In this article, we discuss the waveguide dimensions optimization aiming to reduce the Vπ. For that purpose, various cover materials are investigated leading to a minimum effective core area " Aeff". The index contrast (core-cladding) at λ= 1550 nm, is varying from 0.07 to 0.21. As a result, the Aeff decreases from 12 μm2 down to 2.3 μm2, the total thickness of the waveguide is thus reduced and consequently the Vπ. Optimal parameters were calculated at λ= 1550 nm for single mode inverted-rib waveguides structure. The PAS1 a new polymer is used as electro-optic material for the core. An analytical model taking account the losses by tunnelling, allowed us to estimate the optimum distance between electrodes to reduce the Vπ which could be about 1.6V ( 0.8 V in a push-pull configuration). Related with the bandwidth of the modulator, permittivity measurements were carried out on core and cladding polymers as well. The process of waveguides fabrication is described in details and several waveguides are performed. Finally, a new experimental technique for precision measurements of the propagation losses in waveguides is presented. The principle is simple, and the propagation losses measured is found to be independent of coupling conditions.