# Material dispersion calculation (optical fiber)

1. Oct 21, 2007

### johnchau123

Material dispersion in optical fiber is defined as D = (-λ/c)×(d²n/dλ²)
λ is wavelength, c is speed of light and n is refractive index.

I was given a graph of λ²×(d²n/dλ²) against λ, refractive index of core of fiber, index difference and diameter of the core and cladding.

What I would like to ask is the stuff I have to find out is (-λ/c)×(d²n/dλ²) = (-1/cλ)× [λ²×(d²n/dλ²)]. Since I know λ²×(d²n/dλ²) from the graph and I know c and λ, then I could calculate the dispersion immediately.

Then, what is the use of the information provided, such as refractive index of core of fiber, index difference and diameter of the core and cladding??

Are they extra to this question or I skip something?

Thanks.

John

2. Nov 2, 2009

### gmzyildizz

hi, firstly thanks the information that you explained. I have a project about the dispersion in fiber optic. The project is a programme that calculate the modal dispersion for different types of fiber optic, in MATLAB. I searched in the internet but only I could find the calculation about intramodal dispersion (waveguide and material dispersion) I need to find the calculation of intermodal dispersion. I know it's about the group delay, too. but I can't how I can obtain the function for calculating or anything. Do you have any idea about this?
thanks