Temperature-Independent Gas Pressure Sensor with High Birefringence Photonic Crystal Fiber-Based Reflective Lyot Filter

Fabricating Air Pressure Sensors in Hollow-Core Fiber Using Femtosecond Laser Pulse

In this paper, a hollow core fiber was spliced with standard single-mode fibers to form a fiber optic gas pressure sensor, and its sensing characteristics with single hole or multi-holes punched on the hollow core fiber with femtosecond laser pulses were investigated. The experiments demonstrate that the air pressure sensitivity of the single hole sensor was -3.548 nm/MPa, with a linearity of 99.45%, while its response times for air pressure's rise and fall were 4.25 s and 2.52 s, respectively. The air pressure sensitivity of the ten-hole sensor was up to -3.786 nm/MPa, with a linearity of 99.47%, while its response times for air pressure's rise and fall were 2.17 s and 1.30 s, respectively. Theoretical analysis and experimental results indicate that the pressure sensitivity of the sensor with an anti-resonant reflecting guidance mechanism mainly comes from the refractive index change of the air inside the hollow core fiber. The proposed device with multi-holes drilled by a femtosecond laser has the advantages of fabrication simplicity, low cost, fast response time, good structural robustness, high repeatability, high sensitivity to air pressure, and insensitivity to temperature (only 10.3 pm/°C), which makes it attractive for high pressure sensing applications in harsh environments.

Silicone Rubber Fabry-Perot Pressure Sensor Based on a Spherical Optical Fiber End Face

To improve the fringe contrast and the sensitivity of Fabry-Perot (FP) pressure sensors, a silicone rubber FP pressure sensor based on a spherical optical fiber end face is proposed. The ratio of silicone rubber ingredients and the diameter and thickness of silicone rubber diaphragm were optimized by a simulation based on experimental tests that analyzed elastic parameters, and the influence of the radius of a spherical optical fiber and the initial cavity length of the sensor on the fringe contrast was investigated and optimized. Pressure sensor samples were fabricated for pressure test and temperature cross-influence test. Gas pressure experimental results within a pressure range of 0~40 kPa show the average sensitivity of the sensor is −154.56 nm/kPa and repeatability error is less than 0.71%. Long-term pressure experimental results show it has good repeatability and stability. Temperature experimental results show its temperature cross-sensitivity is 0.143 kPa/°C. The good performance of the proposed FP pressure sensor will expand its applications in biochemical applications, especially in human body pressure monitoring.

Optical Devices Constructed From Responsive Microgels for Polyphenols Detection

Polyphenols are used as antioxidants in various foods and beverages, which are considered to be a health benefit. The measurement of polyphenols contents is of great interest in food chemistry and health science. This work reported a microgels based photonic device (etalon) to detect polyphenols. Dopamine was used as a model compound of polyphenols. Herein, we proposed a “block” concept for dopamine detection. The dopamine was oxidized and formed dopamine films catalyzed by tyrosinase on the surface of etalon. As the etalon was immersed in ZnCl₂, the dopamine films blocked the ZnCl₂ diffusion into etalon that caused optical property changes. The film thickness is associated with the concentration of dopamine which can be readout via optical signals.