In this paper, a FMF sensor with double gourd structure is prepared. The transmission spectrum and mode changes of double gourd structure with different lengths are studied, the temperature sensitivity and linearity of the sensor are analyzed. Five sensors with different FMF lengths are prepared. The waist-enlarged spacing are 0.7cm, 1.0cm, 1.3cm, 1.6cm and 1.9cm, respectively. The FMF length are 4.1cm, 5cm, 5.9cm, 6.8cm and 7.7cm, respectively. The experimental results show that the highest temperature sensitivity of FMF sensor is 86.95pm/℃. There is no one-to-one correspondence between the temperature sensitivity and the length of the sensor.
The strong evanescent field of micro/nanofiber enables it to have a stronger interaction with the outside world and to better sense the changes of the external environment, thus realizing many types of chemical, biological, and environmental sensors. We applied micro/nano-optics for ocean exploration and proposed a sensing probe based on an elliptical microfiber. The sensor probe utilizes the stability of polarization intermode interference of an elliptical fiber and the high sensitivity of the microfiber evanescent wave coupling to achieve a high accuracy measurement of seawater salinity. Laboratory salinity sensitivity of 45.6 nm/% was achieved under seawater environment using an elliptical microfiber with a diameter of 2.8 μm and an ellipticity of 0.3, which is two or three orders of magnitude higher than that of conventional salinity measurements. This sensing probe is used to measure the salinity of seawater in the coastal area of Qinhuangdao, samples were taken for 7 days in September, and the average salinity of the seawater was measured to be 2.956%, which is basically consistent with the data in the Marine Environmental Impact Assessment Report Form of Qinhuangdao Government Service Center.
In view of the current poor learning initiative of undergraduates, the idea of creating a good learning environment and motivating active learning enthusiasm is proposed. In practice, the professional tutor is allocated and professional introduction course is opened for college freshman. It can promote communication between the professional teachers and students as early as possible, and guide students to know and devote the professional knowledge by the preconceived form. Practice results show that these solutions can improve the students interest in learning initiative, so that the active learning and self-learning has become a habit in the classroom.
A refractive index sensor based on taper Michelson interferometer in multimode fiber is proposed. The Hydrofluoric acid corrosion processing is studied in the preparation of single cone multimode optical fiber sensor. The taper Michelson interferometer is fabricated by changing corrosion time. The relationship between fiber sensor feature and corrosion time is analyzed. The experimental results show that the interference spectrum shift in the direction of short wave with the increase of the refractive index. The refractive index sensitivity can reach 115.8008 nm/RIU. Thereby, it can be used in detecting the refractive index in different areas including the environmental protection, health care and food production.
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