Wavelength Division Multiplexing Questions and Answers

Q: The physical mechanism behind the operation of an Acousto-optic filters in WDM is the :

Acousto-optic filters work by the photoelastic effect.An acoustic wave launched into a crystal creates a periodic pattern of compression and rarefaction. Through the photoelastic effect, this strain changes the refractive index periodically, forming a moving diffraction grating. Only light of the wavelength that satisfies the Bragg condition is diffracted, and changing the acoustic frequency tunes the selected wavelength, which is how the filter picks out WDM channels.The photoelectric effect is the emission of electrons by light, the electro-optic effect is a change of refractive index with an electric field (used in modulators), and electromagnetic effects are not the mechanism here.

Q: Grating based demultiplexers use the phenomenon of .............. from an optical grating.

Grating demultiplexers use diffraction (Bragg).A diffraction grating sends each wavelength in a different direction, given by the grating equation, so the wavelengths combined in a WDM signal are spread out in angle and can be collected by separate output fibres. Fibre Bragg gratings use the same principle along the fibre, reflecting a narrow band around the Bragg wavelength.Scattering spreads light in random directions without separating wavelengths in a controlled way, and plain reflection or transmission does not separate wavelengths at all.

Q: The following can be used as WDM component in optical communication :

The key gives optical filters.Wavelength division multiplexing sends several channels on one fibre, each at its own wavelength. Separating or combining them needs wavelength-selective components, and optical filters, such as thin-film interference filters, fibre Bragg gratings and arrayed waveguide gratings, are the basic WDM components that pass one wavelength and reflect or block the rest.A general fibre coupler splits or combines power without selecting wavelength, a graded index lens is used to collimate and focus light between fibres, and an epoxy splice simply joins two fibres. None of them separates wavelengths on its own.

The physical mechanism behind the operation of an Acousto-optic filters in WDM is the :

A.Photoelectric effect
B.Electro-optical effect
C.Electromagnet effect
D.Photoelastic effect

Exam Year(s)

MH SET - 2023, SET Exam - 2023,

Answer: D

Acousto-optic filters work by the photoelastic effect.

An acoustic wave launched into a crystal creates a periodic pattern of compression and rarefaction. Through the photoelastic effect, this strain changes the refractive index periodically, forming a moving diffraction grating. Only light of the wavelength that satisfies the Bragg condition is diffracted, and changing the acoustic frequency tunes the selected wavelength, which is how the filter picks out WDM channels.

The photoelectric effect is the emission of electrons by light, the electro-optic effect is a change of refractive index with an electric field (used in modulators), and electromagnetic effects are not the mechanism here.

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Grating based demultiplexers use the phenomenon of .............. from an optical grating.

A.Diffraction (Bragg)
B.Scattering
C.Reflection
D.Transmission

Exam Year(s)

MH SET - 2023, SET Exam - 2023,

Answer: A

Grating demultiplexers use diffraction (Bragg).

A diffraction grating sends each wavelength in a different direction, given by the grating equation, so the wavelengths combined in a WDM signal are spread out in angle and can be collected by separate output fibres. Fibre Bragg gratings use the same principle along the fibre, reflecting a narrow band around the Bragg wavelength.

Scattering spreads light in random directions without separating wavelengths in a controlled way, and plain reflection or transmission does not separate wavelengths at all.

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The following can be used as WDM component in optical communication :

A.Fibre coupler
B.Optical filters
C.Graded index lens
D.Epoxy splicer

Exam Year(s)

MH SET - 2023, SET Exam - 2023,

Answer: B

The key gives optical filters.

Wavelength division multiplexing sends several channels on one fibre, each at its own wavelength. Separating or combining them needs wavelength-selective components, and optical filters, such as thin-film interference filters, fibre Bragg gratings and arrayed waveguide gratings, are the basic WDM components that pass one wavelength and reflect or block the rest.

A general fibre coupler splits or combines power without selecting wavelength, a graded index lens is used to collimate and focus light between fibres, and an epoxy splice simply joins two fibres. None of them separates wavelengths on its own.

Discuss in Forum

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Wavelength Division Multiplexing Questions and Answers

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