The digital transmission system entered in a RF region as digital system use IC chips of the speeder edge rate and clock speed nowadays. Optical path really was used in order to obtain the more capacity. In this paper, we described importance of electrical interconnect to get the signal integrity in optical module by simulation and experiment. 12 channel${ imes}$2.5 G/ps optical parallel transmitter modules were manufactured by two different method ; access lines with microstrip and stripline type. We have clearly shown that the optical module adopting microstrip type with S$sub$11/ $geq$ -10 dB presents distortion but the optical module adopting stripline type with S$sub$11/ $leq$ : 15 dB obtains eye opening in 2.5 Gbis optical eye pattern response.