the relation between 1-air hole diameter 2-lambda 3-refractive index in PCF

hi
I read in a journal paper thet :
At the end to have a stronger conclusion, referring
the relation between nf, d, and lambda, by basic
electromagnetic equations ?c/n=lambda*f? for light, we can
find a relation between these parameters.
but what is the relation between these three parameters in photonic crystal fibers?

This is simple speed of light and wavelength math.

c = speed of light in vaccum 3e8 m/s
n = refraction index
lambda = wavelength
f = frequency

I know this, but I ask what is the relation between n, d and lambda?