1. __________ in glass arise from microscopic variations in the material density, from compositional fluctuations.
Bandwidth Losses
Scattering Losses
Radiation Losses
All of the above
Answer:2. Scattering Losses
Explanation:
Scattering losses in glass arise from microscopic variations in the material density, from compositional fluctuations, and from structural inhomogeneities or defects occurring during fiber manufacture.
Scattering the common source of attenuation in optical fibers is the loss of optical energy due to molecular imperfections or lack of optical purity in the fiber due to the manufacturing process and form the basic structure of the fiber.
2. Rayleigh scattering and Mie scattering are the types of ________
Linear scattering losses
Non-linear scattering losses
Fiber bends losses
Splicing losses
Answer:1. Linear scattering losses
Explanation:
For linear scattering, the amount of light power that is transferred from a wave is proportional to the power in the wave. It is characterized by having no change in frequency in the scattered wave.
Linear scattering processes are further classified into Rayleigh and Mie scattering which is related to the losses in glass arising from microscopic variations in the material density, from compositional fluctuations, and from structural inhomogeneities or defects occurring during fiber manufacture.
3. Stimulated Raman scattering may have an optical power threshold of maybe three orders of magnitude ________
Lower than Brillouin threshold
Higher than Brillouin threshold
Same as Brillouin threshold
Higher than Rayleigh threshold
Answer:2. Higher than Brillouin threshold
Explanation:
Stimulated Raman scattering (SRS) is an important nonlinear process that can turn optical fibers into broadband Raman amplifiers and tunable Raman lasers. It can also severely limit the performance of multichannel lightwave systems by transferring energy from one channel to the neighboring channels.
Stimulated Raman scattering (SRS) is similar to SBS except that a high-frequency optical phonon rather than an acoustic phonon is generated in the scattering process. Also, SRS can occur in both the forward and backward directions in optical fiber and may have an optical power threshold of up to three orders of magnitude higher than the Brillouin threshold in a particular fiber.
4. Dominant intrinsic loss mechanism in low absorption window between ultraviolet and infrared absorption tails is _________
Mie scattering
Rayleigh scattering
Stimulated Raman scattering
Stimulated Brillouin scattering
Answer:2. Rayleigh scattering
Explanation:
Rayleigh scattering results from light interacting with inhomogeneities in the medium that ‘are much smaller than the wavelength of the light.
Rayleigh scattering is the dominant intrinsic loss mechanism in the low absorption window, which is in between the UV and IR absorption tails. Rayleigh scattering is caused when material anomalies within the fiber material are 1/10 of the diameter (or less) of the operating wavelength.
5. The Rayleigh scattering is ______ to the wavelength.
Directly Proportional
Inversely Proportional
Equal
None of the above
Answer:2. Inversely Proportional
Explanation:
Rayleigh scattering is due to small localized changes in the refractive index of the core and the cladding material.
In commercial fibers operating between 700 nm and 1600 nm wavelength, the main source of loss is called Rayleigh scattering.
Rayleigh scattering is the main loss mechanism between the ultraviolet and infrared regions. Loss caused by Rayleigh scattering is proportional to the fourth power of the wavelength (1/λ4).
As the wavelength increases, the loss caused by Rayleigh scattering decreases. Rayleigh scatter is most severe in light with a short wavelength.
6. Stimulated Raman scattering occur in ________
Forward direction
Backward direction
Upward direction
Forward and backward direction
Answer:4. Forward and backward direction
Explanation:
Stimulated Raman scattering (SRS) is an important nonlinear process that can turn optical fibers into broadband Raman amplifiers and tunable Raman lasers. It can also severely limit the performance of multichannel lightwave systems by transferring energy from one channel to the neighboring channels.
Stimulated Raman scattering (SRS) is similar to SBS except that a high-frequency optical phonon rather than an acoustic phonon is generated in the scattering process. Also, SRS can occur in both the forward and backward directions in optical fiber and may have an optical power threshold of up to three orders of magnitude higher than the Brillouin threshold in a particular fiber.
7. 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
Answer:2. Mie scattering
Explanation:
Mie scattering occurs when the size of the inhomogeneities within the optical fiber is comparable to the size of the guided wavelength.
When this scattering inhomogeneity size is larger than 1/10 of the operating wavelength, the scattered intensity which has an angular dependence can be very large.
These imperfections result from the imperfect cylindrical structure of the waveguide and may be caused by fiber imperfections such as irregularities in the core-cladding interface, the differences in the core-cladding refractive indices along the fiber length, strains, and bubbles, diameter fluctuations, etc.
8. High-frequency optical phonon is generated in ________
Rayleigh scattering
Mie scattering
Stimulated Brillouin scattering
Stimulated Raman scattering
Answer: 4. Stimulated Raman scattering
Explanation:
Stimulated Raman scattering (SRS) is an important nonlinear process that can turn optical fibers into broadband Raman amplifiers and tunable Raman lasers. It can also severely limit the performance of multichannel lightwave systems by transferring energy from one channel to the neighboring channels.
Stimulated Raman scattering (SRS) is similar to SBS except that a high-frequency optical phonon rather than an acoustic phonon is generated in the scattering process. Also, SRS can occur in both the forward and backward directions in optical fiber and may have an optical power threshold of up to three orders of magnitude higher than the Brillouin threshold in a particular fiber.
9. Mie scattering has in-homogeneities mainly in _________
Forward direction
Backward direction
All direction
Core-cladding interface
Answer:1. Forward direction
Explanation:
Mie scattering occurs when the size of the inhomogeneities within the optical fiber is comparable to the size of the guided wavelength.
Mie scattering occurs mainly in the forward direction.
When this scattering inhomogeneity size is larger than λ/10 of the operating wavelength, the scattered intensity which has an angular dependence can be very large.
These imperfections result from the imperfect cylindrical structure of the waveguide and may be caused by fiber imperfections such as irregularities in the core-cladding interface, the differences in the core-cladding refractive indices along the fiber length, strains, and bubbles, diameter fluctuations, etc.
10. The in-homogeneities in _______ can be reduced by the coating of fiber.
Rayleigh scattering
Mie scattering
Stimulated Brillouin scattering
Stimulated Raman scattering
Answer:2. Mie scattering
Explanation:
Mie scattering occurs when the size of the inhomogeneities within the optical fiber is comparable to the size of the guided wavelength.
Mie scattering occurs mainly in the forward direction.
When this scattering inhomogeneity size is larger than λ/10 of the operating wavelength, the scattered intensity which has an angular dependence can be very large.
Mie scattering homogeneity can be reduced by removing imperfections due to the glass manufacturing process. Coating of fiber increases relative refracting index difference.
These imperfections result from the imperfect cylindrical structure of the waveguide and may be caused by fiber imperfections such as irregularities in the core-cladding interface, the differences in the core-cladding refractive indices along the fiber length, strains, and bubbles, diameter fluctuations, etc.
11. Determine the threshold optical power in a long single-mode fiber with 0.5 dB km-1 for stimulated Brillouin scattering within the fiber at a wavelength of 1.3 nm. The fiber core diameter is 6 μm and laser source bandwidth is 600 MHz.
1.5 W
1.38 W
80.3 mW
65.2 mW
Answer:3. 80.3 mW
Explanation:
The threshold power is given by:
PB = (4.4 × 10-3) d2 λ2 αdB B Watts
PB = Threshold power
αdB = Fiber attenuation in decibels per kilometer
d = Core diameter in μm.
λ = Operating wavelength in nm
B = Source bandwidth in GHz
Calculation:
With αdB = 0.5, d = 6 μm, λ = 1.3 nm, and B = 600 MHz = 0.6 GHz, the threshold power will be:
PB = (4.4 × 10-3) (6)2 (1300)2 (0.5) (0.6) Watts
PB = 80.30 mW
12. Stimulated Brillouin scattering is mainly a ___________
Forward process
Backward process
Upward process
Downward process
Answer:2. Backward process
Explanation:
Stimulated Brillouin scattering (SBS) is similar to SRS in that energy is transferred from an optical pump beam to longer wavelengths through interaction with the glass medium, except that acoustic phonons are involved, and hence the frequency shift is small, about 11 GHz, and the bandwidth very small, typically 50 MHz.
The scattered light appears as upper and lower sidebands which are separated from the incident light by the modulation frequency. The resultant scattered wave propagates principally in the backward direction in single-mode fibers making SBS a mainly backward process.
13. Raman and Brillouin scattering are usually observed at _______
Low optical power densities
Medium optical power densities
High optical power densities
Threshold power densities
Answer:3. High optical power densities
Explanation:
Raman and Brillouin scattering are usually observed at high optical power densities in long single-mode fibers.
These scattering mechanisms in fact give optical gain but with a shift in frequency, thus contributing to attenuation for light transmission at a specific wavelength.
However, it may be noted that such non-linear phenomena can also be used to give optical amplification in the context of integrated optical techniques.
14. The _______ is a quantum of an elastic wave in a crystal lattice.
Phonon
Photon
Plasmon
Magnon
Answer: 1. Phonon
Explanation:
A phonon is a collective excitation in a periodic, elastic arrangement of atoms or molecules in condensed matter, such as solids and some liquids.
it is often referred to as a quasi-particle, it represents an excited state in the quantum mechanical quantization of the modes of vibrations of elastic structures of interacting particles.
Phonons play a major role in many of the physical properties of solids, including materials thermal and electrical conductivities.
15. A single-mode optical fiber has an attenuation of 0.3dB/km when operating at a wavelength of 1.1μm. The fiber core diameter is 4μm and the bandwidth is 500 MHz. Find threshold optical power for stimulated Brillouin scattering.
11.20 mw
12.77 mw
13.08 mw
12.12 mw
Answer: 2. 12.77 mw
Explanation:
The threshold optical power stimulated Brillouin scattering is given by-
