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A novel photonic crystal fiber (PCF) sensor for refractive index detection based on polydimethylsiloxane (PDMS) is presented in this research, as well as designs for single-channel and dual-channel structures for this PDMS-PCF sensor. The proposed structures can be used to develop sensors with biocompatible polymers. The performance of the single-channel PDMS-PCF sensor was studied, and it was found that adjusting parameters such as pore diameter, lattice constant, distance between the D-shaped structure and the fiber core, and the radius of gold nanoparticles can optimize the sensor's performance. The findings indicate that the detection range of the single-channel photonic crystal is 1.21–1.27. The maximum wavelength sensitivity is 10,000 nm/RIU with a resolution of 1 × 10 − 5 RIU, which is gained when the refractive index is set to 1.27. Based on the results of the single-channel PCF, a dual-channel PDMS-PCF sensor is designed. The refractive index detection range of the proposed sensor is 1.2–1.28. The proposed sensor has a maximum wavelength sensitivity of 13,000 nm/RIU and a maximum resolution of 7.69 × 10 − 6 RIU at a refractive index of 1.28. The designed PDMS-PCF holds tremendous potential for applications in the analysis and detection of substances in the human body in the future. [ABSTRACT FROM AUTHOR]

• A fast-manufactured optical fiber temperature and humidity sensor with compact size was proposed. • The temperature and humidity sensitivities of the proposed sensor were −0.02539 dB/%RH and 11.14 pm/℃. • The measurement humidity sensitivity increased by nearly four times after the addition of nano-ZnO particles to the PVA. [Display omitted] A peanut-shaped optical fiber sensor cascaded with a fiber Bragg grating (FBG) was designed to measure temperature and humidity. A mixed polyvinyl alcohol/nano-zinc oxide (PVA/nano-ZnO) solution was electrospinning into nanofibers, and these nanofibers were then attached to the peanut-shaped structure surface to form a nanofiber film. Humidity changes caused changes in both the refractive index and the thickness of the PVA/nano-ZnO composite nanofiber film that subsequently caused changes in the transmitted light loss. Temperature changes caused a shift in the center wavelength of the FBG. Experimental results showed that the humidity and temperature sensitivities of the proposed sensor coated with the PVA/nano-ZnO composite film were −0.02539 dB/%RH and 11.14 pm/℃, respectively. Compared with an optical fiber sensor using a PVA film alone, the humidity sensitivity of the proposed sensor was increased by nearly four times after the addition of nano-ZnO. [ABSTRACT FROM AUTHOR]

A fiber-optic humidity sensor based on excessively tilted fiber grating (Ex-TFG) wrapped with tin dioxide (SnO 2)/polyvinyl alcohol (PVA) hybrid nanofibers is presented. Relative humidity (RH) rise causes the changes both in refractive index (RI) and geometry size of the film. The transmitted spectrum of the Ex-TFG changes as a result, owing to the strong interaction of the excited forward propagating cladding modes to the surface coating. Experimental results demonstrate the maximum intensity sensitivity of 0.43 dB/%RH in RH range of 35%−75%. Compared with pure PVA film coated ones, the RH sensitivity of the SnO 2 /PVA wrapped grating is vastly enhanced by one order of magnitude. The reticular morphology of electrospun SnO 2 /PVA film around the Ex-TFG promises the unimpeded permeation of water molecules, and then the sensor exhibits an ultrafast response of ∼67 ms and recovery times of ∼83 ms, by monitoring the human breathing with different rhythms. Lastly, the negligible spectral deformation to temperature perturbations verifies the temperature de-correlation of the designed RH sensor. This work indicates that the proposed SnO 2 /PVA nanofibers wrapped Ex-TFG can provide a simple, robust and high-sensitive optic device for healthcare monitoring, environmental and biochemical sensing applications. • Wrapping SnO 2 /PVA nanofibers on an excessively tilted fiber grating. • High intensity sensitivity up to 0.43 dB/%RH with negligible temperature crosstalk. • Monitoring human breathing with ultrafast response speed of 67 ms. • Performing the merits of long-term stability, reliability, and easy fabrication. [ABSTRACT FROM AUTHOR]