We investigate the performance limits of a passive pico-cell system with an electroabsorption modulator (EAM) using the radio-over-fiber technique in a 2.4 GHz wireless local area network (WLAN) environment. WLAN signals from a wireless router can not be detected properly at the WLAN card even in a service range of 1 m for the zero bias voltage to the EAM. To overcome and understand the performance limits, we apply bias voltage to the EAM and vary the optical modulation index (OMI) of the transmitter. Power margins in the links are found to estimate a possible service range, and packet loss rates in the pico-cell system are measured to evaluate the transmission performance. The service range can be extended up to 3 m by applying bias voltage to the EAM or adjusting the OMI of the transmitter.