1. Which of the following statements best explain the concept of material absorption?
A loss mechanism related to the material composition and fabrication of fiber
A transmission loss for optical fibers
Results in attenuation of transmitted light
Causes of transfer of optical power
Answer: 1. A loss mechanism related to the material composition and fabrication of fiber
Explanation:
Material absorption is a loss mechanism related to the material composition and fiber fabrication process. This results in the dissipation of some of the transmitted optical power as heat in the waveguide. Absorption is classified into two basic categories: Intrinsic and extrinsic.
Absorption is a loss mechanism. It may be intrinsic, extrinsic, and also caused by atomic defects.
Intrinsic Absorption:- It is caused due to the interaction of free electrons within the fiber material and the light wavelength. The lightwave propagation covers a wide wavelength spectrum, from UV to IR. This spectrum interacts differently with the atoms of the fiber material.
Extrinsic Absorption:- It is mainly due to the impurities injected into the optical fiber mix during the fabrication process. The metal ions are the most undesirable impurity in an optical fiber mix because the presence of metal ions influence and alter the transmission properties of the fiber. This results in the loss of optical power. The metal-ion contaminant in the fiber mix should not exceed one part per billion (pp.
3. ______ is caused due to the interaction of free electrons within the fiber material and the light wavelength.
Extrinsic Absorption
Intrinsic Absorption
Radiation
None of the above
Answer: 2. Intrinsic Absorption
Explanation:
Intrinsic Absorption is caused due to the interaction of free electrons within the fiber material and the light wavelength. The lightwave propagation covers a wide wavelength spectrum, from UV to IR. This spectrum interacts differently with the atoms of the fiber material.
4. ________ is caused due to the impurities injected into the optical fiber mix during the fabrication process.
Extrinsic Absorption
Intrinsic Absorption
Radiation
None of the above
Answer: 1. Extrinsic Absorption
Explanation:
Extrinsic Absorption is mainly due to the impurities injected into the optical fiber mix during the fabrication process. The metal ions are the most undesirable impurity in an optical fiber mix because the presence of metal ions influence and alter the transmission properties of the fiber. This results in the loss of optical power. The metal-ion contaminant in the fiber mix should not exceed one part per billion (pp.
5. 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
Answer:2.Missing molecules, oxygen defects in glass
Explanation:
Absorption loss is a part of the transmission loss caused by the dissipation or conversion of electrical, electromagnetic, or acoustic energy into other forms of energy as a result of its interaction with a material medium.
Atomic defects are imperfections in the atomic structure of fiber material. e.g. Missing molecules high-density clusters of atom group’s oxygen defects in the glass structure. These imperfections in the atomic structure include absorption by the presence of the above defects. The atomic structure includes the nucleus, molecules, protons, etc. Atomic defects thus contribute towards the loss of molecules, oxygen, etc.
6. The absorption losses is significantly increased due to an increase in ______
Ionization Radiation
Reflection
Refraction
Scattering of light
Answer:1. Ionization Radiation
Explanation:
Usually, the absorption losses due to the atomic effects are negligible compared to the other two absorption effects – intrinsic and extrinsic absorption. However, if the fiber is exposed to ionizing radiation, this absorption might become significant. Radiation damages a material by changing its internal structure. The damage effects depend on the energy of the ionizing rays or particles, the fluence (i.e., particles per square centimeter), and the radiation flux.
7. The effects of intrinsic absorption can be minimized by ________
Ionization
Radiation
Suitable choice of core and cladding components
Melting
Answer: 3. Suitable choice of core and cladding components
Explanation:
Intrinsic Absorption is caused due to the interaction of free electrons within the fiber material and the light wavelength. The lightwave propagation covers a wide wavelength spectrum, from UV to IR. This spectrum interacts differently with the atoms of the fiber material.
Intrinsic absorption is caused by the interaction of light with one or more components of the glass i.e. core. Thus, the intrinsic absorption can be minimized by carefully choosing both the core and the cladding composition. For example, some non-oxide glasses such as fluorides and | chlorides give less attenuation to longer wavelength transmissions (upto 50 µm) compared with oxide glasses.
8. ______ causes significant losses in fiber.
Sharp Bend
Micro Bend
Both 1 and 2
None of the above
Answer: 3. Hondros and debye
Explanation:
Sharp Bend and Micro Bend cause significant losses in fiber.
Bending the fiber also causes attenuation. Bending losses are caused by micro bends and macro bends.
A sharp bend in fiber can cause significant losses as well as the possibility of mechanical failure. The bend in the short length of the fiber causes higher losses.
Micro-bends are small microscopic bends of the fiber axis that occur mainly when a fiber is cabled.
Micro bend-loss results from small variations or bumps in the core-to-cladding interface.
Macrobends are bends having a large radius of curvature relative to the fiber diameter.
Macrobend losses are caused by deviations of the core as measured from the axis of the fiber.
These irregularities are caused during the manufacturing procedures and should not be confused with microbends.
9. Which of the following is not a metallic impurity found in glass in extrinsic absorption?
Fe2+
Fe3+
Cu
Si
Answer:4.Si
Explanation:
Extrinsic Absorption is mainly due to the impurities injected into the optical fiber mix during the fabrication process.
During the preparation of optical fibers, the presence of transition metal impurities like Cr3+, Cu2+, Fe2+, Fe3+, Ni2+, etc. may cause attenuation loss.
In the optical fibers, prepared by melting techniques, extrinsic absorption can be observed. It is caused by transition metal element impurities. In all these options, Si is a constituent of glass and it cannot be considered as an impurity to glass itself.
10. ________ losses are caused by small discontinuities or imperfections in the fiber.
Micro Bend
Macro Bend
Sharp Bend
Twisting Pair
Answer:1. Micro Bend
Explanation:
Micro bend losses are caused by small discontinuities or imperfections in the fiber.
Uneven coating applications and improper cabling procedures increase micro bend loss. External forces are also a source of micro bends.
An external force deforms the cabled jacket surrounding the fiber but causes only a small bend in the fiber.
Micro bends change the path that propagates modes. Micro bend loss increases attenuation because low-order modes become coupled with high-order modes that are naturally lossy (causing an appreciable loss).
