1. What is a fundamental necessity in the fabrication of fibers for light transmission?
Same refractive index for both core and cladding
Pump source
Material composition of fiber
Variation of the refractive index inside the optical fiber
Answer:4. Variation of the refractive index inside the optical fiber
Explanation:
There are many requirements in the selection of material for the fabrication of fibers.
It must be possible to make long, thin, and flexible fibers from the material. The variation of the refractive index inside the optical fiber is a fundamental necessity in the fabrication of fiber for light transmission.
For this purpose. two different materials, which are transparent to light, over operating wavelength range (800 nm to 1700 nm) are required.
Further, the material must exhibit low optical loss. Materials that satisfy these requirements are glasses and plastics.
Normally glass fibers are used for long-distance communication because it exhibits lower signal loss. Plastic fibers are used in short-distance applications and in abusive environments.
2. The operating Wavelength range required for the fabrication of optical fiber is _______
800 nm to 1700 nm
100 nm to 200 nm
300 nm to 600 nm
50 nm to 100 nm
Answer:1. 800 nm to 1700 nm
Explanation:
There are many requirements in the selection of material for the fabrication of fibers.
It must be possible to make long, thin, and flexible fibers from the material. The variation of the refractive index inside the optical fiber is a fundamental necessity in the fabrication of fiber for light transmission.
For this purpose. two different materials, which are transparent to light, over operating wavelength range (800 nm to 1700 nm) are required.
Further, the material must exhibit low optical loss. Materials that satisfy these requirements are glasses and plastics.
Normally glass fibers are used for long-distance communication because it exhibits lower signal loss. Plastic fibers are used in short-distance applications and in abusive environments.
3. Which materials are unsuitable for the fabrication of graded-index fiber?
Glass-like-materials
Mono-crystalline structures
Amorphous material
Silica-based material
Answer:2. Mono-crystalline structures
Explanation:
In order to avoid scattering losses in excess of the fundamental intrinsic losses, scattering centers such as bubbles, strains, and grain boundaries must be eradicated.
This tends to limit the choice of suitable materials for the fabrication of optical fibers to either glasses (or glass-like materials) or monocrystalline structures (certain plastics).
It is also useful, and in the case of graded-index fibers essential, that the refractive index of the material may be varied by suitable doping with another compatible material.
Hence these two materials should have mutual solubility over a relatively wide range of concentrations.
This is only achieved in glasses or glass-like materials, and therefore monocrystalline materials are unsuitable for the fabrication of graded-index fibers but may be used for step-index fibers.
4. ________ produced by liquid-phase melting techniques are less dispersive than step-index fibers.
Monocrystalline Fiber
Graded Index Fiber
Single-mode fiber
Any of the above
Answer:2. Graded Index Fiber
Explanation:
The liquid-phase melting technique does not offer optimum parabolic profile fibers. This parabolic profile yields minimum pulse dispersion.
Graded index fibers prepared using liquid-phase melting techniques are less dispersive but do not have the bandwidth-length products of optimum profile fibers.
Index grading may be achieved through the diffusion of mobile ions across the core-cladding interface within the molten glass.
It is possible to achieve a reasonable refractive index profile via this diffusion process, although due to lack of precise control it is not possible to obtain the optimum near-parabolic profile which yields the minimum pulse dispersion.
Hence graded-index fibers produced by this technique are subsequently less dispersive than step-index fibers but do not have the bandwidth-length products of optimum profile fibers.
5. How many different categories are available for the methods of preparing optical glasses?
1
2
3
4
Answer:2. 2
Explanation:
The methods of preparing the extremely pure optical glasses generally fall into two major categories which are:
( Conventional glass refining techniques in which the glass is processed in the molten state (melting methods) producing a multicomponent glass structure
( Vapor-phase deposition methods produce silica-rich glasses which have melting temperatures that are too high to allow the conventional melt process.
6. What is the first stage in liquid-phase-technique?
Preparation of ultra-pure material powders
Melting of materials
Decomposition
Crystallization
Answer:1. Preparation of ultra-pure material powders
Explanation:
The first stage in this process is the preparation of ultra-pure material powders which are usually oxides or carbonates of the required constituents.
These include oxides such as SiO2, GeO2, B2O2, and A2O3 and carbonates such as Na2CO3 K2CO3 CaCO3, and BaCO3 which will decompose into oxides during the glass melting.
Very high initial purity is essential and purification accounts for a large proportion of the material cost; nevertheless, these compounds are commercially
7. The liquid-phase melting technique is used for the production of fibers ________
With a core diameter of 50μm
With a core diameter of less than 100μm
With a core diameter of more than 200μm
With a core diameter of 100μm
Answer:3. With a core diameter of more than 200μm
Explanation:
The liquid-phase melting technique does not offer optimum parabolic profile fibers. This parabolic profile yields minimum pulse dispersion.
Graded index fibers prepared using liquid-phase melting techniques are less dispersive but do not have the bandwidth-length products of optimum profile fibers.
The multicomponent glass fibers prepared continuously by the liquid-phase melting technique have losses in the range of 5 and 20 dB/km at a wavelength of 0.85μm.
This method is thus used for the preparation of fibers with a large core diameter. Also, this technique is used for the continuous production of fibers.
8. Which processes are involved in the purification stage in liquid-phase-technique?
The first stage in this process is the preparation of ultra-pure material powders which are usually oxides or carbonates of the required constituents.
These include oxides such as SiO2, GeO2, B2O2, and A2O3 and carbonates such as Na2CO3 K2CO3 CaCO3, and BaCO3 which will decompose into oxides during the glass melting.
Very high initial purity is essential and purification accounts for a large proportion of the material cost.
The purification stage in liquid-phase-technique involves Filtration, Co-precipitation, Re-crystallization.
The purification accounts for a large proportion of the material costs. These compounds are commercially available.
9. The minute perturbations and impurities in the fiber drawing process using the preform technique can result in very high losses of ________
Between 500 and 1000 dB/km
Between 100 and 300 dB/km
Between 1200 and 1600 dB/km
More than 2000 dB/km
Answer:1. Between 500 and 1000 dB/km
Explanation:
An original technique for producing fine optical fiber waveguides was to make a preform using the rod in tube process. A rod of core glass was inserted into a tube of cladding glass and the preform was drawn in a vertical muffle furnace.
This technique was useful for the production of step-index fibers with large core and cladding diameters where the achievement of low attenuation was not critical as there was a danger of including bubbles and particulate matter at the core-cladding interface.
The minute perturbations and impurities in the fiber include formations of bubbles and involvement of particulate matter. The losses due to such impurities can be between 500 and 1000 dB/km.
10. At what temperature range, does the melting of multi-components glass systems takes place?
100-300 degrees Celsius
600-800 degrees Celsius
900-1300 degrees Celsius
1500-1800 degrees Celsius
Answer:3. 900-1300 degrees Celsius
Explanation:
A refractive index variation may be achieved by either a change in the composition of the various constituents or by ion exchange when the materials are in the molten phase.
The glass materials are in powdered form and have a relatively low melting point. Thus, the glass materials are melted at relatively low temperatures in the range of 900-1300 degrees Celsius.
11. Fiber drawing using preform was useful for the production of ______
Graded index fiber
Step index fiber
Both 1 and 2
None of the above
Answer:2. Step index fiber
Explanation:
The traditional technique for producing fine optical fiber waveguides is to make a preform using the rod in the tube process. A rod of cone glass is inserted into a tube of cladding glass and the preform is drawing a vertical muffle furnace. This technique is useful for the production of step-index fiber with large core and cladding diameters.
12. Stratified melt process was useful for the production of ______
Graded index fiber
Step index fiber
Both 1 and 2
None of the above
Answer:2. Step index fiber
Explanation:
The stratified melt process technique is used for the production of large core diameter step-index fibers.
This process involves pouring a layer of cladding glass over the core glass in a platinum crucible.
A bait glass rod is dipped into the molten combination and slowly withdrawn giving a composite core-clad. Preform which can be then drawn into a fiber.
