With unique features and advantages, visible light communication (VLC) is considered as a powerful complementary wireless access technology to radio frequency solutions such as WiFi. To handle the frequency-selectivity of VLC channels particularly at high speeds, multi-carrier signaling in the form of orthogonal frequency division multiplexing (OFDM) is typically preferred. Among various variants of optical OFDM, unipolar OFDM (U-OFDM) stands outs with its better error rate performance. In this paper, we present the experimental evaluation of the bit error rate (BER) performance of a U-OFDM-based VLC system. In our experimental set-up, we use the popular software defined platform USRP (Universal software radio peripheral) from National Instruments customized with baseband cards and integrated with VLC front-ends. We first characterize the frequency-selective VLC channel. Then, we present BER performance against the estimated signal-to-noise-ratio and confirm it through comparison with theoretical results.