We propose a generalized definition of principal states of polarization for
an optical pulse with arbitrary spectral components, Similar to the princi
pal states defined by Poole et al,, we show that regardless of the spectral
components of the pulse, there exist two orthogonal input states of polari
zation which minimize/maximize the delay of the pulse. At the output of the
fiber, these two principal states of the pulse, although depolarized, are
also always orthogonal to each other.