Optical Communication Set 1

Electrical Engineering

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This set of Optical Communication Multiple Choice Questions & Answers (MCQs) focuses on Optical Communication Set 1

Q1 | Multimode step index fiber has
  • large core diameter & large numerical aperture
  • large core diameter and small numerical aperture
  • small core diameter and large numerical aperture
  • small core diameter & small numerical aperture
Answer: large core diameter & large numerical aperture
Explaination:
multimode step-index fiber has large core diameter and large numerical aperture. these parameters provides efficient coupling to inherent light sources such as led’s.
Q2 | A typically structured glass multimode step index fiber shows as variation of attenuation in range of                        
  • 1.2 to 90 db km-1 at wavelength 0.69μm
  • 3.2 to 30 db km-1 at wavelength 0.59μm
  • 2.6 to 50 db km-1 at wavelength 0.85μm
  • 1.6 to 60 db km-1 at wavelength 0.90μm
Answer: 2.6 to 50 db km-1 at wavelength 0.85μm
Explaination:
a multimode step index fibers show an attenuation variation in range of 2.6 to 50dbkm-1. the wide variation in attenuation is due to the large differences both within and between the two overall preparation methods i.e. melting and deposition.
Q3 | Multimode step index fiber has a large core diameter of range is                        
  • 100 to 300 μm
  • 100 to 300 nm
  • 200 to 500 μm
  • 200 to 500 nm
Answer: 100 to 300 μm
Explaination:
a multimode step index fiber has a core diameter range of 100 to 300μm. this is to facilitate efficient coupling to inherent light sources.
Q4 | Multimode step index fibers have a bandwidth of                        
  • 2 to 30 mhz km
  • 6 to 50 mhz km
  • 10 to 40 mhz km
  • 8 to 40 mhz km
Answer: 6 to 50 mhz km
Explaination:
multimode step index fibers have a bandwidth of 6 to 50 mhz km. these fibers with this bandwidth are best suited for short -haul, limited bandwidth and relatively low-cost application.
Q5 | 2 BASIC OPTICAL LAWS AND DEFINITIONS, OPTICAL MODES AND CONFIGURATIONS
  • lower purity
  • higher purity than multimode step index fibers.
  • no impurity
  • impurity as same as multimode step index fibers.
Answer: higher purity than multimode step index fibers.
Explaination:
multimode graded index fibers have higher purity than multimode step index fiber. to reduce fiber losses, these fibers have more impurity.
Q6 | The performance characteristics of multimode graded index fibers are
  • better than multimode step index fibers
  • same as multimode step index fibers
  • lesser than multimode step index fibers
  • negligible
Answer: better than multimode step index fibers
Explaination:
multimode graded index fibers use a constant grading factor. performance characteristics of multimode graded index fibers are better than those of multimode step index fibers due to index graded and lower attenuation.
Q7 | Multimode graded index fibers have overall buffer jackets same as multimode step index fibers but have core diameters
  • larger than multimode step index fibers
  • smaller than multimode step index fibers
  • same as that of multimode step index fibers
  • smaller than single mode step index fibers
Answer: smaller than multimode step index fibers
Explaination:
multimode graded index fibers have smaller core diameter than multimode step index fibers. a small core diameter helps the fiber gain greater rigidity to resist bending.
Q8 | Multimode graded index fibers use incoherent source only.
  • true
  • false
Answer: false
Explaination:
multimode graded index fibers are used for short haul and medium to high bandwidth applications. small haul applications require leds and low accuracy lasers. thus either incoherent or incoherent sources like led’s or injection laser diode are used.
Q9 | In single mode fibers, which is the most beneficial index profile?
  • step index
  • graded index
  • step and graded index
  • coaxial cable
Answer: graded index
Explaination:
in single mode fibers, graded index profile is more beneficial as compared to step index. this is because graded index profile provides dispersion-modified-single mode fibers.
Q10 | Multimode graded index fibers with                        
  • single mode fibers
  • multimode step fibers
  • coaxial cables
  • multimode graded index fibers
Answer: single mode fibers
Explaination:
single mode fibers are used to produce polarization maintaining fibers which make them expensive. also the alternative to them are multimode fibers which are complex but accurate. so, single-mode fibers are not generally utilized in optical fiber communication.
Q11 | Single mode fibers allow single mode propagation; the cladding diameter must be at least                        
  • twice the core diameter
  • thrice the core diameter
  • five times the core diameter
  • ten times the core diameter
Answer: ten times the core diameter
Explaination:
the cladding diameter in single mode fiber must be ten times the core diameter. larger ratios contribute to accurate propagation of light. these dimension ratios must be there so as to avoid losses from the vanishing fields.
Q12 | A fiber which is referred as non- dispersive shifted fiber is?
  • coaxial cables
  • standard single mode fibers
  • o-band
  • c-band and l-band
Answer: o-band
Explaination:
ssmfs are utilized for operation in o-band only. it shows high dispersion in the range of 16 to 20ps/nm/km in c-band and l-band. so ssmfs are used in o-band.
Q13 | Fiber mostly suited in single-wavelength transmission in O-band is?
  • low-water-peak non dispersion-shifted fibers
  • standard single mode fibers
  • low minimized fibers
  • non-zero-dispersion-shifted fibers
Answer: standard single mode fibers
Explaination:
standard single mode fibers with a step index profile are called non dispersion shifted fiber and it is particularly used for single wavelength transmission in o- band and as if has a zero-dispersion wavelength at 1.31μm.
Q14 | When the dimensions of the guide are reduced, the number of                        also decreases.
  • propagating nodes
  • electrons
  • holes
  • volume of photons
Answer: propagating nodes
Explaination:
the dimensions of the guide are directly proportional to the number of propagating nodes. as the dimensions are reduced, the number of propagating nodes also decreases.
Q15 |                        waveguides are plagued by high losses.
  • circular
  • planar
  • depleted
  • metal-clad
Answer: metal-clad
Explaination:
all suitable waveguide materials are subject to limitations in the confinement. however, metal-clad waveguides are not so limited. hence, they are plagued by high losses.
Q16 | The planar waveguides may be fabricated from glasses and other isotropic materials such as                        and                              
  • octane and polymers
  • carbon monoxide and diode
  • fluorides and carbonates
  • sulphur dioxide and polymers
Answer: sulphur dioxide and polymers
Explaination:
these materials are isotropic. however, their properties do not affect the fabrication of planar waveguides. their properties cannot be controlled by external energy sources.
Q17 | Which of the following devices are less widely used in the field of optical fibre communications?
  • acousto-optic devices
  • regenerators
  • reflectors
  • optical translators
Answer: acousto-optic devices
Explaination:
acousto-optic devices are less widely used, mainly in the area of field deflection. regenerators, reflectors form a base for the optical fibre communications.
Q18 | Which of the following materials have refractive index near two?
  • ga as
  • zinc
  • inp
  • alsb
Answer: zinc
Explaination:
two basic groups are distinguished on the basis of the respective refractive indices near two and near three.
Q19 | Strip pattern in waveguide structures is obtained through                          
  • lithography
  • cryptography
  • depletion of holes
  • implantation
Answer: lithography
Explaination:
field strength is an important aspect when it comes to strip patterns in waveguide structures. the electron and laser beam lithography is used to obtain stripe pattern in waveguide structures.
Q20 | Propagation losses in slab and strip waveguides are smaller than the single mode fibre losses.
  • true
  • false
Answer: false
Explaination:
the losses are in the range of
Q21 | A passive Y-junction beam splitter is also used as a switch.
  • true
  • false
Answer: true
Explaination:
a passive junction beam splitter finds application where equal power division of the incident beam is required. it can be used as a switch if it is fabricated from an electro-optic material.
Q22 | The linear variation of refractive index with the electric field is known as the
  • linear implantation
  • ionization
  • koppel effect
  • pockels effect
Answer: pockels effect
Explaination:
the change in refractive index is related by the applied field via the linear and quadratic electro-optic coefficients. the variation of r.i with the electric field is known as pockels effect.
Q23 | In a transverse electric magnetic wave, which of the following will be true?
  • e is transverse to h
  • e is transverse to wave direction
  • h is transverse to wave direction
  • e and h are transverse to wave direction
Answer: e and h are transverse to wave direction
Explaination:
in the transverse electric magnetic wave (tem wave), both the electric and magnetic field strengths are transverse to the wave propagation.
Q24 | The cut off frequency of the TEM wave is
  • 0
  • 1 ghz
  • 6 ghz
  • infinity
Answer: 0
Explaination:
the tem waves have both e and h perpendicular to the guide axis. thus its cut off frequency is zero.
Q25 | Which component is non zero in a TEM wave?
  • ex
  • hz
  • ez
  • attenuation constant
Answer: ex
Explaination:
in a tem wave, the wave propagates along the guided axis. thus the components ez and hz are zero. the attenuation is also zero. the non-zero component will be ex.
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