  Classical entanglement refers to non-separable correlations between the
polarization direction and the polarization amplitude of a light field. The
degree of entanglement is quantified by the Schmidt number, taking the value of
unity for a separable state and two for a maximally entangled state. We propose
two detection methods to determine this number based on the distinguishable
patterns of interference between four light sources derived from the unknown
laser beam to be detected. The second method being a modification of the first
one has the interference fringes form discernable angles uniquely related to
the entangled state. The maximally entangled state corresponds to fringes
symmetric about the diagonal axis at either 45{\deg} or 135{\deg} direction
while the separable state corresponds to fringes symmetric either about the X-
or Y-axis or both simultaneously. States with Schmidt number between unity and
two have fringes of symmetric angles between these two extremes. The detection
methods would be beneficial to constructing transmission channels of
information contained in the classically entangled states.
