  Coupled nonlinear Schr\"odinger equations, governing the propagation of
envelopes of electromagnetic waves in birefringent optical fibers, are studied
in this paper for their potential applications in the secured optical
communication. Periodicity and integrability of the CNLS equations are obtained
via the phase-plane analysis. With the time-delay and perturbations introduced,
CNLS equations are chaotified and a chaotic system is proposed. Numerical and
analytical methods are conducted on such system: (I) Phase projections are
given and the final chaotic states can be observed. (II) Power spectra and the
largest Lyapunov exponents are calculated to corroborate that those motions are
indeed chaotic.
