  We study numerically the monopole creation operator proposed recently by
Frohlich and Marchetti. The operator is defined with the help of a three
dimensional model which generates random Mandelstam strings. These strings
imitate the Coulombic magnetic field around the monopole. We show that if the
Mandelstam strings are condensed the creation operator discriminates between
the phases with condensed and non--condensed monopoles in the Abelian Higgs
model with the compact gauge field.
