The physical reason is, that material dispersion and waveguide dispersion cancel out at this wavelength, since both dispersions have an opposite algebraic sign.

At zero dispersion wavelength the signal will not disturbed by the dispersion ( pulse will not broaden) as for as low  power input signal.  at high power the signal getting affected by the non linearity of  this zero dispersion.  we can modify this zero dispersion wavelength through the modification of refractive profile of the  fiber. the refractive index change ( fiber structure modification)  can control the wave guide dispersion and the respective change will reflect in total dispersion.