The phase-sensitive optical time-domain reflectometry (φ-OTDR) is a good candidate for distributed dynamic strain sensing, due to its high sensitivity and fast measurement, which has already been widely used in intrusion monitoring, geophysical exploration, etc. For the frequency scanning based φ-OTDR, the phase change manifests itself as a shift of the intensity distribution. The correlation between the reference and measured spectra is employed for relative strain demodulation, which has imposed the continuous measurement for the absolute strain demodulation. Fortunately, the Brillouin optical time domain analysis (BOTDA) allows for the absolute strain demodulation with only one measurement. In this work, the combination of the φ-OTDR and BOTDA has been proposed and demonstrated by using the same set of frequency-scanning optical pulses, and the frequency-agile technique is also introduced for fast measurements. A 9.9 Hz vibration with a strain range of 500 nε has been measured under two different absolute strains (296.7με and 554.8 με) by integrating the Rayleigh and Brillouin information. The sub-micro strain vibration is demonstrated by the φ-OTDR signal with a high sensitivity of 6.8 nε, while the absolute strain is measured by the BOTDA signal with an accuracy of 5.4 με. The proposed sensor allows for dynamic absolute strain measurements with a high sensitivity, thus opening a door for new possibilities which are yet to be explored.

We proposed a novel temperature-compensated multi-point refractive index (RI) sensing system by the combination of the cascaded Fabry-Perot (FP) sensors and the frequency modulated continuous wave (FMCW) interferometry. The former is used for simultaneous sensing of RI and temperature, and the latter is used for multiplexing a series of the cascaded FP sensors to realize multi-point sensing. By means of Fourier transform-based algorithms, the interference spectra of each sub-FP sensors can be divided and demodulated independently. Experimentally, three cascaded FP sensors are multiplexed to verify multi-point RI and temperature sensing ability. RI sensitivity up to ∼1200 nm/RIU is obtained within RI range from 1.3330 to 1.3410, and temperature sensitivity up to ∼0.17 nm/°C is obtained within temperature range from 20 °C to 80 °C. The RI precision is as high as 10−5 RIU and the temperature precision is as high as 0.05 °C. In addition, the prospective multiplexing number could reach about 4000 estimated by the minimum detectable light power. The proposed sensing system has potential advantages in the practical applications that require a large number sensing points.

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With the change of social situation, the traditional physical education teaching in colleges and universities is facing a comprehensive and deepening reform. Cultivation of students' awareness of lifelong physical education makes students effectively improve their comprehensive literacy. This paper analyzes the differences between the traditional physical education teaching mode and the lifelong physical education teaching mode in colleges and universities, making educators be clear of the new teaching mode. By improving the teachers' professional accomplishment and combining the effective resources inside and outside the school, the thought of lifelong physical education is rooted in the heart of the students, so that the students can fully realize the good influence of lifelong physical education in their behavior consciousness, and that they can cooperate independently. Based on the existing teaching related problems, some suggestions are proposed from the aspects of guiding ideology, reform goals, organizational forms, teaching content, evaluation and assessment.

We proposed a temperature-compensated distributed refractive index (RI) sensor using an etched multi-core fiber (MCF) in optical frequency domain reflectometry. The MCF contains inner and outer cores and is etched until the outer core is exposed. Therefore, the outer core can be used for distributed RI sensing, and the inner core can be used for temperature compensation. The sensing length of 19 cm and the spatial resolution of 5.3 mm are achieved in the experiment. The RI sensing range is as wide as 1.33–1.44 refractive index units (RIU), and the maximum sensitivity of 47 nm/RIU is obtained around 1.44 RIU. Additionally, the temperature sensitivity is 9.8 pm/°C. Using this sensor, we successfully detected the glycerol diffusion process in water.