While the contours of 6 G are still being defined, integrated sensing and communication (ISAC) has been identified by the International Telecommunications Union (ITU) as a key feature of next-generation wireless communications. Given the maturity already demonstrated for data transmission on the one hand, and positioning on the other hand, optical wireless communications (OWC) could offer promising solutions for ISAC implementation, especially in indoor scenarios. In this paper, we propose and implement an OWC-based ISAC system that relies on multi-band carrierless amplitude and phase ( m -CAP) modulation associated with received signal strength (RSS)-based positioning to achieve data transmission and localization from the same signal. This m -CAP/RSS system is deployed in a 1.2 ×1.2× 2.16 m 3 room using four access points installed on the ceiling, and can provide a communication link at a data rate of 12 Mbps with a bit error rate of less than 3.8×10−3 to any user in a reception plane 20 cm above the ground, while estimating its position with an error of less than 5.9 cm in 90% of cases.