With the rapid development of the marine economy, the underwater Internet of Things (IoT) is facing urgent demands for intelligence and convenience. The separation of traditional communication and sensing modules has led to large device sizes and high costs, which restrict the overall system performance. This has spurred the development of Integrated Sensing and Communication (ISAC) systems, especially Optical ISAC (OISAC) systems based on Underwater Wireless Optical Communication (UWOC), which have become a current research hotspot. Although OISAC systems offer the advantages of high spectral efficiency and low latency, they still face challenges in clock synchronization and hardware implementation in practical applications.

To address these issues, the paper proposes an Optical Integrated Communication and Ranging (OICAR) system based on spread-spectrum signals. The paper employs a spread-spectrum communication scheme to transmit communication information, which effectively combats channel fading caused by the transmitter light source and the transmission channel, thereby ensuring the successful transmission of communication information. Additionally, the paper incorporates timestamp information into the chips of the duplex spread-spectrum signals. By utilizing the timestamp information of the master and slave transceivers, the autocorrelation properties of the spread-spectrum code, and the Frequency Control Word (FCW), the system achieves high-precision underwater ranging with asynchronous transceivers. Furthermore, the paper constructs a real-time hardware implementation system using Light Emitting Diode (LED) arrays and a Field Programmable Gate Array (FPGA) processing system, providing a hardware verification platform for the development of the underwater OICAR system.

Communication and ranging experiments are conducted on the OICAR real-time system in a towing tank. Results demonstrate that the designed system achieves a maximum underwater communication distance of 63.5 m while maintaining ranging accuracy within ±0.25 m.

These findings indicate that the proposed OICAR system can realize efficient underwater communication and precise ranging functions in real time.