Question

Question 1

Select the correct statement(s) regarding fiber optic cable.

a. The core and cladding within a fiber optic cable must have the same refractive index in order to achieve TIR (Total Internal Reflection)

b. Only single mode fiber (SMF) can be constructed with either a “step” or “graded index” core

c.  Mulimode optical fibers (MMF) are vulnerable to modal dispersion

d. All statements are correct

Question 2

Using a direct sequence spread spectrum (DSSS) technique spreads a narrow band channel so that it occupies greater frequency spectrum. By doing this, the signal has greater immunity from narrow band noise.

True

False

Answer 1

Question 1
Answer)
The correct statements regarding the fiber optic cable are:
c. Mulimode optical fibers (MMF) are vulnerable to modal dispersion

There should be some difference for the refractive index of the cladding and the core which allows the TIR (Total Internal Reflection). Multi-mode optical fibers are the ones that can be constructed with either graded index or step-index. MMF are in fact the ones which are vulnerable to the modal dispersion depending on the cross-sectional index of refraction profiles.

Question 2
Answer)
True

The direct sequence spread spectrum (DSSS) allows the signals to spread across a wide bandwidth and thus making it difficult to intercept, demodulate, and intercept and thus the spread is over a wide band which allows the spread-spectrum signals to be less likely to interfere with the narrowband communications.

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