The refractive index variation with the change of glass structure depending on the temperature profile parameters using arc discharge is utilized to fabricate optical devices. The unequal heating in 2×2 couplers by placing the coupler waist away from the arc flame produces phase mismatch between the fibers. A theoretical model for splitting ratio versus wavelength with repeated discharges to increase the phase mismatch considering temperature profile parameters is developed. The theoretical curves are compared with the experimental results of 3 dB couplers and wavelength insensitive devices.