Editing Graded-index fiber (section)

==Pulse dispersion==
Pulse dispersion in a graded-index optical fiber is given by{{Citation needed|reason=This formula seems to assume that a pulse will happily travel along the cladding. In reality, I thought the whole point of GRIN fibre was to make the pulse travelling down the centre of the fibre go slower (due to higher refractive index) than the pulse travelling on a sinusoidal path close to the cladding. If there's a distinction between modal and pulse dispertion that I'm missing, then this should definitely be expounded upon here.|date=March 2013}}

<math display=block>\mathrm{Pulse~dispersion} = \frac{k \delta n\ n_1\ l}{c} \,\!,</math>
where

<math display=inline>\delta n\,\!</math> is the difference in refractive indices of core and cladding,

<math display=inline>n_1\,\!</math> is the refractive index of the cladding,

<math display=inline>l\,\!</math> is the length of the fiber taken for observing the pulse dispersion,

<math display=inline>c \approx 3\times 10^8~\mathrm{m/s}\,\!</math> is the [[speed of light]], and

<math display=inline>k\,\!</math>  is the constant of graded index profile.