Fiber-based photonic integrated sensing and communication: enabling technologies and key challenges

Optical communication networks constitute a critical component of modern information infrastructure, characterized by extensive coverage and high deployment density. The integration of sensing functionalities into optical networks has given rise to photonic integrated sensing and communication (P-ISAC) systems, which enable advanced functions such as network diagnosis, spatial positioning, and ocean observation, thereby accelerating the evolution toward intelligent optical networks. This review begins by outlining the main categories of P-ISAC, including visible-light-communication-, free-space-, fiber-, and microwave-photonics-based technologies, and briefly introduces their characteristics and application scenarios. A primary focus is concentrated on fiber-based P-ISAC systems, encompassing both forward and backward sensing mechanisms. In such systems, the overall performance is constrained by differing power requirements and signal properties between communication and sensing functions. Key technical challenges include designing optimized system architectures, achieving high spectral efficiency, and approaching or even surpassing the performance limits of integrated communication and sensing. The review further elaborates on recent advances in fiber-based P-ISAC organized by the level of system integration, such as wavelength-division multiplexing (WDM), frequency-division multiplexing (FDM), space-division multiplexing (SDM), and time–frequency multiplexing (TFM), analyzing their respective benefits and representative use cases. Finally, future development trends and key technologies in P-ISAC are outlined.