Podcast
Questions and Answers
What is the critical angle defined as?
What is the critical angle defined as?
Which term is commonly used to measure the magnitude of the acceptance angle?
Which term is commonly used to measure the magnitude of the acceptance angle?
What does numerical aperture describe in an optical fiber?
What does numerical aperture describe in an optical fiber?
What does a larger magnitude of numerical aperture indicate about an optical fiber?
What does a larger magnitude of numerical aperture indicate about an optical fiber?
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What do absorption losses in optical fibers result from?
What do absorption losses in optical fibers result from?
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What are the factors that contribute to absorption losses in optical fibers?
What are the factors that contribute to absorption losses in optical fibers?
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What is the main cause of Rayleigh scattering loss in optical fibers?
What is the main cause of Rayleigh scattering loss in optical fibers?
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How can chromatic distortion be eliminated in optical fibers?
How can chromatic distortion be eliminated in optical fibers?
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What is a common characteristic of microbends in optical fibers?
What is a common characteristic of microbends in optical fibers?
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Which type of bends in optical fibers are caused by differences in thermal contraction rates?
Which type of bends in optical fibers are caused by differences in thermal contraction rates?
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Why do light rays emitted from an LED and propagated through an optical fiber experience chromatic distortion?
Why do light rays emitted from an LED and propagated through an optical fiber experience chromatic distortion?
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In optical fibers, what contributes less than 20% to the total attenuation?
In optical fibers, what contributes less than 20% to the total attenuation?
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What phenomenon occurs when each ray of light in a fiber reaches the far end at a different time?
What phenomenon occurs when each ray of light in a fiber reaches the far end at a different time?
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In a single-mode step-index fiber, why is modal dispersion virtually eliminated?
In a single-mode step-index fiber, why is modal dispersion virtually eliminated?
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What type of fibers show multiple modes of light propagation?
What type of fibers show multiple modes of light propagation?
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Which device is commonly used as a light detector in fiber-optic communications systems?
Which device is commonly used as a light detector in fiber-optic communications systems?
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What is the basic construction of a PIN diode?
What is the basic construction of a PIN diode?
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How does the refractive index affect the velocity of light rays in a fiber?
How does the refractive index affect the velocity of light rays in a fiber?
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What is the Acceptance Angle or Acceptance Cone Half Angle?
What is the Acceptance Angle or Acceptance Cone Half Angle?
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What is Numerical Aperture (NA) used to measure?
What is Numerical Aperture (NA) used to measure?
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Which of the following is a requirement for light sources used in optical transmission?
Which of the following is a requirement for light sources used in optical transmission?
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What type of light sources are Light Emitting Diodes (LEDs)?
What type of light sources are Light Emitting Diodes (LEDs)?
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What makes Injection Laser Diodes (ILDs) stand out among light sources?
What makes Injection Laser Diodes (ILDs) stand out among light sources?
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What is a key advantage of LEDs in terms of coupling power?
What is a key advantage of LEDs in terms of coupling power?
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What can be a consequence of the imperfections in the mechanical interface used to house the light detector and attach it to the cable?
What can be a consequence of the imperfections in the mechanical interface used to house the light detector and attach it to the cable?
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What type of loss can be introduced due to splicing multiple sections of optical cable together?
What type of loss can be introduced due to splicing multiple sections of optical cable together?
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In fiber optics, what can happen if an optical cable is bent at too large an angle?
In fiber optics, what can happen if an optical cable is bent at too large an angle?
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How do splices in optical cables impact the signal according to the text?
How do splices in optical cables impact the signal according to the text?
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What is the primary concern when an optical cable undergoes large angle bending?
What is the primary concern when an optical cable undergoes large angle bending?
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What is the impact of imperfections in the mechanical interface on the light entering the detector according to the text?
What is the impact of imperfections in the mechanical interface on the light entering the detector according to the text?
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Study Notes
Acceptance Angle and Numerical Aperture
- Acceptance angle (θin) is the maximum angle at which external light rays can strike the air/fiber interface and still propagate down the fiber.
- Numerical aperture (NA) is a figure of merit that measures the light-gathering or light-collecting ability of an optical fiber.
- NA = sin θin = √(N1² - N2²)
Light Sources
- Light sources must have a wavelength between 300 microns and 0.5 microns.
- Requirements for light sources:
- Monochromatic light (single frequency)
- Capable of being easily modulated (PCM) for better noise immunity
- High intensity light output
- Small, compact, and easily coupled to fibers
- Inexpensive to manufacture
- Light Emitting Diodes (LEDs) are low-cost, low-heat, and reliable light sources.
- Injection Laser Diodes (ILDs) make efficient use of electric energy.
Optical Fiber Losses
- Absorption losses: impurities in the fiber absorb light and convert it to heat.
- Factors contributing to absorption losses:
- Ultraviolet absorption
- Infrared absorption
- Ion resonance absorption
- Rayleigh scattering loss: light rays that escape due to impurities in the fiber.
- Chromatic dispersion: different wavelengths of light travel at different velocities, causing chromatic distortion.
Radiation Losses
- Caused by small bends and kinks in the fiber.
- Types of bends:
- Microbends: miniature bends or geometric imperfections along the axis of the fiber.
- Constant-radius bends: bends with a constant radius.
Modal Dispersion
- Occurs in multimode fibers, where different rays of light take different paths.
- Results in a stretched pulse that is reduced in amplitude at the output of the fiber.
Light Detectors
- PIN diodes: depletion-layer photodiodes used to detect light energy in fiber-optic communications receivers.
- APDs: used to detect light energy in fiber-optic communications receivers.
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Description
Test your knowledge about the different types of losses that occur in optical fiber systems, such as absorption, scattering, connector loss, and splicing loss.
