LEVEL 1 — EASY
14/03/2026
50 Questions — Based on Your Notes |
Optical Fiber Communication (CITS)
Q1. What is the most important part of an optical fiber?
A) Cladding
B) Core
C) Jacket
D) Buffer
✓ Answer: B
Q2. The core of an optical fiber is made of which material(s)?
A) Copper or
iron
B) Plastic,
silica or glass
C) Rubber only
D) Aluminum
✓ Answer: B
Q3. What is the shape of the core in an optical fiber?
A) Square
B) Triangular
C) Cylinder
D) Hexagonal
✓ Answer: C
Q4. The core of optical fiber has which type of refractive
index?
A) Low
B) Zero
C) High
D) Negative
✓ Answer: C
Q5. The cladding of an optical fiber is made of:
A) Copper
B) Silica
C) Rubber
D) Iron
✓ Answer: B
Q6. Compared to core, the refractive index of cladding is:
A) Higher
B) Equal
C) Lower
D) Zero
✓ Answer: C
Q7. The coating in optical fiber is made of:
A) Silicon
B) Copper
C) Aluminium
D) PVC only
✓ Answer: A
Q8. What does the coating in optical fiber protect against?
A) Only water
B) Bending
loss and other losses
C) Only heat
D) Only
vibration
✓ Answer: B
Q9. The buffer jacket of an optical fiber is made of:
A) Glass
B) Plastic
C) Silicon
D) Metal
✓ Answer: B
Q10. Buffer jacket provides protection against:
A) Signal loss
only
B)
Environmental, mechanical and physical damage
C) Only heat
D) Only bending
✓ Answer: B
Q11. When light travels from denser to rarer medium, it bends:
A) Toward the
normal
B) Away from
the normal
C) No bending
D) Parallel to
normal
✓ Answer: B
Q12. When light travels from rarer to denser medium, it bends:
A) Away from
normal
B) Toward
the normal
C) No change
D) Reflects
back
✓ Answer: B
Q13. At the critical angle, the refracted ray travels at:
A) 0°
B) 45°
C) 90°
(along the interface)
D) 180°
✓ Answer: C
Q14. Total Internal Reflection occurs when the angle of
incidence is:
A) Less than
critical angle
B) Equal to 0°
C) Greater
than critical angle
D) Equal to 45°
✓ Answer: C
Q15. Total Internal Reflection requires light to travel from:
A) Rarer to
denser medium
B) Denser to
rarer medium
C) Air to water
D) Any medium
to vacuum
✓ Answer: B
Q16. In optical fiber, light stays inside the core due to:
A) Absorption
B) Refraction
only
C) Total
Internal Reflection
D) Diffraction
✓ Answer: C
Q17. The condition for TIR is n1 compared to n2:
A) n1 < n2
B) n1 = n2
C) n1 >
n2
D) n1 = 0
✓ Answer: C
Q18. Light rays injected outside the acceptance cone will:
A) Stay in core
B) Be
refracted into cladding and leak out
C) Reflect from
jacket
D) Travel
faster
✓ Answer: B
Q19. SMF stands for:
A) Single
Mode Fiber
B) Straight
Mode Fiber
C) Small Mono
Fiber
D) Step Mode
Fiber
✓ Answer: A
Q20. MMF stands for:
A)
Multi-Material Fiber
B) Multimode
Fiber
C) Mono Mode
Fiber
D) Micro Mode
Fiber
✓ Answer: B
A) 40 µm
B) 62.5 µm
C) 8–10 µm
D) 100 µm
✓ Answer: C
Q22. The core diameter of MMF is approximately:
A) 8–10 µm
B) 40 µm or
50–62.5 µm
C) 1 µm
D) 200 µm
✓ Answer: B
Q23. SMF is used for which type of communication?
A) Short
distance only
B) Long
distance travel
C) Local area
only
D) Satellite
only
✓ Answer: B
Q24. MMF is used for which type of communication?
A) Long
distance
B) Short
distance travel
C) Submarine
cable
D) ISP backbone
✓ Answer: B
Q25. The colour of SMF cable jacket is:
A) Orange
B) Blue
C) Yellow
D) Green
✓ Answer: C
Q26. The colour of MMF cable jacket is:
A) Yellow
B) Orange
C) Red
D) Blue
✓ Answer: B
Q27. SMF is mainly used in:
A) Data centre
and audio/video applications
B) WAN, MAN
and ISP Backbone
C) Only home
networks
D) Only LANs
✓ Answer: B
Q28. MMF is mainly used in:
A) WAN/MAN/ISP
backbone
B) NAN, SAN,
Data Centre, Audio/Video applications
C)
International cables
D) Mobile
towers
✓ Answer: B
Q29. The acceptance angle of SMF is approximately:
A) 25–30°
B) 7–14°
C) 45°
D) 90°
✓ Answer: B
Q30. The acceptance angle of MMF is approximately:
A) 7–14°
B) 25–30°
C) 5°
D) 60°
✓ Answer: B
Q31. Numerical Aperture (NA) of SMF is approximately:
A) 0.2 to 0.5
B) 0.1 to
0.14
C) 0.8 to 1.0
D) 0.5 to 0.8
✓ Answer: B
Q32. Numerical Aperture (NA) of MMF is approximately:
A) 0.1 to 0.14
B) 0.2 to
0.5
C) 0.9 to 1.0
D) 0.01 to 0.05
✓ Answer: B
Q33. Numerical Aperture (NA) represents the:
A) Speed of
light in fiber
B) Light
collecting/gathering ability of an optical fiber
C) Fiber
diameter
D) Signal
bandwidth
✓ Answer: B
Q34. Light rays injected within the acceptance cone:
A) Leak into
cladding
B) Remain in
the fiber core
C) Absorb in
the jacket
D) Reflect from
buffer
✓ Answer: B
Q35. Step index fiber has a refractive index that:
A) Gradually
decreases from center
B) Is
uniform in the core and drops sharply at core-cladding interface
C) Increases
from center
D) Varies
randomly
✓ Answer: B
Q36. Graded index fiber has a refractive index that:
A) Is uniform
throughout
B) Decreases
gradually from core center toward cladding
C) Is zero at
center
D) Is equal to
cladding RI
✓ Answer: B
Q37. The maximum refractive index in graded index fiber is at:
A) Cladding
B) Buffer
jacket
C) Center of
the core
D) Coating
✓ Answer: C
Q38. Step index fiber is manufactured by doping high-purity
silica glass with materials like:
A) Copper and
iron
B) Titanium,
germanium or boron
C) Sodium and
chlorine
D) Rubber and
plastic
✓ Answer: B
Q39. Attenuation in optical fiber is the measure of:
A) Increase of
signal strength
B) Decay or
loss of signal strength/light power
C) Speed of
light
D) Fiber length
✓ Answer: B
Q40. The formula for attenuation A(dB) is:
A) A = Pout ×
Pin
B) A = 10
log(Pout/Pin)
C) A = Pout +
Pin
D) A = Pout /
Pin directly
✓ Answer: B
Q41. The unit of attenuation in optical fiber is:
A) Watts/m
B) dB/km
C) Hz
D) Volts
✓ Answer: B
Q42. Bending loss in optical fiber has two types:
A) Linear and
non-linear
B)
Micro-bending and macro-bending
C) Intrinsic
and extrinsic
D) Modal and
chromatic
✓ Answer: B
Q43. Absorption loss is caused by:
A) Fiber length
B)
Impurities mixed without our knowledge
C) Connector
type
D) Core
diameter
✓ Answer: B
Q44. Dispersion means:
A) Signal
amplification
B) Spreading
of light pulse as it propagates through fiber
C) Reflection
of light
D) Absorption
of light
✓ Answer: B
Q45. The refractive index of glass is:
A) 1.0003
B) 1.33
C) 1.5
D) 2.42
✓ Answer: C
Q46. The refractive index of water is:
A) 1.0
B) 1.33
C) 1.5
D) 2.42
✓ Answer: B
Q47. The refractive index of diamond is:
A) 1.33
B) 1.5
C) 2.42
D) 1.0003
✓ Answer: C
Q48. Speed of light in glass is approximately:
A) 299,700 km/s
B) 225,000 km/s
C) 200,000
km/s
D) 124,500 km/s
✓ Answer: C
Q49. Encoding of light means:
A) Measuring
the fiber length
B) The
process of modulating signal/data on a light ray
C) Splicing the
fiber
D) Amplifying
the signal
✓ Answer: B
Q50. Modulation is defined as the process of:
A) Measuring
signal loss
B)
Superimposing a low-frequency signal on a high-frequency carrier signal
C) Removing
noise
D) Increasing
fiber diameter
✓ Answer: B
LEVEL 2 — MEDIUM
14/03/2026
50 Questions — Based on Your Notes |
Optical Fiber Communication (CITS)
Q1. Which layer of optical fiber is transparent with high
refractive index?
A) Cladding
B) Buffer
C) Core
D) Jacket
✓ Answer: C
Q2. The main function of cladding is to:
A) Amplify
signal
B) Provide
total internal reflection by keeping light in the core
C) Protect from
moisture only
D) Increase
fiber speed
✓ Answer: B
Q3. Silicon coating on optical fiber protects against:
A) High voltage
B) Bending
loss and other mechanical losses
C) Only
temperature
D) Chemical
corrosion only
✓ Answer: B
Q4. Strength member in optical fiber cable is made of:
A) Silica
B) Aramid
(Kevlar) fibers
C) Copper
D) Rubber
✓ Answer: B
Q5. The outer jacket (black polyurethane) in optical fiber
cable provides:
A) Signal
amplification
B) Colour
coding and external mechanical protection
C) Refractive
index control
D) Core
alignment
✓ Answer: B
Q6. Which part of the optical fiber directly guides light?
A) Buffer
jacket
B) Outer jacket
C) Strength
member
D) Core
✓ Answer: D
Q7. The formula n = c/v in optical fiber refers to:
A) Noise
formula
B)
Refractive index = speed of light in vacuum / speed in medium
C) Numerical
aperture
D) Attenuation
formula
✓ Answer: B
Q8. The cladding of optical fiber is also transparent with:
A) Higher RI
than core
B) Lower
refractive index than the core
C) Equal RI to
core
D) Zero RI
✓ Answer: B
Q9. Snell's law relates the angles of incidence and refraction.
When going from denser (n1) to rarer (n2), sin(θ2)/sin(θ1) equals:
A) n2/n1
B) n1/n2
C) n1 × n2
D) n1 + n2
✓ Answer: B
Q10. At critical angle, the refracted angle is 90°. The critical
angle θc = sin⁻¹(n2/n1). If n1=1.5, n2=1.0, θc ≈
A) 90°
B) 41.8°
C) 30°
D) 60°
✓ Answer: B
Q11. In a step-index fiber, light travels in a:
A) Curved path
B) Zigzag
(bouncing) path due to TIR
C) Straight
line only
D) Spiral path
✓ Answer: B
Q12. For TIR to occur in optical fiber, which condition must be
satisfied?
A) θi < θc
and n1 < n2
B) θi >
θc and n1 > n2
C) θi = 45°
always
D) n1 = n2
✓ Answer: B
Q13. The condition rθ > iθ in notes represents:
A) Absorption
condition
B) The
refracted angle is greater than incident angle in denser-to-rarer transition
C) TIR
condition
D) Critical
angle formula
✓ Answer: B
Q14. When the angle of incidence exactly equals the critical
angle, what happens?
A) Total
reflection
B) The
refracted ray travels along the interface (90°)
C) Full
transmission
D) Absorption
occurs
✓ Answer: B
Q15. The cladding diameter for both SMF and MMF is
approximately:
A) 50 µm
B) 70 µm
C) 125 µm
D) 10 µm
✓ Answer: B
Q16. SMF supports transmission distance of:
A) Less than
500 metres
B) More than
100 km (with amplifier, approximately 1400 km)
C) Only 1 km
D) Only 10 km
✓ Answer: B
Q17. MMF supports transmission distance of:
A) More than
1000 km
B) Less than
500 metres
C) 100 km
easily
D) 1400 km
✓ Answer: B
Q18. The working temperature range for SMF is:
A) 0°C to 50°C
B) -40°C to
+75°C
C) -10°C to
+40°C
D) 0°C to 100°C
✓ Answer: B
Q19. The wavelength range used by SMF is:
A) 850–1300 nm
B) 1310–1550
nm
C) 400–700 nm
D) 200–500 nm
✓ Answer: B
Q20. The wavelength range used by MMF is:
A) 1310–1550 nm
B) 850–1300
nm
C) 200–400 nm
D) 1600–2000 nm
✓ Answer: B
Q21. Which fiber type has higher bandwidth?
A) MMF
B) SMF
C) Both are
equal
D) Plastic
optical fiber
✓ Answer: B
Q22. The cable cost comparison: SMF vs MMF:
A) MMF is more
costly
B) SMF is
slightly more costly; MMF is cheaper
C) Both same
cost
D) SMF is
always cheaper
✓ Answer: B
Q23. The formula for Numerical Aperture is NA = sin(φ_max) =
√(n1² - n2²)/n0. What does φ_max represent?
A) Critical
angle
B) Maximum
acceptance angle of the fiber
C) Angle of TIR
D) Refraction
angle
✓ Answer: B
Q24. If n1=1.46, n2=1.44, n0=1.0, NA = √(1.46²-1.44²) ≈
A) 0.02
B) 0.241
C) 1.46
D) 0.44
✓ Answer: B
Q25. A higher NA means:
A) Smaller
acceptance cone
B) Larger
acceptance cone, more light gathering ability
C) Less light
entering fiber
D) More signal
loss
✓ Answer: B
Q26. NA is dimensionless because:
A) It is a
ratio of lengths
B) sin(φ) is
dimensionless and refractive indices are dimensionless ratios
C) It is always
zero
D) It cancels
with wavelength
✓ Answer: B
Q27. For SMF with NA = 0.12, the acceptance angle is
approximately:
A) 12°
B) 6.9°
C) 45°
D) 25°
✓ Answer: B
Q28. The Numerical Aperture represents the light-collecting
ability of an optical fiber. Which has higher NA?
A) SMF
B) MMF
C) Both same
D) Depends on
wavelength only
✓ Answer: B
Q29. In step index fiber, the refractive index profile is mainly
seen in:
A) Only
multimode fibers
B)
Single-mode and some multimode fibers
C) Only plastic
fibers
D) Only graded
index fibers
✓ Answer: B
Q30. In graded index fiber, the core refractive index decreases
as it moves:
A) Toward the
core center
B) Away from
the core center toward the cladding
C) Along the
fiber length
D) In the
buffer region
✓ Answer: B
Q31. Graded index fiber is used primarily in:
A) Single mode
applications
B) Multimode
fiber applications to reduce intermodal dispersion
C) Long
distance submarine cables
D) Only WAN
applications
✓ Answer: B
Q32. Step index fiber is manufactured by doping silica glass.
Doping materials mentioned in notes are:
A) Copper,
zinc, lead
B) Titanium,
germanium and boron
C) Sodium,
potassium
D) Carbon,
nitrogen
✓ Answer: B
Q33. Attenuation affects which system parameters as per notes?
A) Only cost
B)
Performance, information transmission, efficiency and overall capacity
C) Only
bandwidth
D) Only
connector loss
✓ Answer: B
Q34. Pin in the attenuation formula A(dB) = 10 log(Pout/Pin)
represents:
A) Cable output
power
B) Cable
input power
C) Peak power
D) Pulse
intensity
✓ Answer: B
Q35. Scattering loss in optical fiber has two types as per
notes:
A) Micro and
macro
B) Linear
scattering and non-linear scattering
C) Intrinsic
and extrinsic
D) Modal and
waveguide
✓ Answer: B
Q36. Scattering loss occurs when:
A) Fiber is
bent
B)
Imperfections at manufacturing level cause light-to-molecule level interaction
C) Temperature
rises
D) Connector is
dirty
✓ Answer: B
Q37. To reduce scattering loss, as per notes, we should:
A) Increase
fiber diameter
B) Remove
imperfections and carefully control fiber coating and size
C) Add more
amplifiers
D) Use yellow
jacket
✓ Answer: B
Q38. Macro-bending loss occurs due to:
A) Gradual
slight bending
B) Sudden
abrupt change in fiber direction causing massive signal loss
C)
Manufacturing defect
D) Chemical
absorption
✓ Answer: B
Q39. Micro-bending loss means:
A) Large bend
causing massive loss
B)
Slowly/gradually light ray decreases causing some losses
C) Absorption
by impurities
D) Connector
reflection
✓ Answer: B
Q40. Intrinsic absorption loss occurs:
A) Due to metal
ions only
B) Inside
the fiber due to molecular vibrations in silica
C) At
connectors
D) Due to
bending
✓ Answer: B
Q41. ISI stands for:
A) Intrinsic
Scattering Index
B) Inter
Symbol Interference
C) Internal
Signal Intensity
D) Index Shift
Interference
✓ Answer: B
Q42. ISI is described in notes as:
A) A type of
connector loss
B) A
critical signal distortion where pulses spread and overlap causing adjacent
bits to interfere
C) A bending
loss type
D) An
absorption type
✓ Answer: B
Q43. Intermodal dispersion occurs in:
A) Single mode
fiber only
B) Multimode
fiber (MMF)
C) Step index
SMF only
D) Graded index
SMF only
✓ Answer: B
Q44. Intramodal dispersion (chromatic dispersion) occurs in:
A) Only MMF
B) Single
mode fiber (SMF)
C) Only plastic
fiber
D) Only
multimode step index
✓ Answer: B
Q45. Intermodal dispersion is caused by:
A) Different
wavelengths of a source
B) Different
modes traveling at slightly different velocities in MMF
C) Material
absorption
D) Connector
mismatch
✓ Answer: B
Q46. Material dispersion arises due to:
A) Fiber
geometry
B) Variation
of refractive index of core material as a function of wavelength/frequency of
light
C) Core
diameter variation
D) Cladding
absorption
✓ Answer: B
Q47. Group velocity is the velocity at which:
A) A single
photon travels
B) Energy in
a particular mode travels along the fiber; velocity of a group of wavelengths
C) Phase of
wave travels
D) The cladding
absorbs light
✓ Answer: B
Q48. Phase velocity is the velocity at which:
A) Energy
travels
B) The phase
(crest/trough) of the wave travels
C) Group of
wavelengths travel
D) Pulse
envelope travels
✓ Answer: B
Q49. The refractive index of vacuum as per notes is:
A) 1.33
B) 1.0000
C) 1.5
D) 2.42
✓ Answer: B
Q50. Demodulation is defined in notes as:
A)
Superimposing low frequency on carrier
B)
Extracting the original information signal from a modulated carrier wave
C) Encoding
data on light
D) Measuring
signal strength
✓ Answer: B