Distributed antenna systems (DASs) using Radio-over-fiber (RoF) links is a promising candidate to provide flexible coverage and high data rates. For simulcast Wireless local-area network (WLAN) use in RoF systems, the stations covered by different Remote antenna units (RAUs) contend for the wireless medium using Media access control (MAC) mechanism. Severe inter-RAU hidden nodes problem will happen due to the stations in different RAUs cannot detect each other very well. In order to alleviate this inter-RAU collision problem, a promising detection-switching-assisted Distributed coordination function (DCF) mechanism is presented using in the uplink. The control delay issues of the proposed mechanism are also discussed in this paper.