

A.

Air to vacuum

B.

Vacuum to denser

C.

Denser to rarer

D.

Rarer to denser

5 $What must be true of the angle of incidence for total internal reflection to occur?$

Total internal reflection Easy

A.

It is below the critical angle

B.

It exceeds the critical angle

C.

It equals zero degrees

D.

It equals the refraction angle

6 $What does the acceptance angle of an optical fiber represent?$

Acceptance angle Easy

A.

Reflection angle at the fiber end

B.

Critical angle at the fiber axis

C.

Minimum output angle for guided light

D.

Maximum input angle for guided light

7 $The set of directions from which an optical fiber can accept light forms the acceptance:$

Acceptance angle Easy

A.

Cone

B.

Plane

C.

Ring

D.

Cylinder

8 $What does the numerical aperture of an optical fiber measure?$

Numerical aperture Easy

A.

Its mechanical strength

B.

Its electrical resistance

C.

Its light-gathering ability

D.

Its thermal conductivity

9 $For a fiber in air, which expression gives its numerical aperture when the core and cladding indices are and ?$

Numerical aperture Easy

A.

B.

C.

D.

10 $Which expression defines the relative refractive index difference for a fiber?$

Relative refractive index Easy

A.

B.

C.

D.

11 $If and , what is the relative refractive index difference ?$

Relative refractive index Easy

A.

B.

C.

D.

12 $Which fiber properties are included in the normalized frequency, or V-number?$

V-number Easy

A.

Fiber length, density, and temperature

B.

Cladding radius, voltage, and pressure

C.

Core radius, numerical aperture, and wavelength

D.

Core mass, resistance, and wavelength

13 $For a step-index fiber, which condition indicates single-mode operation?$

V-number Easy

A.

B.

C.

D.

14 $How does the refractive index change at the core-cladding boundary of a step-index fiber?$

Step-index and graded-index fibers Easy

A.

It changes gradually

B.

It changes abruptly

C.

It becomes zero

D.

It remains constant

15 $How does the core refractive index generally vary in a graded-index fiber?$

Step-index and graded-index fibers Easy

A.

It alternates between two values

B.

It remains uniform throughout

C.

It increases abruptly outward

D.

It decreases gradually outward

16 $Which fiber type is designed to reduce intermodal dispersion by gradually varying its core refractive index?$

Step-index and graded-index fibers Easy

A.

Hollow glass tube

B.

Metallic-core fiber

C.

Graded-index fiber

D.

Step-index fiber

17 $Which optical fiber loss occurs when light energy is converted into heat within the material?$

Losses associated with optical fibers Easy

A.

Bending loss

B.

Connector loss

C.

Dispersion loss

D.

Absorption loss

18 $Which loss is produced when an optical fiber is curved too sharply?$

Losses associated with optical fibers Easy

A.

Scattering loss

B.

Material dispersion

C.

Bending loss

D.

Absorption loss

19 $Which application commonly uses optical fibers to transmit high-speed digital information?$

Applications of optical fibers Easy

A.

Hydraulic braking systems

B.

Steam heating systems

C.

Mechanical gear systems

D.

Telecommunication networks

20 $Which medical instrument uses optical fibers to view internal parts of the body?$

Applications of optical fibers Easy

A.

Thermometer

B.

Sphygmomanometer

C.

Stethoscope

D.

Endoscope

21 $Why can an optical fiber carry information over long distances more effectively than a conventional copper cable in many communication systems?$

Introduction to fiber optics Medium

A.

It converts all optical signals into radio waves

B.

It eliminates the need for signal modulation

C.

It provides high bandwidth with low attenuation

D.

It amplifies light continuously along the core

22 $A fiber has a core refractive index of and a cladding refractive index of . What feature primarily confines light to the core?$

Optical fiber as a dielectric waveguide Medium

A.

The core continuously generates additional light

B.

The core index is less than the cladding index

C.

The core index is greater than the cladding index

D.

The cladding absorbs light entering the core

23 $The core and cladding indices of a fiber are and, respectively. What is the critical angle at the core-cladding interface, measured from the normal?$

Total internal reflection Medium

A.

B.

C.

D.

24 $A light ray inside a fiber core of index strikes the cladding of index at to the normal. What happens at the boundary?$

Total internal reflection Medium

A.

The ray is absorbed completely by the cladding

B.

The ray undergoes total internal reflection

C.

The ray travels along the boundary indefinitely

D.

The ray passes completely into the cladding

25 $A step-index fiber has and . What is its numerical aperture in air?$

Numerical aperture Medium

A.

B.

C.

D.

26 $An optical fiber has a numerical aperture of and is surrounded by air. What is its acceptance half-angle?$

Acceptance angle Medium

A.

B.

C.

D.

27 $A fiber whose intrinsic numerical aperture is is immersed in water of refractive index . What is its acceptance half-angle in water?$

Acceptance angle Medium

A.

B.

C.

D.

28 $For a fiber with core index and cladding index , what is the relative refractive index difference ?$

Relative refractive index Medium

A.

B.

C.

D.

29 $A weakly guiding fiber has and . Using, estimate its numerical aperture.$

Relative refractive index Medium

A.

B.

C.

D.

30 $A fiber has a core radius of, numerical aperture, and operating wavelength . What is its approximate V-number?$

V-number Medium

A.

B.

C.

D.

31 $A step-index fiber has at . If it is operated at with all other parameters unchanged, which conclusion is correct?$

V-number Medium

A.

Its V-number becomes about, reducing confinement

B.

Its V-number becomes about, allowing higher-order modes

C.

Its V-number remains, independent of wavelength

D.

Its V-number becomes about, preserving single-mode operation

32 $A multimode step-index fiber and a multimode graded-index fiber have comparable dimensions and numerical apertures. Why does the graded-index fiber generally transmit shorter pulses with less broadening?$

Step-index and graded-index fibers Medium

A.

Its core permits only one propagation mode at a time

B.

Its refractive-index profile reduces differences in modal transit times

C.

Its cladding reflects every mode at exactly the same angle

D.

Its refractive index is constant throughout the core

33 $For a multimode step-index fiber with, approximately how many guided modes are supported, assuming the weak-guidance approximation?$

Step-index and graded-index fibers Medium

A.

B.

C.

D.

34 $A parabolic graded-index fiber has . Approximately how many guided modes does it support under the weak-guidance approximation?$

Step-index and graded-index fibers Medium

A.

B.

C.

D.

35 $An optical signal decreases from to after traveling through of fiber. What is the average attenuation?$

Losses associated with optical fibers Medium

A.

B.

C.

D.

36 $If Rayleigh scattering is the dominant loss mechanism, how does the scattering loss change when wavelength increases from to ?$

Losses associated with optical fibers Medium

A.

It decreases to approximately one-sixteenth

B.

It decreases to approximately one-fourth

C.

It increases by approximately four times

D.

It increases by approximately sixteen times

37 $A fiber cable develops a sharp bend during installation, causing some guided light to radiate into the surroundings. Which loss mechanism has increased?$

Losses associated with optical fibers Medium

A.

Macrobending loss

B.

Material absorption

C.

Connector reflection

D.

Rayleigh scattering

38 $Two fiber sections are joined with a small lateral offset between their cores. Which loss is most directly produced by this defect?$

Losses associated with optical fibers Medium

A.

Intrinsic absorption loss

B.

Chromatic dispersion loss

C.

Splice coupling loss

D.

Rayleigh scattering loss

39 $An optical fiber sensor is used near high-voltage equipment where strong electromagnetic fields are present. Why is fiber preferable to a metallic signal cable?$

Applications of optical fibers Medium

A.

It is immune to electromagnetic interference

B.

It produces electrical shielding currents

C.

It increases the surrounding magnetic field

D.

It requires a conductive return path

40 $In a medical endoscope, one fiber bundle illuminates internal tissue while another forms an image. What property must the imaging bundle possess?$

Applications of optical fibers Medium

A.

The relative positions of fibers must remain ordered

B.

The cladding must absorb all reflected illumination

C.

Every fiber must support many propagation modes

D.

The fibers must be randomly rearranged at each end

41 $An engineer claims that increasing the core refractive index will simultaneously improve confinement, eliminate absorption, and increase the maximum data rate. Which assessment is physically correct?$

Introduction to fiber optics Hard

A.

Index contrast controls absorption, while confinement and data rate depend only on wavelength.

B.

Core index controls data rate, while absorption and confinement depend only on cladding thickness.

C.

Core index affects absorption, while confinement and dispersion remain independent of the index profile.

D.

Index contrast affects guidance, while absorption and data rate also depend on material loss and dispersion.

42 $A weakly guiding fiber has,, and normalized propagation constant, where What is the effective modal index?$

Optical fiber as a dielectric waveguide Hard

A.

B.

C.

D.

43 $A meridional ray in a step-index fiber with and travels at to the fiber axis. What occurs at the core-cladding boundary?$

Total internal reflection Hard

A.

It undergoes total internal reflection because its axial angle exceeds the critical angle.

B.

It propagates along the interface because its incidence angle equals the critical angle.

C.

It refracts into the cladding because its incidence angle is below the critical angle.

D.

It undergoes total internal reflection because its incidence angle is greater than .

44 $A fiber with and is immersed in water of refractive index . Neglecting end-face curvature, what is its acceptance half-angle in water?$

Acceptance angle Hard

A.

B.

C.

D.

45 $A step-index fiber has and relative index difference . What is its exact numerical aperture in air?$

Relative refractive index Hard

A.

B.

C.

D.

46 $A step-index fiber has core radius and . Determine the cutoff wavelength above which it is single-mode, using .$

V-number Hard

A.

B.

C.

D.

47 $Two weakly guiding multimode fibers have the same large V-number. One is step-index and the other has an ideal parabolic graded-index profile. Using the usual large- approximations, what is the ratio of their guided mode counts ?$

Step-index and graded-index fibers Hard

A.

B.

C.

D.

48 $A graded-index fiber follows within its core. If,, and, what is ?$

Step-index and graded-index fibers Hard

A.

B.

C.

D.

49 $For a step-index fiber with and, estimate the maximum intermodal delay between the axial ray and the limiting meridional ray. Take .$

Step-index and graded-index fibers Hard

A.

B.

C.

D.

50 $Two identical single-mode fibers are laterally misaligned by . Under the specified Gaussian coupling model with, what is the splice loss?$