Normal dispersion occurs where shorter wavelengths travel slower than longer wavelengths. Anomalous dispersion occurs when shorter wavelengths travel faster than longer wavelengths.

The zero dispersion point for optic fibres is around 1550 nm, which is why most communications systems use this wavelength.

No.

The average of the deviations, or mean deviation, will always be zero.

The standard deviation is the average squared deviation which is usually non-zero.

the three types of dispersion are:

1. Intermodal Dispersion

2. Chromatic Dispersion

3. Waveguide Dispersion

the three types of dispersion are:

1. Intermodal Dispersion

2. Chromatic Dispersion

3. Waveguide Dispersion

Absolute dispersion usually refers to the standard deviation, a measure of variation from the mean, the units of st. dev. are the same as for the data.

Relative dispersion, sometimes called the coefficient of variation, is the result of dividing the st. dev. by the mean, hence it is dimensionless (it may also be presented as a percentage). So a low value of relative dispersion usually implies that the st. dev. is small in comparison to the magnitude of the mean, as in a st. dev. of 6cm for a mean of 4m would give a figure of 0.015 (1.5%) whereas with a mean of 40cm it would be 0.15 or 15%.

However with measurements either side of zero and a mean close to zero the relative dispersion could be greater than 1.

As is usual, interpret with caution.