Fiber-optic communication represents a fundamental technology for access networks, metropolitan area networks, backbone networks, and trans-oceanic communication networks. This technology enables long-distance, high-speed data transmission and serves as the foundation for digitalization and information transformation. The real-time monitoring of fiber-optic communication networks is essential for maintaining reliable and secure data transmission. Fiber sensing technology, when integrated into fiber-optic communication networks and forming fiber-based integrated sensing and communication (F-ISAC) networks, enables continuous monitoring of network status, ensuring optimal operational performance. Additionally, F-ISAC networks possess the capability to monitor environmental parameters surrounding optical cables, including temperature, strain, vibration, and displacement. While fiber sensing technology can be incorporated into fiber-optic networks, establishing a system that optimizes both sensing and transmission performance presents significant challenges. The development of an integrated system combining high performance, integration, and efficiency remains crucial for advancing the intelligence of optical communication networks.

First, we introduce the origin of the F-ISAC technology, from technologies to applications. Then the main F-ISAC techniques are introduced according to the difference of sensing technologies, including forward transmission-based and backscatter-based F-ISAC techniques. With respect to the above two major types of F-ISAC technologies, the integration techniques, including space division multiplexing (SDM), wavelength division multiplexing (WDM), frequency division multiplexing (FDM), time-frequency reuse, and communication-sensing sharing, are further introduced. With regard to the above technologies, this paper introduces some representative solutions in each technology category, hoping to help readers have a better understanding of the advantages and characteristics of these solutions.

F-ISAC technology and applications demonstrate potential to enhance the extensive coverage capabilities of optical communication networks, offering novel approaches for intelligent network operation and maintenance, while contributing to advancements in smart cities and smart transportation. Current challenges and research directions in F-ISAC include 5 aspects. 1) Communication-sensing crosstalk and suppression: addressing the integration of high-performance sensing technology while maintaining communication quality represents a critical challenge. 2) Development of multi-functional optoelectronic devices: designing devices that optimize both sensing and communication capabilities remains essential for F-ISAC implementation. 3) Integrated signals design and processing: developing efficient ISAC signals and appropriate receiving and demodulation algorithms to enhance F-ISAC efficiency and performance constitutes a significant challenge. 4) Sensing and communication collaboration mechanisms: while fiber-optic communication and sensing systems demonstrate inherent trade-offs, opportunities exist for synergistic integration, such as sensing-assisted communication optimization through dynamic channel parameter adjustment and communication-enhanced sensing through improved event detection accuracy. 5) Standardized deployment frameworks: conventional fiber-optic sensing requirements often conflict with standardized telecommunication fiber deployment methods. Additional research must evaluate F-ISAC implementation strategies and their adaptability across various application scenarios.