Single-Mode-Multimode-Single-Mode Fibre Structure for Sensing Applications: A Review

Single-mode-multimode-single-mode (SMS) fibre structures have attracted great attention for their sensing applications in recent years. A typical SMS fibre structure is simply fabricated by sandwiching a multimode fibre (MMF) between two single-mode fibres (SMFs). Owing to its compact structure, easy of fabrication and low-cost, SMS structures are widely applied in a variety of parameter measurements such as temperature, curvature, displacement, magnetic field, refractive index (RI) and humidity, etc. To meet the requirement of high precision measurement, some post-processes for SMS fibre structures are also intensively investigated to improve its sensing performance. The development of the SMS fibre structures based sensors is reviewed in this paper, in which also contains a briefly theoretical introduction for a traditional SMS fibre structure.