In this paper, we propose the generation of all four polarization-entangled Bell states in a potassium titanyl phosphate waveguide device. This is achieved through non-degenerate spontaneous parametric downconversion and quasi-phase-matching with special non-uniform poling in different lengths. These biphoton states consist of the signal being emitted in a telecommunication wavelength. Through their joint spectral amplitude, we study the frequency correlation properties of the photon pairs. Polarization-entangled photon pairs are used as a resource of entanglement in various quantum optics experiments and there is a demand for generating all four photonic Bell states in a single waveguide-based device in quantum information applications.