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WorksheetsCEC 357 UNDERWATER WIRELESS COMMUNICATION
Total questions: 45
Worksheet time: 31mins
A silica optical fiber with a large core diameter has a core refractive index of 1.5 and a Cladding refractive index of 1.47. Determine the acceptance angle in air for the fiber.
(a)
A silica optical fiber with core diameter large enough to be considered by Ray theory has a core refractive index of 1.5 and cladding refractive index of 1.47.Determine numerical aperture.
(a)
calculate the cut off wavelength of a single mode fibre with core radius of 4 m and index difference= 0.003
(a)
The significance of fourth generation optical communication system is
Optical amplifier
Optical source
Optical coupler
splicers
A multimode step index fiber has a normalized frequency of 72. Estimate the number of guided modes.
2846
2592
2432
2136
An optical fiber has core-index of 1.480 and a cladding index of 1.478. What should be the core size for single mode operation at 1310nm?
7.31μm
8.71μm
5.26μm
6.50μm
A multimode fiber has refractive indices n1 = 1.15, n2 = 1.11 and an operating wavelength of 0.7μm. Find the radius of curvature?
8.60μm
9.30μm
9.1μm
10.2μm
Absorption losses due to atomic defects mainly include ___________
Radiation
Missing molecules, oxygen defects in glass
Impurities in fiber material
Interaction with other components of core
The scattering resulting from fiber imperfections like core-cladding RI differences, diameter fluctuations, strains, and bubbles is?
Rayleigh scattering
Mie scattering
Stimulated Brillouin scattering
Stimulated Raman scattering
Consider a single mode fiber having core refractive index n1= 1.5. The fiber length is 12m. Find the time taken by the axial ray to travel along the fiber
1.00μsec
0.06μsec
0.90μsec
0.30μsec
A multimode step-index fiber has a core refractive index of 1.5 and relative refractive index difference of 1%. The length of the optical link is 6 km. Estimate the RMS pulse broadening due to intermodal dispersion on the link.
92.6 ns
86.7 ns
69.3 ns
68.32 ns
The index profile of a core of multimode graded index fiber is given by?
N (r) = n1 [1 – 2Δ(r2/a)2]1/2; r<a
N (r) = n1 [3 – 2Δ(r2/a)2]1/2; r<a
N (r) = n1 [5 – 2Δ(r2/a)2]1/2; r>a
N (r) = n1 [1 – 2Δ(r2/a)2]1/2; r<a
A multimode step index fiber has source of RMS spectral width of 60nm and dispersion parameter for fiber is 150psnm-1km-1. Estimate rms pulse broadening due to material dispersion.
12.5ns km-1
9.6ns km-1
9.0ns km-1
10.2ns km-1
A multimode fiber has RMS pulse broadening per km of 12ns/km and 28ns/km due to material dispersion and intermodal dispersion resp. Find the total RMS pulse broadening.
30.46ns/km
31.23ns/km
28.12ns/km
26.10ns/km
The beat length in a single mode optical fiber is 8 cm when light from a laser with a peak wavelength 0.6μm is launched into it. Estimate the modal birefringence.
1×10-5
3.5×10-5
2×10-5
4×10-5
Which of the following is not related to Kerr effects?
Self-phase modulation
Cross-phase modulation
Four-wave mixing
Stimulated Raman Scattering
Optical fiber couplers are also called as ______________
Isolators
Circulators
Directional couplers
Attenuators
When optical fibers are to be installed in a working environment, the most important parameter to be considered is?
Transmission property of the fiber
Mechanical property of the fiber
Core cladding ratio of the fiber
Numerical aperture of the fiber
Optical fibers for communication use are mostly fabricated from ___________
Plastic
Silica or multicomponent glass
Ceramics
Copper
Which process gives the laser its special properties as an optical source?
Dispersion
Stimulated absorption
Spontaneous emission
Stimulated emission
A semiconductor laser crystal of length 5 cm, refractive index 1.8 is used as an optical source. Determine the frequency separation of the modes.
2.8 GHz
1.2 GHz
1.6 GHz
2 GHz
Considering the values given below, calculate the mode separation in terms of free space wavelength for a laser. (Frequency separation = 2GHz, Wavelength = 0.5 μm)
1.4×10-11
1.6×10-12
1×10-12
6×10-11
Which kind of dispersion phenomenon gives rise to pulse spreading in single mode fibers?
Intramodal
Intermodal
Material
Group Velocity
Silicon has indirect band gap energy of __________________
1.2 eV
2 eV
1.14 eV
1.9 eV
A technique used for determining the total fiber attenuation per unit length is ________ method.
Frank
Cut-off
cut-back
Erlangen
Determine the total carrier recombination lifetime of a double heterojunction LED where the radioactive and nonradioactive recombination lifetime of minority carriers in active region are 70 ns and 100 ns respectively.
41.17 ns
35 ns
40 ns
37.5 ns
In surface emitter LEDs, more advantage can be obtained by using ____________
BH structures
bQC structures
DH structures
Gain-guided structure
The optical bandwidth is _____________ the electrical bandwidth.
Smaller
Greater
Same as
Zero with respect to
Determine the 3 dB electrical bandwidth at 3 dB optical bandwidth Bopt of 56.2 MHz.
50.14
28.1
47.6
61.96
A photodiode should be chosen with a ________________ less than photon energy.
Absorption coefficient
Direct absorption
Band gap energy
Wavelength range
________________ photodiodes have large dark currents.
GaAs
Silicon
GaSb
Germanium
The fraction of incident photons generated by photodiode of electrons generated collected at detector is known as __________________
Quantum efficiency
Absorption coefficient
Responsivity
Anger recombination
______________ is caused due to thermal interaction between the free electrons and the vibrating ions in the conduction medium.
Thermal noise
Dark noise
Quantum noise
Gaussian noise
The minimum pulse energy needed to maintain a given bit-error-rate (BER) which any practical receiver must satisfy is known as ___________
Minimal energy
Quantum limit
Point of reversed
Binary signaling
A digital optical fiber communication system requires a maximum bit-error-rate of 10-9. Find the average number of photons detected in a time period for a given BER.
a) 19.7
b) 21.2
c) 20.7
d) 26.2
19.7
21.2
20.7
26.2
A silicon p-i-n photodiode incorporated in an optical receiver has following parameters:
Quantum efficiency = 70%
Wavelength = 0.8 μm
Dark current = 3nA
Load resistance = 4 kΩ
Incident optical power = 150nW.
Bandwidth = 5 MHz
Compute the photocurrent in the device.
67.7nA
81.2nA
68.35nA
46.1nA
Determine the attenuation per kilometer for a fiber whose length is 2 km, output voltage is 2.1 V at a wavelength of 0.85μm. The output voltage increases to 10.7 V when the fiber is cut-back to leave 2 metres. Determine the attenuation per km for the fiber at wavelength 0.85μm.
2.8dB/km
3.1dB/km
3.5dB/km
8dB/km
___________ is an example of a static circuit-switched network.
OXC
Circuit regenerator
Packet resolver
SDH/SONET
What is OTDR
Optical Time Domain Reflectometer
Optical Transient Difference Recorder
Open Transform Direct Receiver
____________ is a multi-functional element of optical network.
Hop
Optical node
Wavelength
Optical attenuation
What is the full form of LASER
Light Amplification by Stimulated Emission of Radiation
Long And Strong Emission Range
Light Amplification by Sustained Emission and Radiation.
Lower Range Amplification of Signal
What are the three optical windows in fiber optics communication?
750nm, 1350nm, 1600 nm
850nm, 1300nm, 1550nm
800, 1100, 1600
850nm, 1300nm, 1450nm
850mm, 1300mm, 1550nn
What is the range of fiber optics communication?
10^12 to 10^15 Hz
10^10 to 10^20 Hz
10^11 to 10^21 Hz
Which is the fundamental mode of propagation in fibers?
LP01
LP11
LP21
LP22
SONET is a ___________ TDM System
asynchronous
synchronous
statistical
None of the above
