All Solid Photonic Crystal Fiber Enabled by 3D Printing Fiber Technology for Sensing of Multiple Parameters

Using the flexibility and diversity of material and structure designs possible with 3D printing fiber technology, an all-solid photonic crystal fiber (PCF) is fabricated using borate (B₂O₃) doping. The geometry, material, and optical properties of this 3D printed PCF are characterized and analyzed using optical microscopy, scanning electron microscopy (SEM), fiber index profilometry, and Fourier transform infrared (FTIR) microscopy. Analysis demonstrates that B₂O₃ doped in fabricated PCF has experienced evaporation leading to mass loss during drawing. In addition, there is no observable difference between the structure of substrate silica (SiO₂) and the SiO₂ nanoparticles. However, microdomain differences may explain enhanced reflectance. Furthermore, a Mach–Zehnder interferometer (MZI) sensor is constructed with this 3D printed solid PCF and applied to temperature, refractive index, tensile force, and bending sensing. The specially designed 3D printed PCF has maximum temperature sensitivity up to Δλ/ΔT ≈0.075 nm °C⁻¹. When immersed in 76.34 wt.% glycerol-water solution, the sensitivity can be further improved. These results demonstrate that 3D printing fiber technology enables the custom fabrication of highly sensitive optical fiber sensors, increasing opportunities for the development of diverse and flexible sensors and devices for future internet-of-things (IoT) applications.