  In this work we revisit the problem of the quantization of the
two-dimensional O(3) non-linear sigma model and its one-parameter integrable
deformation -- the sausage model. Our consideration is based on the so-called
ODE/IQFT correspondence, a variant of the Quantum Inverse Scattering Method.The
approach allowed us to explore the integrable structures underlying the quantum
O(3)/sausage model. Among the obtained results is a system of non-linear
integral equations for the computation of the vacuum eigenvalues of the quantum
transfer-matrices.
