This paper reports on recent numerical and experimental studies about the effects of the fabrication parameters on the Long Period Gratings (LPGs) sensitivity to the surrounding refractive index. The LPGs are fabricated by Electric Arc-Discharge (EAD) technique and the fabrication parameters are optimized by acting on the arc duration, power and electrodes gap. This permits to fabricate several LPGs in standard fiber with period ranging from 400 to 500 µm gratings where the coupling is with LP05 and LP06 cladding modes. Furthermore, we have investigated the surrounding refractive index (SRI) sensitivity of the LPGs as function of the grating period and compared the experimental results with numerical analysis based on coupled mode theory. As we show here, we achieve a good agreement between numerical and experimental results.