This set of Optical Communications Multiple Choice Questions & Answers (MCQs) focuses on “Optical Fibers”.
1. Multimode step index fiber has
a) Large core diameter & large numerical aperture
b) Large core diameter and small numerical aperture
c) Small core diameter and large numerical aperture
d) Small core diameter & small numerical aperture
Explanation: 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.
2. A typically structured glass multimode step index fiber shows as variation of attenuation in range of
a) 1.2 to 90 dB km-1at wavelength 0.69μm
b) 3.2 to 30 dB km-1at wavelength 0.59μm
c) 2.6 to 50 dB km-1at wavelength 0.85μm
d) 1.6 to 60 dB km-1at wavelength 0.90μm
Explanation: 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.
3. A multimode step index fiber has a large core diameter of range
a) 100 to 300 μm
b) 100 to 300 nm
c) 200 to 500 μm
d) 200 to 500 nm
Explanation: A multimode step index fiber has a core diameter range of 100 to 300μm. This is to facilitate efficient coupling to inherent light sources.
4. Multimode step index fibers have a bandwidth of
a) 2 to 30 MHz km
b) 6 to 50 MHz km
c) 10 to 40 MHz km
d) 8 to 40 MHz km
Explanation: 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.
5. Multimode graded index fibers are manufactured from materials with
a) Lower purity
b) Higher purity than multimode step index fibers.
c) No impurity
d) Impurity as same as multimode step index fibers.
Explanation: Multimode graded index fibers have higher purity than multimode step index fiber. To reduce fiber losses, these fibers have more impurity.
6. The performance characteristics of multimode graded index fibers are
a) Better than multimode step index fibers.
b) Same as multimode step index fibers.
c) Lesser than multimode step index fibers
Explanation: 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.
7. Multimode graded index fibers have overall buffer jackets same as multimode step index fibers but have core diameters
a) Larger than multimode step index fibers.
b) Smaller than multimode step index fibers.
c) Same as that of multimode step index fibers.
d) Smaller than single mode step index fibers.
Explanation: 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.
8. Multimode graded index fibers with wavelength of 0.85μm have numerical aperture of 0.29 have core/cladding diameter of
a) 62.5 μm/125 μm
b) 100μm/140 μm
c) 85 μm/ 125 μm
d) 50 μm/ 125μm
Explanation: Multimode graded index fibers with numerical aperture 0.29 having a core / cladding diameter of 100μm/ 140μm. They provide high coupling frequency LED’s at a wavelength of 0.85 μm and have low cost. They are also used for short distance application.
9. Multimode graded index fibers use incoherent source only. State whether the following statement is true or false.
Explanation: 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.
10. In single mode fibers, the most beneficial index profile is
a) Step index
b) Graded index
c) Step and graded index
d) Coaxial cable
Explanation: 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.
11. The fibers mostly not used nowadays for optical fiber communication system are
a) Single mode fibers
b) Multimode step fibers
c) Coaxial cables
d) Multimode graded index fibers
Explanation: 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.
12. Single mode fibers allow single mode propagation; the cladding diameter must be at least
a) Twice the core diameter
b) Thrice the core diameter
c) Five times the core diameter
d) Ten times the core diameter
Explanation: 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.
13. A fiber which is referred as non-dispersive shifted fiber is
a) Coaxial cables
b) Standard single mode fibers
c) Standard multimode fibers
d) Non zero dispersion shifted fibers
Explanation: A standard single mode fiber having step index profile is known as non-dispersion shifted fiber. As these fibers have a zero dispersion wavelength of 1.31μm and so are preferred for single-wavelength transmission in O-band.
14. Standard single mode fibers (SSMF) are utilized mainly for operation in
d) C-band and L-band
Explanation: SSMFs are utilized for operation in O-band only. It shows high dispersion in range of 16 to 20ps/nm/km in C-band and L-band. So SSMFs are used in O-band.
15. Fiber mostly suited in single-wavelength transmission in O-band is
a) Low-water-peak non dispersion-shifted fibers
b) Standard single mode fibers
c) Low minimized fibers
d) Non-zero-dispersion-shifted fibers
Explanation: Standard single mode fibers with a step index profile is 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.
Sanfoundry Global Education & Learning Series – Optical Communications.
To practice all areas of Optical Communications, here is complete set of 1000+ Multiple Choice Questions and Answers.