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Questions and Answers
What is the principle behind the working of an optical fiber?
What is the principle behind the working of an optical fiber?
What is the critical angle of incidence?
What is the critical angle of incidence?
What happens when the angle of incidence is greater than the critical angle?
What happens when the angle of incidence is greater than the critical angle?
What is the formula to calculate the critical angle of incidence?
What is the formula to calculate the critical angle of incidence?
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What is the purpose of an optical fiber communication system?
What is the purpose of an optical fiber communication system?
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What is the innermost region of an optical fiber called?
What is the innermost region of an optical fiber called?
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What is the phenomenon when light travels from a medium of higher refractive index to a medium of lower refractive index and is reflected back?
What is the phenomenon when light travels from a medium of higher refractive index to a medium of lower refractive index and is reflected back?
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What is the shape of an optical fiber?
What is the shape of an optical fiber?
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What is the condition for Rayleigh scattering loss to occur?
What is the condition for Rayleigh scattering loss to occur?
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What type of bend in an optical fiber leads to attenuation due to small discontinuities or imperfections in the fiber?
What type of bend in an optical fiber leads to attenuation due to small discontinuities or imperfections in the fiber?
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What is the maximum number of modes supported by a step-index fiber?
What is the maximum number of modes supported by a step-index fiber?
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What is the advantage of optical fiber over copper cables in terms of security?
What is the advantage of optical fiber over copper cables in terms of security?
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What is the advantage of optical fiber over copper cables in terms of weight?
What is the advantage of optical fiber over copper cables in terms of weight?
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What is the application of optical fiber in medical field?
What is the application of optical fiber in medical field?
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What is the benefit of using optical fiber in aircraft or ships?
What is the benefit of using optical fiber in aircraft or ships?
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What is the characteristic of light propagation in graded-index fiber?
What is the characteristic of light propagation in graded-index fiber?
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What is the characteristic of single-mode fiber?
What is the characteristic of single-mode fiber?
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What is the range of attenuation in multimode fiber?
What is the range of attenuation in multimode fiber?
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What is the classification of optical fibers based on refractive index profile?
What is the classification of optical fibers based on refractive index profile?
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What is the diameter of the core in a single mode step index fiber?
What is the diameter of the core in a single mode step index fiber?
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What is the reason for scattering losses in optical fibers?
What is the reason for scattering losses in optical fibers?
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What is the unit of attenuation in optical fibers?
What is the unit of attenuation in optical fibers?
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What is the cause of absorption in optical fibers?
What is the cause of absorption in optical fibers?
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What is the wavelength range of operation for silica glass?
What is the wavelength range of operation for silica glass?
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What is the effect of impurities on fiber attenuation?
What is the effect of impurities on fiber attenuation?
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What is the term for the reduction of signal strength over the length of the fiber?
What is the term for the reduction of signal strength over the length of the fiber?
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What is the name of the scattering mechanism that occurs between the ultraviolet and infrared regions?
What is the name of the scattering mechanism that occurs between the ultraviolet and infrared regions?
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What is the type of fiber that has a core diameter of around 100um?
What is the type of fiber that has a core diameter of around 100um?
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What is the primary purpose of the cladding in an optical fiber?
What is the primary purpose of the cladding in an optical fiber?
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What is the outermost region of an optical fiber known as?
What is the outermost region of an optical fiber known as?
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What is the minimum thickness required for the cladding to keep light within the core?
What is the minimum thickness required for the cladding to keep light within the core?
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What is the condition for total internal reflection to occur in an optical fiber?
What is the condition for total internal reflection to occur in an optical fiber?
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What is the sine of the acceptance angle of an optical fiber called?
What is the sine of the acceptance angle of an optical fiber called?
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What is the purpose of the buffer in an optical fiber?
What is the purpose of the buffer in an optical fiber?
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What is the ratio of the difference between the refractive indices of the core and the cladding to the refractive index of the core?
What is the ratio of the difference between the refractive indices of the core and the cladding to the refractive index of the core?
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What is the maximum angle that a light ray can have relative to the axis of the fiber and still propagate through the fiber?
What is the maximum angle that a light ray can have relative to the axis of the fiber and still propagate through the fiber?
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What is the term for the light ray within the cone having a full angle of 2𝜃𝑚?
What is the term for the light ray within the cone having a full angle of 2𝜃𝑚?
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What is the typical length of an optical fiber?
What is the typical length of an optical fiber?
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What is a unique property of laser beams that makes them useful for communication?
What is a unique property of laser beams that makes them useful for communication?
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In which medical application is laser used to fix detached retinas?
In which medical application is laser used to fix detached retinas?
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What is the advantage of using laser beams in surgery?
What is the advantage of using laser beams in surgery?
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What is the application of lasers in industrial cutting and drilling?
What is the application of lasers in industrial cutting and drilling?
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What is the term used to describe the type of surgery performed using laser beams?
What is the term used to describe the type of surgery performed using laser beams?
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What is the most exciting application of lasers, according to the text?
What is the most exciting application of lasers, according to the text?
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What is the primary difference between conventional light sources and laser sources in terms of phase?
What is the primary difference between conventional light sources and laser sources in terms of phase?
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What is the reason for the high intensity of laser light?
What is the reason for the high intensity of laser light?
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What is the function of the chromium ions in the ruby crystal?
What is the function of the chromium ions in the ruby crystal?
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What is the purpose of the helical photographic xenon flash lamp in the ruby laser?
What is the purpose of the helical photographic xenon flash lamp in the ruby laser?
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What is the state of the chromium ions after absorbing the green component of the spectrum?
What is the state of the chromium ions after absorbing the green component of the spectrum?
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What is the wavelength of the laser beam emitted by the ruby laser?
What is the wavelength of the laser beam emitted by the ruby laser?
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What is the application of laser beams in civil construction work?
What is the application of laser beams in civil construction work?
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What is the advantage of laser light over conventional light?
What is the advantage of laser light over conventional light?
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What is the shape of the ruby rod used in the ruby laser?
What is the shape of the ruby rod used in the ruby laser?
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What is the purpose of the coolant around the ruby rod?
What is the purpose of the coolant around the ruby rod?
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What is the primary purpose of fiber optic devices in industrial applications?
What is the primary purpose of fiber optic devices in industrial applications?
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What is a characteristic of ordinary light?
What is a characteristic of ordinary light?
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What happens when a photon of energy is incident on a single free atom in a ground state?
What happens when a photon of energy is incident on a single free atom in a ground state?
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What is the process by which an excited atom returns to the ground state by emitting a photon of energy?
What is the process by which an excited atom returns to the ground state by emitting a photon of energy?
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What is the characteristic of laser light that makes it different from ordinary light?
What is the characteristic of laser light that makes it different from ordinary light?
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What is the purpose of pumping in a laser?
What is the purpose of pumping in a laser?
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What is the characteristic of laser light that makes it coherent?
What is the characteristic of laser light that makes it coherent?
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What is the difference between spontaneous emission and stimulated emission?
What is the difference between spontaneous emission and stimulated emission?
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What is the characteristic of laser light that makes it monochromatic?
What is the characteristic of laser light that makes it monochromatic?
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What is the purpose of using fiber optic devices in fiber guided missiles?
What is the purpose of using fiber optic devices in fiber guided missiles?
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Study Notes
Fiber Optics
- Fiber Optics deals with the transmission of light through glass or plastic as thin as a human hair, designed to guide the light waves along their length.
- The optical fiber works on the principle of total internal reflection.
Principle of Total Internal Reflection
- When a ray of light passes from a denser medium to a less dense medium (rarer), some part of the light is reflected back into the denser medium, and the rest is refracted into the less dense medium.
- The reflected ray is weak in intensity, but the refracted ray is bright with maximum intensity.
- As the angle of incidence increases, the angle of reflection also increases, and at some angle of incidence, the angle of refraction is 90°, and the refracted ray travels along the boundary.
- This angle of incidence is called the critical angle (𝜃𝑐).
- When the angle of incidence increases slightly, the reflected ray becomes bright, and all the incident light energy is reflected back into the denser medium.
Construction of Fiber Optics
- An optical fiber has three coaxial regions: the core, cladding, and sheath (protective jacket).
- The core is the innermost region, surrounded by the cladding, and the outermost region is the sheath.
- The core and cladding are made of glass or plastic, and the refractive index of the core is always greater than the refractive index of the cladding.
- The purpose of the cladding is to keep the light within the core.
- The sheath or buffer protects the cladding and core from moisture and abrasion.
Acceptance Angle and Acceptance Cone
- When a light ray enters a fiber, it makes an angle with the axis of the fiber, and if this angle is greater than the critical angle, the light is totally internally reflected and propagates through the fiber.
- The acceptance angle is the maximum angle that a light ray can have relative to the axis of the fiber and still propagate through the fiber.
- The acceptance cone is the light ray within the cone having a full angle of 2𝜃𝑚 that is accepted and transmitted through the fiber.
Fractional Refractive Index Change and Numerical Aperture
- The fractional refractive index change (Δ) is the ratio of the difference between the refractive indices of the core and the cladding to the refractive index of the core.
- The numerical aperture (N.A.) is the sine of the acceptance angle and signifies the light-gathering power of the optical fiber.
Classification of Optical Fiber
- There are two main types of optical fibers: single-mode and multimode fibers.
- Depending on the refractive index profile, there are three types of optical fibers:
- Single-mode step index fiber
- Multimode step index fiber
- Multimode graded index fiber
Attenuation in Optical Fiber
- Attenuation is the reduction of signal strength over the length of the light-carrying medium.
- The main causes of attenuation in optical fibers are:
- Absorption
- Scattering
- Bending
- Different mechanisms of attenuation include:
- Intrinsic absorption
- Extrinsic absorption
- Rayleigh scattering
- Microscopic and macroscopic bending
Advantages of Optical Fiber over Conventional Communication
- Higher bandwidth
- Smaller size and lower weight
- Absence of cross-talk
- Easy maintenance
- Signal security
- Low cost
- Longer lifespan
- Electrical isolation
Applications of Optical Fiber
- Communication applications (telephone, teleconferencing, cable TV, digital data transmission)
- Medical field (endoscopic applications, eye surgery, cardiology)
- Military applications (aircraft, ships, tank wiring, fiber-guided missiles)
- Industrial applications (inspection or control of operations in inaccessible areas)
LASER (Light Amplification of Stimulated Emission of Radiation)
- Laser light is monochromatic, directional, and coherent, with a focused beam and a high intensity.
- Laser light is produced by stimulated emission, which occurs when an excited atom is forced to emit a photon of the same energy and in phase with the incident photon.
Characteristics of Laser
- Monochromaticity
- Coherence
- Directionality
- Divergence
- Brightness
Ruby Laser
- Ruby is a crystal containing chromium ions, which gives it a pink or red color.
- The chromium ions have absorption bands in the blue and green regions of the visible spectrum.
- The ruby laser works on a three-level system, with the energy levels of the chromium ions in the crystal lattice.### Energy States and Laser Beam Generation
- The xenon discharge generates a beam of white light, which is absorbed by Cr3+ ions, exciting them from the ground state (E1) to the excited state (E3).
- The excited state (E3) is highly unstable, lasting only 10^(-8) seconds, and rapidly loses energy to transition to the metastable state (E2).
- The metastable state (E2) accumulates Cr3+ ions for a few milliseconds, allowing for population inversion between E2 and E1.
- Spontaneous emission of a photon by Cr3+ ions at E2 initiates stimulated emission by other ions in the metastable state, producing a strong laser beam.
Characteristics of Ruby Laser
- The laser beam is red in color, with a wavelength of 6943A0.
- The green light plays the role of pumping agent, not the amplified component.
- The effectiveness of the Ruby laser is low, as only the green component of the pumping light is utilized.
Applications of Laser
Scientific Applications
- Laser beam is used for precision measurement of distances and alignment in civil construction work due to its directionality and coherence.
- The distance between the Earth and the Moon has been precisely measured using laser beams.
- Laser can be used for determining the shape of objects and structure deformations.
Engineering and Industrial Applications
- Laser is used in communications due to its high directionality and energy density.
- Laser is used as a heat source for cutting, drilling, welding, etc.
- Laser can be used to investigate the structure of molecules.
Medical Applications
- Laser is used for diagnosis in endoscopy, allowing for the examination and photography of inner body parts using an optical fiber.
- Laser is used in eye surgery, fixing detached retinas and treating glaucoma and cataract.
- Laser is used in general surgery, making clean cuts and sealing blood vessels, minimizing blood loss.
- Laser is used in dentistry to destroy germs in tooth cavities without pain.
Holography
- Laser is used in holography to obtain a 3D view of an object.
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Description
Learn about the fundamental principles of fiber optics, including the transmission of light through thin glass or plastic fibers and the concept of total internal reflection.