ECE · all questions

Optical Communication
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Q181

Which one of the following statement is correct?
The model noise in multimode fibers cannot be reduced by

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Q182

For a photo-diode with responsivity of 0.50 A/W & optical power of about 12 µW, what would be the value of generated photocurrent?

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Q183

Generally, the SM fiber will have a core diameter of

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Q184

Optical storage devices employ

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Q185

For a silica fiber the refractive index of core layer is 1.56 and that of cladding is 1.35. Calculate numerical aperture

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Q186

The bandwidth of the optical signal having a rise time (response time) t_r is 500 MHz. Find the value of rise time.

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Q187

The modal dispersion in a fiber is 20 ns/km. What will be the overall pulse spread in 10 km long fiber? Assume material dispersion to be zero

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Q188

Which is the transmission medium for VLF electromagnetic waves especially applicable for aeronautical and submarine cables?

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Q189

When the mean optical power launched into an 8 km length of fiber is 120 µW. The mean optical power at the fiber output is 3 µW. Find the signal attenuation

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Q190

Not an example for actuator

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Q191

In the design of a single-mode step index optical fiber close to upper cutoff, the single-mode operation is not preserved if

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Q192

Total internal reflection at the fibre wall can occur only if two conditions are met. One of the condition is the glass inside the fibre core must have a/an . . . . . . . . index of refraction than/as the index of refraction of the material surrounding the fibre core.

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Q193

Which one of the following fibers has the distinct advantage of low intermodal dispersion?

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Q194

An optical link uses a fiber having a power loss of 1 dB/km. A typical photo detector has responsivity 0.5 A/W. If the link is 3 km long and the detector is required to produce a current of 25 µA, the required transmitted power is

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Q195

The least attenuation of standard single mode optical fibers are at

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Q196

Coherent radiation in LASER is caused by

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Q197

A multimode step index fiber with a core diameter of 80 µm and a relative index difference of 1.5% is operating at a wavelength of 0.85 µm . If the core refractive index is 1.48, then the normalized frequency for the fiber is

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Q198

Consider the following advantages of optical fiber-cables:
1. Small diameter
2. Immunity to cross talk and electromagnetic interference
3. Laser and LED modulation methods lend themselves ideally to digital operation.
Which of these advantages are correct?

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Q199

What is the device used for measuring the power in an optical signal?

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Q200

Polarization mode dispersion (PMD) is mainly observed in

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