In order to share access infrastructure between mobile and access network, integration of wireless services on optical access network with Radio over Fibre (RoF) technologies is a potential solution for operators. In this paper, we propose an overlay Universal Mobile Telecommunication System (UMTS) or third generation (3G) signal transmission on a Gigabit Passive Optical Network. Main advantages of this transmission scheme are the use of only one laser to feed the signal and one photodiode to receive it. A trade-off between extinction ratio and laser linearity has been found and the penalty induced by the 3G signal overlay is small. We demonstrate a 1x32 PON over 20km, which can distribute UMTS signal for remote base station, and binary signal at 1.25Gbit/s for others users.