Optical Fiber Material MCQ || Optical Fiber Material Questions and Answers

1. The requirement for selecting optical fiber is

  1. Thin fiber material can be made
  2. The material must be transparent
  3. Different Refractive Indices
  4. All of the above

Answer:4. All of the above


In selecting materials for optical fibers, a number of requirements must be satisfied.

  • It must be possible to make long, thin fibers from the material.
  • The material must be transparent at a particular optical wavelength in order for the fiber to guide light efficiently.
  • Physically compatible materials that have slightly different refractive indices for the core and cladding must be available.

Materials that satisfy these requirements are gasses and plastic.


2. Which of the following fiber materials are used in the optical fiber?

  1. Glass
  2. Plastic
  3. Photonic Crystal
  4. All of the above

Answer: 4. All of the above


An optical fiber is a flexible, transparent fiber made by drawing glass (silica or plastic).

Optical fibers are used most often as a means to transmit light between the two ends of the fiber and find wide usage in fiber-optic communications, where they permit transmission over longer distances and at higher bandwidths (data transfer rates) than electrical cables.

The types of optical fiber cable are

  1. Glass fiber
  2. Halide Glass fiber
  3. Active Glass fiber
  4. Chalgenide glass fiber
  5. Plastic optical fiber
  6. Photonic Crystal Fiber


3. The optical fiber material is good _______

  1. Insulator
  2. Conductor
  3. Semiconductor
  4. Any of the above

Answer: 1. Insulator


Optical fibers are made up of silica-based glass or plastic that are insulators and therefore have no currents flowing in them. As a result, fibers are immune to electromagnetic interference. In addition, no tapping of information is possible with fiber communications.


4. Glass fiber is made by fusing mixtures of metal oxides and _____

  1. Graphite
  2. Carbon
  3. Selenides
  4. All of the above

Answer: 3. Selenides


  • Glass fiber is made by fusing mixtures of metal oxides, sulfides, or selenides.
  • The resulting material is a randomly connected molecular network rather than a well-defined ordered structure as found in crystalline materials.
  • When glass is heated up from room temperature, it remains a hard solid up to several hundred degrees centigrade.
  • As the temperature increases further, the glass gradually begins to soften until at very high temperatures it becomes a viscous liquid.


5. Fibers are used instead of metal wires because

  1. Low electromagnetic interference
  2. Low losses
  3. No corrosion
  4. All of the above

Answer:4. All of the above


  • Fibers are used instead of metal wires because signals travel along with them with less loss.
  • In addition, fibers don’t suffer from the electromagnetic interference that troubles metal wires.
  • Fibers are also used for illumination and imaging and are often wrapped in bundles.
  • Specially designed fibers are also used for a variety of other applications, some of them being fiber optic sensors and fiber lasers.
  • Another advantage of optical fibers is that they do not corrode and can be placed near a chemical environment.
  • The bandwidth and speed of optical fiber communication systems are large, compared with any other communication system that exists today.


6. The refractive Index of Silica Glass fiber is

  1. 10 to 20 nm
  2. 50 to 10 nm
  3. 1.45 to 850 nm
  4. 2 to 5 nm

Answer:3. 1.45 to 850 nm


The most common material for optical fiber is silica (Si02), which has a refractive index of 1.458 at 850 nm.


7.  The silica glass optical fiber material is generally doped because

  1. To increase material strength
  2. To increase flexibility
  3. To make different indices of Refraction
  4. To increase transmission power

Answer:3. 1.45 to 850 nm


The most common material for optical fiber is silica (Si02), which has a refractive index of 1.458 at 850 nm. To produce two similar materials that have slightly different indices of refraction for the core and cladding, either fluorine or various oxides (referred to as dopants), such as B2O3, GeO2, or P2O5 are added to the silica.


8. Which of the following are the advantages of Glass optic fiber?

  1. Withstand High temperature
  2. Low Losses
  3. High Bandwidth
  4. All of the above

Answer:4. All of the above


The following are the advantages of glass optical fiber:

  • Glass optical fibers are durable and withstand low to high temperatures in the range -40oF to +900oF. For that reason, they are useful for high-temperature appliances such as ovens, furnaces, condensers, and more as well as low-temperature areas such as cold storage warehouses.
  • Due to lower loss per kilometer, glass fibers are best for long-distance communication.
  • Glass fiber optics can support high bandwidth signal transmission. As a result, it is ideal for home networking.
  • Glass optical fiber cable is immune to electromagnetic interference (EMI) and radio magnetic interference (RMI).
  • Glass optical fibers are thin and light in weight. Therefore, they are optimal for small spaces and small targets.


9. The material used in plastic optical fiber is

  1. Polycarbonate
  2. Acrylic
  3. Carbon
  4. Propylene

Answer:2. Acrylic


Plastic optical fiber, polymer optical fiber or POF, is an optical fiber that is made out of plastic. Traditionally, it comprises PMMA (acrylic as the core (96% of the cross-section in a fiber 1mm in diameter) that facilitates the transmission of light, and fluorinated polymers as the cladding material.


10. Which of the following are the advantages of Plastic optical fiber over glass fiber?

  1. Less Expensive
  2. Easy Troubleshooting
  3. More Flexible
  4. All of the above

Answer: 4. All of the above


Advantages of Plastic fiber

  • It is generally less expensive and makes use of less costly connectors.
  • It is substantially tougher – it can be looped more tightly than glass in a wire closet.
  • Plastic fiber is extremely easy to troubleshoot because it uses visible light, rather than infrared light: a user can actually look into the connector and see whether data is flowing on the line.
  • Traditionally come in a wide variety of diameters ranging from 0.15-2 mm (small core) and even up to 20 mm (large core).
  • More flexible and able to bend farther without cracking or breaking.
  • Able to withstand vibration and unsteady environments.


11. Which of the following are the disadvantages of Plastic optical fiber over glass fiber?

  1. High attenuation
  2. Narrow Numerical aperture
  3. Highly Flammable
  4. All of the above

Answer: 4. All of the above


Disadvantages  of Plastic fiber

  • Signal attenuation and dispersion are very high. Hence they are not useful for long-distance communication systems.
  • The Refractive index of the core and cladding part varies rapidly at higher temperatures. Hence NA and mode pattern of the plastic fiber deviates.
  • It offers low quality compare to glass optical fiber.
  • It is flammable and hence needs to be used in selected applications after proper analysis.
  • More narrow numerical aperture – 0.48 – .063 
  • Not able to withstand harsh environments and will easily degrade/yellow over time 
  • Can only transmit a narrow spectrum of visible light (400 – 700 nm) 


12. What is the application of Plastic optical fiber?

  1. Used in Illumination
  2. Long Distance transmission
  3. Low signal Atteunation
  4. All of the above

Answer: 1. Used in Illumination


Application of Plastic Optical Fiber

  • The largest application of POF has been in digital audio interfaces for short-distance (5 m), low-speed communication between amplifiers, and built-in digital-to-analog converter and digital audio appliances, such as CD/MD/DAT players and BS tuners.
  • The noise-immune nature of POF contributes to creating the sound of high quality and low jitter. Because of its flexibility and immunity to factory floor noise interference, rugged and robust POF communication links have been successfully demonstrated in a tough industrial manufacturing environment.
  • Lightweight and durable POF networks could link the sophisticated systems and sensors used in automobiles, which would increase performance and overall efficiency.
  • POF could be used to incorporate video, minicomputers, navigational equipment, and fax machines into a vehicle. Another short-haul application for POF is home networking, where appliances, entertainment and security systems, and computers are linked to create a smart home.
  • Plastic fibers are preferred for more illumination and decorative applications, such as backlighting and trim lighting. Due to the flexibility and vibration resistance of plastic fibers, they are also great for automotive and industrial lighting purposes.


13. Photonic crystal fibers also called as ______

  1. Conventional fibers
  2. Dotted fibers
  3. Stripped fibers
  4. Holey fibers

Answer: 4. Holey fibers


In the early 1990s researchers envisioned and demonstrated a new optical fiber structure. Initially, this was called a holey fiber and later became known as a photonic crystal fiber (PCF) or a microstructured fiber.

The difference between this new structure and that of a conventional fiber is that the cladding and, in some cases, the core regions of a PCF contain air holes, which run along the entire length of the fiber.


14. The periodic arrangement of cladding air holes in photonic bandgap fibers provides for the formation of a photonic bandgap in the _________

  1. H-plane of fiber
  2. E-plane of fiber
  3. E-H-plane of fiber
  4. Transverse plane of the fiber

Answer:4. Transverse plane of the fiber


  • Photonic bandgap (PBG) fibers are a class of microstructured fiber in which a periodic arrangement of air holes is required to ensure guidance.
  • This periodic arrangement of cladding air holes provides for the formation of a photonic bandgap in the transverse plane of the fiber.
  • As a PBG fiber exhibits a two-dimensional bandgap, then wavelengths within this bandgap cannot propagate perpendicular to the fiber axis (i.e., in the cladding) and they can therefore be confined to propagate within a region in which the refractive index is lower than the surrounding material.
  • Hence, utilizing the photonic bandgap effect light can, for example, be guided within a low-index, air-filled core region creating fiber properties quite different from those obtained without the bandgap.


15. In index-guided photonic crystal fiber structure, the dark areas are air holes. What do white areas suggest?

  1. Air
  2. Silica
  3. Water
  4. Plasma

Answer:4. Plasma


A photonic crystal is a low-loss periodic dielectric medium constructed using a periodic array of microscopic air holes that run along the entire fiber length.

Index-guided photonic crystal fibers have greater index contrast because the cladding contains air-holes having a refractive index.

Both indexes guided and conventional fibers arise from the manner in which guided mode interacts with the cladding region. The dark areas are air holes while the white areas are silica.

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