Abstract
A high sensitivity refractive index sensor based on a single mode-small diameter no core fiber structure is proposed. In this structure, a small diameter no core fiber (SDNCF) used as a sensor probe, was fusion spliced to the end face of a traditional single mode fiber (SMF) and the end face of the SDNCF was coated with a thin film of gold to provide reflective light. The influence of SDNCF diameter and length on the refractive index sensitivity of the sensor has been investigated by both simulations and experiments, where results show that the diameter of SDNCF has significant influence. However, SDNCF length has limited influence on the sensitivity. Experimental results show that a sensitivity of 327 nm/RIU (refractive index unit) has been achieved for refractive indices ranging from 1.33 to 1.38, which agrees well with the simulated results with a sensitivity of 349.5 nm/RIU at refractive indices ranging from 1.33 to 1.38.
Highlights
Optical fiber sensors have shown great potential for different applications such as detection of biomolecules, measurements of the concentrations of various chemicals, structural health monitoring (SHM) of vital civil engineering structures and composite materials, power systems condition monitoring, and many others due to their inherent advantages such as high sensitivity, low cost, immunity to electromagnetic interference, good corrosion resistance, durability, flexibility, small size, and capability for remote operation [1,2,3,4,5,6,7]
Sensors are usually associated with fabrication fabrication processesevanescent or expensive fabrication equipment such as complicated excimer lasers or fiberprocesses tapering or expensive equipment such ashigh excimer lasers or fiber tapering systems, and suffer systems, and fabrication suffer from relatively cost [28,29]
From Compared relatively high costtechnologies to the above, an single mode-multimode-single mode (SMS) fiber structure based refractometer has the Compared to the technologies above, anand structure based refractometer the additional additional advantages of easy fabrication
Summary
Optical fiber sensors have shown great potential for different applications such as detection of biomolecules, measurements of the concentrations of various chemicals, structural health monitoring (SHM) of vital civil engineering structures and composite materials, power systems condition monitoring, and many others due to their inherent advantages such as high sensitivity, low cost, immunity to electromagnetic interference, good corrosion resistance, durability, flexibility, small size, and capability for remote operation [1,2,3,4,5,6,7]. SMS fiber structure baseda structure based is low based interference modes within refractometer is based on multimode interference between modes within a no-core/small-core no-core/small-core fiber, which can be influenced by the surrounding RI [30,31,32,33,34,35,36,37]. To avoid the need for chemical etching, a commercially available small core single etching, a commercially available small core single mode fibercandidate (SCSMF) has been demonstrated to be a mode fiber (SCSMF) has been demonstrated to be a good to replace the etched no-core good to replace etched as a sensing butpaper, with limited sensitivity [33].
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