Mao-qing Chen

Small and Practical Optical Fiber Fluorescence Temperature Sensor

A small optical fiber temperature sensor employing the fluorescence lifetime of Mn4+ doped oxyfluoride germanate phosphor was presented and experimentally demonstrated, which has a fairly good temperature measurement precision. The performance of the fluorescent materials for temperature measurement was compared and analyzed. A small temperature sensing probe with a diameter of 1.8 mm was proposed. For the first time, the integrated tee-light-path structure was put forward, the transmission and separation of excitation light and fluorescence in only a single optical path was realized. Experimental results showed that standard deviation errors of 0.45 °C were obtained within the temperature range from 0 °C to 90 °C.

Small Curvature Sensor Based on Butterfly-Shaped Mach–Zehnder Interferometer

A novel and small curvature sensor based on the butterfly-shaped Mach–Zehnder interferometer is proposed and experimentally demonstrated. The sensing element is a tapered hollow-core fiber sandwiched between two single-mode fibers. The fusion-collapsed region around the first fusion interface excites the high-order modes, and the butterfly-shaped structure couples the high-order modes back into the core and interferes with the fundamental mode in the second fusion-collapsed interface. Simulation of the butterfly-shaped structure is carried out by the beam propagation method to determine an optimized size of sensing element. The experimental results show that the light intensity variation of the interference spectrum is almost linearly proportional to the change of curvature, and the curvature sensitivity and resolution of the proposed sensor can be up to −10.9041 dB/m−1 and 0.000917 m−1, respectively, in the range from 0.387 to 1.285 m−1. The proposed curvature sensor is compact in size, high sensitive, and inexpensive. The excellent electromagnetic interference resistance and fabrication simplicity make the device an attractive candidate for curvature measurement in harsh environments.

Research Advances in Microfiber Humidity Sensors

An overview of the numerous latest research in microfiber humidity sensors is carried out with a specific focus on measurement methods, humidity sensitive materials, probe structures, and sensing properties of different sensors. First, five mainstream measurement structures, including taper, fiber grating, coupler, resonator, and interferometer are reviewed. It is concluded that these measurement structures sense the physicochemical property variations of microfibers or sensitive films and exhibit the change of optical signal when exposed to environment. Second, the basic preparation methods, humidity-sensing properties, and their advantages and disadvantages as humidity sensitive material are addressed. Then, the advantages and disadvantages of all the above sensing structures are also discussed and compared. Finally, the main existing problems and potential solutions of microfiber humidity sensors are pointed out.

A novel and small curvature sensor based on butterfly-shape Mach-Zehnder interferometer

A novel hollow-core fiber (HCF) curvature sensor based on a tapered HCF sandwiched between two single mode fibers (Butterfly-Shape Structure) is proposed and experimentally demonstrated. The collapsed region around the first fusion interface excites the high-order modes, and the butterfly shape couples the high-order modes back into the core and interferes with the fundamental mode in the second fusion interface. Simulation of the butterfly-shape structure is carried out using the beam propagation method to determine an optimized size of sensing element. The experimental results show that the variation of the interference spectrum light intensity is almost linearly proportional to the change of curvature, and the curvature sensitivity and resolution of the proposed sensor can be up to −10.9041dB/m−1 and 0.000917m1 respectively in the range from 0.387 to 1.285m−1. The proposed curvature sensor is compact size, high sensitive, and inexpensive.

Highly sensitive curvature sensor based on an asymmetrical Mach–Zehnder interferometer

ABSTRACT Mach–Zehnder interferometers have attracted attention due to their flexible structures and extensive applications. In this study, a simple and highly sensitive curvature sensor based on an asymmetrical Mach–Zehnder interferometer comprising an up-taper and a peanut-like section was theoretically and experimentally characterized. A simulation was conducted to investigate the influence of structural parameters on the interference spectrum. Experimental measurements show that a high curvature sensitivity of −35.3 nm/m−1 from 1.35 to 2.20 m−1 was obtained and high mechanical strength was demonstrated. The temperature–curvature cross-sensitivity of 4.44 × 10−4 m−1/°C was lower than the curvature resolution. The high curvature sensitivity and low temperature cross-sensitivity make this sensor a candidate for practical applications.