Review of no-core optical fiber sensor and applications

The unique structural characteristic of no-core fiber (NCF) have extended the sensing applications based on multimode interference self-imaging, evanescent wave absorption and materials coating, which are widely used in the measurement of various physical, chemical and biological parameters. An overview of the NCF-based sensing applications is spread out with specific emphasis on measurement methods, structural improvements and the combination of sensitive materials. Different prototypes of NCF-based sensors are meticulously outlined. First, the single NCF-based sensors with different analysis principles are reviewed, and the advantages of structural improvement including fiber taper, lateral-offset fusing and internal waveguide writing are compared. Second, the cascading of NCF with fiber gratings or other structures to realize multi-parameter measurement and widen the application field are also discussed. Then, NCF combines sensitive materials to measure physical/chemical parameters or coats metal film to excite surface plasmon resonance are addressed, and representative examples of the latest research progress are presented to confirm the potential value of NCF-based sensors in biosensing. What’s more, the sensing characteristics of applying NCF structure in different ways are also introduced. In a whole, this article detailedly summarizes the sensing applications, concludes the challenges and points out the research direction in the development of NCF-based sensors.