We examine the nonclassical effects arising in waveguide modes of a no
nlinear coupler operating via degenerate down-conversion at different
dynamical regimes. Codirectional and contradirectional geometries are
investigated and it is shown that the contrapropagating geometry provi
des better efficiency for squeezing of vacuum fluctuations in single m
odes, whereas the copropagating geometry results in more efficient squ
eezing in compound modes.