  We introduce higher level $q$-oscillator representations for the quantum
affine (super)algebras of type $C_n^{(1)},C^{(2)}(n+1)$ and $B^{(1)}(0,n)$.
These representations are constructed by applying the fusion procedure to the
level one $q$-oscillator representations which were obtained through the
studies of the tetrahedron equation. We prove that these higher level
$q$-oscillator representations are irreducible. For type $C_n^{(1)}$ and
$C^{(2)}(n+1)$, we compute their characters explicitly in terms of Schur
polynomials.
