Question 1: Define solitons.

Answer: A soliton is a pulse or wave that travels along an optical fiber without changing the shape. It is experimentally found that due to fiber non-linearity, the refractive index of the fiber starts depending on the intensity of the light in addition to the wavelength of light. Therefore, the intensity of light itself can influence the velocity of the pulse in the fiber. Thus in solitons, the decrease in velocity due to the decrease in wavelength can be compensated by increasing the intensity of the low wavelength components in comparison to the high wavelength components of the wave. Therefore all the components of the wave travel with equal velocity in an optical fiber and pulse dispersion does not take place.

Question 2: Name the optical sources used for optical fibers.

Answer: Laser diodes and light emitting diodes are the most common sources. These devices require very less power for operation.

Question 3: What are optical detectors?

Answer: Optical detectors are the devices or instruments used at the output terminal of an optical fiber. These devices directly convert optical radiation into electrical signals and respond quickly to the changes in the optic power level.

Example: Photodiode, photomultiplier tube, PIN photodiode etc.