Oscillator versus prefundamental representations

For the case of quantum loop algebras $mathrm U_q(mathcal L(mathfrak{sl}_{l + 1}))$ with $l = 1, 2$ we find the $ell$-weights and the corresponding $ell$-weight vectors for the representations obtained via Jimbos homomorphism, known also as evaluation representations. Then we find the $ell$-weights and the $ell$-weight vectors for the $q$-oscillator representations of Borel subalgebras of the same quantum loop algebras. This allows, in particular, to relate $q$-oscillator and prefundamental representations.