  A pre-order and equivalence relation on the class of positive real Hilbert
space operators are introduced, in correspondence with similar relations for
contraction operators defined by Yu.L. Shmul'yan in [7]. It is shown that the
pre-order, and hence the equivalence relation, are preserved by certain linear
fractional transformations. As an application, the operator relations are
extended to the class $\fC(\cU)$ of Carath\'eodory functions on the unit disc
$\BD$ of $\BC$ whose values are operators on a finite dimensional Hilbert space
$\cU$. With respect to these relations on $\fC(\cU)$ it turns out that the
associated linear fractional transformations of $\fC(\cU)$ preserve the
equivalence relation on their natural domain of definition, but not necessarily
the pre-order, paralleling similar results for Schur class functions in [3].
