Highly sensitive sensor for simultaneous underwater measurement of salinity and temperature based on highly birefringent asymmetric photonic crystal fiber

• Published in: Results in optics 2023-05, Vol.11, p.100406, Article 100406
• Main Authors: Liu, Xingyu, Yin, Bin, Li, Haisu, Wang, Muguang, Yan, Ran, Li, Yongchang, Zong, Chenxi, Wu, Songhua
• Format: Article
• Language: English
• Subjects: Optical fiber sensors; Photonic crystal fiber; Salinity sensors; Sensitivity; Temperature sensors; Two-parameter measurement
• ISSN: 2666-9501; 2666-9501
• DOI: 10.1016/j.rio.2023.100406

•Simulation modeling implements a highly sensitive salinity-temperature fiber sensor.•A highly birefringent, asymmetric, full-circular hole PCF is designed by modeling.•PCF air holes serve as fluid microchannels to measure the refractive index.•Fill PCF specific air holes with ethanol to improve temperature sensitivity.•Temperature and salinity sensitivity reach about 5 nm/% and −0.8 nm/°C, respectively. This paper describes a novel compact fiber sensor with high sensitivity for the simultaneous measurement of underwater salinity and temperature by simulation. The structure is based on a highly birefringent, asymmetric, full-circular hole photonic crystal fiber (HB-A-FCH PCF), which achieves the birefringence value of 2.83 × 10-3 at the wavelength of 2.2 µm. In addition, with ethanol-filled specific air holes, the temperature sensitivity of HB-A-FCH PCF is remarkably improved. Therefore, considering the high birefringence property, we simulate a Michelson interferometer-based sensor setup with air holes as fluid microchannels and simultaneously measure salinity and temperature through the spectral responses of the x- and y-polarization state. Theoretical analysis shows the sensor can achieve the salinity and temperature sensitivity up to 5.1472 nm/% and −0.8987 nm/°C in x-polarized fundamental mode, respectively, whereas the salinity and temperature sensitivity up to 4.5386 nm/% and −0.8000 nm/°C in y-polarized fundamental mode, respectively.