  We study a proposal of generating macroscopic continuous-variable
entanglement with two coupled waveguides respectively carrying optical damping
and optical gain. Moreover, a squeezing element is added into one or both
waveguides. We show that quantum noise effect existing in the process is
essential to the degree of the generated entanglement. It will totally
eliminate the entanglement in the setup of adding the squeezing element into
the waveguide filled with optical damping material, but will not completely
damp the entanglement to zero in the other configurations of having the
squeezing element in the gain medium or in both gain and damping medium. The
degree of the generated continuous-variable entanglement is irrelevant to the
intensities of the input light in coherent states. Moreover, the relations
between the entanglement and system parameters are illustrated in terms of the
dynamical evolutions of the created continuous-variable entanglement.
